Mystery idle problem still a problem - help!

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vrmilionzx
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Mystery idle problem still a problem - help!

Post by vrmilionzx »

Hey All,

I've been dealing with this problem for what seems like FOREVER, and everything I've done so far has either done nothing for it, or appeared to fix it for a short period of time.

Posted this in another thread, where others were having similar issues:
viewtopic.php?t=52692&postdays=0&postorder=asc&start=0

So far I've looked for vacuum leaks (found none, but I'm sure I could have missed one), cleaned the MAF, checked the MAF wires, replaced dizzy cap, replaced wired, replaced plugs, removed and cleaned IACV, replaced EGR and BPT valves, replaced coolant temp sensor, added grounding wires, re-grounded the tps ground in the harness (can't find the thread that was mentioned in atm).......

So here's where we stand. The last thing I did was replace the coolant temp sensor about 2 weeks ago. For the first week, car drove like a dream, problem seemed to be fixed. Mileage was awesome. Then about 9 days in, I started to notice the rpms dipping a little when i pressed in the clutch. each day it got a little worse, until finally, it was back to it's old self, dropping to around 300rpms, and today it died twice on the way to work.

I've noticed that when it's at idle, and i press and release the brake, the idle tends to "hop" up about 50-75 rpms right after i release, then drop to it's normal idle point.

I'm going to be checking the TPS voltage this evening or this weekend, and checking to see if the throttle body is gunked up, and not letting any air by at idle.
Also on my list is injectors/injector o-rings... but after that, I'm just about stumped.
When this is ocurring, I'm getting terrible gas mileage, something along the lines of 22mpg (that's mixed highway and city. Previously, i was hitting around 26 regularly. And i've made sure I'm using good gas).

So if I can't get this figured out soon, I'll be opening a thread to give away some charred s13 parts, because I'm gonna light this thing on fire and push it off a cliff.

Any help or recommendations would be HUGELY appreciated...
arias pistons (8.8:1), pauter rods,
cometic headgasket
garrett t3/4 50 trim
mild p&p, pdm cams, 3" turbo back,
jwt flywheel and ecu, clutch specialties clutch
740cc injectors, ebay fmic,
elec fans, msd, stock vlsd, z32 brakes and mafs, safc2, hks evc 4, Koyo Radiator, protective layer of dirt.
-"stock" s13 dd - Project MPG
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cleantune
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Re: Mystery idle problem still a problem - help!

Post by cleantune »

Well on the positive side, if nothing else, you are trying very hard and your engine is getting closer to being brand new with all of the parts that were replaced :roll:

On a more serious note, it would be a good idea to start with the basics (as I'm sure you have) fuel and spark. You had mentioned that the car is getting worse gas mileage now, which would mean that the engine has the gas, it is just not using it to its full potential; so I would suspect that it is not a fuel related problem.

I read in the other thread that it could have been a possible electrical problem. If the spark is not what it should be, more gas will be "wasted"; so I would recommend making sure the spark plugs you have replaced are all giving spark.

The brake induced idle change behavior you had mentioned may have something to do with the brake booster's vacuum priority. (I know you probably know about the brake booster, but for anyone looking at this thread who doesn't)... The brake booster has two sections; one closer to the pedal and one closer to the brake master cylinder. Both of these sections are always under vacuum (and connected) when no brake pressure is applied, but when the brake is pressed the side closer to the pedal shuts off the connecting passages to the other side and gains atmospheric pressure. My guess would be that either the engine is "choked" a bit when the brake is applied or that it just gains some extra air when the brake is released.

I also read that you have checked and cleaned the IACV. It may be a good idea to check for any obstructions in air flow to and from the engine (pinched line or something clogging the hose that runs from the cold pipe into the IACV, cleanliness of the air intake filter, any other obstructions in the piping going to the throttle body; also I'm not sure what kind of exhaust setup you are running ( i may have missed it somewhere when reading), but an obstruction in the exhaust can have similar stalling issues. A friend ran into some stalling issues with his RX8; the catalytic converter element had broke and was clogging the passages and a new catalytic converter corrected the problem.
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Post by vrmilionzx »

Thanks for the response! And yes, much of the car is like new now. The problem with this for me is that it's supposed to be an efficiency project; I want 40mpg (highway), and if it costs a boatload of money to get there, it's kind of counter to the point.

While I've checked some of it, I'm going to see about pulling the cat off, and see if that does it - it's the stock (original) exhaust, so it's possible the damn thing is falling apart too. I'm also in the process of going through and checking the vacuum lines around the EGR system, because I rechecked the EGR valve, and when I press up on the diaphragm, there's no change in the idle. I'm assuming this means something is clogged or sticking, or there's a leak/kink in one of the lines, because the valve itself was fine when I swapped it in.

I changed the fuel filter, and verified there was fuel getting to the cylinders as well. I'm thinking I might replace all the fuel hoses, just for giggles.

I changed the spark plugs and wires last year, when it started doing this, and there was no change at all. That was the same time at which I checked the dizzy and changed the cap and rotor.

Just to make sure it wasn't the brake booster (or check valve), I tested the check valve by blowing air into/creating vacuum on the line into the valve, it worked. The only strange thing to me was the short hissing sound I got from the booster itself when it was subjected to vacuum. I tried to isolate the brake assist system by plugging the vacuum line that feeds the brake assist at the source (on the manifold). The problem persisted, so it's not a leak in the brake system. Or, if there IS a leak there, it's not the one causing this issue.

I also made a grounding kit last year, in hopes it would help. While the car revs a little easier, and the lights are a bit brighter, it didn't solve the issue. The TPS testing revealed that it's almost within spec - I need to adjust it next time I have the time and daylight, the only reading that's a little off is running with the throttle closed. It's at around .38 when it should be around .45.

I'm going to double check the MAF voltage, just because I haven't looked specifically at the voltage coming off the MAF. Might as well be as thorough as possible.

As a final step, there's a vacuum plug that needs an allen wrench below the throttle body, in the intake mani. I'm going to pull that (I think it's an 11? Can anyone confirm that?) and run a seafoam soaked pipe cleaner through it, as I've read that it'll sometimes get clogged with crap over time.
arias pistons (8.8:1), pauter rods,
cometic headgasket
garrett t3/4 50 trim
mild p&p, pdm cams, 3" turbo back,
jwt flywheel and ecu, clutch specialties clutch
740cc injectors, ebay fmic,
elec fans, msd, stock vlsd, z32 brakes and mafs, safc2, hks evc 4, Koyo Radiator, protective layer of dirt.
-"stock" s13 dd - Project MPG
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Post by cleantune »

No prob, here to help :]

One of the symptoms of a clogged cat is a rattling noise when the engine is revved. Often excessive heat, exhaust flow, or with just the age of the cat; the catalytic element breaks and the pieces can get get lodged and block flow. The 8 that had the problem that I had mentioned had a fluctuating idle and would pull hard until a certain rpm and then fall on its face at higher rpm's. Have you noticed any rattling or loss of power in higher rpms?

Thats good you rechecked the EGR and if nothing else it seems as though you have made a lot of progress on narrowing down the possible problems. Thats a good idea to check the Maf voltage. On a previous thread someone asked about the maf voltage (if you need it).

viewtopic.php?t=54746&sid=e276057194242 ... a7040ce59a

I'm not too familiar with the vacuum plug you mentioned (I have an s14 KA), but my engine has a stud with an allen key hole to adjust the angle at which the throttle pulley stops when the gas pedal is fully lifted. Maybe your engine has one too? I know its probably not what you had mentioned, but maybe it could help raise the idle a little.
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Post by vrmilionzx »

I think the allen bolt is just the path into the intake from the EGR valve.
I'll check the one you noted too, not sure it's there on the s13 intake mani.

I do get a bit of a metallic rattle on decel and very low throttle around 2600 rpms, though it seems to pull just fine all the way to the top. I suppose it could be the cat. I just assumed it was part of the heat shielding. I'll be sure to check for broken cat-bits too.

Thanks for the MAF voltage link - that'll save me some time!
arias pistons (8.8:1), pauter rods,
cometic headgasket
garrett t3/4 50 trim
mild p&p, pdm cams, 3" turbo back,
jwt flywheel and ecu, clutch specialties clutch
740cc injectors, ebay fmic,
elec fans, msd, stock vlsd, z32 brakes and mafs, safc2, hks evc 4, Koyo Radiator, protective layer of dirt.
-"stock" s13 dd - Project MPG
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Post by Freise »

Wow that thread brought back some memories.
I still haven't figured this damn problem out, but I quit trying because it no longer dies it just drops idle to around 500rpm but has always recovered, I have noticed, however, that the problem is more pronounced in cold weather (for example less than 70*F) as opposed to a higher ambient temperature, where the problem appears to be less common.
It also will not die while the car is warming up, I'm not sure if it's just the raised idle that causes it to run fine or what. Once it warms up, the problem appears.
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Post by vrmilionzx »

Yup, that sounds like it. Doesn't die on warmup, but once warm, it's a crapshoot.
Somtimes it dies, sometimes it stutters, and sometimes it miraculously catches itself at the 800 rpm mark, then drops another 50 to idle fine.

Freise - what did you check?
arias pistons (8.8:1), pauter rods,
cometic headgasket
garrett t3/4 50 trim
mild p&p, pdm cams, 3" turbo back,
jwt flywheel and ecu, clutch specialties clutch
740cc injectors, ebay fmic,
elec fans, msd, stock vlsd, z32 brakes and mafs, safc2, hks evc 4, Koyo Radiator, protective layer of dirt.
-"stock" s13 dd - Project MPG
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Post by Freise »

To be entirely honest I'm not sure what I did to get it to (at the very least) stop dying. It seemed to make an improvement after I cleaned up my intake manifold: New upper and lower gaskets, cleaned IACV, AAV, and tube, new gasket on those, Blocked off PCV connections, removed vacuum gallery, gave entire IM a good scrubbing and soaked with degreaser. I also cleaned my injectors and replaced O-rings in the process. But, although better than before the problem is still present and I changed too much to pinpoint what the cause was and how I was getting closer. Part of me wants to lean towards fuel related issue. I think I've found a pattern that is caused by decel that is causing the engine to go super rich before coming to a stop. Whether it is in fact too much fuel getting in or not enough air... I need more time and better weather conditions to play with this some more and see if I've found a lead, but if I make any progress we can make this the "official" thread to report it in!
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Post by vrmilionzx »

Super rich makes sense, given the way it's guzzling gas, but I'm not getting a CEL. Since it's not consistent, and only on decel, I'm less inclined to think it's an injector o-ring.

I'm down to keep posting, and make this the official "decel gremlin" thread.

I'm even more excited to find and fix the issue, because it's been persistent for entirely too long. I think it's interesting that some things will help a little, but ultimately it keeps coming back to the same point....
arias pistons (8.8:1), pauter rods,
cometic headgasket
garrett t3/4 50 trim
mild p&p, pdm cams, 3" turbo back,
jwt flywheel and ecu, clutch specialties clutch
740cc injectors, ebay fmic,
elec fans, msd, stock vlsd, z32 brakes and mafs, safc2, hks evc 4, Koyo Radiator, protective layer of dirt.
-"stock" s13 dd - Project MPG
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Post by Walperstyle »

does the problem happen more often at night, with the lights on, heater going, stereo on, while using the windows?

Just checking if its still a voltage issue.
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Post by vrmilionzx »

Nope, independent of electronics. Daytime, night time, all the time. And the windows draw no power (other than driver power), so I'm pretty sure they're innocent in this case.

That's what I was worried about, which is why I double checked a bunch of connections, grounds, and made a grounding kit.
arias pistons (8.8:1), pauter rods,
cometic headgasket
garrett t3/4 50 trim
mild p&p, pdm cams, 3" turbo back,
jwt flywheel and ecu, clutch specialties clutch
740cc injectors, ebay fmic,
elec fans, msd, stock vlsd, z32 brakes and mafs, safc2, hks evc 4, Koyo Radiator, protective layer of dirt.
-"stock" s13 dd - Project MPG
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Post by Freise »

How long should the fuel system maintain fuel pressure after priming? Google is all over the place, saying 10 seconds to two hours.
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Post by vrmilionzx »

That's a good question - I really haven't the slightest clue. Is that in the FSM? I can't check at the moment (it's on my laptop at home).
arias pistons (8.8:1), pauter rods,
cometic headgasket
garrett t3/4 50 trim
mild p&p, pdm cams, 3" turbo back,
jwt flywheel and ecu, clutch specialties clutch
740cc injectors, ebay fmic,
elec fans, msd, stock vlsd, z32 brakes and mafs, safc2, hks evc 4, Koyo Radiator, protective layer of dirt.
-"stock" s13 dd - Project MPG
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Post by Freise »

It's not specified other than what the psi should be, but I've been doing some research in this area, the idea of a pressure leak appear to fit along with the symptoms, especially if it is a pressure leak and not a full blown gasoline leak... If I have any luck when the weather warms up a bit I'll let you know.
The question still stands though to anyone who knows: How long should the fuel system maintain pressure after being primed?
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Post by vrmilionzx »

Update time...

Per a suggestion from S1495, I checked the voltage coming off the MAF - and found something strange. Input voltage was good, so it's not an alternator issue (at least, not at the maf). The output with the ignition on and the car off was 0.021. With the car on at idle, it was the same. Also the same when I revved it. Obviously, this is a problem, and suggests the MAF might be bad.
I also checked the ground for continuity, and found something interesting. With the car running, and the negative lead of the multichecker connected to the battery negative terminal, i touched the ground wire (from the back of the plug), and the idle jumped up. Very interesting. So I revved it via the throttle body, and it revved, came back down, didn't stutter, was solid. I removed the lead from the ground, and idle dropped and got rough. I repeated it, to make sure. Seems I have a grounding issue, not a MAF issue. Which means it's time to start hunting backwards to find the bad ground in the harness. I'm going to try to verify that this is the problem by rigging a ground directly from the maf, rather than through the harness, and drive it for a couple days to see if that resolves the issue.

This does, however, explain why replacing the MAF before didn't solve the issue.

So I'll update when I have the results of my ghetto-ground test. I remember reinforcing the ground in the harness near the fuel rail about a year ago, and that ground was pretty trashed too.
It is a ground for (I think) 3 components; apparently MAF isn't one of them.
arias pistons (8.8:1), pauter rods,
cometic headgasket
garrett t3/4 50 trim
mild p&p, pdm cams, 3" turbo back,
jwt flywheel and ecu, clutch specialties clutch
740cc injectors, ebay fmic,
elec fans, msd, stock vlsd, z32 brakes and mafs, safc2, hks evc 4, Koyo Radiator, protective layer of dirt.
-"stock" s13 dd - Project MPG
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Post by airman »

On the right track - here's the most helpful piece of information on the entire internet:

http://www3.telus.net/kreen/wiring/wh150dpi.png

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Post by nissanfanatic »

I fought with idle for a long time. I ended up fixing mine by pouring some Seafoam through the IACV with the car running. After that, it never stalled again. Mine was most likely years of carbon buildup. You will have to give the engine some throttle to keep it going.

....

You can eliminate the MAFS by unplugging it and starting the car. Just be advised that the car won't go into open loop mode IE over about 3000rpm.
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Post by vrmilionzx »

Oh, yeah, ran seafoam through the intake via iacv, even pulled it off to clean it.

Quick question for the electrical ninjas here - I want to verify that I'm good doing my ground this way.

Based on the link above (thanks Airman), the ground is pretty much a straight shot to the ecu. So, I want to effectively add a third wire (think of it as a "t") to that, and run it initially to the battery negative terminal, then if it works, to the chassis. This shouldn't cause any issues, right? I mean, a ground should be a ground, yes?

Thanks for any help!
arias pistons (8.8:1), pauter rods,
cometic headgasket
garrett t3/4 50 trim
mild p&p, pdm cams, 3" turbo back,
jwt flywheel and ecu, clutch specialties clutch
740cc injectors, ebay fmic,
elec fans, msd, stock vlsd, z32 brakes and mafs, safc2, hks evc 4, Koyo Radiator, protective layer of dirt.
-"stock" s13 dd - Project MPG
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Post by nissanfanatic »

Yea. I wouldn't waste the time running it to the battery negative. Just run it to a chassis ground point.

or...

Measure resistance between the harness wire and chassis ground using a multimeter. Look for a short, or very low resistance. If resistance is very low, then another ground is not needed for the ECU.
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Post by erich »

airman wrote:On the right track - here's the most helpful piece of information on the entire internet:

http://www3.telus.net/kreen/wiring/wh150dpi.png

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Your welcome.

I assume you've tested the O2 sensor? They're cheap so I'd replace it anyway.
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Post by erich »

vrmilionzx wrote:Oh, yeah, ran seafoam through the intake via iacv, even pulled it off to clean it.

Quick question for the electrical ninjas here - I want to verify that I'm good doing my ground this way.

Based on the link above (thanks Airman), the ground is pretty much a straight shot to the ecu. So, I want to effectively add a third wire (think of it as a "t") to that, and run it initially to the battery negative terminal, then if it works, to the chassis. This shouldn't cause any issues, right? I mean, a ground should be a ground, yes?

Thanks for any help!
You should not add a ground in parallel to the ECU sourced ground. The A/D converter fro the MAF is 16 bit and high precision. Typically they have differential inputs and their own isolated ground. Adding a ground in parallel <i>might</i> not screw things up but if there is any difference in the MAF ground sourced by the ECU and chassis ground you will end with a ground loop. A ground loop is the voltage induced by current flow between grounds of different potential. There could be quite a bit of current flow and it could damage the ECU. It's really complicated dealing with high precision analog circuitry in a noisy environment and keeping grounds separate usually helps.
I'd make sure that the ground line to the MAF from the ECU is not screwed up instead of adding a new ground,
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Post by vrmilionzx »

Thanks for the additional input!

Yep - checked the o2 sensor (replaced it recently as well).

Unfortunately, I didn't see your post (Erich) until after I'd run the ground in parallel. I drove it for a day, and in about 50 miles of driving, didn't have the stalling issue. This is not necessarily indicative that the problem is resolved, because it occasionally runs well with no (apparent to me) changes in anything else.

I'll see about checking the ground wire all the way back to the ecu, as well as checking the ECU ground to make sure it's not screwed up. I'll pull it off the negative terminal, and ground it to the chassis just to try to avoid any additional noise there while I trace the ground wire to the ECU.
arias pistons (8.8:1), pauter rods,
cometic headgasket
garrett t3/4 50 trim
mild p&p, pdm cams, 3" turbo back,
jwt flywheel and ecu, clutch specialties clutch
740cc injectors, ebay fmic,
elec fans, msd, stock vlsd, z32 brakes and mafs, safc2, hks evc 4, Koyo Radiator, protective layer of dirt.
-"stock" s13 dd - Project MPG
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Post by erich »

If the ECU isn't fried then I guess it won't hurt anything! Good luck.
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Post by vrmilionzx »

Yeah, ECU seems fine - haven't had the chance to take off the parallel ground yet, been out of town for several days. On the upside, I'll have some time to play with it tonight, then i'll be driving it to SD (120 miles each way). That should be a good chance to see what kind of difference it makes over a full tank.

Interestingly, it'll still kind of "step down" from about 850rpms to about 600 or so when I'm in decel or at a stop light. I thought the brake was related, but sometimes it does it independent of braking, so I'm going to work under the assumption that it's not for the time being. The idle is a little rough, but nothing too terrible. I just notice it because of the semi-solid motor mounts, I think.
arias pistons (8.8:1), pauter rods,
cometic headgasket
garrett t3/4 50 trim
mild p&p, pdm cams, 3" turbo back,
jwt flywheel and ecu, clutch specialties clutch
740cc injectors, ebay fmic,
elec fans, msd, stock vlsd, z32 brakes and mafs, safc2, hks evc 4, Koyo Radiator, protective layer of dirt.
-"stock" s13 dd - Project MPG
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Post by vrmilionzx »

Update time!

After moving the MAF ground to the chassis, I drove to San Diego and back. On the way down, I had 25 miles on the clock before leaving, and got about 30mpg. Coming back up, I filled up right before leaving, and it's a little higher, I'm estimating around 32, which is where it should be given the mods on there. Interestingly, however, this level of efficiency is only seen at higher speeds (rpms over about 2900). I don't know if this applies in all gears, because I'm usually only in 5th at that RPM level for any prolonged amount of time.

That said, it is behaving a little strangely in lower RPM situations, seemingly more when it's still cold (or warming up). When I say strangely, it feels almost like it's hesitating in low gears on the way up to the shift. The feeling is similar to a slipping clutch, without the slipping clutch symptoms (it's grabbing just fine). It generally gets more peppy around 2600-2800 rpms, and then seems fine. Almost like it's changing to a less crippled fuel map, or adding like, 8* of timing back in. Without a Nistune or other data cable to monitor/record live, there's no way I can watch that as I'm driving, so I don't know for sure.

Any thoughts? I'm driving it to class this evening in some traffic, it'll be mostly city, so I will see if the decent mileage is maintained for those miles.
Also, I'm thinking that my cooling setup is too efficient - when I was coasting down the hill (decel), the temp gauge was pegged at the bottom. IE, too cold. Verified this with the heater, it was cool. Outside temp was probably around 60-65, with some wind chill. The temp sensor is new, replaced the thermostat about a year ago, so all of that should be good. Temp went back up when the road leveled out, but again, shouldn't get that cool....right?
arias pistons (8.8:1), pauter rods,
cometic headgasket
garrett t3/4 50 trim
mild p&p, pdm cams, 3" turbo back,
jwt flywheel and ecu, clutch specialties clutch
740cc injectors, ebay fmic,
elec fans, msd, stock vlsd, z32 brakes and mafs, safc2, hks evc 4, Koyo Radiator, protective layer of dirt.
-"stock" s13 dd - Project MPG
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Post by vrmilionzx »

Update #2.

Second tank of gas, with about 200 miles on the freeway, and about 80 miles in traffic, and it maintained decent mileage - about 27.5 per gallon. For that mix, and the traffic I was in, I'll take that.

HOWEVER, the car still seems to have some kind of idle issue. It doesn't die, but it still drops occasionally past the idle point (I have it set to around 800) for a couple seconds, then comes back. I'm still suspicious of the EGR system, because when I manually open the valve (pressing upward on the diaphragm), there's no change in idle. This suggests that the valve is staying open, and allowing exhaust gas to leak in, making the car run in a less than ideal way. I'm going to try to either get a nickel in the egr feed at the exhaust to simulate egr removal, or I'm just going to remove the EGR system. Of course, that way I can't verify that it's not just a vacuum leak.

Along those lines, maybe someone can help me by verifying the way the EGR system is supposed to work for me: because the EGR system should only open while cruising, I'm assuming that means higher vacuum (less throttle), suggesting perhaps that the EGR valve is usually held open by vacuum when the vacuum is high enough?
arias pistons (8.8:1), pauter rods,
cometic headgasket
garrett t3/4 50 trim
mild p&p, pdm cams, 3" turbo back,
jwt flywheel and ecu, clutch specialties clutch
740cc injectors, ebay fmic,
elec fans, msd, stock vlsd, z32 brakes and mafs, safc2, hks evc 4, Koyo Radiator, protective layer of dirt.
-"stock" s13 dd - Project MPG
erich
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Post by erich »

If the temperature is dropping after the car has warmed up then the thermostat is sticking open.
The ECU will do cold enrichment so it's possible that you're running way too rich near idle.

Do you have a consult cable? Check the ECU's engine temperature reading. If the ECU thinks the engine is cold it will be dumping fuel.
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vrmilionzx
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Post by vrmilionzx »

Unfortunately I don't have a consult cable - I'm going to look into that shortly as well.

Thank you!
arias pistons (8.8:1), pauter rods,
cometic headgasket
garrett t3/4 50 trim
mild p&p, pdm cams, 3" turbo back,
jwt flywheel and ecu, clutch specialties clutch
740cc injectors, ebay fmic,
elec fans, msd, stock vlsd, z32 brakes and mafs, safc2, hks evc 4, Koyo Radiator, protective layer of dirt.
-"stock" s13 dd - Project MPG
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vrmilionzx
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Post by vrmilionzx »

Swapped the thermostat out, and now I'm running into another problem - it overheats. (details here: viewtopic.php?p=472765#472765).

When I brought it back home with the heat a little high, the idle bounced again. :roll:

Next is checking the radiator and the water pump (water pump was done fairly recently, I think, need to check my records).
arias pistons (8.8:1), pauter rods,
cometic headgasket
garrett t3/4 50 trim
mild p&p, pdm cams, 3" turbo back,
jwt flywheel and ecu, clutch specialties clutch
740cc injectors, ebay fmic,
elec fans, msd, stock vlsd, z32 brakes and mafs, safc2, hks evc 4, Koyo Radiator, protective layer of dirt.
-"stock" s13 dd - Project MPG
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schmauster920
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Post by schmauster920 »

Bump i know you are still having issues

You should try cleaning the throttle body if you havent
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