SOHC Stutter/Miss Issue

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EDixon
NooB
Posts: 5
Joined: Fri Nov 13, 2015 6:29 am
Location: Aiken, SC

SOHC Stutter/Miss Issue

Post by EDixon » Sat Mar 05, 2016 8:49 pm

Hey all, I am currently having an issue that has me baffled. First off, the car is an '89, 15k on stock spec rebuild, not turbo (yet), EGR/PAIR/AIV butterfly delete, Walbro 255 (new), aeromotive FPR, BRM 2.5" catback, header, intake. The car has a slight audible miss at idle, and on part throttle it breaks up and stutters quite bad. Once I go past probably 1/2 throttle and above, it drives fine. Anytime I tip the throttle, it breaks up.
What I have done so far: New fuel pump, regulator, filter, clean maf, no ECU codes, CTS resistance is good, just went through the entire engine harness and fixed some suspect wires and connectors, TPS voltage is good and smooth, new o2 sensor, good idle speed, good timing, no vacuum leaks (performed boost leak check with soap solution).
With the o2 sensor unplugged, the car runs great. It is an issue with closed-loop operation. In diagnostic mode 2, the red and green led's never blink together -> a/f mixture is off. Checked all wiring and sensors per FSM to no avail. Hopefully ya'll can throw some ideas my way that I haven't thought of, or share some similar experiences. Thanks in advance.

EDixon
NooB
Posts: 5
Joined: Fri Nov 13, 2015 6:29 am
Location: Aiken, SC

Re: SOHC Stutter/Miss Issue

Post by EDixon » Fri Mar 18, 2016 11:22 am

Ok, so I've been able to do some more troubleshooting, and I seem to be having a ground feedback issue. With the ignition off, resistance from the negative terminal to block/chassis/head/IM/etc are all less than 2 ohms. Same result with ignition on. With the engine running, resistance between the terminal and the block/head/IM is around 95 ohms, while it is still <2ohms between chassis and battery. To try and narrow down where the issue could lie, I disconnected iacv/aac/o2/maf/cts/iat/tps one at a time with the car running, and the resistance value didn't change. Any additional insight is greatly appreciated.

Liteemup39496
Knows Some Stuff About 240's!
Posts: 465
Joined: Sat Jul 07, 2007 11:35 am
Location: North Jersey

Re: SOHC Stutter/Miss Issue

Post by Liteemup39496 » Mon Apr 11, 2016 5:55 am

your o2 sounds like its no good new or not its transmitting bad signal on closed loop , common issue with SOHC
'89 KAe-T Coupe - on the road to a goal of 400whp with A/C
'91 Hatch - VH45 powered, track duty
'05 Titan - I/H/E VK56 - Tow rig and Daily
Single Jingle love

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