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I'm kinda going crazy here trying to figure this out. Any help would be greatly appreciated.
A few details, the truck is at 250k miles and the previous owners butchered up some of the wireing harness near the driver side AFM sensor and headlight.
The Problem: the truck runs ruff at low RPM and seems to run even worse after it's warmed up. Things I've replaced so far
Cap, Rotor, Coil, Plugs, Wires, Fuel Filter, Thermo Time Switch Sensor, Water Pump.
It's throwing codes.. It's blinking out a AFM code and a O2 code. I've bench tested the AFM and it seems to be within spec. The O2 Sensor appears to be new on the header. Though the previous owner threw me another curveball by welding in a cat that has a O2 sensor that has no wire going to it. I'm wondering if '87 efi's have (2) O2 sensors and if they do, where is the wire/connector located on the harness? I thought there was only one port on the ECU harness for the O2 sensor but I've noticed some people say their '87s have 2 x O2's and that one of them is a 4 wire O2.
Im hearing the timing chain rattle also after I let off the throttle, could a loose timing chain cause it to run rough at low rpm? The guide seems to be in place, though it seems way looser on the driver side than the passenger side.
Ive done a compression test, and it seems to be within spec 60-90-120-170.
Last edited by solidfunker; 05-26-2017 at 06:14 PM.
you might want to look at a diagram of your ecu to see if it has two O2 terminals. maybe if it's CA emission vehicle. can't help you there. my '86 only has one. a secondary O2 doesn't have much if any effect on performance, anyway. the primary one makes the difference. i'd have to go back and review how the O2 cycles, but i don't believe it's causing the problem.
i will say, also, it depends on the O2 code. is it saying the air/fuel mix if off....ie, lean or rich? or is it just not getting an O2 signal at all?
i'd test the afm wiring at the ecu. maybe the thermal sensor on the afm is not reading correctly if at all. and, test the coolant temp sensor. it's right next to the thermal time switch
Is is there a legit wiring diagram anywhere? I have the Haynes manual but it covers a lot of different models and years.
Originally Posted by thook
you might want to look at a diagram of your ecu to see if it has two O2 terminals. maybe if it's CA emission vehicle. can't help you there. my '86 only has one. a secondary O2 doesn't have much if any effect on performance, anyway. the primary one makes the difference. i'd have to go back and review how the O2 cycles, but i don't believe it's causing the problem.
i will say, also, it depends on the O2 code. is it saying the air/fuel mix if off....ie, lean or rich? or is it just not getting an O2 signal at all?
i'd test the afm wiring at the ecu. maybe the thermal sensor on the afm is not reading correctly if at all. and, test the coolant temp sensor. it's right next to the thermal time switch
um...on the forum front page, there's a thread with stickies and links to fsm's. yours may be there somewhere. pretty sure it is. i'll have a look if you don't find it first
well, i can't find a link in a quick search. i'm sure someone would have the info and would post the diagram happily. i know it's around here posted already. so maybe run some searches first, i suppose, for '86/22re ecu diagram.
for that matter, 4crawler i'm sure can help you out. send him a pm?
oh, and don't drive that thing until you fix the timing chain. if it fails, you're gonna have even bigger problems. 6 bent valves on mine when that happened
I just beeped through all the wires from the ECU to the AFM and the O2. Does anyone know if it's standard to have the O2 on the manifold or the cat? The Haynes manual is saying that only turbo has the O2 on the manifold..
Im starting to think maybe this has a slightly bent valve.
The 2 trouble codes are going to drive me crazy, though I suppose I could just replace the sensors and give it a try.
check the amount of voltage getting to the ecu. continuity is one thing, but proper voltage is another.
standard is on the manifold. mine is not a turbo. it's on the manifold, so not sure what the hell haynes is jivin' about
bent valve.... test compression, of course. what makes you think bent valve, though?
replace sensors? as in replace afm? that's pretty expensive. just sayin'. again, check the voltage first. plug your tester into the terminals at the ecu with the key on. check the movement on the flapper for the afm, too...as in the signal it's trying to give. if it's dropping out at the lower range, then it would of course affect how it runs
I'll try to check the voltage at the ECU.. I was holding off on replacing the AFM for last. I know if it and the O2 sensor were bad it would run rich/lean.
I think it may be a bent valve or sloppy timing chain that's making it feel like a slight miss at low RPMs. I did a compression test and it was within the proper range after 2-4 cranks but would only jump to 60ish on the first crank then to 170ish by the 4th compression stroke.. I was told that if it builds compression as it cranks then it could be valves.
I'm also suspect of the injectors since it's a slight miss and seems to run out of balance (more vibrations) at low RPM 800-2000. I did check with a long screw driver to hear if the injectors were clicking and they all seem to be working.
Im really stuck between getting a new motor, or doing the timing chain. But neither would fix the AFM \ O2 problem.
It it seems like a new motor would be almost as much work as a timing chain and might give me a chance to inspect the harness more as well.
Last edited by solidfunker; 05-26-2017 at 07:30 PM.
I just beeped through all the wires from the ECU to the AFM and the O2. Does anyone know if it's standard to have the O2 on the manifold or the cat? The Haynes manual is saying that only turbo has the O2 on the manifold..
Turbo o2 sensor is in the downpipe, not the manifold. dont trust haynes. check the way back machine for the FSM. only way to find them now.
i'd read something about some company doing a crack down on online fsm's when i was looking for subaru info. reportedly this company has bought up all the rights or something?
05-26-2017, 01:46 PM
