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Discussion Starter #1
I can't for the life of me figure out what is wrong with my car. Basically it started to hesitate yesterday going down the road so I pulled over. Car feels like it's running on 3 cylinders. It will not hold an idle at all. The computer codes I pulled from it said the AFM signal so I swapped it with a different one and nothing changed. I have spark and fuel and the timing is set correctly. What else could it be? Please if you have any suggestions let me know.

Thanks
Erik G.
 

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Did you reset the ecu? is it still showing afm code? Check your wiring from afm to ecu. check for continuity and shorts to ground. Check the afm reading to make sure it's good. Could also be ecu.

Christian
 

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Did you reset the computer and codes when you chagned the AFM? Probably wouldn't fix it but you should do it just in case.

Could be allot of things.

Cap/Rotor/plugs
maybe a BHG, pull the plugs and look for one that is white. Any white smoke out the pipe?
Throttle Position Sensor
Vac hose came off maybe?
Fuel pump or filter

What is the engine code?
 

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Discussion Starter #4
Ok, I know it's not a BHG as that was taken care of not that long ago with an HKS MHG and ARP studs. I reset the computer but didn't change anything. Fuel pump is a fairly new Walbro and you can hear the thing whine when you turn the key. Also I checked all my plugs and they are wet with fuel. But I'm also getting spark to the cylinders so it makes me think that the timing is not right for some reason. So I checked the timing and it's right on. The cap and rotor are recently replaced and they look good. When the car starts it runs horribly and belches out black smoke out the tailpipe. The AFM and wires seem to be fine. I can't figure this thing out. And it's been running beautifully lately. All of the sudden it just runs like shit for no reason.
 

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If it runs extremely rich, it is getting a reading that is telling the ECU to add more fuel. The sensors that tell the ecu to add more fuel are the TPS and AFM (there are others, but would not add fuel to that degree). I would get my multimeter out and start checking readings at the ecu if I were you...

--BillyM
Viva La AutoX!
 

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Do a compression test also.What boost are you running? Have any boost spikes lately?
 

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Discussion Starter #7
I plan on doing a compression test also just to make sure there are no mechanical problems. I'm starting to think that it's probably the coil pack and/or resistor. But it's just a guess.
 

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Check your oxygen sensor if its loose if so thighten it.
 

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Discussion Starter #9
Well, I still haven't figured out what's wrong with my car. Tomorrow I'm going to swap out the coil/ignitor to see if that takes care of it.
 

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had a car that ran like that.....check your coil.
 

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Are you running a RRFPR?? Sure sounds like something is causing too much fuel to be delivered, either from way too much fuel pressure or from the injector pulse width being too wide. If the ECU is still detecting that something is wrong with the AFM circuit, I would troubleshoot that problem first and go from there. Lets say there's an open circuit somewhere in the AFM Vs circuit and the Vc circuit checks out OK, that would make the ECU think that the AFM flap is wide open regardless of RPM. Take a good luck at the AFM connector on the engine wiring harness and see if any of the wire connections have broken, etc.. You've already swapped the AFM itself so the next step is to check the wiring, voltages, connections, etc..
 

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Hey I would double check your firing order if you are getting spark in every plug and all your plugs are wet the engine can't possibly be firing at the right time

so check
your firing order
your plugs
your wires
your coil
your distrbuter
 

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since the 6 injectors run into 2 wires that go to the resistor i might check the wires, like the clamp points or the resistor itself
 

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Discussion Starter #14
Now is it more likely that the coil is bad or the ignitor is bad?
 

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Discussion Starter #15
Well guys, I replaced the coil and ignitor pack and still no help. So I"ll do a compression check and see what's up. Maybe it's a collapsed lash adjuster or something like that. We'll see.
 

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Discussion Starter #16
Ok, finally got my car home yesterday and was able to look it over a little bit more. Ran a compression check and engine has good compression. Basically the way it sits now is that it will start but run horribly unless you rev it up then it will smooth out a little but belch black smoke out the back like it's just dumping fuel into the engine. I pulled the spark plugs out and they are black and sooty. So the AFM, Distributor, Coil/Ignitor, wires cap and rotor and timing are perfect so what's the next thing to check? I know a few of you said that the ECU might be bad. Maybe one of you has one that you could let me try out to see if that fixes the problem? I'd need one for an '85 Auto.
 

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How about a failed EGR? The symptoms could be caused by that? Cold start injector stuck open?
 

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Discussion Starter #18
I thought about the EGR valve so I checked it and it looks to be operating perfectly. I have an extra fuel pressure regulator that I'll be swapping out tomorrow and I might as well swap out the cold start injector too. Don't see how it will hurt anything.
 

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Discussion Starter #19
FINALLY!!!! I finally figured out what was causing my car to run so horribly. My Cartech RRFPR was stuck closed on the inside causing a huge increase in fuel pressure. So I took it apart and lubricated it and now all is well. Thanks for all the help and suggestions. You guys are the best!
 

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Where is the RRFPR in relationship to the FPR?
I'm having this same bad idle problem and getting codes 23/31/32....AMF circut errors.
 
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