Well, for as long as I've had my '86 2m6 4spd, it's had a really weird pulsating idle.

Last night I was driving in 4th gear going about 80mph and all of a sudden it seemed to stumble and lose power. I let off the gas and afterwards it was fine. The engine sounded great again.
I parked it for the night and started it this morning to go to work. It was running for about 5 minutes without a problem before I left and I got about half-way to work and it started stumbling again but in low city speeds. The RPM's kept rocking back and forth from 2K - 500 and it died. I coasted into a parking lot and tried to start it again to no avail.

After a few tries and it starting briefly and then dieing, it finally started working. I drove it the rest of the way to work, without a problem!

After work I tried a few times to start it and it would start for a second and sound fine then die.
When I try to start it, and push the gas pedal hard, it dies instantly. If I feather the gas pedal after I start it I can keep it running but it doesn't want to stay running. If I just start it and do nothing, it will die shortly after.

My first 2 guesses are IAC or TPS.
Any input would be greatly appreciated! And as always, any help will receive a + from me!

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'86 2.8L Bottle-Fed In Progress...
'86 2.5L turbo put to sleep

fieroperformancemods@yahoo.com

Any SES codes in the ECM?

Fuel pump could be on it's way out, ignition coil or the ignition module could be failing (heating up dying then will restart when cooled off but die again when reheated). Also because of the higher speed problems the EGR could also be failing. Bad valve will cause an erratic idle and stalling/hard starting conditions definite loss of power ontop of it.

As Minn said let us know if there was any SES trouble codes, and jumper into diagnostics mode and let us know which codes I'm sure we can help further~

Good luck!

[This message has been edited by USFiero1 (edited 05-13-2004).]

Well, I went back to the car and tried to check codes and there was nothing new.

I get code 32 (EGR) all the time on the highway (Since I've had the car) and it was the only stored code.

I have an MSD 6A ignition box and MSD blaster coil. I unplugged the 6A box and identical problem, so I don't think it's the MSD equipment.

I played with the spark plug wires and all of the electrical connections I could find and still no improvement.

I tried to start it after it had cooled down and it did not work. I don't know. I was really hoping to get some more informative codes...

Sounds like a fuel problem, check your fuel pressure with the key in "on" position.

When's the last time the fuel filter was replaced? Fuel pump?

I bought the car in january with 75 miles on the engine, so I'm GUESSING the filter is new... Could be wrong. The more I think of it, I am thinking it's a fuel problem.

Hopefully I can have this thing ready for the dyno day then...
Any more ideas?

And also, how do I check the fuel pressure??

Ignition Module. Mine did the same thing. New one solved it.

Hey synth!
Good to see ya.
You going to the dyno day on the 22nd?

I'll be down near the Cities on the 22nd, but no. No money to run it.

The pick-up coil could be bad, Remove the distributor cap and you can see if it has corrosion on it.
Ignition module could be bad, You can have them tested and most auto parts stores.
Ignition coil could be bad/weak.
Fuel pump could be weak, (or the fuel pressure regulator) You should have 30-34psi when it's running at idle.
If you think it's a bad sensor, Try shorting the ALDL connector (like when you set the timing) and see if it idles.
If it still doesn't chances are it's not a sensor.
Does it smell/look like its running too rich?
The cold start sensor/injector could be stuck on. Or an injector could be bad/leaking.
The catalytic converter could also be clogging.

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Happiness isn't around the corner...
Happiness IS the corner.

Synth- Hopefully we'll meet up with you sometime then.

Oreif- You are a freakin' GOD! Every time I look into a tech posting, you are like an open textbook. The knowledge you share freely with the needy people on this forum is amazing!

I have no cat.
I just replaced the ign. module a few mins ago and still no luck.
I'll short the ALDL real quick and see if that works out.
It does not smell or look like it's running rich at all.

My next plan of action is to test fuel pressure. Where should I do that at? At the throttle body, or at the passenger side of the upper intake plenum?

Thanks for all the help everyone. +'s going around!!

And on a nerve calming note:
It's times like these (When I want to light the Fiero on fire and feed the endless stereotypes...) that I feel like simply remembering a better, warmer, not-working-on-a-Fiero time...

quote Originally posted by Oslo: My next plan of action is to test fuel pressure. Where should I do that at? At the throttle body, or at the passenger side of the upper intake plenum?

The pressure valve is located on the passenger side of the fuel rail right under the MAP sensor.

thanks. first thing tomorrow morning!

About this time last year my car was doing the same thing. It ended up being the plastic hose inside the gas tank that attached to the fuel line from the fuel pump. The plastic hose had a spilt in it and it would pump just enough gas to start once in a while but most of the gas was going right back into the fuel tank. If that is your problem I would buy a new fuel pump and strainer and the little plastic hose comes with the new fuel pump. I hope that is not your problem, taking the tank off was a pain in the butt.

Good luck let us know what you found out to repair it.

mine does teh same thing after being on and idleing for about 5 seconds then driving for abour 1-2 minutes goes from 2k down to 500 then back up like nothing ever happend and its a real pain when your going up hill and its an auto!!! im thinkin fuel pump too aswell as ign. mod., cap., rotor. P.U. Coil...

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'86 Fiero GT

www.KylesFiero.tk
www.XoticRydz.tk

Well, I checked the fuel pressure at the spot that I'm pretty sure I was supposed to:

I circled the spot where I got the line. Is that the schrader valve?

It read 5.5 psi:

It wasn't leaking, or losing pressure. The first prime brought it up to 3psi, and then after a few more primes and cranking it once it got up to 5.5

I think it's time to look for a new fuel pump...

Looks like you have found the problem! Good isolation techniques.

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hmmm... I am still curious as to the confirmation of my suspiscion if what I had circled is the "schrader valve"...

Any insight on that one?
Thanks.

Well, I had a feeling that the fuel pressure guage I was using was not reading accurately because I tried it on a few other things with not too good of results. It only goes to 15psi anyways, so it wasn't the best tool for the job.

Anyways, I went and bought a new guage system and retested it and got proper fuel pressure.
So, what's the problem?
I had it nailed down to the fuel pump and the ign. module. I replaced the ign. mod. and the fuel pump seemed to be working, so I had the ign. module tested and found that it was faulty. So, I replaced it and all is well!

Runs just fine now...

But I still need to know if that is the schrader valve or not...

that is the schrader valve. you done good...

quote Originally posted by Synthesis: Ignition Module. Mine did the same thing. New one solved it.

Remember this one? :P

Glad you got it running.