Ok. So here it goes.

Me and my father started this project a years ago. Now we got a fresh 2.8l fully rebuilt and works perfectly!!!
The engine is back in the car since 2 weeks now.

We got it to work, everything is fine, theres no vacuum leaks...
Now we got the test ride.

We have 2 problems "'remaining'' right now

Problem 1 : Gm recommand fiero to idle at 800-850 rpms.
But when we put it down at 850 the engine varies between 850-1100... it's not constant...

Problem 2 : I'm running the car at 50km/h everything is fine... but for no reason... sometimes theres no more sounds coming from the engine... it just stops...
So I have to press back on the gas to ''bring'' back the engine to work... It happens under 50... but not over.

Now probably with the same problem... when I stop at a light the car stops... so I put it back on Park, start back the engine and it will fire normally.

(for the second problem, we already had it with the old 2.8we had in the fiero a years ago... we're thinking about gas pump or electronic problems)

Any clue???

sounds like the IAC motor isnt working properly.

personally id pick up a data loging cable and check to see what the sensors are reading.

the iac could do allt he things your saying, unsteady idle, stalling at a stop, and stalling at cruise.

[This message has been edited by hookdonspeed (edited 06-13-2010).]

quote Originally posted by Softpants: Problem 1 : Gm recommand fiero to idle at 800-850 rpms. But when we put it down at 850 the engine varies between 850-1100... it's not constant...

What do you mean by "when we put it down?" Are you adjusting the stop screw on the throttle body? If so, that's a big part of your problem. That screw is set at the factory and is not supposed to be touched; it even has (or had) a plug blocking access to it.

Idle in the Fiero V6 is controlled only by the IAC motor/valve, as commanded by the ECM. If there is no vacuum leak, "hunting idle" in a Fiero V6 is usually caused by either 1) a misadjusted throttle stop screw, 2) a dirty or sticking IAC, or both. You might also check that the EGR valve isn't leaking.

So where is the Father/Son/Car picture?

#1 Yes you don't mess with the throttle set screw. The ecm sets the idle speed the screw is a preset.
You might try backing it out until the throttle plate just starts to stick closed and then turn it back in a bit.
The idle up and down is a common Fiero problem with hunting idle. Many have it but a perfect solution have not been found by many. I have it on my 85Gt also. Sometimes vacuum leaks can cause it, bad O2, sticking iac, air of coolant temp sensors, ignition issues, etc. Still have not found what is causing mine. It tends to occur more often when the air temps are in the 60's or so. Less when cold and very hot.

#2 The ecm (at least on the early year manuals not sure on autos) turns off the injectors on deceleration when above 1500 rpm as a gas saving measure. Could be what your experiencing.

On Auto models if the engine dies when coming to a stop it can often be a sticking TCC lock solenoid. The torque converter lock once you get above 40 or so. If the solenoid sticks then when you stop it kills the engine. The way to test is to unplug the TCC which in on the front of the transmission pointing toward the drivers seat. If the problem disappears then that is the problem.

[This message has been edited by Dodgerunner (edited 06-13-2010).]

quote Originally posted by Dodgerunner: #2 The ecm (at least on the early year manuals not sure on autos) turns off the injectors when above 1500 rpm as a gas saving measure. Could be what your experiencing.

Dodge... that's the first I've heard of this. Can you elaborate? Where did you read/learn about this?

quote Originally posted by Bloozberry: ... that's the first I've heard of this.

Starting in the late 1960s, a lot of cars had something like this. Originally it done more for emission control than for fuel economy, since trailing-throttle deceleration is just about the highest-pollution regime of engine operation.

This closed-throttle deceleration fuel cutoff (you often see it abbreviated DFCO) was difficult to implement with carburetors but relatively easy to do with fuel injection. Even my 1969 Porsche 911S, which had Bosch mechanical timed-multiport fuel injection, had a DFCO feature. When you feathered the throttle during deceleration (or as the engine RPM descended through 1500 with the throttle fuly closed) you could feel and hear the exhaust crackle back to life. More modern electronic fuel injection systems do a better job of it.

[This message has been edited by Marvin McInnis (edited 06-13-2010).]

Just because someone asked. This is the car today. We just finish with the body.

Yeah, bumbers and rocker are on the primer until I decide the color... probably for next year.






Yeah when I say put it down. It's using the screw on the throttle.

Hey, that's the bumper mod Irvin's takin' the heat for. Pull him out of the fire
by tellin' him how you did it. God knows it was "rocket science" to "git 'er done"! ;^)
Looks like your dad and you work well together, savor the good times together.
I know I did when I was young and mine was was alive.

Norm

[This message has been edited by gt88norm (edited 06-13-2010).]