1986 Fiero SE Won't Run (Page 5/7)
72and86 OCT 09, 07:51 PM

quote
Originally posted by buddycraigg:


Stop buying stuff.

We need to diagnose the problem.

I cannot help anymore until you tell me what happened when you tried to make it idle with using your finger over the hole when you took the IACM out.



Ok here's chapter 12. As you asked: With the IAC removed the car starts and runs 3000 RPMS for about 8 seconds and dies. With the IAC hole PLUGGED car starts and runs but dies after 3 seconds. Car will run if you keep feeding gas with the throttle, as soon as you let go of the throttle car dies.

[This message has been edited by 72and86 (edited 10-11-2021).]

72and86 OCT 09, 07:59 PM

quote
Originally posted by Rexgirl:

I am also wondering if your cold start tube (#5 in pic) is okay and not leaking? It connects under the throttle body and feeds the intake manifold.



See a pic from a few days ago when we took the plenum off. We checked, double-checked and triple checked for leaks or cracks. Everything around the engine looks real good. Wheres this cold start tube?
Xenoblast OCT 09, 08:22 PM

quote
Originally posted by 72and86:


See a pic from a few days ago when we took the plenum off. We checked, double-checked and triple checked for leaks or cracks. Everything around the engine looks real good. Wheres this cold start tube?




Pretty sure this is it.


also its not a cold start tube its the tube that feeds the engine so that it can idle while the throttle is closed.
buddycraigg OCT 10, 03:47 PM

quote
Originally posted by 72and86:

With the IAC removed the car starts and runs 1000 RPMS for about 8 seconds and dies.



There is a problem with that. It should have had a very high idle. Probably higher than 3000.

There are 2 fuses for the injectors on the V6. Each row has its own fuse. Check both of the fuses. If one of them is blown, then only one bank will spray.
I'm also curious to see what your fuel pressure is when it is trying to run after you get your gauge.

[This message has been edited by buddycraigg (edited 10-10-2021).]

Rexgirl OCT 10, 04:49 PM
As I understood, the tube I indicated supplies air to the cold start injector, so if it leaked a lean condition would happen. But maybe that was incorrect?
Patrick OCT 10, 05:22 PM

quote
Originally posted by Rexgirl:

As I understood, the tube I indicated supplies air to the cold start injector, so if it leaked a lean condition would happen. But maybe that was incorrect?



I've never heard it described as being there for that particular purpose.

As I understand it, air entering the indicated IAC port below is metered by the IAC valve and then passed through the tube at the back of the TB and into the intake plenum.




quote
Originally posted by Patrick:

"Cold start tube"? Doesn't that tube supply air that's been controlled/regulated by the IAC valve?


[This message has been edited by Patrick (edited 10-10-2021).]

72and86 OCT 11, 10:46 AM

quote
Originally posted by buddycraigg:


There is a problem with that. It should have had a very high idle. Probably higher than 3000.

There are 2 fuses for the injectors on the V6. Each row has its own fuse. Check both of the fuses. If one of them is blown, then only one bank will spray.
I'm also curious to see what your fuel pressure is when it is trying to run after you get your gauge.




Yeah it was probably closer to 3000 RPM, not 1000. I will check those fuses if I can find them.
72and86 OCT 11, 12:46 PM

quote
Originally posted by buddycraigg:


There is a problem with that. It should have had a very high idle. Probably higher than 3000.

There are 2 fuses for the injectors on the V6. Each row has its own fuse. Check both of the fuses. If one of them is blown, then only one bank will spray.
I'm also curious to see what your fuel pressure is when it is trying to run after you get your gauge.




Pulled fuses and they all check out with multimeter. They are fine.
Next?
buddycraigg OCT 11, 09:58 PM

quote
Originally posted by 72and86:


Yeah it was probably closer to 3000 RPM, not 1000. I will check those fuses if I can find them.



Well then you gave me bad information the first time.
So did it really idle around 3000 with the IAC removed?

I think you said you have a fuel pressure gauge on order.
The next thing I want to see is how the fuel pressure responds while it is running/stalling.
72and86 OCT 12, 10:48 AM

quote
Originally posted by buddycraigg:


Well then you gave me bad information the first time.
So did it really idle around 3000 with the IAC removed?

I think you said you have a fuel pressure gauge on order.
The next thing I want to see is how the fuel pressure responds while it is running/stalling.



Well its hard to remember all the combinations we tried to get this car running, must be 50 or more things we tried.

Its important to understand it doesn't idle, it SURGES to an RPM, in this case roughly 3000 then dies. Run time is only a few seconds. BUT If i keep pumping the gas pedal it will continue to run but very choppy and Im really "on the pedal". I let off, it dies.

Also this car was purchased last year as not running. We got it running by new distributor/coil parts, but idle was always choppy and high. It only has been yard driven cause I dont trust it. It has never seen under 1300RPM at idle when it ran. I thought it was the inherant problem with the TACH computer board. But even then when I drove it around the block it had a bad low end dead spot, no power.

Yup Fuel Gauge on order.