5.7 tbi stalling at idle and running out of options

[Kglazier]

Hi everyone I'm new to the forum but not new to 88-98 gm trucks. I like to think I know my way around an engine but this problem has got me stumped. If anyone can help me out it would be amazing! I recently bought a 95 suburban with a bad fuel pump and upon purchase noticed a vortec under the hood (bonus!) with a 4bbl intake and tbi adapter. Ok, so first things first I replaced my fuel pump and fuel filter. It then fired right up and about 5 min later stalled but fired right back up. For about a month now it has been stalling in traffic whenever at idle. I have already replaced fuel pump, filter, rebuild throttle body including fpr, TPS, iac, cts and connector, map sensor, coil and cleaned all grounds. The only code I get is for a knock sensor #43 and ocassionally #15 cts but hasn't been back in a few days. I am stumped please help me.

 

[magimerlin]

Get the icm(ignition control module) checked. A lot of time they will not throw a code but fail when warmed up. When they test it do it a few times do it does heat up and lightly tap on it while testing it. Most auto parts stores that Ian aware of can test them. You have to remove them icm to test it. When putting it back on, if it tests good, do not forget to put the heat transfer paste back under it. Most new ones should come with the paste.


Sent from what use to be a great country.

 

[slippy3002]

Let's start with the basics first, since you already threw money at it.

Fuel, air, and spark. You already replaced the coil, so how are the plus and wires? Vortecs also require a bigger gapped plug.

When you screwed on the IAC, did you bottom out the pintle? Don't over tighten them, because that is how they idle.

Sent from ®obland

 

[great white]

X2 on verifying the extension on the IAC pintle is correct.

There is a measurement, I just can't recall what it is. Should have been on a piece of paper that came with your new IAC motor.

If the pintle is too long, it will close down the idle air path and kill the engine.

There is also the simple things to check for such as intake/TB gaskets or vacuum leaks.

 

[Kglazier]

I checked for vacuum leaks and have none I can find also the iac was replaced with a used one of another tb I had laying around but when I tightened it I turned it all try way by hand then turned 1/16 turn as instructed but the pintle wasn't even close to the seat also I tried my jumper wire in the diagnostic pins a and b like I was pulling codes because I read that in doing so the pintle should eject all the way out but niether of mine did so. Does anyone know the procedure for this Or how to test them. And the measurement for installation and learn process? Also I will get the icm tested ASAP and report back with results. Thanks, ken

 

[slippy3002]

I believe the length is 1.0625

Sent from ®obland

 

[Kglazier]

I forgot to mention that it smells as though it's running rich as well as acts like it is searching for idle

 

[slippy3002]

Did anyone screw with the base timing?


Does it have good power throughout the power band?

Sent from ®obland

 

[Kglazier]

I have not messed with the timing yet but yesterday I took it to a shop to get looked at and they told me the timing was off and my cts looks like it's never been changed when I informed him I changed it Tuesday he told me I was wrong and it was the one on the head lol then I asked him to time it but they apparently don't have a timing light in shops anymore. His solution was to "slap a carb on it". Since I just put a 200 dollar fuel pump/sending unit in it that is not an option!

Edit: yes it has great power and instant throttle response I could melt my 35's if I wanted to

 

[slippy3002]

I believe the iac is in here. Check that out.
http://www.gmt400.com/forum/showthread.php?p=264596

Also, your timing is controlled by the computer. By setting the properly it must be disconnected from the computer, and that is only base timing at idle.

The only other thing I could possibly think of would be bad injectors, or an o2 sensor.

Sent from ®obland