Any GM TBI experts out there? (1 Viewer)

[Broknrunner]

I have a junkyard TBI setup on the 2F in my 84 FJ60. It came on it when I bought it and initially ran really well but last few years I’ve been having a lot of issues with it. Some came down to faulty ICMs but I have an issue now that I thought was related to the ICM failures but might not be.

Here is the current issue, in cold ambient weather it will not start, injectors do not fire. If I dump some fuel into the throttle body it will fire and then idle fine but stumble on acceleration like the ICM is not advancing the timing appropriately. I do not understand why the injectors won’t fire on attempting to start but will after I add fuel to get it to fire. Anyone have any ideas?

I have only been putting up with this problematic TBI setup because I plan to swap a 6.0l eventually but it did run fairly well at one point.

 

[Seth S]

What does it use for a coolant temp sensor?

 

[Broknrunner]

What does it use for a coolant temp sensor?

If I remember correctly it’s a obd0 setup from an 88 Astro van 4.3 and uses the standard coolant temp sensor for that engine. I haven’t checked it recently but have replaced it in the past while trying to troubleshoot idle issues.

 

[Broknrunner]

I just came across this which makes some sense if it’s an issue with the ecm but it does kick the pump on for a few seconds when the ignition is turned on. I’ll dig into it a bit further as soon as I can.

 

[Lead Head]

A buddy had a Jeep Comanche with a 2.5L TBI engine. It used a GM-Style TBI system (although I think it used a Renix computer, rather than GM). It turned out the TPS was broken, making the computer think the throttle was WOT. Apparently the throttle being WOT during cranking puts the computer into a clear-flood mode that turns the injectors off while cranking.

From what I can tell, the GM TBI PCM implements similar logic. A quick test is apparently just unplug the TPS and try to start it. It should set a code, but start.

...and also, have you tried pulling the codes?

 

[Broknrunner]

A buddy had a Jeep Comanche with a 2.5L TBI engine. It used a GM-Style TBI system (although I think it used a Renix computer, rather than GM). It turned out the TPS was broken, making the computer think the throttle was WOT. Apparently the throttle being WOT during cranking puts the computer into a clear-flood mode that turns the injectors off while cranking.

From what I can tell, the GM TBI PCM implements similar logic. A quick test is apparently just unplug the TPS and try to start it. It should set a code, but start.

...and also, have you tried pulling the codes?

Just tried the TPS, no luck. Codes are 12, 13, 32, 45 but I don’t know when those were last cleared. I’ll investigate the MAP sensor but I’m not sure if that would cause a no start condition.

 

[Lead Head]

I'd clear the codes, get the engine started, and check the codes again.

 

[Broknrunner]

I'd clear the codes, get the engine started, and check the codes again.

I just cleared them and took it for a drive. No codes other than 12 now. I’m about ready to set this thing on fire. The TBI system, not the 60…