Been chasing a random dying issue on my rebuilt L98. I have been able to duplicate the issue and posted a link here. It has been running great aside from this minor issue. Yesterday it got down in the 30's car was in the garage all night and started fine in the morning. It sat outside and my sons school all day and would not start in the afternoon without giving it gas. Would not hold an idle until it came to operating temperature that leads me to the cold start injection side but i dont think that solves my random dying issue. Any thoughts?

www.facebook.com/video.php?v=10205388824469215

 

Just figured out how to pull the codes and got an oxy sensor code. I am using headers but not a heated ocxygen sensor. Could this be the source of my issues?

 

Shouldn't be an issue, if the O2 sensor doesn't get warm enough, the ECM will just stay in Open Loop...shouldn't cause it to die.

That said, you O2 fault, might be contributing to your issue, was it rich or lean fault?

 

not really sure if it was rich or lean, the motor is in a 68 firebird using a painless harness. was able to jumper the ALDL to generate the code 13. I have a programmer looking at it but I can say from tearing this engine down it appears the car was running rich

 

still learning about these engines Mike, can you elaborate on open loop vs closed loop?

 

Open loop, the ECM isn't compensating for much, cloed loop it's looking at all sensors inputs, and adjusting according for emissions and drivabiity.

If I recall, 3 things are needed for closed loop

Coolant temp at a certain degree
A certain number of O2 cross counts (i/e toggling the voltage above and below 450mv's via O2)
And a certain about of "time" the ignition is on, or engine running.

Code 13 you say?



I think code 13 is the "open circuit" fault for the O2...I believe it means it is getting voltage reading at all.

The book says if no input, then ECM will stay in Open Loop...again, I don't think that would cause it to stall...unless it's severely fouling the plugs.

But after re-reading you you initial post, it seems this is more of a startup issue, rather than random stalling?

What year TPI setup are you running?

 

thanks Mike,
this car is a daily driver for my son. the initial problem I was having was a random stalling issue. It happened every other day after he started the car and pulled out of the parking lot. It would start right back up and then be fine. Yesterday it got really cold outside and the only way he could get it to run would be by giving it some gas. Once it got warmed up it would idle fine. its a tpi out of an 87 iroc z

 

I'd suggest an inexpensive scan tool, easy to see what the CTS, TPS, etc are reporting.

But, next time it dies out when trying to start, have him unplug the connector to the MAF sensor before trying to keep it running, then try to start as normal.

 

thanks Mike,
will check it but the MAF is less than 2 months old. I've got a tuner coming to scan the computer now. In the process of changin IAC valve, TPS and cleaning and new gaskets on the throttle body. Any thoughts about deleting the cold start injector?

Thought on a scan tool?

 

only other thing i can come up with is a possible vaccuum issue but i believe i have them all plugged

 

I'm not sure who makes the inexpensive ones now, used to be AutoXray back in the day.

Was the MAF a reman?

In order to delete the CSI, you need to remove it and plug both the rail and runner...then start with an '89 memcal with VAT's deleted, for proper fuel enrichment at start up...very possible your Tuner Guy will know who to do this anyways.

 

Thx Mike. Tuner is working on the delete on the memcal do I have to remove the injector or will it just no longer function? MAF was reman I believe but can't remember. In the garage all night car started fine this morning. Can the outside temp be messing with the MAF

 

Not really...but the CTS could be a bit goofy...reman MAF's are hit and miss though...alternative is a 500/600 dollar OEM one..

The injector needs to be pulled and things plugged up...IIRC the CSI is operated by a stand alone thermal resistor, somewhere inn the intake, maybe?...follow the wires to see...but it's not controlled by ECM...I'm unsure what would happen by just unplugging the connector...possible that is all you might need to do? as no signal to open it would be present....but again, I'm not 100% on that.

 

Think I got this resolved. New TPS and IAC. Seems to have resolved the dying issue. Could not simulate it again. Have the car sitting out in the cold to see if it resolves my cold starting issue I had yesterday

 

Good deal, hope the best for ya!

 

Thx for your help Mike

 

hi there I just came across your post about 3 years ago I worked on a gm car doing the same thing . it went to four different shops , when the car gotwarm it would ideal and run then get real rich . then let it sit out side til it got cold and it would not run.
when I put my scanner on I looked at real time reading sensors I found the coolant sensor was reading -40 degrees when the car was cold . when I finally got it warmed
up it was reading 250 degrees . funny thing is the computer never thrown a code .you need to get a scanner that will read in real time , an old snap on scanner is what I used
most mechanics call it a brick because it looks like well a brick

 

All good...

And yes, I have an MT2500....aka The Brick