I have a '89 305 TPI in my '85 TA, the ecm is still stock '85(will change soon). No cold start injector.
The car will not idle very well when it is cold out. The colder it is the harder it is to keep the car running. The engine will turn over then die. The car will stay running if I hold/pump the pedal. The ses light comes on though. The car will eventually start but the idle is unstable and low. The car somtimes will eventually die if idled too long. The IAC has been replaced. The mechanic who replaced it also screwed out the throttle body stop screw out to the point where its threads are showing. Noticed this problem goes away when the engine is warm and in closed loop. Warm starts are fine. With the engine warm the car will idle at 1000-1100 rpm in neutral.
I think MAF. The car will also stall under sudden deceleration. Could the MAF also cause that?
I'm out of ideas. Please help.

Matt

 

Was the stock '85 prom ever changed? There was a service bulliten on them, they were exposed to light after they were programmed and it slowly erases itself.

 

BUT... you said you used a TPI system with NO cold start injector..right? And you're running the '85 870 CRAPPY ECM and PROM ( Like me ). ???

Well seems to me that's the problem... I mean the '85 ECM is thinking you have a cold start injector, so it seems if you actually had the cold start injector, it wouldn't be a bear to deal with in th cold, since you said it runs / starts fine when warm.


Now, I'm no expert BY ANY MEANS, but from everything I've read, the '89 TPI was the 1st year for NO cold start injector...it's job was handled exclusively by different programming in the PROM. So isn't that causing the problem you're having? I mean the 85 PROM has no way of knowing that you're engine doesn't have a cold start injector, and it's got no other way to compensate.


Waiting for a more experienced TPI guru to clue me in too.

 

No, I am currently running a 165 ECM (86-89) with the ARAP (89) code and the coldstart injector disabled.


The coldstart injector was not run by the ECM. It is run by the thermo-time switch that screws into the front of the intake manifold next to the coolant temp sensor. When coolant temp is below 95 deg F it turns on the coldstart injector for a varied amount of time (depending on temp)
And yes, 89 was the first year without a coldstart injector.
To use the 89 setup wothout a CSI you need to move to the 165 ECM and 89 code on a prom chip with VATS disabled.

 

The ORIGINAL topic starter posted this:

This means he has a '870 ECM with STOCK PROM, that is set up to have a cold start injector, and he's using a TPI system that doesn't have said CSI....

Right?


HE then posted this:

Maybe I am lost, but I would think that a 870 ECM that is setup for a CSI, trying to work w/o a CSI would cause just this kind of issue. The PROM in the '870 does not control cold idle like the later 165 did when the CSI was eliminate.

Did I get crossed up here or what?



Later
Chris
85 IROC
Couple 'o' mods

 

I am going to update to the '89 ecm and prom so I don't have the starting problem.
Now, the '89 ecm and prom controlled the cold idle speed? Could you possibly program the idle speed into the chip?

Thanks

Matt

 

Do some research on the DIY / PROM board. You won't be able to use the '89 ECM and STOCK chip...it had VATS built in ( Vehicle Anti-Theft System ), and you're '85 doesn't have VATS. But, you could easily convert to a '86-88 '165 ECM and PROM. I'm hoping to do the same thing with my '85 IROC very shortly.




HTH
Chris
85 IROC

 

Nope I did, sorry in my tired and dazed mind I thought you were Matto responding to me, teach me to post when tired and sick.

The CSI only gives a squirt of extra gas during start and has shut off by the time the engine reaches a stable idle. His problem sounds more like badly leaking injector/s or a prom that is slowly failing and not getting the open loop idle mixture right. add to that the other problems he has and that he has had a code 34 tripped before. False code 34 was one of the symptoms of the bad prom chips.

 

could a bad IAC or misadjusted iac be the culprit? As far as leaking injectors: I have the Multec style injectors, how good are those?

Any other ideas?

 

Everyone says those injectors are crap, I don't know personally. I have only dealt with Bosch and Accel.
you said in your first post that the check engine light will come on on the first start, what code does it set?
If the IAC is stuck fully extended it will make cold starts quite difficult, since minimum air is set at less than 500 RPM from the factory.

 

I'm not sure what the iac is set at, I didn't install it. All I know is the idle stop screw is screwed out. Somtimes I smell this wierd "burning" smell. Maybe its lean. I don't know what a lean mixture smells like. I haven't had time to pull codes yet. I will post them when I get them.
Does the '86-'89 have a set cold idle speed programmed in the prom?

Thanks,
Matt

 

Kind of, the iac is commanded to a position for high idle, then as the car warms up it moves to the curb idle. But if the minimum air is set incorrectly to be gin with then the IAC won't be able to control the idle correctly.