Already posted this in the PFC tuning group, but figured I would give it some more exposure here.

So I have had this problem for the past two months, and just have now started to address it after it got really bad.

When I go to start my car, it has a really hard time idling. It fires pretty quick, but then kind of bogs and almost fires every other time. I usually have to throttle it up past 2000 RPMs, then it clears itself out and idles correctly. Really weird. Sometimes I have to hold in the throttle so long for this dirty idle sequence, the wideband will heat up and tell me my AFR is 16-17. Other times this is not a factor and it just starts normally.

Things started to get worst on it and the car would die at stoplights. I thought it was the IAC. So I pulled it off, cleaned it (wasn't really dirty), cleaned the port for it and bench tested it with a multimeter. It tested fine. On the higher end for resistance, but within spec. Reinstalled and nothing improved.

Then I looked at my voltage on the PFC commander for the throttle position sensor (VTA1). It was too low. It readjusted my throttle cable and the TPS was now at the right voltage. This fixed the stalling issue, but I still have the weird half start issue, where I have to open the throttle a little while after the car starts to get it to idle.

Last thing, I did a compression test, just to be safe. My engine was rebuilt very recently. Front rotor averaged 122 PSI on all faces and rear was 114 PSI.

Got any tips?

 

just to clarify... this is only with cold starts and then its fine? does it only do funky stuff when warming up and then its fine when its to operating temp?

 

Yup the car is fine after starting. I have had a little bit of idle surge, but I think the throttle cable adjustments have cured that. It does so happen that the car will have a hard time starting and idling after it is warm, but not nearly as bad as when it is cold. The guys in the PFC tuning group have narrowed it down to either a bad coolant seal or a leaking fuel injector. I am currently pressure testing the coolant system. I do not know how to test side feed injectors.

 

well i was going to say a temperature correction table is off since its temperature dependent. add fuel in the lower temp section of the tables and see if it fixes it. you can do it through the commander

 

I know you tested compression and would’ve seen them, but except for the stalling at stop lights you kind of described what I get when plugs need changing….a lumpy cold start idle.

 

Because I like to close out threads for future searchers.... I have a blown coolant seal.

I did a pressure test on the coolant system to check for leaks. I pumped it up to 20 PSI as per the '94 service (BTW they revised it to 15 PSI for '95 I did not know until after). It slowly lost pressure overnight. When I went to start the car the next morning it would not start. I pulled the plugs and the rear plugs were covered in coolant. Put fresh plugs in the car and with a lot of coaxing it started. It of course was a smoke grenade and the engine started to climb in temperature way too fast, so I shut it off.

I am not surprised by any of this and while I do think the 20 PSI sent it over the edge it was slowly dying anyways. My coolant buzzer would constantly go off every time I would go to start the car. The car always had a sweet, burnt coolant smell to it. It sometimes would start with a puff of white smoke. I always attributed this to residual oil from the OMP, but once or twice it would happen while shutting the car off to pump gas. Last week my daily was in the shop, so I was running errands in the FD. The car got up to 110C in traffic and the coolant light when off. When I started moving again it went away.

All of this points to seal failure. Those revs at start to get the engine going was most likely just clearing the engine of a little coolant. I refused to believe it was seal failure, because the engine was rebuilt last year for this same reason. Most likely the iron or housing has warped itself from overheating and developed a pinhole leak. We will see when we tear down the engine.

 

Props for following up.

Sucks you have to go through a rebuild again.

 

Damn..... sorry 😔😔

 

I was going to post coolant seal the other day. Mine is due fir rebuild too.

 

It crossed my mind, but seems many sort of default to that as the worst scenario, so I didn’t bring it up. Sorry that ended up the case.
In any event you don’t want to wait too long with it. The irons can pit and end up junk.

 

Thanks for following up, and sorry for the rebuild.