`92 LT1 Idle Issues During Initial Starts

[92BlackVette]

I have been chasing this issue for a while. The problem use to be rare, however lately it has become very persistent.

This issue occurs at the following temperature range (40F - 190F). What you can get out of that is this problem occurs when hot and cold. I see the issue 1 out of every 5 starts.

The idle will be at about 200-400 RPMS when this happens, and it has all it can take to keep running. So as you can imagine I fix it by barley, and I mean barley touching the gas petal. I touch the petal so lightly that I could probably set a wrist watch around it and it would idle at the typical ~700-ish RPM range.

So when does it go away.....I drive it around for a while (5 - 15 miles), and guess what? it idles fine again without my wrist watch....

I have recently checked the vacuum lines, with a gauge and a vacuum creating device. It wouldn't hurt to check it again because I am sure someone will be persistent about me checking it again.

This engine has 160,000 miles and I am equipped with a FSM but I wasn't sure where to start. I am thinking the idle air valve is questionable, but I don't mind my other method of keeping the idle up for now, until I get a second, third, forth..... opinion.

This issue was rare before but since replacing the Opti/Fuel Injectors. The issue has become more persistent. Other than the idle issue, the car runs great; the fuel injectors from FIC really made a difference!

I have checked for codes too.....;help

 

[boomdriver]

I'd say the idle/air is dirty or sticky. I am not sure of the process and why, but the idle air valve and passages will collect a gum that looks almost like soot. Alot like whats seen in EGR passages. It restricts the small passages and prevents the valve from seating properly. Idle air control is fairly delicate and precise.
anyway, cleaning that out often gets more consistant idle performance. If the IAC valve sticks or leaks, thats all it takes to effect the idle regardless of the temp.

 

[tmkassin]

Saw your post on my issue. Now mine is idling low too. It might be because the battery is low from having the hood open too long. A low battery can cause some strange issues. Scanner said it was in open loop and I suspect that it has been running open all along because of the injector issue. Replacing the IAC didn't make any difference. There are not ANY vacuum leaks. Checked several times. The injectors are definitely bad and I have been suspecting that for a while.

 

[Paul Higg]

Yeah, sounds like open loop to me too.

Any codes?

 

[92BlackVette]

I have noticed, and I am sure this is thanks to the K&N system, but there was a lot of air cleaner oil/residue on the throttle body. I used a rag and saw lots of oil residue after cleaned. So I am sure this is the case too with the IAC.

 

[Paul Higg]

When I had my 94, a couple of years ago I removed and thoroughly cleaned the TB, IAC, EGR, MAP, radiator, and assorted parts in the general vicinity.

When I put it all back together and test drove it I smoked the tires unintentionally.

What a difference.

 

[John Robinson]

More ideas

I also have been chasing rough idle and intermittent performance. Here is what I found.

The EVAP system was not working correctly because I had pinched off the vacuum hose to the EVAP valve and the PCV hose was too loose at the head. I remade the hose to the valve using a tee and new hose to eliminate the kink in the hose and I used a hose clamp to tighten the PCV hose. After I did this I discovered that the first restart was a rough but as soon as the system cleared itself the restarts are now smooth.

Another contributing factor was the discovery that the ENG1 fuse was blown and the car was running in closed loop (or is it open loop not sure).

So check the ENG1 and ENG2 fuses to be sure they are ok.

Hope this helps