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Few Questions about idle

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LucifersChild

15+ Year Contributor
35
0
Feb 19, 2004
Austin, Texas
I recently bought a '92 AWD turbo laser with a JDM engine and a turbo back exhaust.

My questions are:

1)What is most people's normal idle?
From what I can tell I'm idling to high at ~1600 RPMs.

2)Is the idle suppose to surge slightly?
My car idles very steady at 1600 RPMS until it gets warmed up, then it will drop 100 RPMs every few seconds. When this happens the A/F gauge says that it runs completely lean and the exhaust makes a kind of "airy", almost like it backfires, but not as bad.
The aftermarket boost gauge is sitting at -18ish the entire time it idles, even when it drops the 100 RPMs, but the dash gauge sits at -7psi and moves slightly down.


If this isn't normal do you think it could be corrected by adjusting the Base Idle Set Scre? I haven't seen any vacuum leaks, but could this also be a potential problem?
 
Not a problem.
I had the same issue a few years ago and I adjusted the BISS and also timed it. It has never done it again. I think the key is to time it right , though. Lots of guys just start messin around the the BISS and do not get out a timing light to see how its running. But you have to disconnect one wire and ground it so the computer doesn't see that you are messing with the BISS and automatically adjust itself.
 
Okay, today I got put a timing light and checkrd the ignition timing, it was near perfect. I decided to try adjusting the BISS so I grounded everything and started adjusting. The farther I turned to the left, the higher the RPMs shot, and the better it ran, although it never got rid of the problem completely. I decided to turn it right to see how it would run by taking the RPMs down a little bit more, and the farther I turned it, the worse it got. I got it semi-steady at 850 RPMs, but everytime it surged the car almost died. I finally just set it at 1700 RPMs and left it alone, but I still have the same problem. What's next? Should I try cleaning the throttle body out? Maybe I should put some Fuel Injector cleaner in the gas tank and see if that fixes anything.

Maybe even the spark plugs and wires could cause it? I'll have to check them tomorrow.

There is a JDM engine in the car, could that be why it idles so high? It still seems too high though...
 
I was going to check the ISC when i noticed that the multimeter was dead. I had the hood open so I decided to give it another look. I saw that the blow off valve return hose was severely kinked in 2 spots, so I got some twisty ties and put them around the kinks to open them up. The idle stays at a constant 1700 RPMs now and the a/f ratio gauge doesn't move from rich to lean anymore. I can still slightly hear the muffler noise and the vacuum pressure still bounces down a little when it happens. I think i will check for a leak in the BISS. Tomorrow night i will try and adjust the idle again and see what happens. Thanks alot for the help so far.
 
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