High idle??

[JEFNLSA]

It seems that my LT4 idles a bit high....especially when I first come to a stop. It will sit at around 1000rpm and then after a few secs drop down to around 800 or so. It does have a BBK TB on it and I'm also inclined to believe that it has an after market cam in it because of the lope at idle (especially when it drops down to 800) and the way it runs. I bought the car from a Vette dealer in Tempe, Az and the salesman ( although he knew about the BBK....because it was visual) didn't know the history of the engine internals. What should this baby idle at and is it normal for it to idle a bit higher when I first come to a stop? Also (since I'm unfortunately not the mechanic I'd like to be) what is the right way to adjust the idle down if I need to or should I have a "mechanic" do it? It's safe to say that the car sounds alot more "right" when it is idling lower and 800 still sounds a bit high to me. Any opinions/suggestions would be greatly appreciated......It sounds to me like 600 would be just right but I don't know:confused
Thx again...Jeff

 

[Hib Halverson]

It seems that my LT4 idles a bit high....especially when I first come to a stop. It will sit at around 1000rpm and then after a few secs drop down to around 800 or so. It does have a BBK TB on it and I'm also inclined to believe that it has an after market cam in it because of the lope at idle (especially when it drops down to 800) and the way it runs. I bought the car from a Vette dealer in Tempe, Az and the salesman ( although he knew about the BBK....because it was visual) didn't know the history of the engine internals. What should this baby idle at and is it normal for it to idle a bit higher when I first come to a stop? Also (since I'm unfortunately not the mechanic I'd like to be) what is the right way to adjust the idle down if I need to or should I have a "mechanic" do it? It's safe to say that the car sounds alot more "right" when it is idling lower and 800 still sounds a bit high to me. Any opinions/suggestions would be greatly appreciated......It sounds to me like 600 would be just right but I don't know:confused
Thx again...Jeff

I'd say the problem is more likely to be with the aftermarket throttle body, which you probably don't need, anyway, or the OE ECM calibration not working properly with the aftermarket TB. I'd look for those two problems first, before, I'd look for a problem caused by an aftermarket cam.

The idle speed is not user or technician adjustable though it can be changed on an aftermarket basis by altering the ECM cal.

 

[JEFNLSA]

Can you expand on the aftermarket ECM cal thing cuz I'd like to get it right ASAP....thx. Oh yeah, what is the proper idle rpm?

 

[MARLTON LT-4]

Jeff,


I just had a BBK TB installed on my LT-4. The internals of the engine have not been touched. My car idles perfectly. Before taking your car to a qaulified tech, disconnect the battery then start the car letting it idle for at least 20mins( do not rev the engine!!) This will give the car's computer time to read the new components. Good luck. Let me know what happens.

CP
:confused :confused

 

[JEFNLSA]

[

My car idles perfectly. .

CP
:confused :confused[/QUOTE]What is perfectly....RPM wise. I'd like to try what you suggested before I have to pay someone to get it right. Being new to Vettes I'm not really sure how it is supposed to idle yet now that I have installed the Magnaflow SS system on it I can really hear as well as feel the idle and it seems high to me. If I do need it "fixed", what can "they" do for me to solve the problem.

 

[jhong321]

I am not sure if it's the same way for the LT4 motor but in my ZR1 i had this problem. Has the chip been changed in your car? I had the same problem it would idle high on start up and when i come to a stop (about 1000 rpm for about 2-3 secs then go back down) I put in a new chip and everything was fine after.

 

[Hib Halverson]

Can you expand on the aftermarket ECM cal thing cuz I'd like to get it right ASAP....thx. Oh yeah, what is the proper idle rpm?

What part of the "ECM cal thing" are you interested in learning about. I don't know what the desired idle speed is with the LT4, however, most scan testers will display that data.

I am not sure if it's the same way for the LT4 motor but in my ZR1 i had this problem. Has the chip been changed in your car? I had the same problem it would idle high on start up and when i come to a stop (about 1000 rpm for about 2-3 secs then go back down) I put in a new chip and everything was fine after.

I'm sure you're trying to help but experience with the LT5 isn't really germain to the discussion because the LT5 is a speed density motor and the LT4 is a mass air-flow motor. Also, the LT4 ECM has no "chip". It uses a nonremovable "flash PROM". To change the cal in an LT4 ECM you "reflash" the PROM with the new calibration data using a TECH 2 scan tester or other device which can do reprogramming.

 

[JEFNLSA]

Thx for the input....I'm planning on taking my car to the dealer later this week (I know..I know:L ). Can they reprogram it for me w/ their scanner? I bought a warranty w/ the car and although I'm sure this kind of thing is not covered I'd like to have this problem fixed at the same time. For the 3rd time since I bought it, the SES light has come on and although it goes off after a day or two something obviously is up....so I'm taking it in for an all around "checkup". The car runs great BUT the idle thing is strange and the SES has me concerned.

 

[redc4corvette]

I think you might have a tpis problem check your voltage.

Yes the dlr can reprogram your computer I use tuner cat to set mine and when in a hurry for little stuff i use the hypertech.

 

[JEFNLSA]

Voltage is a constant 14.4 Dealer said it is throwing no codes and that every thing they saw seemed normal so I guess I'm gonna live w/ it, at least for now. They did say that I have an aftermarket cam in it which, after getting back in touch w/ the seller, is the "Hot" cam. Other than the idle thing it runs perfect so who knows, and it only idles high for the 1st few secs after I come to a stop, then it drops to around 800. :confused