Ray the Rat

iTrader: (1)

My 88 2.8/T-5 Camaro idles high (about 1500 rpm) until the car comes to a complete stop. Then it drops to 750-800 the way I think it should idle.

Question is: is this something the ECU/IAC system does normally? At one time I had wonna them cars with a blue oval on it (a 78 302) and it had what they called a "BCDD" (Boost Control Deceleration Device) that kept the motor from going to an idle as soon as the throttle was lifted. I disabled that and it ran a lot better. But the car hated me so I gave it to my wife...maybe that's why she's my ex-wife now.

Anyway, if this is the way the thing's sposeta run, that's fine. I'll move onto other things like working on my Suburban (needs a muffler) and my race car (I broke it but good on the salt flats...pinion yoke snapped under power and the driveshaft beat the hell outta the underside of the car and took out the transmission while it was at it:
http://www.chevyasylum.com/85monte/85monte28.html )

TIA,

dsmith124

Did you ever figure this out, I have the same problem?
My issue is not a vacuum leak, it definitely has to do with the car moving.
As long as I am coasting, it is 1500, once I come to a complete stop, and not until then, it drops down to where it should be.
Other than that, car performance is fine, no rough idle, no stalling, just the high idle.

fasteddi

iTrader: (2)

I know mine will do that if I dont do the idle learn when i reset the computer, also mabey a Iac problem??? Ray the rat, you have a manual so disregard the idle learn as im not sure if that applies to manuals. But dsmith if you have a auto try this.

Try this, disconnect your battery for like 1 minuet then re-attatch it, then start the car up and let it idle for 10 minuets. Dont turn the lights on, dont do anything to put a load on the engine. Then sit in it and put it in drive for 5 minuets, while its idling and you have your foot on the brake. Then drive it for 10 minuets normally. If that fixes it then you should be ok. If not is there a check engine light on?? Your IAC sensor may be dirty/or bad and then it gets stuck when coming to a stop and then slams shut when you come to a complete stop, causeing the sudden drop in RPMS.

project89

iTrader: (1)

some of the early v6 cars with sticks had a decceleration valve, which i belive was bolted to the alternator bracket.dont recall what year v6 manual cars had this but there is a thread somewere inthe v6 section about this valve

dsmith124

Actually mine is also a T-5 like the post I replied to. Mine also will idle at 1500 until the car has come to a complete stop, then it drops down to 700 or so.
There is no check engine light, no codes, absolutely no problems with rough idle, surging, or any other drive ability issues, just the fast idle when moving.
All sensors check good, the TBI base gasket has been changed, there are no vacuum leaks and the IAC valve is new.

I also am beginning to believe that this is the intended behavior, maybe I can find someone to burn me a chip to disable what I believe is the throttle follower feature.

fasteddi

iTrader: (2)

What year camaro??? Is yours.

Ray the Rat

iTrader: (1)

In answer to the question, no, I haven't found a solution, but I haven't looked real hard lately. Too much other stuff goin on. I'm considering replacing the IAC valve, but it sounds like that didn't help dsmith. Still confused about it, but it's not a big enough issue for me to go work on it in the cold. (Race car is in the garage.)

RtR

project89

iTrader: (1)

like i mentioned before locate the valve and remove it and cap the lines
https://www.thirdgen.org/forums/v6/1...ick-2-8-a.html

Ray the Rat

iTrader: (1)

Are you suggesting removing the IAC valve and capping the lines? I didn't quite understand that.

Woops. I take it back. I guess you're talking about the Deceleration Valve? I read that "it's only on 2.8 F-bodies of those years." I'm still, confused. Is it only Firebirds, or does that include Camaros (I know the F-body is both, just don't understand what's being said.)

The Deceleration Valve is exactly what I was describing in the initial post. Those F**d things had 'em back in 78...on both manual and automatic transmission cars. They were much more pleasant to drive when they were removed.

RtR

project89

iTrader: (1)

well there snot entirely a while lot of info on them unfortunatly.
ur best bet is to go over the engine and see if u do infact have one, if u do i would simple remove it and cap off the lines

if u do have it and u do remove it i suggest not breaking it and holding onto it, ppl come on the boards looking to buy those valves from time to time, and it is a discontunued item

sorry i couldnt be more help but like i said there is very limited information on the deceleration valves and some ppl end up with them on there engines even though the information provided on here says that there year or model car shoulsnt have one, and also cars that should have them dont

SDTransAM

iTrader: (5)

My '89 RS did the same thing.

Ray the Rat

iTrader: (1)

I finally ventured out into the cold (I had to...I made a service call on a friend's computer) and while I was out, I looked under the hood. I found the suspect part, unplugged the only vacuum line I could find going to it (it was almost dark) and plugged the line with some high-tech stick that I saw lying on the ground. Viola! (A 4-stringed exclamation.) The engine rpm dropped immediately and stayed there. Now I need to adjust the idle speed and we'll be in business.

I've also added a battery tender because there's some sort of current leak (or I've had 2 bad batteries in a row...brand new...the last one showed as bad, so I got another one under warranty.) that I can't find with a meter. So I'll just plug the tender in when it's sitting in my driveway and hope to limp it thru the winter that way.

My Burb has developed some problems that feel like an ignition issue...it runs rough as hell sometimes..and clears out after it hits about 3000 rpm...but it's too cold for me to work on it. I got some heart trouble that limits my circulation. I'll deal with it when it warms up.


Here's a photo shot with my baby camera, a Panasonic point 'n shoot:



The arrow points to the idle control valve...or whatever it is.

project89

iTrader: (1)

id carefully remove the valve and out it in a safe place, somone will come on here evetually looking for one of those valves for there cars

Ray the Rat

iTrader: (1)

I'll prolly do that when some warm weather shows up.