Hey all yasterday morning i flashed up the car( its a 1988 camaro sport coupe, 305 TBI 5 speed) to head to the show and my car was running like crap


it has this horiffic hissing sound comming from the TBI unit, so with no time to spare i left the car at home and took the 1LE.

today i tore in to it and have noticed that on the TBI base there is a air hole that leads to the IAC valve, if i put my finger in the hole the hissing was reduced, so i tried cleaning the IAC and then reinstalling it but no difference, so I went and bought a new IAC, re flashed the ECM, installed the new IAC (cheked all the measurements on the IAC) and one again no difference.

The car is definetly running excessively rich as u can see the black some come from the pipes, and it is also idling at 1500rpm, thats way to high.

I pulled the codes from the ecm and all i got was a 22, but that was due to when i pulled the TPS sensor off to see if any changes would happen. I did check all the vaccum lines at the throttle body and followed them to there connections and they seem ok.

i did remove the IAC and start the car and put my finger in the IAC hole, it seemed to get rid of the hissing sound but it was still idling high,

the one thing that has been lingering in the back of my mind is that the TBI unit has 330,000kms on it, im wondering if the mating surface for the pintle on the IAC hs worn out inside the throttle body unit its self is this possable?

so anyone have ideas? where to start or what to try?. im kinda stupmed and pissed off!

 

welp ive checked the vaccum lines and they all appear ok to me. ive also tried a different throttle body, its from a chevy truck and it bolted right on, this seems to have eliminated my well known surging idle. but im still having a hissing sound as well as the car is running extremly rich(the back wall of my shop has 2 10" black circes from the exhsut pipes). the car seems to run ok for the first few minutes of operation (open circut), but once it warms up a bit the car falls on its face.

i just replaced the O2 sensor tonight and its a delco brand sensor and still no difference..
i pulled the codes and got a few of them, but some were due to me playing with sensors, but i did flash a code 15 (coolant temp sensor). i didnt play with this sensor. so my idea...

is it possable that if the coolant temp sensor is not working correctly, that it would end up resulting in the IAC valve remaning full open(this is where the hissing sound is comming from). i can see the pintle is totaly withdrawn from the sealing orfice. and if the IAC is fully open id assume that the injectors would want to add more fuel to compensate for the extra air being introduced by the open IAC valve.

 

I had a similar problem with my 5.0L TBI L03. Rough running, high idle (around 1200rpm), extremely rich mixture with carbon out the tail pipes... It ended up being the TPS. Other than that, I have no idea.

Now, what interests me is the hissing sound and your CTS code. I've been having a hell of a time with my engine running like crap lately. If I pull off the CTS while the engine is running, it dies with a loud hiss. Once it's restarted, you I can remove and plug in the CTS as many times as I want and it wont die. If I reset the computer, the car runs perfectly until it starts to warm up. I replaced my CTS, and the exact same thing happens...

I don't know anything about these engines, I'm just comparing notes here... Does that hissing noise go away after a minute or so of idling? Mine does... Does your car still run, but very rough, like it's down a cylinder or two? Mine does.

 

I'm this close to ripping my stereo out and burning this car to the ground. I had the battery disconnected ALL night and this morning it still ran like crap... Even cold, with a fresh reboot. This is completely random! As for the sucking sound, please let me know if it is continuous or if it stops after a moment. Like i said before, if I yank my CTS sensor plug while engine is idling, it'll hiss and sputter, sometimes stalling sometimes not stalling.

Can anyone point either of us in a direction here? i'm working on building an ALDL cable, but I still have no idea what to work for...

Car randomly runs good, usually after a computer reboot... Runs like crap randomly... possibly linked to the CTS?

 

when my car is cold it runs fine, but as soon as it warms up then it falls on its face and the hissing is constant, but if i put my finger over the inlet to the IAC valve u cna hear the hissing sound go away, but there is huge suction on the finger as it is trying to suck air thru that inlet

if i disconnect the CTS the engine wants to go to a high idle u can hear a steady increase in the engine RPM.

 

Weird... I just replaced some vacuum hoses, and I'm currently waiting on the computer to reset itself. If I find any solution to my problem, I'll pass it on. Sounds like our engines are acting up for different reasons, but who knows.

 

The Holley 650 carb in my shop is looking oh so tempting right now!

 

picked up a new CTS tonight, gunna try it tomorrow

 

You could try, but I don't think that's it. I spent the whole day troubleshooting this engine and the CTS seems to be completely unrelated to the problem, although it caused some bizarre quirks in my trial and error stuff... I'm looking for a new vehicle now, this thing isn't worth the trouble.

Best of luck.

 

meh the sensor is only $30 not to bad, i can live with that.
i wish i could do the same thou, but ive had my car for 6 yeras now, no way will i part with it, and i allready bought another car this year, its a 91Z28 Players camaro!

 

30 bucks! i paid 6 dollars for a new cts for my car. go to autozone and ask for a cts for your car. they ahve a TON of them.

 

for me to go to autozone and get a $6 dollar sensor ill end up paying hundreds of dollars!, tends to happen when i live on an island in canada!

 

what

well regardless, they sell two kinds of the cts (we ARE talking about the thing that screws in near the thermostat RIGHT?) they sell one with just the cts, and they sell one for about 10 more US dollars that also included about 3 inches of wire and a new plug with it. get the one you need.

 

yeah i got the new one with the Pig tail wir harness , figured i may as well since my existing wire clip is broken!

PS no autoZones arround where i live

 

ALL FIXED
i replaced the CTS today and it seems to be running execlent now!, time for a much needed cruise!