Bad IAC? - Third Generation F-Body Message Boards

bowtieboy42 · 08-26-2009, 12:13 AM

Hi everyone. I have an 89 camaro LB9, and she doesnt like to start/idle. have to crank on it for a while with the throttle wide open, and she might start. Then, throttle is required to keep it at idle.

Just for kicks and giggles I unplugged the IAC. Starts much easier, and holds an idle in park (still needs a little more while in drive).

Is it far to assume replacing the IAC will cure my problems or is there something else I'm missing?

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Chevy8588 · 08-26-2009, 01:00 AM

i'd replace and reset the IAC and TPS

PV9685 · 08-26-2009, 09:41 AM

I would verify IAC operation before replacement - along with the cleanliness of the IAC airways.

You can always turn the throttle plate stop set screw. This will keep the plates slightly open allowing more air in until you fix the problem. However, idle speeds will not be desireable...

bowtieboy42 · 08-26-2009, 10:02 PM

I had time to put a new TPs in today... No change. Tomorrow I'm putting the IAC in and attempting to find a voltmeter so I can check the TPS

Chevy8588 · 08-26-2009, 10:08 PM

i meant repace the Iac and reset the iac and TPS, also, update your profile so we know what you have

bowtieboy42 · 08-28-2009, 10:38 AM

Okay so I just bought a voltmeter, but I'm a little confused. I read the adjusting IAC and TPS thread, but its not quite specific enough for stupuid me.

I have the 11 setting multimeter, what setting do I put in on? 2 volts?

Where do I put the leads? I tried all 3 holes on the plug/TPS, and I never got a reading of more then .003 or 4 volts....

Help!

Thanks again guys, your the best!

Chevy8588 · 08-28-2009, 05:12 PM

blue and black wire,s blue is the signal wire.

88l98ws6 · 08-28-2009, 05:31 PM

and the car turned to accesory power if i recall corectly volts at the 12v setting will give you what u need

bowtieboy42 · 08-28-2009, 06:23 PM

Okay I just got it tuned in to .540 volts. at WOT its like 4.20. Still have an idle problem. Will idle alright in Nuetral 9not perfect, idle jumps around a lot), but as soon as I put it in drive (or reverse), if my foots not on the gas it stalls.

Any other ideas?

bowtieboy42 · 08-28-2009, 06:40 PM

Also wanted to add the car takes a little to get it started. I usually have to hold the throttle wide open to even get it to start.

Also, I replaced all the gaskets, plugs, wires, cap, rotor, cleaned the throttle body, and all that hoo hah.

Where is the throttle adjusting screw? Although at idle in neutral, it idles around 1200-1500 RPMs already...

Also, I think my coolant temp sensor might be bad... It reads 220-240 on the dash even though it just got a new thermostat, coolant flush, etc. Fans are running and all that. Could that effect idle?

bowtieboy42 · 08-29-2009, 01:09 AM

Anybody? I'm leaving for college sunday morning (3 hour drive) so I'd really like to get this squared away tomorrow. I'm going to change the fuel filter, maybe replace the cts, and I dont know what else... Any ideas/suggestions would be greatly appreciated!

Chevy8588 · 08-29-2009, 03:53 AM

1200 - 1500 RPMS is too high, WAY too high, 220 degress is normal operating temp, i could see it getting to 240 too if your just sitting idle, the CTS is a good place to start though, 10 dollar insurance, replace the one in the manifold, NOT the head, the one in the head is for your guages ONLY and obviously is working properly. it sounds like you IAC is still acting up though if its idling that high, but you need to give it gas initially.

bowtieboy42 · 08-29-2009, 11:46 AM

Where is the CTS located on the intake? I looked all over and couldnt see anything.

Also, my EGR temp sensor wire is disconnected... Could this cause a problem?

I'm also missing whatever sensor goes into the left head. What is it, and could it cause my problem?

No SES light, idle in P or N at 1500 RPM, and stalling in drive while stopped.... I'm at a loss here...

EDIT: I messed around with the idle screw just to see if I could get it driveable without needing 2 feet. The lowest idle I could set without it stalling was 2500 RPM out of gear (about a grand in gear) if this helps...

bowtieboy42 · 08-29-2009, 08:55 PM

Also, when starting cold, I have to unplug the tps to get it to start sometimes. It throws a code when I start start it without it. Plug it back in after starting, and the SES light goes off and there is no noticable change in performance.

Chevy8588 · 08-29-2009, 10:38 PM

hmm thats odd... CTS is on the front of your TPI manifold near the water outlet for the TB

omnipotentgoku · 09-17-2009, 12:50 PM

I am having similar problems and I have a thread going about it. i don't have a solution yet, however this may be helpful to you. Here is the thread.

http://www.thirdgen.org/techboard/te...ml#post4285364 (Seriously need help. No Job. Daily driver IROC dead)

Good luck.

bowtieboy42 · 09-25-2009, 12:55 PM

Well i finally got around to plugging off the egr valve. Still not better. In fact it seems a little worse. I lost one of the plenum screws, and I'm afraid it fell down into the intake. If this happened would it be very noticable?

Any other thoughts on the idle problem? I still dont have a car to drive...

Chevy8588 · 09-25-2009, 02:49 PM

aside from it maybe digging into the piston head or your cylinder wall? nah not at all :P

Chevy86 IROC-Z · 09-26-2009, 01:03 AM

WHAT

! You dropped a bolt into the intake manifold!!!!! Bro get a magnet and secure it tightly to a string and drop that into the suspected intake port. Be sure not to snag anything because then you have 2 foreign objects in the block. If all else fails, remove the heads. Itll take you about 2-4 hours to remove everything including the heads. Hi Chevy8588. Havent gotten back to my Camaro but Im sure ill hit it on Sunday. bowtieboy42,,, Good luck man. Have patience.

bowtieboy42 · 09-27-2009, 02:29 PM

I'm really not sure. I honestly dont think it went down the intake, because I only had the plenum off, so it would have had to have fallen down the tubes. And that doesnt really make sense. It was only scaring me because I lost a bolt.

Any thoughts on the stall/idle issue though? I really dont want to have to take it to a shop but it looks like i might have to...

Chevy8588 · 09-27-2009, 02:31 PM

have you tried a ECM at all?

bowtieboy42 · 09-27-2009, 08:13 PM

Not really, but theres no ses soon codes. And what is there to do besides replacing it?

Chevy8588 · 09-28-2009, 11:22 PM

first off you only get code 12? have you tried swapping your ECM?

bowtieboy42 · 09-28-2009, 11:47 PM

Well last time I checked I had a 22, 32, and 33. However, I have since replaced/readjusted TPS, and plugged the EGR valve. And the MAF code was from when I started the car with the MAF unplugged by accident.All these codes are stored from before. When the car is running I have no codes.

And no, I dont know anyone to swap with...

I was going to try to change the fuel filter today but I only have a scissor jack up at school, and the car fell off the jack

bowtieboy42 · 09-30-2009, 07:50 PM

Got the fuel filter changed at a shop today. A little better, but still pretty crappy. Car makes a tapping noise when I'm on the throttle too, but if I'm cruising or at idle it doesnt. I cant figure out of its valvetrain or an exhuast leak.

omnipotentgoku · 11-07-2009, 05:43 PM

Try unscrewing your IAC altogether and see if it runs better. I don't suggest running it like that, but I just did that and came to realize that my car seems to be starving for air.