Hello All,

Here's the scoop, Camaro RS '91, 305 TBI, automatic, stock.
The idle is very very very poor most of the time at start up (i.e. every day), it doesn't matter if the engine is cold or hot. The RPM bounces around in a very wide range. After I rev it up to about 3000 RPM for 1 or 2 secs. for a couple of times it gets back to normal operation. In some cases, when I start it up, it is just fine. A couple of days ago, when I left work it was just great, no idle hesitation, good throttle response; I drove on the highway for about 20 mins and went to a store (another 20 mins), when I started the engine again it was fine, I put it in reverse and it felt OK (no hesitation, firm gear engagement, etc), I decided to turn on the AC and the hesitation showed up again, well, with the car in reverse and gas pedal not pressed, the RPM almost dropped to zero, picked up again, then almost zero, you get the picture. I turned the AC off and revved it up, I got some power but still poor idle. I drove the car for about 1/4 mile with jolts and then it was fine. In some cases if I don't rev it up, the engine just dies.

About 1 month ago I took it to a mechanic and he changed the wires, cap, rotor, plugs and coil (he says) but that still didn't fix the problem. I also flushed the injectors, changed the intake manifold, gaskets and seals and the temperature sensor (not the one for the gage).

What do you think, could it be the O2 sensor? Not sure it is related to the AC as I could not reproduce the experiment but it seems to happen more often when the AC is on, mind you the AC robs some power too. Any suggestions are more than welcome.

Thanks.

Vortex91

 

My guess would be the EGR valve. Hard to say what exactly is going on, maybe a the valve is getting bits of carbon in it and holding it off the seat?

 

Idle air control valve.

 

Yep, that's what I would have guessed. Take off your IAC and give it a good cleaning.

 

Thanks, I'll have to try that.
Any advice on how to do it properly?

Vortex91

 

Hi there,
Just a follow up on my idle problem.
After I rebuilt the TBI with a $80CDN kit from NAPA the idle was very good and the engine had a lot of kick. So I figured the problem was fixed.
After a while, my idle was getting bad again, not as bad as before but more noticeable as in the engine would just die on me.
One morning when I was ready to go to work, the engine wouldn't start at all. To me it sounded like there was no gas/spark to make it turn. After about 20 tries it finally started. Revved it up a few times and then decided to turn it off and call the GM dealer for an appointment.
Long story short, once I got to the dealer the car wouldn't start at all, they had to push it.
Turns out my catalytic converter was plugged.
$1500CDN later my car had a new cat. I questioned the price and it turns out the cat is $1100 (dual stage blah blah blah) and labor about 1.5 hrs.
They run a pressure test and guess what? My fuel pump is only pushing 4psi when I need up to 10.
This time is going to cost me $700CDN.
The car is running fine now but once in a while it hesitates a little just enough to scary me, (I didn't need to spend that much money just to start all over again.)
I feel like the dealer took me for a ride (now we're debating the 9 day rental car).
So for those of you with similar problems, check the cat as well.

BTW, when I rebuilt the TBI, my IAC had a little groove due to friction, you could easily feel it with your nail. I used some 600 grit sand paper to smooth it out. I also shaved the "little walls" around the bores in the body just beneath the fuel injectors to increase the air flow. I guess, after I worked on the TBI, the engine created enough pressure to push some of the stuff in the cat away to make a passage for the exhaust gases.

I hope this helps anyone out there before spending a lot of money.

D.

 

if it's not too late, do the fuel pump yourself if it's not a in-tank one. The mounted ones are so easy to take out.... 1 hour. Just take off the smog pump, and then you've got plenty of access to the fuel pump!

 

It's all done now. The pump is in the tank. I was going to do it myself but when I looked at the tank at the dealer I could see it was a lot of work (if its done in the driveway). The mechanic confirmed it too, he said it was a 4 hrs job.


Vortex91

 

As most of us can confirm, a miserable four hour job. Rusted bolts, bushings, fuel line fittings. Hate to spend that much money but it's worth every penny. Hope you're back on the road and running fine.

 

it might be worth every penny to some, but to others who are still in college / short on funds realize that 4 hours / 100 dollars+ an hour from dealer + the pump itself that they overprice = too much money

I'll spend my 20 dollars on a pump and spend a weekend working on it myself and spend the other 500 dollars on something important... like gas to get from my house to 7/11 4 times

 

Sellmab, you're right. I'm short with money too and I can see where you're coming from.
On the other hand, I don't have anyone to help me with things like this. I moved in a new house about 1 year ago and the people I've met in this area are not exactly car people..
My garage is well set (power tools, etc.) but sometimes you just need a 2nd pair of hands or just somebody to consult with.
There is the mailing list from TFBM for people in the Toronto area but (no offence TFBM guys), I was quite disappointed that I didn't get any answers at all after I'd asked the same question on their mailing list.
Anyway, it hurts to see ads for cats from $100 & up knowing that I paid $1500 for an OEM cat from GM.
The car's been back on the road for about 2 weeks now and I'm loving every second I'm driving it. Since I got it in 2001 my wife only drove it once for a VERY short distance, that changed not long ago, now she just loves to drive it.
BTW, the car is running GREAT but at idle has vibration with a cicle of about 1sec or so. It is always there and you can't miss it. The car seems to idle (in drive) below 500 RPM. Any ideas?


Vortex91

 

man $1500 CDN bucks!? You can get one around here for about $60 USD lol.

 

Rub it in Urbanhunter44.
Why do you think I'm not happy with how the whole thing turned out?
They got me and there wasn't much I could do about it.
Anyway, live and learn.
My only hope is that somebody else can learn from my experience.

Vortex91

 

At least you have the car working again. I paid 100 bucks US to Firestone once for diagnosis on an S10 Blazer that was running rich but throwing a lean code. I was told the O2 sensor wires were OK, but that I needed a new fuel pump. So, a miserable 6 hours later in 100 degree Arizona heat, I had a new fuel pump....but the problem was still there. So, after throwing more parts at it(and more $$$), I found that the wires for the O2 sensor, where I couldn't see them at the back of the engine, were grounding out on the block.

I only lost 100 bucks on the diagnosis, but I spent close to 600 bucks and countless hours trying to fix it after receiving "expert" help. I wasn't happy with that tech, but hey, the truck works fine now....except for the fuel tank leak I've developed from where the sending unit gasket has failed....grrr....If I hadn't paid for bad info...........

 

Yep, I hear you. I have no money and spending what I have on my car when it's not necessary or planned is not exactly great. The first $1200 was a colossal waste of money.
On the other hand, the car is running GREAT now (after the next $2500). I only wish I had gone to the second place first!

D.