This car is all stock, engine, trans, carb. Everything runs great for having 136,000 miles on it. The problem I'm having is the car idles at 500 RPM. The car vibrates kind of bad at idle. Every once in a while i'll get a small backfire, and sometimes trouble getting it to idle. It stalls sometimes when first started, but it is extremely cold here right now.

I changed spark plugs, checked firing order, changed oil, changed air, oil, and fuel filters.

Any Ideas? Timing not right? Need Carb Adjustment??? HELP

1987 Camaro Z28, 305, V8, 4BBL Carb

 

Gangsta,

Welcome Aboard!

Just a few rudimentary questions...

Is the choke plate closing when the engine is cold?

Does the choke open one the engine is running and warms up?

Have the throttle bores been cleaned lately?

Does the 500 RPM idle happen only when cold, or also once it is fully warmed?

If you haven't adjusted the ignition timing since the engine was running correctly, I wouldn't advise altering it now. It likely hasn't changed on its own.

Since you've chance the plugs and wires, I'd suggest checking the plug wire routing and firing order once again. It's possible that a wire(s) is being pinched, grounded by its routing, or that you have inadvertently installed the wires in an incorrect order. It is very easy to mistakenly exchange the #5 and #7 wires, since they are adjacent both physically on the head, and in the firing order. I'd hate to even try to count the number of times I've done that one.

 

If its shaking it could be a vacuum leak. check the vacuum line to your carb and the one up near the very top near the firewall. I replaced mine and my idle was better and it stopped shaking.

Nate

 

I have the exact same problem word for word....I need help to

 

im havin the same problem......but mines TPI..not carb

 

you could have installed your fuel filter on backwards which would restrict gas flow enough to deprive the engine...

doubtfully though

 

when i had my car worked on, they said the fuel filter was collapsed which is why my car was running that way, they fixed it but a bit later its doin it again

 

are you using a vented or non-vented gas cap?

The Trickster!!!!!!!!!!!!

 

im using an emissions legal cap so im guessing its non vented?

 

I had a similar problem. It was caused by a vacume leak in the HVAC line. It's a hard plastic line that goes from the intake to the control head in the dash and another hard plastic line that goes from the control head to the heater control valve under the hood. With the age of our cars this plastic line becomes very brittle and easy to break.

 

ok im looking at the vacuum lines diagram for my car. Where is the vacuum motor located? Are there any lines in the cabin under the dash to check as well?

Also i removed the stock air cleaner and put in a chrome one. I had to plug the end of the vacuum line that was connected to the air temp sensor in the aircleaner, could this be a problem>?

 

Sometimes i'll start the car, and it will idle real low, loose it, and stall. Most of the time i can get it to idle about at 1,000 at cold start up. But it's those other times that stump me. Im not getting a check engine light. Sounds like the carb but im not sure.

 

i had a hard plastic line break on my car it was labled ECM for some reason, my car doesnt have an ECM so i thought nothing of it and taped the end off, maybe thats a problem as well?

sorry for hijacking the thread but i am having the same things happen to my car as well

 

As long as you sealed both ends of the broken plastic line it should not have affect on the idle, but you won't be able to control the heater. If you clamp off the rubber lines one at a time, and see how it changes the idle it will tell you where your leak is, if you have a leak.

 

i do have the heater working, just doesnt come out the right spots when i move the slider

 

The heat comes out the defroster vents right. That is the default setting. If you fix the line you taped off you will be able to control which vent it comes out of.

 

I didnt tap into any lines. Anyhow i checked all my vacuum lines on the engine and plugged them better, the car ran a bit better but was still backfiring and idling low.

 

The backfiring could be caused by a restricted exhaust. Have you scraped the bottom of your car possibly pinching an exhaust tube? A clogged cat or exhaust valve problems are also possibilities. A way to check for restricted exhaust is to have someone rev the engine while you feel the air coming out of the tail pipe.

 

I put a brand new exhaust on headers all the way back, i noticed the car seems to "pop" when i hit the gas at around 500 RPM , ya my RPM'S are way too low as well.