erratic idle on carbed 86 TA - Third Generation F-Body Message Boards

19transam86 · 10-19-2008, 09:39 AM

i have a little problem with my car. At cold startup it idles fine, around 900rpms, but then once the engine heats up it acts very weird. When i idle the car will go from about 1000rpms and then for whatever reason it will jump up to 15 or 1600rpms and then a fairly loud popping noise comes from somewhere. I only know the engine isn't the popping sound. is then a hole in the manifold or the cat? It's gotten worse since i put a new cat back system on it and i'm guessing thats because there is more back pressure to the exhaust. Any input will help,
thanks, Matt

19transam86 · 11-16-2008, 11:41 AM

so i have 48 veiws and not a single reply, please i would like some help

stroker_SS · 11-16-2008, 12:22 PM

Quote:

Originally Posted by 19transam86

i have a little problem with my car. At cold startup it idles fine, around 900rpms, but then once the engine heats up it acts very weird. When i idle the car will go from about 1000rpms and then for whatever reason it will jump up to 15 or 1600rpms and then a fairly loud popping noise comes from somewhere. I only know the engine isn't the popping sound. is then a hole in the manifold or the cat? It's gotten worse since i put a new cat back system on it and i'm guessing thats because there is more back pressure to the exhaust. Any input will help,
thanks, Matt

how long ago did this problem start? And I don't think that putting an aftermarket cat back on would increase backpressure.

19transam86 · 11-17-2008, 05:58 PM

it was a problem ever since i got the car but then i got a new master cylinder and it stopped. Then i replaced the passenger side head gasket, and to do that i needed to unhook a couple of computer plugs in the engine. when reassembeld it started idling high again. Did unplugging those plugs "reset" the computer?

jreigner · 11-18-2008, 09:26 AM

I have an 86 TA, E4ME carb also and I believe a number of things could have changed by replacing the head gasket. Which side head did you work on? How does the car run otherwise? Do you have any missing or lack of power issues otherwise? Does it start right? I dont think the OBD-I ECM is capable of losing any settings. This car doesnt even have many sensors on the car(in general comparison). Has any codes come up when this popping occurs? It may also be largely vaccum related.

19transam86 · 11-18-2008, 11:43 AM

the car has all the same power and starts right up as always. i beleive it may be a vacuum, would you know possibly what vacuum is leaking or incorectly installed to make this idle possible
Thanks

naf · 11-18-2008, 01:15 PM

Vacuum leak is possible. Maybe at EGR or intake manifold. Spray some starter fluid around and note if the idle quality changes.