cold weather starting

[rwiggs]

I have a 95 z34 that will not idle right when trying to start in cold weather. It will race to about 3000rpm, and then drop to about 1000rpm, and sometimes die. If it does stay running, it will imedietly jump back up to 3000 rpm, and back down. It will continue doing this until it warms up it seems. Took it to a mechanic, he said it was the o2 sensor, plugs, and wires. Replaced all that, and no good. I also notice and smell my catalytic converter getting extremely hot. Any ideas?

[teske]

it sounds like theres something wrong with ur choke. i dont know any thing about catalatic converters so someone else will have to help u with that one. if it were me i would take the catalatic converter off and replace it with about a foot of pipe. but thats just me. most of the time cars run much better with out the cc

[maxwedge]

It should be scanned to check for coolant temp sensor readings first, also fuel pressure should be checked cold with the sensor checks, post back results. This should be done left overnite of course. Possibly related may be vacuum leaks aggravating the condition when cold only, but less likely.

[rwiggs]

catalytic converter problem solved, it was the vaccum line from the back of the plentum to the brake booster. the idle is still a problem. everytime i hook it up to the scanner, the only trouble code i get is the o2 sensor, which has been replaced. all other volatages and temperatures are within normal parameters. i have heard that intake gaskets cause the engine to idle abnormaly, has anyone seen this to be true?

[corning_d3]

Unhook the ground on the battery for a few minutes to reset the PCM. If you run with a vacuum leak for a while, the PCM sees the extra oxygen in the exhaust and injects more fuel, which in turn makes your catalytic converter hot. After resetting it, start the car and let it idle for a few minutes. If it dies start it right back up. Let it idle for a few minutes to relearn its idle. If the problem isn't solved, check the O2 sensor wires and make sure they aren't pinched or burnt. A small intake gasket leaking air will usually cause high idle, and possibly an IAC trouble code. As maxwedge said, have the temp sensor and fuel pressure checked.