peeeot

I have a 1995 3.4 5-speed camaro with 88000 miles. About a month ago, every time I started the car when it had cooled completely, as at the start of the day, it would idle very poorly when I pushed the clutch until the coolant temp had exceeded 160 degrees. The tach needle would jump from as low as 400 rpm to as high as 1100 of its own accord. If I let off the clutch pedal it would idle normally, and if I revved the engine with the clutch down it would rev normally. Again, once warmed to above 160, it would operate normal all the time. I was advised to replace the 24x crank sensor, and did so, and the problem vanished.

Now, a week or so later, it's back, only now it idles even worse (even has stalled) and keeps idling badly when the clutch is depressed until coolant temp reaches about 180. I should also note that the engine has always been slow to drop rpms when revved or even when shifting gears; it usually takes a second or two to change rpms at all when I put the clutch in to shift. This improves when the car is warmer. I have had intermittant SES lights and security lights, and regularly get around 21.5-22 mpg city driving with normal shifting at or before 2500 rpms. The car has new plugs and wires, a new fuel filter and pcv valve, new oxygen sensors, and a new 24x crank sensor. I have run fuel injector clearner through the system and cleaned the throttle body as well.

Does anyone know what I'm dealing with? Even when it's working normally, the car isn't as smooth as I'd expect a low mileage computer-fuel-injected car to be, particularly at idle. I'd appreciate anything anyone can give me. Thanks!

GALIATHON

Check your MAP sensor and the wires and hose that goes----could be a bad injector---- fuel pump maybe, not to sure on that one-- but check the first 2 first...

6SpdLT1Z

Coil Packs?

I've also had to replace my 02's and Crank Sensor within the last year. (Rolling around 102k sometime this week!)

peeeot

Thanks for responding! this problem has really been bothering me altely and I have made no headway. I'll check the MAP sensor and wiring as well as the coil packs ASAP. I'm going to check the ECT and IAT sensors as well. Just need to lay my hands on a multimeter....

peeeot

I wasn't able to test the coolant temp sensor because I couldn't get to it, and I was only able to check secondary resistance in one of the coils and it was within spec. AS for the MAP sensor and the air intake charge temp sensor, well my haynes manual expected a reference voltage of 5 volts for both of those but it was more like 6.6 volts. For the MAP sensor, it said the signal voltage should be between 4.5 and 5, but it was somewhere between 5.5 and 6 I think. I don't know whether this means the sensor needs to be replaced or not.

The SES lights I get periodically never occur when I'm having this startup problem; they come randomly when I'm driving and everything feels fine with the car. Because of this I suspect they are not affiliated.

I feel like the problem is not in the ignition components or the fuel delivery components, but in the computer's instructions to these systems. So what does the computer use to control idle? I know of the 24x crank sensor (replaced), the ECT, the MAP, perhaps the IAT, and the IAC valve. Am I leaving anything out? It may be cheaper for me to replace all those sensors then to take the car in for diagnostics....

peeeot

Update: I went through the Hanes manual and tested EVERY engine control sensor except the knock sensor. They all checked out to spec, except that the signal voltage on the cam sensor was high (10.91 volts). I replaced it (no change) and the coolant temp sensor because it was cheap and I had had some questionable readings and neither has made any difference. This is maddening. Oh, I also added an extra engine to frame ground strap to eliminate the possibility of poor ground. What else is there?