TPeye

First, my L98 had a rough hunting idle between 400 and 700rpm. The timing is 10 BTDC, fuel pressure is 34psi, TPS is .54 volts, IAC and oxygen sensor are about a year old, injectors all read 16.4 ohms, there is spark, and there aren't any trouble codes. After disconnecting the battery to reset the ECM the car cranks but will not start. What could be the problem?

RRT vette

Spray some starting fluid in the throttle body while cranking. If it starts and runs with the starting fluid, then you have a fuel delivery problem or the injectors are not recieving the ref pulses from the ECM.

The hunting idle sounds like a vacuum leak. Did you hear any hissing when the idle goes down? What year vette?

AGENT 86

I see you have a 90, this info is from my 86, but may help. As RRT stated, try some starting fluid.
http://members.shaw.ca/corvette86/En...ButWontRun.pdf
http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf

TPeye

Thanks for the help guys. It is a '90 vette. I got it started after putting the wires in the TPS weatherpak in their proper positions, don't ask. The rough hunting idle is still there, and when making a hard stop it drops to about 400rpm and feels like it is going to stall the way a carburated car would. I checked for vacuum leaks using propane and did not find any.

RRT vette

Just make sure that you have checked and double checked for vac leaks. There are vac lines all over the engine bay. If the runner gaskets are bad, it can cause a vac leak also.

Does it run rich or lean? pulled the plugs lately?
Have you checked your injectors out? Leak down? ohms?
How about the O2 sensor?

TPeye

The o2 sensor only has about 3000 miles on it, the plugs looked good (light tan), and the injectors all have 16.4 ohms. I will check again for a vacuum leak, but I will most likely have to bring the car in to have a scanner hooked up.

rick lambert

As suggested, vacumn leak(s), and they can be a mother to find, I've used propane before, some guys prefer other things but it takes a careful diligent check to find them.

RRT vette

As Rick (how are you doing BTW Rick?) suggested, propane is good to use and is how I found my leak. You can also use starting fluid, WD-40, Seafoam in the brake booster, and some have introduced a good bit of smoke into the thottle body to find leaks with good results.

A scan tool will not tell you that you have a vac leak, only show you that a leak is potential depending on the readings. A hunting idle is usually a vacuum leak causing the ECM to contol the IAC motor in and out.

joe paco

this thread has some info that might help with the 91 no start problem

joe

jfb

10 degrees BTDC is too far advanced and might be the cause of your idle hunting and hard starting.

Ricky 91 vette

I agree, and I would also do an idle relearn, and try to scan It to check ur counts( I think they should be between 30 to 50 on idle with no ac)