keycool1

1995 camaro z28 6 speed. All stock. When idling the BLM;s goes down to about 122 on the left and right side after going into closed loop and stays there. Is this normal or do I have a problem. Also I recently changed the intake manifold seals and gasket to fix an oil leak at the back. Have checked for vacuum leaks but found none.

Injuneer

A BLM of 122 indicates the engine would be runnng very slightly rich if the low BLM wasn't pulling out a bit of fuel. Generally, a vacuum leak would cause the opposite.... engine would be running lean, BLM would go above 128 to add the missing fuel.

BLM's within +/- 5% (122-134) are usually not cause for concern.

What do the other low load/low RPM cells look like? If everything is skewed to the low side of 128, might try cleaning the MAF sensor, checking the fuel pressure, check for EGR sticking open (generally produces rough idle), check for fuel leak into FP regulator vacuum line.

keycool1

Thanks for the fast response. Just put on a new egr valve to help pass emissions test, I failed first time for high NOx level. The guy said I was running a little rich and might have a slight misfire but I barely passed the test the second time. He said the HC level barely passed but NOx level went way down. I will try your suggestions tomorrow. Thanks again!

keycool1

@Injuneer: I checked the fuel pressure and with key on it was at 38 lbs... When idling it dropped to 34 lbs.. When I removed the vacuum line from the regulator it went to 44 lbs.. I also noticed that with the key off the pressure went from 38 lbs to 33 lbs in 5 minutes..

Injuneer

Fuel pressure sounds OK. You don't want the fuel pressure to drop rapidly when the pump shuts down, and yours is OK. You want 43.5psi at idle with the vacuum line off, GM accepts anything in the range of 41-47psi as within spec - your's is fine. And when you reconnect the vacuum line, the pressure should drop by about 8psi from the no-vacuum reading. That's with the stock cam.... more aggressive cam will drop less. Yours is a bit less drop than normal for a stock cam, but not enough to cause any problems. You wouldn't see 5% excess fuel flow until your pressure was about 5psi above spec.

Main concern was to make sure the pressure was not excessive, and that the vacuum line was pulling down the pressure like it is supposed to at idle.

The fact the NOx went down, and the HC went up is interesting. What about CO? Running rich will generally increase HC and CO, while dropping down NOx. If only HC went up, might be looking at a leaky injector. But since you indicate the BLM's are low, but similar on both sides, you would have to have a leaking injector on both sides.... not likely.