high idle verses vacuum

My 97 firebird was always idling at 1500rpm, I fixed the issue but now when it's idling at 900 rpm I get lean bank reading on each engine bank. This motor always pulls 21 inches of vacuum but could the sudden rpm drop have made a vacuum leak more pronounced and the ecm caught it?

since I got the rpm to come down to lower levels I now have P0171 P0174 P0300.

so could these lean conditions cause a random missfire detected? The engine does shake a bit but has plenty of power.

I need to fix these issues before I cn smog the car.

What are the BLMs at? Is there some kind of AIR juink on it? Most likely it is being a cali car. It should be smelly and run rich with those codes. Somewhere there's an air leak into the ehxaust most likely from the AIR system. Maybe the switching valves not switching properly

Still that misfire code? The misfire could actually be the cause of the lean exhaust reading

Twin_Turbo said:

What are the BLMs at? Is there some kind of AIR juink on it? Most likely it is being a cali car. It should be smelly and run rich with those codes. Somewhere there's an air leak into the ehxaust most likely from the AIR system. Maybe the switching valves not switching properly

Still that misfire code? The misfire could actually be the cause of the lean exhaust reading

Click to expand...

The lean bank codes are gone, that was being caused by a broken 1 way check valve that fed the vacuum reservoir.

This car has no air injection nor does my 97 3.8 camaro so it was never on the car.

I can't read blm's or stuff like that.

my only problem now is P0300 (random missfires detected) I have heard these engines are picky on what kind of spark plug goes in them.

apparently this check valve didn't cure the p0171 and 174 codes. They stayed gone for about 1/2 the day the came back with a new code P1441 which is related to my evap system (purge detected during non purge time or something like that)

So I'm curious if the evap canister is leaking vacuum and causing the lean conditions and the lean conditions are causing the random missfires.

Twin_Turbo said:

What are the BLMs at? Is there some kind of AIR juink on it? Most likely it is being a cali car. It should be smelly and run rich with those codes. Somewhere there's an air leak into the ehxaust most likely from the AIR system. Maybe the switching valves not switching properly

Still that misfire code? The misfire could actually be the cause of the lean exhaust reading

Click to expand...

You mention smelly and running rich but that doesn't seem to be the case. Out the tail pipe it has no odor nor any black deposits on bumper.

However it did have a strong fuel odor when motor was first put in the car after it was shut off. I know my 97 camaro has no evap issues so I will try its evap canister and see if that helps any.

Well the lean conditions came back and I think I found the problem. The flange my egr valve mounts to has a metal pipe that goes to the plenum and it was cracked in half. That finally cured my lean conditions however I still have p0300 (random misses)

I have also been noticing sometimes you have to crank the motor for about 10 seconds maybe more before it starts. So I'm wondering if the fuel pressure regulator or pump is going. Once it starts though it stays at about 43psi.