I've been having an ongoing issue with a surging idle while the car is warm and cold. I have replaced the 02 sensor,coolent sensor,pcv valve,egr is blocked off, replaced the TPS and set to .54, removed cleaned and adjusted the IAC, new distributor,plugs and wires. I swapped out my MAF sensor for a friends and still had surging. A few months back i had to replace the lower intake gasket that had a vacuum leak. Car was always lean with the lower intake leak but the AF is much better now and only shows intermittent lean idle in park or neutral,under a load its better. If I watch the wide band 02 sensor the lean condition follows the surging. I looked for vacuum leaks with propane and carb cleaner with no luck, any ideas??

 

just checked and no codes

 

ok, so I'm still working on this surging idle. today I checked the grounds to the heads-3 on passenger 2- on drivers all tight and clean. I also did and ohms test on all 8 injectors(FMS 30lbs) all came back at .014 ohms. So being they all came back over 12 ohms and all reading the same I'm thinking they are ok. I also checked my TPS again, it was .59v and I corrected it to .54v. I also took my fuel pressure and it was 43lbs at the fuel rail.Checked the base timing and it was where I wanted it 8*BTDC.. I started the car and the idle went to 1500 then to 1000 after a few mins. The wide band 02 was showing the AF mixture fluxuating between 13.8-17.0 in neutral. When I put the car into gear the idle is much better, almost perfect! and the wide band 02 stays between 14.5 and 15.5. I have adjusted and cleaned IAC, new 02 sensor,TPS,fuel filter,wires,plugs,cap,pcv,coolent temp sensor, rotor, distributor,coil. I also swapped out my MAF sensor. It was better after the TPS ajustment today and is great in gear when warm, but when I take it out of gear after a few mins it will start to surge between 800-1200rpms and the AF mix is intermittently lean then. I also went over everything looking for vacuum leaks and havent found any. Any Ideas??????????

 

you've done everything I would have recommended at this point.

sometimes I use starting fluid to detect vacuum leaks, may try that.

Can you datalog the car while it's running?

Don't know why this popped into my head but make sure that the diaphragm on the fuel pressure regulator is not ruptured and leaking raw fuel up the vacuum line into the plenum. My IROC did this a while back and I played hell trying to find it but my O2s were showing rich and yours aren't....

 

got to check for vacuum leaks with a smoke machine today. Found a leak on my in line oil seperater thats between my pcv and lower intake. Surging is better now I hear the car pinging at high rpms under load, always something.

 

It sounds like you might benefit from a drivabilty tune on a dyno. My LS1 vette was doing that and it was a dirty maf. Can you check your AF ratio at wide open throttle? It sounds lean.

 

I had the car dyno tuned, 8* btdc...34* total timing...I have a wide band 02 gauge and it doesnt show lean at WOT.

 

check the readout on the coolant temp sensor. If it is reading colder than the engine actually is, the ECM could be adding more timing than is needed. Is the knock sensor picking up any knock counts?

 

Big issue with the crossfire cars is people messing with the balance adjustment screws as well as dirty/failing IACs that get un-balanced because the ECM is blind to their actual positions.