1993fast_z

Ok, so i have a 99 camaro ls1 engine with roughly 125k miles on it. Just bought the car. Noticed the car hesitates tremendously until you get to 3500-4000 rpm, then it launches like a rocket. This is intermittent. does not do this all the time. I have a decent scan tool(snap on mt2500) and it is saying that it is #1 cyl. I swapped coil packs, plug wires,replaced plugs and replaced injectors. still doing it. if you take the car up to about 2500 rpm, #3 starts missing as well. Im out of ideas. Im thinking either engine harness or a lifter collapsing. I dont think it is a head gaskets because it does not do it at cold start and i wouldnt think it would be intermittent. When it does it and you shut the car off and start it back up, it is gone. Please give me any advice or thoughts on what you think the issue could be. Thanks

crainholio

iTrader: (2)

4000 RPM is where the PCM ignores MAF sensor input, and during cold starts the PCM is running in open loop ignoring the O2 sensors.

Any error codes stored?

I'd try disconnecting the MAF sensor to see if the engine's behavior changes. If so, grab a can of aerosol MAF cleaner and carefully clean the wire filament in the MAF sensor and re-test with it connected.

1993fast_z

Just got 3 codes to set. P0300-Random misfire, P0154-Bank 2 sensor 1 Limited Activity and p0332 for bank 2 knock sensor short/low circuit. Looked at my o2 sensor data and found b2 s1 just sitting at 450-470.

crainholio

iTrader: (2)

Any chance you mixed up Bank 2 (passenger side) front & rear O2 sensor connectors during the ORY install? Or damaged the front sensor or harness?

Do the MAF stuff next either way, but rule

1993fast_z

the rear o2's are disabled. i used the connectors with the o2 extensions, so i dont believe they are mixed up. my rear o2's are steady at 450 so im certain that isnt it. I just drove it and it ran fine. no problems. b2 s1 reading 90-190 b1 s1 reading 1100 steady.. do you see any problems with the o2 readings? im gonna get an o2 sensor and try it. Do u think it would be safe to rule out the lifters? wouldnt that be an all the time thing?

crainholio

iTrader: (2)

O2 readings while in Closed Loop should fluctuate between ~100mV and ~800mV.

Scan and post your Long Term Fuel Trim (LTFT) values for banks 1 & 2 at steady idle and while cruising. Should be between -10% and +10%, with no more than 1 to 3% variation between the two banks in any data frame.

LS_toys

bump...curious cuz I'm having a similar problem. feels rough untill 4000 rpm and its like flipping a switch. at 4k it smoothes out and pulls much harder. anything else besides MAF ignored at 4k?