Misfires After Tune
01-23-2013, 03:13 PM
#1
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Misfires After Tune 98 Trans Am. Build consisting of: new valve covers (OEM), new dual valve springs (Brian Tooley), new rocker arms (OEM), new heads (243 heads), new oil pump (Melling High Flow), new cam (TSP 224R), new exhaust (TSP LTH 1-7/8", TSP ORY, Flowmaster Catback), new spark plugs (NGK), all appropriate new gaskets. Maybe a few things I'm forgetting but these are the basics. Got the car finished. Everything's fine except for the clearance on the headers. I need to get the engine mounts replaced. Here lies a problem that I'm trying to fix right now: at around 45-50MPH (only in 5th) the car starts shaking violently. This started happening after the tune. Also note the car was daily driven for about a week before the tune but not driven sporty like it would be on a dyno tune.
I'm hitting the following check engine codes:
Oxygen Sensor Heater Circuit Bank 2 Sensor 1
No DTC definition found. See service manual
Random - Multipe Misfire detected
Oxygen Sensor Circuit Slow Response Bank 1 Sensor 1
When it's missing around 45-50 MPH, the check engine light isn't flashing, it's staying solid. I was told that GM vehicles are supposed to flash a 'check engine' light upon misfire being detected. Thoughts on the matter?
I'm hitting the following check engine codes:
Oxygen Sensor Heater Circuit Bank 2 Sensor 1
No DTC definition found. See service manual
Random - Multipe Misfire detected
Oxygen Sensor Circuit Slow Response Bank 1 Sensor 1
When it's missing around 45-50 MPH, the check engine light isn't flashing, it's staying solid. I was told that GM vehicles are supposed to flash a 'check engine' light upon misfire being detected. Thoughts on the matter?
01-23-2013, 03:22 PM
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are all of the spark plugs ohming out ok with a meter? are all spark plugs ok? I had a plug wire that wasn't on all the way and caused a similar issue.
You just did a header swap, are you certain all plug wires & plugs are connected & installed properly. Just asking to check basics.
does the car shake violently at 20mph in 3rd? what happens if you shift into 3rd gear at 15mph and give it gas, does it shake? Mine did it with a high load, low rpm.
You just did a header swap, are you certain all plug wires & plugs are connected & installed properly. Just asking to check basics.
does the car shake violently at 20mph in 3rd? what happens if you shift into 3rd gear at 15mph and give it gas, does it shake? Mine did it with a high load, low rpm.
01-24-2013, 10:02 AM
#3
Check for a burnt wire or ones to close to your headers. It sounds like something is touching your new headers maybe?
Also check to see if they didn't raise the threshold for misfire events in the tune. With those cams, sometimes you have to raise them so it don't show false kr.
IF they did raise them, then you have a bad plug or wire usually.
Also check to see if they didn't raise the threshold for misfire events in the tune. With those cams, sometimes you have to raise them so it don't show false kr.
IF they did raise them, then you have a bad plug or wire usually.
