97 tahoe random misfire HELP!!! Everything has been replaced...
pignessx1
04-10-2011, 05:37 PM
My husband and I decided to rebuild my truck last year. It has new and reman parts from transfer case to water pump. Basically everything has been replaced.
At the time the only thing that wasn't replaced was the distributor, spider injectors and o2 sensors...Now all now all of that has been replaced. We thought it might have been Cat Convertors since they were original. I had those cut off and replaced including a new muffler. We've been picking at this truck for a year now trying to figure out the random misfire. This weekend we finally nutted up and got into the upper intake and replaced the injectors. We also changed the pcv valve and the spark plugs (today). The misfire is not as severe, but it is still there. We are both at a loss.
It has Fuel, Fire and Air... The misfire is worse when it's really humid, rainy, and foggy.. What next. Could it be as simple as it's just slightly out of time? We thought we had it time out, but maybe it's just a hair off.:banghead:
Living on the coast we have sea fog occasionally. Today, when I first started running it everything was fine, but when I got down to the beach in the fog that's when I noticed the misfire again.
At the time the only thing that wasn't replaced was the distributor, spider injectors and o2 sensors...Now all now all of that has been replaced. We thought it might have been Cat Convertors since they were original. I had those cut off and replaced including a new muffler. We've been picking at this truck for a year now trying to figure out the random misfire. This weekend we finally nutted up and got into the upper intake and replaced the injectors. We also changed the pcv valve and the spark plugs (today). The misfire is not as severe, but it is still there. We are both at a loss.
It has Fuel, Fire and Air... The misfire is worse when it's really humid, rainy, and foggy.. What next. Could it be as simple as it's just slightly out of time? We thought we had it time out, but maybe it's just a hair off.:banghead:
Living on the coast we have sea fog occasionally. Today, when I first started running it everything was fine, but when I got down to the beach in the fog that's when I noticed the misfire again.
777stickman
04-10-2011, 06:35 PM
Welcome to the forum.
1st, you need to tell us what motor and tranny.
2nd, with a misfire, there should be DTC's, either active or stored in memory.
3rd, timing is controlled by the VCM. To set base timing requires a high end scan tool to access that function (cam offset/cam retard).
4th, did this happen after the "rebuild" or was it going on before?
1st, you need to tell us what motor and tranny.
2nd, with a misfire, there should be DTC's, either active or stored in memory.
3rd, timing is controlled by the VCM. To set base timing requires a high end scan tool to access that function (cam offset/cam retard).
4th, did this happen after the "rebuild" or was it going on before?
pignessx1
04-10-2011, 08:21 PM
5.7 Vortec (crate) & 4L60E (reman)
code for random misfire was and still is P0300
I have a timing light anytime I need it.
No it wasn't doing this before the rebuild. When we finally decided
to change injectors it was after changing all other bolt on and sensors
that we and the parts house could come up with.
code for random misfire was and still is P0300
I have a timing light anytime I need it.
No it wasn't doing this before the rebuild. When we finally decided
to change injectors it was after changing all other bolt on and sensors
that we and the parts house could come up with.
777stickman
04-11-2011, 10:34 AM
What's BASE timing set at? Needs to be 0 +/- 2 degs at 1200-1500 rpm's.
Did you do the CKP Variation Learn Procedure?
Did you do the CKP Variation Learn Procedure?
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