QuestionQUESTION: Hi Ted,
My truck just started hesitating under load. Under steady throttle (seemingly before reaching operating temp) it will start bucking and it sounds like it's backfiring. If I go to full peddle it will accelerate. the problem seams to go after the truck is warm,
Codes show a misfire in 1 and while running the precat o2 returns 0 volts.
All filters replaced, plugs done. MAF and throttle body cleaned.
I'm at a lose of where to go from here. Could the O2 sensor cause this?
-Mac
1997 4runner sr5 3.4 175K auto
.
ANSWER: Since the misfire is isolated to the #1 cylinder only there are a couple of possible causes. A common problem is that one of the fuel injectors is sticking in which case it should be replaced, since it's temperature related it may be a tight valve, this is not very common but a possibility, if you suspect this then a compression test of the engine should be done and possibly a valve adjustment may be needed but I'm leaning towards the injector problem since this is the most common.
---------- FOLLOW-UP ----------
QUESTION: Hi Ted,
I recently replaced the injector on #1 with no change and compression in that cylender was good.
-Mac
ANSWER: The #1 cylinder is at the front of the right bank(passenger side) is this the injector that was replaced?
---------- FOLLOW-UP ----------
QUESTION: Yes, I replaced it when I could find no other reason for the misfire and with the backfiring I thought the injector
might be going.
AnswerYou are getting a misfire code for the #1 cylinder which would be a P0301 code, is this correct? Are there any other codes other than this one? If the 301 is the only one then the problem is isolated to the #1 cylinder. Since just about everything has been tried I only have a couple of more ideas: There is a vacuum leak on the intake system near the #1 cylinder,the timing belt timing may be off due to a jumped timing belt,there is a tight valve or broken valve spring, neither one of these conditions may show up on a compression test.
