Misfire no codes

Asked by Jul 08, 2017 at 02:53 PM about the 2004 Chevrolet TrailBlazer LS 4WD

Question type: Maintenance & Repair

So I have a 2004 Chevy trail blazer 4.2 engine. I
have owned the vehicle since February. It is
misfiring but there is no check engine light. I have
had it scanned now 6 times and have no codes
that are popping up or stored. I have replaced
cylinder 1 and 2 could packs, all plugs have been
replaced.  I took into a local Chevy dealership paid
117 for a diagnostic to be told it was bad coil pack
on cylinder 1 and the sensor in the gas pedal.
Everything was replaced with new parts and it is
still misfiring with no light or code.. please help

2 Answers

70,295

Turn on the ignition but don't start the engine. The check engine light should be on steady. If not, the bulb is likely burned out. If the check engine light is working and the engine is truly misfiring the check engine light will be flashing. If not there's something else going on. Another thing to be aware of is a "hard" misfire code won't usually set until the check engine light remains on. But with no check engine light or trouble codes look for something that can mimick a misfire. Such as a bad motor mount, or even a transmission problem that may be causing the vehicle to shake or jerk. Since the Chevy Dealer already worked on it, take it back. Wait for the vehicle too, don't drop it off. They'll get to it right away and be more prone to have answers if you're there and not on the telephone. HTH. -Jim

1 of 1 people found this helpful.
215

I 2nd the other items that can "mimick" a mis-fire. Bad motor mounts and/or tranny mounts will do it for sure.

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