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Engine Misfire Due to Worn Valve Seat on Chevrolet Trailblazer

Problem Description and Possible Solution

The engine may develop a misfire due to worn valve seats. This fault will cause the Check Engine Light to illuminate. Replacement of the cylinder head may be required to correct this concern.

Problem Data
RepairPal Verified
Average mileage: 120,621 (54,000–260,000)
Engine affected: 4.2L 6 Cylinder
6 model years affected: 2002, 2003, 2004, 2005, more2006, 2007
72 people reported this problem
Comments
Viewing 1 - 20 of 30 comments
The truck began to have a noticable misfire and the "Check Engine Light began to blink, replaced coil packs and spark plugs on all cylinders. Still misfiring, engine light alternates between blinking and staying on.
misfire in #6 cylinder. replaced fuel injector, coil, spark plugs. inspected by 4 mechanics and agree vehicle needs valves replaced. lowest quote is $1800. I know of 3 other Trailblazer owners that have or is experiencing the same thing.
gas gauge not working, hard miss on #6, no one can figure out what is wrong-code says coil, injector, knock sensor, all have been replaced still hard miss
Misfire in the engine, check engine light displayed...Spark plugs, coil packs replaced only to need deep diag. done at Chevi place and #2 cylinder bad...Need NEW MOTOR..
Engine mis fire code for cyl #2--leakdown compression
check showed #2 at 15% and 200 psi, #3 at 15% and 190 psi
Dealer removed and had valve job done on it, adv replaced
9 broken bolts in the process. No help from GM on this
cost me $2380.67 !!!
No hard driving with this veh and changed oil every 4 to 6
thousand miles, what gives????
Engine mis fire code for cyl #2--leakdown compression
check showed #2 at 15% and 200 psi, #3 at 15% and 190 psi
Dealer removed and had valve job done on it, adv replaced
9 broken bolts in the process. No help from GM on this
cost me $2380.67 !!!
No hard driving with this veh and changed oil every 4 to 6
thousand miles, what gives????
Heavy miss during cold start only gets slightly better after warm up.
2 coil packs replaced and plugs replaced. No change
had blowby in airbox intake engine idiling rough loose or worn valve stem seats had head rebuilt solved problem
I have a burned exhaust valve in the engine. I have not had it repaired yet but I'm sure it is a valve seat issue and a known defect.
Rough idle when engine is warm with 2 occasions stalling at a red light. The dealer just diagnosed it as burned exhaust valve on cylinder #6 and said I have to replace the whole top end as it comes as one unit with all new intake and exhaust valves - price will be $3000. Am trying to decide if it is worth it at this age or will I just find out that other expensive repairs will be just around the corner (transfer case? transmission?) have been very happy with this car but don't want to become a slave to it.
Check engine light came on. Mechanic's diagnostic was valve #1 had to be replaced. Had it replaced but check engine still came on, now i find out that the whole cylinder head has to be replaced.
"05 TRAILBLAZER ENGINE MISS
I bought this cream puff 05 TB on 3/15. I needed it for work. Should've seen the red flag when the "Used car dealer" told me he would "drop it down to $3000 from 3900 if I really wanted it". It Had the obligitory disfuntional instrument gage panel. On 9/15 It started missing on #6 2 weeks ago. I replaced the plugs but it got worse and idles very rough now with bad pickup. The Check Engine light is flashing. I'm going to put a computer tester on it to check for miss's and do a compression test but all indicators are pointing to worn/bad valves,seats. Seems the remedy is a new Head with New valves & a head gaskit. I'll let you know what I find out...
(which is more than GM will do for ya)
Engine had a misfire blinking ses light dealer says no compression on cylinder 1. cylinder does not hold on leak down test. Dealer says valve job needed. $2400 to repair. Oil was changed every 3000 to 4000 miles only mid grade fuel used. I have 130,000 miles on it. Im going back to Fords.
Actually is in the shop now. The check engine lite kept illuminating. Was still under 30 day warranty thank god for that.the dealer replaced two coil packs and the thermostat also pulled the pcm and froze it in the freezer overnite. Still had some sort of misfire. So they pulled the head and are having it sent to a machinist to check for worpped issues. Or to replace it.wish i had never purchased this trailblazer.
Multiple cylinder misfire depending on conditions will depend on how bad the misfire is real placed all plugs coils was ok but went back to misfire at idle only fuel pressure is good, no leaks from intake system. Any clue on why this is happening to all the 4.2 cyl heads????