Trailblazer 302 low compression

[cruizer]

Pull the valve covers off, see if you have a loose rocker and a bent pushrod. This is generally caused by running dinosaur oil in a cold environment. Moisture from the oil gets in the lifters and freezes. This bends a pushrod.

Now the compression is normal so that's not the issue.

Oil must be a diesel or 4 stroke motorcycle oil

[Schafe]

Thanks Guys

Cruizer- Try this MA80002M I thought we were not supposed to give full serial for some stupid reason. Sorry bout that. I will check the spark strength. I hope I don't need to pull those coils because I think the compressor would have to come out first. Tryagn5- I have changed oil filter,plugs and fuel filter. Used a 10-30 regular grade oil. Only oil I use around here is 15-40 Diesel oil so I just bought some regular stuff and put it in. Which oil would you recommend? Fuel was right full when I got it but I also thought of that. I will drain it and put in new after the other tests. P.S. I was also leaning towards the hydraulic lifters not pumping properly. I did 2 compression tests and each time it took different readings taking less or longer revolutions to build up each time. I may be jumping the gun here thinking the issue is more serious then it really is and that's why the guy sold it.

[cruizer]

True, but a weak idle and especially backfiring tells me, that your missing spark on one side, usually the left one. best pull the plugs to verify spark. betcha you have a fizzled coil. (there are 2)

[Tryagn5]

Greetings all.... great to be here among the pros. I recently purchased this used 302 with air pack Serial MA18xxxxM Kohler Command Pro CH 750. It has an unsteady idle and backfires when comming down off 3500 rpms at times. Has a slight serge at higher rpm's also, takes a while to rev. up at start up. Compression test....130 one side and 150 on the other. does this sound like a valve problem or what can you suggest to do. 1000 hrs on engine and 750 on compressor. Thanks for any input.

Nope not a valve probelm. Compression would be much lower, bettar to do a bleed test, but doubt its an engine condtion. Would bet either, oil is dirty, needs 10w30 diesel grade(when kohlers get dirty oil, or run the wrong oil the hydraulic lifters do not pump up well), or carb needs to be cleaned. So do a service, oil and filter, spark plugs, and fuel filter, run fresh fuel as old fuel if it has ethanol has short shelf life. If shes still running bad would bet you have a weak coil, or clogged carb.
Kevin

[cruizer]

You must think that we need the serial# for stupid maybe criminal reasons. but no I take that #, punch it into a tech site, and it tells me everything i need to know. You blanking out the #'s doesn't help your case...


Welcome to the site, but it seems either we don't get serial#'s, or get partials. Tough to troubleshoot on vagueness.

[Schafe]

Greetings all.... great to be here among the pros. I recently purchased this used 302 with air pack Serial MA18xxxxM Kohler Command Pro CH 750. It has an unsteady idle and backfires when comming down off 3500 rpms at times. Has a slight serge at higher rpm's also, takes a while to rev. up at start up. Compression test....130 one side and 150 on the other. does this sound like a valve problem or what can you suggest to do. 1000 hrs on engine and 750 on compressor. Thanks for any input.