1995 Chevy Blazer Engine runs rough. Help

DEPRIJ1

MEMBER
1995 CHEVROLET BLAZER
6 CYL
4WD
AUTOMATIC
15,500 MILES

Engine runs rough at idle and sputters an back fires when driving down the road. Starts perfect every time then slowly starts to run worse. I have put new wire, plugs, cap & rotor, Oxygen sensor, air inlet sensor and spider injector in it. Tried two different computers but the problem never changes. The vacuum is good when first starting but go's down as the truck starts to run rough. The fuel pressure checks out good. Blocked off the EGR valve but no change, I cleaned it out any way and seems to operate o.K. The cat has been pulled out of the exhaust a long time ago. The one thing I still need to replace is fuel filter. My buddy thinks maybe a vacuum leak in the manifold gasket because when you spray carb cleaner in the air intake the truck smooths right out. We hooked up a scanner and all sensors are operating in range. No engine codes come up. Any one have any other ideas?

3 Replies

RHALL77

MECHANIC
3,361 POSTS

I think your buddy is right. Check with a scann tool and see if you are getting a lean condition. Have him spary the carb cleaner and see if the o2 sensor changes to a rich signal. Also do check the fuel filter and see if it is plugged, let me know what you find.

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Tuesday, March 24th, 2009 AT 3:46 PM

DEPRIJ1

MEMBER
3 POSTS

Thanks for repling. I put a new fuel filter on and yes the old one was clogged. I started it up and let the computer reset itself. Seem to run fine but hesitated and lacked power, but ideled perfect. Went back out and tried later but did not run or idle good. This has happened before after resetting the computer were it runs good and later runs like crap again. I thought maybe I had it fixed. Buddy is coming over with scan the tool again this weekend. I am going to recheck the new fuel filter just to be sure.

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Wednesday, March 25th, 2009 AT 5:49 AM

DEPRIJ1

MEMBER
3 POSTS

I rechecked the new fuel filter and it was still good. My buddy suggested to pump some fuel into a jar and let it sit to check for water seperation in the gas. Then the fuel pump would not operate. Banged on the tank with a rubber mallet, then it started to work again. Disconected the battery and put back original computer and air inlet sensor. Started truck which ran a little rough for a while until computer relearned. Truck was running great after all this. The whole time I was tring to fix this truck the fuel pump always worked and fuel pressure always read good. I am going to drive it for a while and see if it acts up. If it does I will be replacing the fuel pump which was replaced only 2 years ago with not more than 15,000 to 20,000 on it. I hope this infromation can help other people.

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Friday, March 27th, 2009 AT 5:48 AM