1999 Chevy Truck

LGCASA

MEMBER
1999 CHEVROLET TRUCK
V8
2WD
AUTOMATIC
268,000 MILES

Gets worst as the day gets warmer. Engine pings under load mod to hard accell or up hill. Backfire when de accell or down hill. And when cruising at about 70 mph and rpm 2200- 2500 truck will buck and cause the drive shaft to ping.

Thursday, January 15th, 2009 AT 8:42 PM

5 Replies

JACOBANDNICKOLAS

MECHANIC
109,869 POSTS

Hi:
The easiest thing to try is better gas. If that doesn't help, move to the knock sensor. If you have a backfire on deceleration, check for exhaust leaks or engine vacuum leaks.

Let me know what you find.

Joe

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Thursday, January 22nd, 2009 AT 3:48 PM

LGCASA

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5 POSTS

I was suspecting the timeing chain. A friend of mine has a analyzer that is able to read the cam sensor. THe info I got is its should be 0 degrees to -2. And it should stay there all throught the RPM range. Its all over the scale from +6 to -16. I haven't taken it apart yet if I keep my speed down its ok. Do I understand this properly. Am I possible on the right trake?

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Thursday, January 22nd, 2009 AT 9:29 PM

JACOBANDNICKOLAS

MECHANIC
109,869 POSTS

It sounds like you are on the right track. You may want to check the pick up coil in the distributor too. There may be a problem there too.

Joe

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Friday, January 23rd, 2009 AT 3:26 PM

LGCASA

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5 POSTS

I'll double check that. Thanks for your help
Gil

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Monday, January 26th, 2009 AT 4:48 PM

LGCASA

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5 POSTS

Found the problem. The harmonic balancer came loose and the crank sensor reluctor was rocking and ate the key notch out a whole key width the chain and cam sprocket were pretty worn also. Replaced these parts and it runs like new.