[Sean-Alex Smith]

Hey I have a 2002 GMC Sierra 1500 with the 5.3. This truck has not ran right for a while, and am trying to fix it up. It has sort of hit or miss power loss. Half the time, it runs ok, as in you can floor it and it will go, the other half of the time it is hardly pulling its own weight! It acts like it is starving for air/fuel. This truck has a new fuel pump, and fresh tune-up done this week. The o2 sensors were pulled off to test if the cats were clogged, and it just ran worse with them off.(yes, the air cleaner is clean) It still runs like crap! Any suggestions??? This truck has 170,000 miles on it.

 

[dobey]

170K miles is a lot. Timing chain could be stretched and skipped a tooth or two. Have you tried to run it with a data logger hooked up to see what's actually going wrong, when it goes wrong?

 

[Sean-Alex Smith]

No have not tried that yet... I drove it about 30 minutes ago. It will go if you floor it about half the time. Other times it just runs awful! It also seems to have a long throw in it when you do floor it before the rpm's kick up.

 

[RayVoy]

What did your "fresh tune up" consist of?

 

[Sean-Alex Smith]

new plugs & wires. New air filter about 3,000 miles ago and still clean.

 

[RayVoy]

what does the distributor cap look like? Do you think it could be original?

Never mind, just check the year, you don't have one, sorry.

 

[Sean-Alex Smith]

I have not checked the dist. cap. I know for a fact it is original though.

 

[thegawd]

new distributer? they always get over looked... check and make sure the vents in the housing are there and not blocked. clean them out and if no vents drill a couple... moisture gets stuck in there and has no where to go if vents are plugged or not there. my truck didnt have any vents in dist cap housing, I couldnt get my truck to run, finally put new dist on after doing everything else and I think it was written in instruction manual for new dist to check for vents... something sooooo simple creates such a huge problem. ny truck started right up and has continued to run perfectly ever since.

Al

 

[thegawd]

ok nvm...

 

[dobey]

What did the tips on the coil packs look like? Carbon build-up can cause misfires. Does the Check Engine Light come on?

You really need to scan the computer and get some log runs in with it having problems, so you can look at air, fuel, spark, etc… numbers and see what's wrong.

 

[mnmhays]

Have you checked your accelerator cable. I have had 2 come apart on me in the past. One in my Ford F250 diesel, top speed was about 60 until the frays in the cable stuck and then I had to stall the clutch to shut it down. Another one went bad in my Dodge Durango...both times it mimicked a power loss. Just another possible direction to go in.

 

[RayVoy]

Maybe a compression check as well.

 

[99'HEARTBEAT]

Sean-Alex Smith, When was the Last Time the Throttle Body-n-Injectors were Cleaned, Along with a New Fuel Filter??....and you Mentioned "The o2 sensors were pulled off to test if the cats were clogged, and it just ran worse with them off".....did you Install the Old Ones Back On, or Did you Install New 02 Sensors???.......also What Brand of Plugs did you Go with and Install???