hardbody backfiring through exhaust

[cjtimp]

I have a 97 hardbody w/4 cyl engine and a 5sp trans, At 2200 rpms and higher it backfires slightly in the exhaust. Could this be timing? Vacuum leak? Any ideas.....This truck otherwise runs well....has 325K......

[AZhitman]

Is the backfiring on decel? If so, it's fairly normal, means a bit of a rich condition upstream and maybe a small exhaust leak.

If it's ALL the time, then there's a few possibilities: Check the IACV and PCV systems, look for a vacuum leak, and it wouldn't hurt to do a Seafoam treatment (could simply just be a ton of carbon build-up) : how-to-seafoam-your-engine-the-right-wa ... 83-40.html

[cjtimp]

Thanks for the advice......im gonna check for vacum leaks, and do the seafoam treatment as i know theres likely carbon build up with the amount of miles i have. I did discover im missing a bolt on the exhaust manifold. (very front one holding manifold to head.) so i know i have an exhaust leak too.....thanks again

[AZhitman]

Mind popping back in and keeping us posted on what you find out?

By the way, you can check for intake manifold and vacuum leaks by spraying starter fluid around all of the gasket surfaces and throttle body. If the idle jumps up, there's your vacuum leak.

[CanuckQx4]

Does it have to be starter fluid that you use to check for leaks?? I think I have a vaccum leak but dont exactly know how to trace it.

I was debating just changing every vacum line there was lol

[krash]

Yup, starter fluid works the best, it'll change the idle when it gets into the cylinders. So if you spray it on a vacuum hoses etc and the idle jumps, then the starter fluid is getting to the cylinders from that part.

[AZhitman]

^ That.