Backfireing and low acceleration power

[bmaley79]

I have an 86 2.5 that i just put in the truck and it backfires every once in awhile right after you turn the ignition off. And it stumbles and is weak on take off sometimes. Any suggestions would help. Thanks.

[Geonovast]

O2 sensor would be the first thing I'd check.

[bmaley79]

i noticed that my bolts on my valve cover were a little lose so that have been it. Or at least it has a little more power. lol

[bmaley79]

I changed out the o2 sensor and it is still backfiring. Is there anything else that would cause this?

[Wildman]

I do not know 2.5 engines that well.

 

Generally back fire is caused by the timing being off.

 

That means the distributor is off time, or the timing chain is stretched.

 

I'm thinking the 2.5 has an "guide" on the timing chain, and others have had problems with the guide being worn and causing the timing chain to "slop" around.

 

I don't even know it the timing can be set on the 2.5, I know it can't on the 4.0.

 

If you can, check the timing off the marks, and see if it's even close to specs, before you start tearing into the engine.

 

How many miles you have on this '86??

[bmaley79]

Well its not the orginal engine and it has been rebuilt during some part of its life. This is the first 2.5 i have ever worked on. I'm use to the i6 love them. Ill try to see about the timing. Ill have to see if any one has a timing gun even.

[BLHTAZ]

Wildman hit it on the edge ;) . The 2.5L uses the same timing chain set-up as the 4.0L, but the 2.5L has a chain tensioner that the 4.0 does not have. When the tensioner wears out, you get the exact problem described.

[bmaley79]

Does any where sell the tensinor? or do you have to get entire kit?

[Geonovast]

The tensioner will probably not come with a timing kit. You may want to get the kit anyway, as slop in the chain may have allowed it to stretch.

 

I bought a replacement tensioner once, and the cheapest I found was $28 for that stupid thing.

[Wildman]

Here.......I just looked this up on Rockauto.com - '86 2.5 engine. Timing chain Kit.

 

CLOYES Part # 94023S

Includes: Cam, Crank, Chain, Tensioner, Damper $46.89

 

http://info.rockauto.com/Cloyes/DetailR ... -4023S.jpg

 

And don't forget this -

 

FEL-PRO Part # TCS45458 {Timing Cover Set w/Sleeve}

OHV engine; Timing Cover Set w/Sleeve; w/Sleeve 'N' Seal® $15.40

 

But, like I said, I would check the timing marks on the harmonic balancer first to see how close they are. Thats if you can.

 

And.......here's a 5% discount code for ya..... 1873533514609 ...good until 8-16-2009.

 

Just the guide is $8.13, but all the work to get to it........change the whole kit and be done ;)

[bmaley79]

I think ill just order and change the entire thing out since I'm sure it is pretty worn. Thank for the help and that web site. The prices are a lot better than what i can get it for around here and everyone has to order it so not much diffrence in waiting time either. Now I just need to find a 4wd transmission and ill have the truck on the trails. I'm tired of the 2 wd trans. Its summer and i want to have fun again. Thanks again for all the help.