Help with my 91 navajo!!

[swatsw3t6f]

when i got the navajo about 6 months ago i had to put a new fuel pump in so we dropped the tank and drained all of the gas out of it bc it had a lot of water in it so idk how there would rly be that much dirt in it and it doesnt do anything wen i unplug the MAF so what does that mean. ive read some threads where ppl unplug it and the conditions get better so the MAF is bad or dirty in that condition so idk where im at with that.

 

[MrShorty]

What do i do to do a fuel pressure test?

see the "fuel pressure test mini-diary in the under the hood forum.

 

[Reejerey]

whats the fuel pressure at the fuel rail? and whats the manifold vacuum?

Sounds to me like a fuel pressure problem, specifically the fuel pressure regulator. Low fuel pressure could cause the sputtering/stalling, and if the fuel pressure in the rail isn't staying up after the engine is shut off when hot, the fuel system could be vapor locked.

Without some real tests and numbers its going to be hard to give you any real direction, other than "it could be" type statements, throwing parts at it is going to cost you lots of money in the long run. If you don't feel comfortable doing the tests yourself it may be time to take it in to the shop, you'll probably save some money.

 

[nitro71]

Fix the check engine light codes first off. That would be my first step.

 

[swatsw3t6f]

okay im probly gonna buy a pressure gauge then and check it but i changed the injectors in it and it had good pressure then and weve hit the pressure valve before and it seemed good but idk. when i first tried starting it today it stalled without hitting the gas and then started again and would stay running but if i hit the gas it would stall dead unless i kept the gas in very little it would rev up. It also sucks real hard from the air box wen i first hit the gas...if you use the throttle under the hood you can here it and its loud but sitting it the vehicle and doing it you cants rly but thats besides the point...should it do that?

 

[swatsw3t6f]

well i started it witch took a couple times to get it to stay running and then it shut off and wouldnt start so i turned to key of and off a couple times to get the fuel pump running and then it started...dont kno if thats a coincidence bc i never had to do that before. its acting different everytime i mite find whats wrong with it. now once it sits and runs for a little and gets warm it runs kinda alright and then i drive it and it gets the sputters and **** out and runs fine pretty much. idk guess check the fuel pressure and go from there

 

[Mettler]

It could be that your fuel pump has crapped out again. They do that. My brother and I changed his fuel pump in his car and then a year and a half later it died again. Having a plugged filter would make the pump work harder and die faster. Fuel pressure regulators die too. Make sure that your gas cap holds pressure as designed. That will have an effect aswell.

 

[swatsw3t6f]

idk if the fuel pump if bad tho bc it kicks on everytime.

 

[fixxxer]

The pump can run but still not pump enough fuel to the fuel rail and injectors. You can often rent or borrow tools like a fuel pressure gauge at most auto parts stores like Autozone/O'Reilley's and so on...

 

[swatsw3t6f]

now when i start it it takes a couple trys and then it will idle and if i give it a little gas it will go to like 2 grand and bounce from like 1.5 to 2 and keep doing that and if i push the gas down it will suck real hard from the air box and try to stall but wen it gets down to like .5 or lower it crackles a lot and backfires in the intake a lot and then stalls. would it be the cats clogged or something else maybe?

 

[backfrmcolorado]

i sugested the cats a while back on the post...

 

[Gadget X]

Just my $.02, but check the resistances between the coil packs, it sounds like you may need a new coil.

 

[swatsw3t6f]

When i first posted about the navajo it was running different than it is now. How would i check to see if the cats are clogged...i unplugged the o2 on the exhaust and it didnt change the idle or anything. and ive put 3 different coil packs on it and still isnt running right.

 

[MrShorty]

A couple of different things to look for when testing cats:

1) Put a vacuum gauge on the engine. Normally the vacuum should run 15-20 in Hg. If the vacuum runs lower than that, or if the vacuum drops off at higher RPM and doesn't recover, that indicates a clogged exhaust system.

2) Cats should be hotter downstream. If you have a way to test temperature, measure the exhaust temperature upstream of the cat and downstream of the cat. If the downstream temperature isn't significantly hotter than upstream, a problem is indicated.

 

[swatsw3t6f]

okay thanks shorty ill give that a try