Not a fuel prob... still cant figure it out

[jworm420]

well for those of you have not read any of my posts yet, haveing a car problem, when driveing, sometimes it feels like the fuel was shot off or the car was shut off and the car jerks, when it does you can not hear the motor running and then it is and isnt and back and fourth.... well i got a fuel pressure tester, the pump primes at 40 psi and holds it....i let it sit for over an hour and it did not drop a smidge... and with the car running it holds at 37 psi, or if its in a higher rpm its at 35 psi, whitch is perfectly normal...turn the car off and let it sit, and the gauge still says 37... so i really dont think its a fuel system probelm now unless i have some bad injectors that work only sometimes... ive rueld out the possablity if the IAC, now im thinking the TPS Sensor... Would O2 sensors cause this problem ? i dont think so cause no check engine light has coem on... now how about the TCC sylinoid, Where is it and what does it do exzactly... never had to change one befor ?... i may end up blwoing this car up out of spite at this point... Think im going to go pick up a noid tester and check and make suer that the injectors are getting constant voltage... Hopefully its not a computer takeing a hefty shit on me.

[draaaca]

Your problem sounds similar to what I am having on a 98 Pontiac Trans Sport/Montana

this is my problem, posted in the Pontiac forum, but still without answer:

My 98 Trans Sport Montana, 3.4L, has developed a problem.

When driving along, it intermittantly "surges" or "hesitates" , I don't know how to describe it really. It is like it is loosing all power but then it drives proper again.

No dash lights come on, no service engine light. I don't notice the tach reving high or falling off.

I am suspecting the fuel system. I had the fuel filter replaced and the pump tested. Mechanic said it had good pressure. But since it is intermittant maybe the pump is only running full pressure most but not all the time. Don't know if engine need makes it pump more or should always be one pressure..

It seems to have the problem when the vehicle is under load...like climbing a hill or wanting to get up to speed. If it is babied, I don't recall it happening.

To me it is similar to a chain saw problem...you get a piece of saw dust in the tank, and occasionally it blocks the fuel line by the piece getting in the flow, but then you shake it and it gets out of the way and then runs well again until that piece gets stuck in the line again. Does that make sense?

When the fuel filter was replaced, the mechanic said it was really plugged up, he could hardly blow through it
Could there be crap in the tank...how would I check?

Any constructive advice would be appreciated.

Thank you.

[richtazz]

My wife's 97 Trans Sport did the same thing and it ended up being a blown head gasket. She was losing compression in the #1 cylinder. The symptom was like you tapped teh brakes slightly at speed, you could feel the van surge, but no check engine light. The tach would drop very slightly, so little that unless you were looking right at it when the van surged, you'd never notice it drop. Have a compression check done, preferably when the engine is warm (no easy task on the rear bank of cylinders). There should be no more than a 5% variance between any adjacent cylinders, and no more than 10% between any non-adjacent cylinders.

[jworm420]

Im pretty sure that its not a head gasket... about 30 k miles ago i blew one and had the bouth the heads taken off, pressure checked and re milled... im starting to think its a computer problem... today on my way to work it did it and while it was doing it the oil, and fuel lghts starting blinking like a christmas tree and the speedo starting going up and down real fast... 10 mph then 80 then down and up, you get the idea... so im gunna un hook the batt and let the computer reset its self and see how it runs after that... otherwise im gunna replace it with a unit from a local salvadge yard for 45 bucks and 60k miles on it.

[starla3366]

Hey,

Check this thread out:

http://www.automotiveforums.com/vbul...d.php?t=442455

[tblake]

have you tried a fuel injector balence test? You have a fuel pressure guage, just do a balnece test. It will help rule out any injector problem.

[richtazz]

check teh underside of your underhood relay center. They get exposed to road salt and such and can corrode on the bottom causing all kinds of electrical gremlins. Also check the battery posts (take the cables off and see if they are corroded where they connect to the battery) and have the battery load tested. Most electrical anomolies can be traced back to corrosion or bad connections.

[JOWRM]

Well i cant use JWORM420 Any more, tried for qwite a while to sign in today and it would not let me so im now jowrm.... but any way, i went and talked to a guy i know who owns JBR Automotive service, Jim told me that he has had this problem on a few cars, told me to pull the ignition module and have it tested, he said more than likely that is the problem, and if not check the ignition coil, and ciol packs... that was around the lines of what i was thinking, but was not sure. So im gunna dig into this damn car some more tonight!, i will let all of you know what i find out, and ill check the relay box's and what not for corrosion any way, you never know what you may find....... until tomarrow............................

[da_kingpin]

Have you considered checking your MAP(Manifold Absolute Pressure) sensor? As engine load and speed change so does the intake manifold pressure. That sensor monitors the pressure changes. the pcm uses the sensor to control fuel delivery and ignition timing.

Originally Posted by draaaca

Your problem sounds similar to what I am having on a 98 Pontiac Trans Sport/Montana

this is my problem, posted in the Pontiac forum, but still without answer:

My 98 Trans Sport Montana, 3.4L, has developed a problem.

When driving along, it intermittantly "surges" or "hesitates" , I don't know how to describe it really. It is like it is loosing all power but then it drives proper again.

No dash lights come on, no service engine light. I don't notice the tach reving high or falling off.

I am suspecting the fuel system. I had the fuel filter replaced and the pump tested. Mechanic said it had good pressure. But since it is intermittant maybe the pump is only running full pressure most but not all the time. Don't know if engine need makes it pump more or should always be one pressure..

It seems to have the problem when the vehicle is under load...like climbing a hill or wanting to get up to speed. If it is babied, I don't recall it happening.

To me it is similar to a chain saw problem...you get a piece of saw dust in the tank, and occasionally it blocks the fuel line by the piece getting in the flow, but then you shake it and it gets out of the way and then runs well again until that piece gets stuck in the line again. Does that make sense?

When the fuel filter was replaced, the mechanic said it was really plugged up, he could hardly blow through it
Could there be crap in the tank...how would I check?

Any constructive advice would be appreciated.

Thank you.

[draaaca]

It's been a while since I posted my problem.

I had it checked out and a couple of things came back.

The mechanic found that one of the battery cable was almost off of the bat. So it was causing some intermittent problems.
But after that it still had some surgeing.

A code was found and it related to the Transmission. I took it to a transmission shop and they said it indicated a bad sensor on the trans. I have no specifics on what the sensor is or does.

After that was replaced, it was a hot day, near 100 degrees and I drove more than my typical 9 mile to work trip, and it had a slight surge/jerk thing a couple of times, and along with at a whine or whistle noise. Was hard to tell.

But it only did it a couple of times after the longer drive in the heat. Later the same day, going back home for the short drive it made no noise aor had any proble, and none since.

The weather is getting cooler now and again, I am not driving a long distance.

So that is the condition for now.


All may be fixed...not sure, but no problem is showing.

[the6]

i have a 95 3.1 lum. it jerked all the time. it started after i changed oil and filter. really hard to start. hot or cold. finally quit.no fuel at tbody. if it has a 3 wire oil pressure sending unit short out the 2 across from one another. instant fuel. looks like i'm going to have to replace oil pump.

[zephram22]

Originally Posted by jworm420

well for those of you have not read any of my posts yet, haveing a car problem, when driveing, sometimes it feels like the fuel was shot off or the car was shut off and the car jerks, when it does you can not hear the motor running and then it is and isnt and back and fourth.... well i got a fuel pressure tester, the pump primes at 40 psi and holds it....i let it sit for over an hour and it did not drop a smidge... and with the car running it holds at 37 psi, or if its in a higher rpm its at 35 psi, whitch is perfectly normal...turn the car off and let it sit, and the gauge still says 37... so i really dont think its a fuel system probelm now unless i have some bad injectors that work only sometimes... ive rueld out the possablity if the IAC, now im thinking the TPS Sensor... Would O2 sensors cause this problem ? i dont think so cause no check engine light has coem on... now how about the TCC sylinoid, Where is it and what does it do exzactly... never had to change one befor ?... i may end up blwoing this car up out of spite at this point... Think im going to go pick up a noid tester and check and make suer that the injectors are getting constant voltage... Hopefully its not a computer takeing a hefty shit on me.

Hmm...Just for kicks you may want to check your battery connections, starter connections and alternator connections.