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Sargee · 09-28-2012, 11:11 AM

check engine light comes on once in awhile right prior to coming on can feel slight hesitation in gas pedal if release gas pedal just for couple seconds light doesnt come on - if on cruise and dont feel the pedal the light comes on and loose some engine power for approx 20 seconds light goes out and full power again. done this going up hill or down hill coasting towards stop sign even.
Will do it 1-2 times on 100 miles. also motor is very very cold blooded need to let warm up for 10 minutes even in warm weather or labors to get going hesitates/gallops etc let it warm up and all is well even while idling can hear when it smooths out.
Was happening more often changed fuel filter and now happens less often and not as harsh.
thanks for any input besides this occasional item engine runs/pulls great up down hills wind etc

Skip426 · 09-28-2012, 01:08 PM

1990, in automotive was a OBD 1 connector, so the newer OBD 2 ( II ) read out box won't do you any good. The cold too long will no doubt be an engine thermostat issue, so you could start with replacing that, engine should reach full operating temp in 3>4 mins if not sooner when moving. Cold too long will set a code, but not always turn on the light, so you may need a scan if the light continues to come on after you replace the T'stat.
From the rest of your discription, I'm thinking , lazy O2 sensor or leaking fuel injector, scan will narrow it down.

Sargee · 09-28-2012, 03:07 PM

I need to add - scan says fuel pump problem - but it doesnt act like a fuel pump at all. a fuel pump in my experience doesnt give you warning at darn sure doesnt only act up when the light is on. I feel its some type of sensor because it does it the same every time and very clsoe to the same length of time again no change on pulling a hill or coasting towards a stop. I simply havent seen anything like this I grew up on farm been around every type of engine imanginable from 2 cylinders to massive diesel engines. thanks for any ideas - safe travels to all

George Schweikle · 09-29-2012, 07:00 AM

Did you change the "Hidden" fuel filter; next to the frame, about halfway between the gas tank & engine?

Quote:

Originally Posted by Sargee

....Was happening more often changed fuel filter and now happens less often and not as harsh...

Sargee · 09-29-2012, 07:13 AM

One fuel filter was changed had local guy do it is there two fuel filters besides the screen inside tank with fuel pump? Thanks

monkey · 09-29-2012, 09:47 AM

Quote:

Originally Posted by Sargee

One fuel filter was changed had local guy do it is there two fuel filters besides the screen inside tank with fuel pump? Thanks

If it's like our 95 chevy, the "screen" in the tank is actually like a "sock", that fits over the end of the pump. (just replaced our in tank pump) and I could see where it could get plugged up. As far as I know, ours has only the one inline filter, also replaced.
Monkey

Skip426 · 09-29-2012, 09:47 AM

Sargee, good possibility that there is a second in-line fuel filter, as George says, only way to be sure is to examine the whole line , tank to engine.
However, the irratic nature of the problem points to the pump.A plugged fuel filter doesn't un-plug.
The fuel pump code, if GM monitors the pump the same as Chrysler, I'm 99% sure they do, the ECM, Engine Control Module, looks at the amount of power the pump is using, if the power draw goes above or below limits the code is set. If fuel pressure drops while driving, good chance that the O2 sensor sees a lean condition and turns on the light; light on indicates an emmissions problem; when the pressure comes back up the O2 sensor & ECM see normal operation and no code for running lean is set, light goes out. This is the kind of problems that OBD 2 corrected with better monitoring of trouble codes and tracking the occourance & storing info to pinpoit the problems.
The only way to test out your problem, would be to road test with both a manual fuel pressure gauge & the scan tool hooked up, and get info when the power loss occours.
A story, and I'm sure this isn't your problem. Pick up came to the shop with an irratic quit problem. Would stop and not restart for 2>3mins. We could not duplicate the condition and decided we had to change the pump ( in tank electric ) Turned out to be a rag floating arround in the tank, it would be sucked onto the pick-up screen and stop the motor, when the truck coasted to the side of the road the fuel slosh in the tank would wash it away from the screen and the motor would re-start.
Murphy's Law , in full force.

jlfbatonrg · 09-29-2012, 09:57 AM

Had a similar problem on a 92 class A with 454 engine. Turned out to be the fuel pump. Rather than dropping the tank, mechanic installed an external fuel pump. Worked great until we upgraded to another coach.

Sargee · 09-29-2012, 10:15 AM

Thank you everyone an in line fuel pump was what local mechanic said to try. It runs so well except those little spurts. Brand new to RV scene enjoying the heck out of it. Thanks all I will be asking more questions.

wonderer1 · 09-30-2012, 04:07 PM

1990 you didn't say is this carburated or throttel body injected or multipot injection. if it were my motorhome, i hate to have a problem that goes away before i can check. that being said i would install a fuel presure gauge in the cab ( i'd tee it so i'd have one on the engine also )so when it acts up i have an idea what and where to look. i love gauges (can't have to many). it's easier for a mechanic to find something if you can say when this happened this is what the gauge did. lots of times it won't act up for the mechanic. but with additional info it can help him, also with the additional gauges he might listen to you more sence you are smart enought to add some more diagusting tools.