bad gas milage =/

[gmanpaint]

True.

Fuel pressure test needs to be performed. Pump may be weak. Filter may be bad.

There could be an injector issue, either mechanical or electrical. Codes should be thrown here tho.

Its kind of sounding like a blown intake gasket, the more I think about it.

 

[Mountaineer50]

try checking the plugs if they are not tight enough then it will run lean. its a quick fix

 

[1AJeremyD]

True.

Fuel pressure test needs to be performed. Pump may be weak. Filter may be bad.

There could be an injector issue, either mechanical or electrical. Codes should be thrown here tho.

Its kind of sounding like a blown intake gasket, the more I think about it.

Good point with the gasket. I saw on here someone ran propane along the gasket and if the engine smooths out then it most likely a leak. The engine might be compensating for the extra air my inducing more fuel into the system. Always worth a shot I guess.

 

[llamaking122]

See thats the thing, if it just had a bad MPG deal then I would say for sure FPR on the rail. Since his stumbles at idle but not under load that just seems more towards fuel not getting to the engine. The FPR would as you said dump fuel into the system and richen everything out and create not just one but maybe multiple misfires if the engine could not compensate for the excess fuel. He could end up having a couple of related problems. Never hurts to rule out all possibilities though

When my dads ex had a crank sensor going out. It acted like a fuel filter and my dads been a mechanic for 30 years even thought it was a fuel filter. For an unrelated issue we replaced the cranks sensor and the feeling that the fuel filter was going out was completely gone.

 

[llamaking122]

Good point with the gasket. I saw on here someone ran propane along the gasket and if the engine smooths out then it most likely a leak. The engine might be compensating for the extra air my inducing more fuel into the system. Always worth a shot I guess.

Will try that! How hard are they to do?

 

[llamaking122]

would starting fluid work as well?

 

[llamaking122]

Ok so today thee idling problem got worse. I started it up and it was surging too 1200 then it would fall and fall and fall until it almost stalls. But it caught itself. It would idle differently even if I had my foot on the gas. Trying too hold the idle steady. Then I put her in gear after it starts too even out and it's idling good. And it did the same thing later in the day. I should have mentioned the other day I was driving around and attempted to come too a stop and it was harder then normal and I stop and the idle is at 2000 rpms I go home pull off the iac and clean it with carb cleaner and viola it's better

 

[llamaking122]

So today I had some free time and looked at my car. Pulled the vacuum hose off of the fuel pressure regulator and plugged it with my finger. And viola the idle smooths out. Did starting fluid around intake manifold and stuff and no change in idle

 

[llamaking122]

ok the other day i replaced the FPR (gas puring out of vacuum line hole thing) and i get better gas milage and the idle is ALOT better no surging what so ever. but im still not getting good gas milages maybe 200miles to a tank. i havent replaced the O2 sensors but looking under there the passenger side O2 sensor looked like it was falling apart almost

 

[llamaking122]

bump!

 

[huntman58]

After replacing the FPR did you reset the EECU?

Best way is to disconnect the neg battery cable for about 5 to 10 mins.

The reason for doing this is your truck has been trying to set its self for the over fuel deal so now it needs to relearn how to run with the right amount and that may also help you MPG also. Just remember when you replace parts that involve the motor to do this as it helps the motor relearn for the new parts even if they are not run by a sensor other things that are affected by them are.

 

[llamaking122]

After replacing the FPR did you reset the EECU?

Best way is to disconnect the neg battery cable for about 5 to 10 mins.

The reason for doing this is your truck has been trying to set its self for the over fuel deal so now it needs to relearn how to run with the right amount and that may also help you MPG also. Just remember when you replace parts that involve the motor to do this as it helps the motor relearn for the new parts even if they are not run by a sensor other things that are affected by them are.

Thought you only did that for idle problems but will try that today

 

[jordan101]

im getting bad gas milage but i tgink mine is from the 02 sensors

 

[mcelwajy]

I have the same issue with MPG but mine is due to an exhaust leak. Excess air is flowing into the exhaust and messing up my O2 readings and the ECU is compensating by running chokingly rich. To be fixed this weekend tho...

 

[clamb]

Can a bad valve cover gasket create a vacuum leak? I have a terrible oil leak from the drivers side valve cover gasket. I tried to tighten up the bolts, but it seems like I may have made it worse, it has split, & pushed out the gasket around the bolts. Will disconnecting negative terminal reset the fuel trim codes. I just took it into the local garage to try to resolve low fuel economy issues, they didn't do anything but clean the MAF sensor, & reset fuel trim codes. I have never been able to pickup a engine code problem, but it has never passed the Evap systems check.

 

[llamaking122]

So replaced one oxygen sensor and then unhooked the battery and ran good for a while. Then it's been missing even more. I did get a little anti seize on the tip but I cleaned It off. But it was fine for about ten miles though then the gas milage went down the toilet. It's kindof like after the computer went back to normal the gas milage when back down the toilet. I'm sort of thinking this weekend after replacing the second oxygen sensor to maybe look for a new computer. What are your guys thoughts

 

[llamaking122]

this weekend i am going too replace the other oxygen sensor. rear abs sensor (unrelated) and engine coolant temperature sensor. i will update you after this is done. and i will pull off the maf and clean it again. mainly because A. im going to replace the aur filter B. i only remember 1 filament on it not 2 but i wasnt looking for that. so i might as well take the 5 mins and pull it back off.

 

[llamaking122]

oh and if it is broken i will be taking a trip too the jyard what all mafs can i put in here? 1994 4.0 OHV

 

[llamaking122]

so i did not replace all that stuff. i thought i would be getting paid more this paycheck but i guess im as good at math as a 5 year old haha. me and my dad are gonna go over it with a fine toothed comb (vac lines) the more i think about it the more i think it may be. or a fuel filter. it does miss under throttle. i feel it more after replacing one O2 i didnt get around too changing the other O2 beacsue my dad shredded 2 tires on his ex in a month so we went to the jyard too get something till he has the money too buy a full set