Fuel issue
#1
CF Beginner
Thread Starter
Fuel issue
I have a 1999 k1500 obs 350 spider injected with the engine and trans out of a 98 with less than 150k on both....when I lay on the throttle it'll shift nice but the engine stumbles like its gettin to much air and not enough fuel or vise versa then after a couple seconds she'll get up and go like normal. I have codes for low voltage on o2 sensors and spark plugs on cylinders 1,5, and 7 have a big white spot just like they're is no fuel or not enough fuel getting to the cylinders. The o2 codes have always been there and this problem just started recently so could it be the injectors, fuel pump, or something else? Any help is greatly appreciated
#2
CF Monarch
I have a 1999 k1500 obs 350 spider injected with the engine and trans out of a 98 with less than 150k on both....when I lay on the throttle it'll shift nice but the engine stumbles like its gettin to much air and not enough fuel or vise versa then after a couple seconds she'll get up and go like normal. I have codes for low voltage on o2 sensors and spark plugs on cylinders 1,5, and 7 have a big white spot just like they're is no fuel or not enough fuel getting to the cylinders. The o2 codes have always been there and this problem just started recently so could it be the injectors, fuel pump, or something else? Any help is greatly appreciated
#4
CF Junior Member
Join Date: May 2014
Location: St. Augustine
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I cannot stress it enough. I just rebuilt the top end on a 98 Vortec 5.7L because the intake gaskets were blown...
If you no nothing about the engine expect these to be bad.
Also, check the coil tower (pics in profile)
If you have a K&N air filter, to much oil will cause a dirty MAF and you'll need to clean it. Just a slight pink hue to the air filter keeps it ok.
If you no nothing about the engine expect these to be bad.
Also, check the coil tower (pics in profile)
If you have a K&N air filter, to much oil will cause a dirty MAF and you'll need to clean it. Just a slight pink hue to the air filter keeps it ok.
#5
CF Beginner
Thread Starter
The only code I have is for bank 1 running lean I don’t remember what the code was but ik that’s what it said and I haven’t cleaned the MAF or checked fuel pressure yet but I’m pretty sure it has good pressure bc it starts up right away with no problems even when it’s 30 degrees but idling you can hear it missing but not while the engine is under load...I’m starting to think it’s my exhaust manifold and/or my intake gaskets leaking
#6
CF Monarch
The only code I have is for bank 1 running lean I don’t remember what the code was but ik that’s what it said and I haven’t cleaned the MAF or checked fuel pressure yet but I’m pretty sure it has good pressure bc it starts up right away with no problems even when it’s 30 degrees but idling you can hear it missing but not while the engine is under load...I’m starting to think it’s my exhaust manifold and/or my intake gaskets leaking
As for the intake gasket leaking, you can spray some WD-40 on it, If it clears up, its bad, if not its easy to clean the WD-40 off. I've known guys to use gasoline to do this but that's a bit dangerous and not a good idea at all, but a leak will speed the motor up. Might want to hook up a vaccum guage and see if it stays steady too. If not you have an issue with a leak or something similar.
#7
CF Beginner
Thread Starter
I’ll do the WD-40 trick and clean my MAF sensor this weekend...I went to buy a new fuel pump last weekend but I didn’t know which one to get does it matter what the GPH are?
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#8
CF Monarch
The main thing is that your fuel pump is putting out enough pressure to the fuel pressure regulator. Technically, I believe the fuel pressure for your vehicle is 60 PSI, but am pretty sure range can be 55 to 62 PSI or so. If you decide to change it out, my personal belief is to stick with a stock AC Delco unit, But Delphi's are supposed to work well.
#9
CF Beginner
Thread Starter
Update: changed the fuel pump with a precision brand and the fuel filter with micro guard from Oriellys and it fixed it for the most part. Pulled the spark plugs and checked them 3 are bad so just gonna do another complete tune up with better plugs, wires and cap