Search the Community
Showing results for tags '1996'.
-
1996 GMC Sierra 7.4 C3500 strange engine problems.
sonicdude10 posted a question in Ask the GM Technician
New guy here with engine problems. All parts are stock. No modifications have been done to engine and engine management to our knowledge. With that said, here is what is going on. Truck is a 1996 GMC Sierra. Crew cab, long bed, C3500, non dually. Has 7.4 454 Vortec and 4l80e transmission. Driveline has 147,000 miles and engine has good compression. All cylinders read 120 to 140 PSI. What's going on is the engine refuses to run properly. First up is the MAF sensor. Had the engine light on the dash so I used our OBD2 scan reader on it. Got P0102 which is Mass Air Flow sensor low output. Replaced the sensor with a Bosch unit and cleared the code. Next engine start that same code came back. I checked all the wires and plugs that section of the harness goes through. It has a good run to the computer. No frays or breaks. I even reset all plugs thinking there might have been some resistance in the connectors. No dice. Code comes back every time I clear it. Any ideas? Next up is the really serious problem that prevents the engine from running properly when cold. Low fuel pressure. According to our gauge it only has 20 PSI max and leaks down as soon as the pump turns off. On the fuel system we have a new pump in tank, fresh filter, and new regulator. That was a pain to install as the top of the intake manifold had to come off. Still have the low pressure and leak down. We thought the injectors were leaky but the thing is lean at idle as we sprayed starting fluid in the intake tube and the idle evened out. When cold it doesn't want to idle at all but will even out at 650 to 750 RPM when warm. Any idea what is going on? We have no idea what type of pump is in the tank as the people who own the truck put it in before we were tasked with fixing it. Still have the stock one. We plan to pressure test it and if it can go up to at least 80 PSI we will just put it back in and see what happens. So, any ideas on what is going on? I can record videos if any of you want to see the engine and hear it running. If anyone can figure this out I would greatly appreciate it as this goes beyond my knowledge of fuel injection problems. -
I have 96 with the 5.7 and it's been running lean for a while bank 1 and 2 and can not figure out what is causing it. I have changed maf sensor tps sensor new spark plugs there was a code for malfunction o2 sensor i replaced that and I also put some injector cleaner in the tank also changed fuel filter. The truk idles fine but when I put it in reverse and drive and im crawling/creeping along like backing out of the drive way its stuttering and running rough like its about to die/shut off and usually ill get on the gas a little and it will start running fine. It runs fine once I get going 10-20mph on up from there its just when I fire it up and get to rolling and foot is barely on the pedal. Also not even a week ago truck gauges would go to 0 and would get stuck in 3rd ended up being a ground on back of the engine. I do hear a small leak under the driver side could be exhaust manifold or where the flange is right under it where the pipe connects but I don't think it would cause it to run lean. Tomorrow i'm going to check fuel pressure, all I can think of is bad fuel pump, regulator, maybe intake manifold gasket even though I don't see any signs or even a bad ecm. Any help would be appreciated. Also should there be a little bit of oil in the air intake tube? its also in that vent that just pops in the side that comes from the top of the valve cover. its oily around the bottom too where it goes into the cover.
-
From the album: random
quite a chore to get these out. -
- 1 comment
-
- 1
-
-
- 1996 gmc sierra
- 1996
- (and 6 more)