Driving Me Nuts Help

[96chevy7.4L]

Hi guys my truck is driving me nuts help. It sputters and misses and just runs like crap when stopping at a stop sign or red light. You can open the driver door and smell it running real rich. No check engine light. Cleaned the mass air sensor, cleaned the throttle body. Checked the fuel pressure at the service port I have 55psi. Put in a can of sea foam to rule out bad gas. Its been doing this for a few days now. Went on a fairly long trip and burned out that tank of gas when it started. It now has shell 93 in it. Yet yesterday it cleared up and now this morning its back to its bad behavior. The TPS is new and so is the MAP sensor. Any ideas before I burn it.

[dwhults]

Vacuum leak? Maybe O2 sensors? When my Jeep had a vacuum leak it ran like shit.

[SierraJoe1110]

I would have to agree. I would start by looking for a vacuum leak and then if you can find one look into the O2 sensor

[Stevens03]

When was the last time you changed the fuel filter? If thats out, then I'm with the others,... possible vacuum leak.

[dlewis1111]

Hi guys my truck is driving me nuts help. It sputters and misses and just runs like crap when stopping at a stop sign or red light. You can open the driver door and smell it running real rich. No check engine light. Cleaned the mass air sensor, cleaned the throttle body. Checked the fuel pressure at the service port I have 55psi. Put in a can of sea foam to rule out bad gas. Its been doing this for a few days now. Went on a fairly long trip and burned out that tank of gas when it started. It now has shell 93 in it. Yet yesterday it cleared up and now this morning its back to its bad behavior. The TPS is new and so is the MAP sensor. Any ideas before I burn it.

 

pcv valve

pcv valve

pcv valve

 

had one do the exact same thing did i say it was the pcv valve?

[96chevy7.4L]

The fuel filter was changed about 5,000 miles ago. I will definitely look at the PCV valve as I haven't changed it in quite a while. A vacumn leak is another great idea. Thanks for the help I will keep you posted.

[pm26]

Make sure that your EGR valve is not stuck open due to carbon buildup. That will cause serious running problems.

[96chevy7.4L]

How do I check the EGR? I know where it is and its never blinked a code. Does it need to be checked with the engine cold? If so it should be in what position? Is there a way to clean it?

[sternforpres]

I had something similar, but it also came with a warm start issue...it was the fuel pressure regulator...easy to check too, just pull the top hose off (vacuum line), if there is fuel in there...replace it.

 

http://www.automotiveforums.com/vbulletin/...;highlight=warm start

[96chevy7.4L]

hi guys just an update. Its not as bad as it was but it still real aggrivating. Where is the fuel pressure regulator on a 99 7.4L engine? Does the upper intake have to come off to change it? Going to pick up a fuel filter today and see if that helps! I will try another PCV valve also. I bought it and its really small. I had the intake off my 96 that I had to put in bigger injectors but didn't see the pressure regulator anywhere. If it was the fuel pressure regulator would it still maintain proper fuel pressure at the service port? Are O2 sensors next as there are 4 and there not cheap. HELP!

[96chevy7.4L]

Turns out the fuel filter didn't work. Didn't improve at all. The EGR wasn't malfunctioning. Fuel pressure in spec. Plugs are clean not real rich or black.n So I went back to basics and come to find out it very well may be a fuel pump relay acting up. I replaced it today and the truck is 100% better. Got rid of that cheap relay that I got at one of the auto parts places and got an AC-Delco. Never even heard of a relay causing these kinds of issues. You would think a relay would either work or it wouldn't. Anyone ever have this problem. Curious to know.

[dwhults]

That's good you found the problem. Another thing to add to my list of areas to check.

[ShoddyHog]

Damn! Thanks for following up...never heard of that.

 

Gerry

[C. Charles Hahn]

We had a similar issue to this with a buddy's Vortec 350.... ended up replacing the ignition coil and that solved the problem.

 

Interesting that a relay would cause that.... I'll have to keep it in mind in case it ever comes up again.