Sluggish 4.3 V6 *Desperate*

Discussion in 'GM Powertrain' started by bigdigv65, Oct 6, 2012.

  1. bigdigv65

    bigdigv65 New Member

    Title says it all. Here is the history.
    I had been having trouble getting my truck to start. 1997 Chevy Cheyenne 4.3 V6.
    I forget the codes but they read "lean"
    I changed my fuel pressure regulator on Friday 10/5/12
    At that time I decided to clean out my EGR valve.
    upon start up it ran terrible. Before it was just a hard time starting it. Now it runs pretty bad.
    I assumed I killed the EGR valve when I cleaned it so I bought a new one. Same problem.
    When I attempted to check the plugs, I broke a plug wire. So it has new plugs and wires.
    Today I stripped everything back down to the fuel spider and fuel pressure regulator to check for leaks. Figured I knocked something loose maybe. No leaks. Everything was dry.
    Put everything back together, crossed my fingers and it still runs rough.
    I took it on a trip. The truck idles fine. When I accelerate it bogs down. If I try to rev the engine it bogs down. Even with cruise control on climbing a hill it bogs down.
    Fuel pressure regulator
    EGR valve
    plugs and wires

    Runs very sluggish.
  2. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    Double check that you did not cross wires when changing them. I would change the distributor cap and rotor also. What about the fuel filter? has that been changed? I would also change that.
  3. bigdigv65

    bigdigv65 New Member

    I posted and it didnt take,
    I have re-checked the plug wires many times.
    I forgot to mention that I changed the fuel filter last week. (tunnel vision here)
    I was reading last night after I posted here that this is classic fuel pump going out. Does that make since?
  4. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    And the air filter

    Maybe, it has been my experience that a fuel pump will work fine, shut off the truck and it will not start ---- pump failed. I have never had one act bad before it failed.

    But, a pressure gauge will give you an instant check.

    While your at it, a compression check might be a good idea.
  5. bigdigv65

    bigdigv65 New Member

    I'm running out of funds here. Is there any way to check the air filter before buying a new one? Can I just take it out and run the truck without it for a few minutes? I don't have a fuel pressure gauge. I'm about to get out there and pull the inlet side of the fuel line to the filter and see what kind of stream I have visually.
  6. bigdigv65

    bigdigv65 New Member

    Sorry to double post. I didn't want to edit the other pot that some may have read.
    I disconnected the "air meter" on my intake tube right next to the air filter. It runs like a champ. No more sluggish acceleration or revving issues.
    Is it safe to say that air meter is bad? I hope that's not a stupid question. Been a very long three days.
    Also, I still have cold start issues? I had to crank my truck 4 times before it fired up this morning. Could this air meter cause that as well?
  7. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    The "Air meter" AKA Mass Air FLow sensor (MAF) could be bad, but what I find odd is I normally have problems with an engine running worse when you disconnect the MAF, some engines wont even start when it's disconnected. Doesnt mean it isnt the problem though.
    Do you know anyone that'll let you borrow a maf long enough to check the system?
    That check is certainly easier than what I was gonna recommend which is to look at the fuel spider, it's been known to be a problematic part on the 4.3.
  8. bigdigv65

    bigdigv65 New Member

    I may have a friend or two that have this on their truck and may let me use it as a test. What scares me is the cost of it. Say I have an electrical problem that blows theirs too. Now I buy two. Does that make since or am I was over thinking this.
    I just drove it to a friends house. Drove fine to and from.
  9. bigdigv65

    bigdigv65 New Member

    More testing today. I took the MAF out and cleaned it with a qtip and rubbing alcohol. I got a lot of dirt off of it.
    I plugged it in with the engine running and the engine's performance remained the same. However, when I plugged in the air temp sensor, I bogged down and backfired into the air filter box.
    I went to the parts store, took it out and tried to clean it. Same.
    I bought a new one, everything seems fine engine wise but it is or was running super rich. I won't know if this helps the cold start issue until tomorrow morning.

    Anyone had a heck of a time with an air temp sensor?
  10. bigdigv65

    bigdigv65 New Member

    It was ultimately the fuel pump. Tested pressure with the key on.....50 PSI. Pressure would bleed down to 10 PSI inside of 15 minutes. Running 40 PSI. Kind of surprised the truck started at all.
    I also found that the sluggish part to this was a dirty MAF and I replaced the air temp sensor by the filter. Air temp sensor had it running bad. Fuel pump made it hard to start cold.

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