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89 TBI Problems (its gonna be long) but need input please

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 83ZZ502_Jimmy, Feb 3, 2004.

  1. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    Ok guys this is gonna be long but I will try and keep it as on topic as possible.

    Background:

    300,000 miles on the motor, but it has 50psi oil pressure hot at 2000RPM and 20 at hot idle. I've owned this since it was new. Been a great truck. Valve covers had never even been off until recently.

    About 10 months ago bad head gasket. R&R all put back together no problem. Ran great put 6000 miles on it. Fantastic!

    Skip ahead --->

    Missing a little at low RPM under load. Skipping a fire every once in a while. No biggie, DTC for a bad EGR valve. Installed new GM valve.
    Problem still there.

    Ok, next I start throwing parts at it. The following are brand new parts installed currently.

    EGR
    EGR solenoid
    Plugs
    Wires
    Cap
    Rotor
    New distributor
    New ignition module
    New 02 sensor
    New MAP sensor
    New coolant temp sensor
    New IAC valve
    New TPS sensor
    New fuel pressure regulator
    New injectors
    New fuel pump and sock
    New fuel filter
    New catalytic convertor
    New timing chain and gears
    Also tried a different (known good) tbi with the same results.
    edit: New GM ECM

    Now the funny part is that it ran ok, and would smoke the tires and idle perfectly. But when I got on the interstate it would start the same missing and now backfiring through the exhaust and manifold.

    But it was still running ok other than this.

    I let it sit for a week, and now it wont even start. WTF /forums/images/graemlins/confused.gif /forums/images/graemlins/angryfire.gif

    I have checked compression and get 140 +/- 4psi between all cylinders. It pulls 22" of vacuum at idle. Not bad for 300k miles.

    I got it to run a while later, but now, it runs terrible. Backfiring and such. The timing is Dead on right. The compression is still the same.

    Well come to present, I triued to start it and drive it around, I think I flooded it, so I was pulling plugs and broke one /forums/images/graemlins/doah.gif /forums/images/graemlins/doah.gif /forums/images/graemlins/angryfire.gif /forums/images/graemlins/angryfire.gif /forums/images/graemlins/doah.gif.

    So I need a new plug maybe all new plugs, cant hurt. /forums/images/graemlins/dunno.gif

    Any ideas from the gurus out there, or do I need a new engine. This truck has sentimental value, and being a 300k truck I am trying to hit 400k.

    I appreciate any responses I get, and thanks to all in advance.

    p.s. I may have left some parts or steps out. I will think of them as we go.
     
  2. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    Have you checked all vacuum lines for small splits that may be opening up under movement but ok when you checked the vacuum? An air leak to the brake servo unit can suck a lot of air, especially if the servo itself is leaking (how's your brakes?) Also, check your cruise diaphram. Apart from that, it sounds like you've changed just about everything else. /forums/images/graemlins/confused.gif No trouble codes?? /forums/images/graemlins/thinking.gif
     
  3. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    All new vaccuum lines. Cruise and brakes are fine. Both work great.

    And apart from that first code of bad EGR, no codes now.

    And I forgot /forums/images/graemlins/dunno.gif New GM ECM /forums/images/graemlins/angryfire.gif

    /forums/images/graemlins/dunno.gif /forums/images/graemlins/dunno.gif

    John
     
  4. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    I can only suggest that you take it to a reputable garage and they can fix it up to a scanner and drive it so they can see what's going on real time as it plays up. A scanner would show any probs as they happen on the road. Good luck! ( if you get a result, post it-I'd like to know what it is!) /forums/images/graemlins/thumb.gif
     
  5. daleearnhardt01

    daleearnhardt01 1/2 ton status

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    Hey John seeing what he wrote about the scanner...next time Im home on the weekend I can bring the laptop and ALDL cable over if you want, It should work with that truck...IM me. /forums/images/graemlins/grin.gif
     
  6. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    Yeah that is if I can get it to run again. It is very, very hard starting now. /forums/images/graemlins/dunno.gif

    John
     
  7. Thunder

    Thunder 3/4 ton status

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    Did you hook up the engine to body ground strap? Also might want to check all other grounds and connections.
     
  8. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    I have checked/cleaned all grounds. Made sure the battery was grounded to the block and body. The block to the frame and body via ground strapping.

    Thanks for the reply,
    John
     
  9. ron88k5

    ron88k5 Registered Member

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    could your cam be going flat /forums/images/graemlins/confused.gif just a thought
     
  10. dave_90_blazer

    dave_90_blazer 1/2 ton status

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    [ QUOTE ]
    could your cam be going flat /forums/images/graemlins/confused.gif just a thought

    [/ QUOTE ]


    I was thinking that too
     
  11. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Pull the distributor cap. Watch the rotor and turn the motor colockwise by hand till you get it on TDC.

    SLOWLY turn the engine backwards by the crank till the rotor starts to turn. Look at the timing tab and see how far you had to turn it. That will give you an idea how much slack is in the timing chain. 8degrees is ehhh....over 8 your starting to have some problems. Valve timing will be off, The cam will pop and that will cause the goofy idle and running.

    As good as the rest of the motor is, 300k is a LOT of miles on a timing chain Especially if it's a nylon covered timing gear style. I had significant slack in a chain (allbee it a chep part from a Legit rebuild errr retrash) and had to change it at 60k.
     
  12. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    Grimmmy-

    I put in a new timing chain and gears.

    John
     
  13. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    The cam going flat will do that? I guess it would. Will a hydraulic roller lifter let the cam go flat? I am sure that this motor has roller lifters. /forums/images/graemlins/confused.gif


    But let me throw this scenario at you guys.

    It was running as stated when it first happened. Changed EGR, no help. Then installed a brand new distributor, this seemed to clear up all problems. It ran like it was brand new. It had lots of power and idled great. Started easy and everything. Then I took it on the interstate and it started acting up it again.

    Now at present, it is very hard to start and idles bad. But, when it runs it will run pretty good and have descent power. And when idling, you can open the hood and barely hear that the motor is running. It is that quiet.

    I have had several GM shops/dealers (where I know the techs) scratch their head on this one. They basically told me to replace everything I already had replaced. They have no idea, and I really dont want to throw more money at it.

    So if you guys really think the cam is flat, so be it, but it just seems funny that it would go bad and still run great, then run bad again. /forums/images/graemlins/dunno.gif /forums/images/graemlins/dunno.gif

    John
     
  14. dyeager535

    dyeager535 1 ton status Premium Member

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    My dad had a cam lobe go flat on his 454 while on the freeway, and it started misfiring. He drove it probably 150 miles before being able to tear into it, but it didn't run that great.

    It sure sounds like a possibility. On his, with the lobe being flat, with the valve cover off, it was obvious as the motor was rotated which cylinder was "dead", since the rocker didn't move at all. Not sure how easy it is for you to get a valve cover off, but if it is easy, it would be a simple task to check.
     
  15. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    Yes, Dorian, that will probably be my next thing to check. I got one side off and the rockers were moving ok, but didnt pull the other side.

    We shall see.

    John
     
  16. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    The '89 350's were hyrdalic flat tappet cams IIRC... roller didn't come in those motors until later on in the 90's.

    I too would look at the cam as the culprit. My 454 did the same thing once, and behaved much like what you are describing.

    Also, get it running again, and have your buddy come out with WinALDL. That will tell you EXACTLY what the ECM is seeing, and what is really going on. If for some reason you aren't getting closed loop, perhaps you aren't getting the codes?

    I gotta say though, hat's off to you for sticking with it this long. Thats one helluva parts list you have going there. However, I wouldn't lay blame on the engine just yet if its pushing proper compression, and pulling decent vacuum as you indicated.

    Have you checked fuel pressure? Is the fuel pump known good? Even though you replaced it, I've heard of new units being defective, after short-lived lives in the tank. Have you replaced the fuel pump relay?

    Last but not least, I've been told that its a good practice to run a sm. gauge ground wire from the block to the case of the ECM. This is to insure that sensors have a good ground to the ECM, as to reduce variance in readings.

    Thats about all I can suggest without WinALDL, or without laying a hand on it. Hope this helps.

    -Dan
     
  17. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Best thing to suggest here is not to forget the basics either. Go back over everything, make sure you have good connections, check filters (fuel especially), AND ACTUALLY...

    check your harness's power wires. All the wires that go to the junction on the firewall.... I've recently been witness to a few trucks running "strangly" due to certain wires there cracking, corroding, or just otherwise flaking out.

    Check the connections at the ign. coil too come to think of it. Anyone who has expereinced this could vouch for me... I'm really not insane... it has happened to two or three trucks that I know of personally.

    Again, hope this helps.

    -Dan
     
  18. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    Well, I have a "little" secret on this one /forums/images/graemlins/whistling.gif, its a 4.3L V6. It does have the roller lifters from what I have researched.

    Could the cam go flat with roller lifters? I am not putting anything past this thing anymore. If it did, would I have the compression and vaccuum that I currently have?

    And yes, I have done the fuel pressure check. I borrowed a friend of mine's (a gm tech) inline guage, drove it around and the pressure never flucuated.

    I am going to try to get it running again, I just had to take a break from it, cause it was making me so angry. When I do get it running, I will definately post up as to what the problem was.

    Thanks for the Kudos on me sticking it out. I am determined to find out what is going on. And, also, thanks for the reply, it is much appreciated. /forums/images/graemlins/bow.gif

    John
     
  19. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    [ QUOTE ]
    Well, I have a "little" secret on this one , its a 4.3L V6. It does have the roller lifters from what I have researched.

    [/ QUOTE ]

    Right, an 89 4.3 could very well be roller. Having said that, I would most likely discount the flat cam theory. But only after verifying that its indeed a roller motor.

    Timing. Where do you have it set right now? I recently dropped a new 4.3 in an aquaintance's truck and found that it would run like a bat out of hell at 11* in WOT situations. It did make for "less desirable" behavior off idle in regular driving situations. I'd start by setting it to around 6-8* and see how that feels. I'm only thinking timing because you say its back firing. If its back firing, its timing related.

    Good luck figuring it out.

    -Dan
     
  20. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    The power wires? Where they go into the cab, or the battery cables themselves? Or all power wires?

    This maybe a new idea, that I have overlooked/missed.

    I will check the coil wires again.

    Thanks
     

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