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Could use some help with engine performance problems

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 1989blazer, Jan 7, 2004.

  1. 1989blazer

    1989blazer Registered Member

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    My Blazer's high-rpm performance has really degraded lately. If I floor it in first, it revs but there's no giddy-up. No miss though. It idles fine, but also has a tip-in miss on slight hills. I had a mechanic check it and he said timing's fine, fuel pressure's fine. No codes. No lights. I had the cat and muffler replaced (flowmasters!), but it only helped low-rpm performance. It's a stock engine with 150k miles. Burns a quart about every 2k miles. I'm wondering ECU? rpm sensor? injectors? This a real head scratcher. I've got WinALDL and a home made cable, but can't seem to get it synced with the ECU. Any thoughts on any of these problems would be appreciated!
     
  2. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    Maybe it's in your tranny, if the motor is running good and sounds good at upper RPM's than I doubt it's the motor.
     
  3. 1989blazer

    1989blazer Registered Member

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    Yeah, I thought tranny too, but it was rebuilt about 5k miles ago and to double check, I had a mechanic check it 2 days ago - he said it's fine, fluid not burnt, engine doesn't rev to heaven when popped (!) out of gear. He claimed a bad torque converter will slip at low rpm as well. But, hey, he could be wrong...
     
  4. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Man, that sounds an awful lot like bad wires or improper plug gaps/fouled plugs. Although I would think that would show up as a code....../forums/images/graemlins/confused.gif
     
  5. tungsten

    tungsten 1/2 ton status

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    The first thing that comes to my mind given what you've told us is a loss of compression on one or more of the cylinders. Have you had a compression test done on it yet?
     
  6. 1989blazer

    1989blazer Registered Member

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    First of all, me being new to this forum, thanks to you all for helping out! WRT to compression - my mechanic said that it was even across at 165 - 170. I asked about plug fouling, but he said there wasn't any. I may double-check this weekend.

    So, I think I figured out my ALDL issue - I need to pull up the transister to 12 VDC because my laptop isn't providing power to the DTC pin. Hopefully, I'll get a reading tonight. I'll post anything interesting. I did a Google search on trouble shooting this kind of thing. Along with ignition wires (Thanks for that!), the fuel filter seemed like the next step. I'm trying to be rational now and start with the cheap stuff first.
     
  7. 1989blazer

    1989blazer Registered Member

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    OK, after driving around this afternoon with the newer louder muffler, it's definitely missing at high rpm. It maxes out at about 3500 RPM with WOT in first - missing the whole way. OK, now were getting somewhere.
     
  8. 1989blazer

    1989blazer Registered Member

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    Well, replacing the fuel filter got me back the giddy-up. Next step: 3/4 ton axles with 4:10 gears.
     
  9. sickquad

    sickquad 1/2 ton status

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    Had the same problem and the fuel filter fixed it. Sorry I didn't see your post earlier.
     

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