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Serious Probem! Very Serious!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 88K5Rhododendron, Oct 14, 2000.

  1. 88K5Rhododendron

    88K5Rhododendron Registered Member

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    This problem is difficult to describe... but I will try to describe it as intricately as possible...

    My blazer.. as the name implies... is an 88 K5... stock 350 tbi... Anyway... I was on my way home from gresham, and when I let off the gas the oil pressure dropped to 0 and the service engine soon light came on (This was at 60 mph) I gunned it a little and the oil pres. popped right back up, and then I let back off and it dropped again. So I pulled into shorty's corner and was completely found myself excrutiatingly confused.... A recurring problem I have had before was poor idling... the scan code checkers returns the MAP sensor as being bad... which made sense... but tonite... it wasn't just idling poorly... it was misfiring! Horribly badly as well! So the idle was all over the place... my oil pressure would drop to 0... it would react and way over rev and be misfiring the whole time... And I can't get it to start up with out the pedal to the floor now... (Plus when I do get it running.. or moving, my power brakes and steering go out when I let off the gas) Please help! I have to go to school on mon!

    Thanks!

    Matt


    gasoline4life! Or rocket fuel... I could see my blazer with some rockets on it... :)
     
  2. 73Jimmy

    73Jimmy Registered Member

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    Broken/Cracked distrbutor cap? You have to look at the inside carefully to see the crack lines.
    I had this problem a couple of times with my rebuilt 350 'til I replaced the distributor
    (used the same old distributor in the rebuilt engine, not recommended, too much slop in the old
    worn out distributor..).

    Unless you have replaced the cap recently, it is an inexpensive thing to try.

    Good luck
    Sj
     
  3. 88K5Rhododendron

    88K5Rhododendron Registered Member

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    Here's a little update.... I just ran it through the scan codes and it returned code '33'... I don't have a manual.. so If someone could tell me what that code is... it would be greatly appreciated... Thanks! Matt

    gasoline4life! Or rocket fuel... I could see my blazer with some rockets on it... :)
     
  4. 90K5

    90K5 1/2 ton status

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    33
    Mass air flow sensor (MAF)- signal voltage or frequency is high during engine idle.
    OR
    Manifold absolute pressure (MAP) sensor- signal voltage is high during engine idle.

    90K5
     
  5. 88K5Rhododendron

    88K5Rhododendron Registered Member

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    Thanks amigo!

    Could the MAP sensor cause it to misfire?

    gasoline4life! Or rocket fuel... I could see my blazer with some rockets on it... :)
     
  6. grtwhite

    grtwhite 1/2 ton status

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    I think 90k5 may have found the culprit. Here's what Chilton's has to say about the Map sensor.
    The Manifold Absolute Pressure sensor measures the changes in intake manifold pressure, which results from the engine load and speed changes, and converts this to a voltage output. It also says the ECM uses the MAP sensor to control fuel delivery and ignition timing. Hope this helps - Jay
     
  7. archer

    archer 1/2 ton status

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    Among the other things you need to check your evaporative emissions controls. They will effect the the other sensors causing trouble codes. EGR valve, PCV, vaccuum dashpots, vac hoses etc. Also make sure that if you have a catalytic convertor the catalyst han't melted. If you've smelled rotton eggs lately that's a good place to start troubleshooting. Good Luck

    "who dares wins"
     
  8. rich'90

    rich'90 1/2 ton status

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    I agree with everyone. Go with a MAP sensor, they are about $35 at Advance. This fixed a bad idle problem with mine.
    good luck

    Go heavy or Go home[​IMG]
     
  9. blazen91

    blazen91 1/2 ton status

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    On my 91, the idle some times goes up and down alittle. It's not bad, it's like a pulse. Could this be the MAF aswell? It's not causing any problems, it's just irrating!!

    blazen91
     
  10. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Start with the simple stuff. You got masive problems that all started at one time. The common denomanator being electrical. The first thing I would do is check wires. Your getting all these random codes from several different items is too much of a coincidence. Your oil pressure dropping to 0 and all the other issues points more to an electrical problem. Check the ground to the fire wall off the back of the passengerside head first. Check for propper charge voltage at the battery (13.5-14v). Could also be a bad Diode in the alternator allowing AC voltage to hit the computer and gages and if AC hit them a electric pressure gage might read Zero. No telling what it would do with sensors or the computer.
    Go through and unplug and check each connector one at a time and run the vehicle between each check to see if the problem goes away so you can isolate the problem. Trace all the harnesses and look for heat damage or abrasions where the harness was worn through.
    If you still find no problem then do a compression check. If a HG blew or a valve burned or the cat plugged you should be able to tell with a compression check. In the case of a burned/ bent / dropped valve it would allow a back flow into the intake and trigger your failure codes as well as you loss of vacume.

    Diging it in the dirt with my K5's
    Grim-Reaper
    http://grimsk5s.coloradok5.com/
     
  11. 88K5Rhododendron

    88K5Rhododendron Registered Member

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    Ok everyone. Thanks for you help so far... but it still doesn't work.... My dad is in town today and he is going to try and find a MAP sensor... that'd be a cheap fix if that's what is wrong... But this morning i went out and turned the key and it started rite up... but was still misfired and the exhaust smelled like pure gasoline... this is new... so the mix is way too rich... how much exactly does a MAP sensor control?!?!

    I Dunno if this new super rich smell will help anyone determine wether sumthing else is at fault here or not... but any new ideas would be greatly appreciated. Thanks!

    Matt (white_majik_2000@hotmail.com)

    gasoline4life! Or rocket fuel... I could see my blazer with some rockets on it... :)
     
  12. Casey 86K5

    Casey 86K5 1/2 ton status

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    the super rich problem can also be caused by a bad MAP sensor- the MAP sensor may be telling the computer that the engine is under load (low vacuum) when it really is not, and that is whats causing the rich mixture.

    Casey 86K5

    http://86blazer.coloradok5.com
     
  13. 88K5Rhododendron

    88K5Rhododendron Registered Member

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    thanks everyone... I hope the MAP sensor is all it is... I have been looking around and it seems like my symptoms are that of a fouled up MAP... poor idling... misfiring... rich exhaust (Which the O2 sensor reported this morning) oh yeah... and to that guy who said his had been idling really low at times... that is exactly how mine started... But anyways! Thanks again!

    Matt

    gasoline4life! Or rocket fuel... I could see my blazer with some rockets on it... :)
     
  14. 88K5Rhododendron

    88K5Rhododendron Registered Member

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    Crap! Dad got back... we put in the the MAP sensor and it's still doing it.... and smoke is coming out like no other... smells like pure gas... misfiring more than ever... I guess I am gonna have to take it to the dealer tomorrow... Cuz it's outta our league... unless anyone can think of anything fairly simple that could account for this...

    Thanks

    Matt

    gasoline4life! Or rocket fuel... I could see my blazer with some rockets on it... :)
     

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