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EST problems

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 90K5, Apr 16, 2002.

  1. 90K5

    90K5 1/2 ton status

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    something is wrong in my EST/ESC system. Sometimes under acceleration I will hear a strange sound coming from the distributor area, and then the check light comes on, with a code 43 (EST circuit problems) I replaced the igntion/EST module, but the problem remains. I chacked out the wires a little bit, need to take some tape off for a better look though. What else is in this system? I know about the electric spark control thing near the front of the manifold, but what sensors and such are connected to this sytem? Thanks
     
  2. txbartman

    txbartman 1/2 ton status

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    your rig has more computers on it than mine, but what about a knock sensor? The only computer my rig ever had was the ESC. And, it was monitored conditions of the engine with a knock sensor mounted in the block. That is how it knew when to electronically adjust the spark. I left it all disconnected when installing my new engine. Just a thought.
     
  3. Stoopalini

    Stoopalini 1/2 ton status

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    I agree with the knock sensor idea. I was getting code 43 in my '92 Camaro (TBI) and a replacement knock sensor seems to have fixed it.

    From what I understand, and I may be wrong here, the knock sensor connects to the ESC and the ESC connects to the main ECM. The code 43, I believe, is called when the pulse from the ESC to the ECM is lower than expected, or stops for a certain period of time.

    If you've already replaced the ESC module, I would try the knock sensor next. If that doesn't do it, maybe you have a bad wire(s) between the ESC and the ECM?

    EST stands for 'Electronic Spark Timing' circuit, and ESC is the 'Electronic Spark Control' Unit. If you're getting just the code 43, then that points to the ESC. Codes 41 and 42, I believe, are for EST problems.

    Good luck,

    Thomas.
     
  4. 90K5

    90K5 1/2 ton status

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    Thats kinda wha ti was starting to think. The noise the engine makes isn't good and sounds like something is wrong insde....the the code 43 comes on.
     
  5. Thunder

    Thunder 3/4 ton status

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    All I have to say is replace your Knock sensor. It works with the EST to retard your timing when it senses a spark knock in the engine. If the sensor goes bad your engine will run at full timing advance all the time causing a spark knock (or ping). That is probabally the noise you hear.
     
  6. 90K5

    90K5 1/2 ton status

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    Thanks. I'm going to replace it today...where is the knock sensor? I looked in my Chilton's and it is a worthless piece of crap.
     
  7. BurbinOR

    BurbinOR 3/4 ton status

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    Screwed into your block probably on the passenger side, just above the starter..........accessed from below...........need a picture of what it looks like, let me know.
     
  8. txbartman

    txbartman 1/2 ton status

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    This confirms what blazin said, but it is from the component location search on AutoZone.com:

    UNDER HOOD, PASSENGER SIDE, LOWER ENGINE AREA, FRONT OF STARTER, MOUNTED IN ENGINE BLOCK

    I knew it was in the block when I swapped engines down at the bottom just above the oil pan, but couldn't remember what side.
     
  9. 90K5

    90K5 1/2 ton status

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    Well, i replaced it, splashing scaling hot coolant all over myself, and it didn't work. I went with a friend to the lake and towed his boat, and the check light was on almost all the time, code 43. The engien still makes that wierd grinding noise and then the light comes on...any more ideas? I really hope I don't have to rebuild this engine any time soon.......
     
  10. 90K5

    90K5 1/2 ton status

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    my manual said one cause of code 43 is low voltage on the EST circuit...what would casue this?
     
  11. txbartman

    txbartman 1/2 ton status

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    Have you checked all the wiring to make sure you don't have a short or bad wire somewhere?

    What lake? I have my boat out at Lake Lavon. Haven't been out to it yet this year. Needs to go into the shop to have the impeller fixed.
     
  12. 90K5

    90K5 1/2 ton status

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    Went to Lavon...it was pretty nice out there, really calm a little chilly around dark when we left. What kinda boat you have?
     
  13. 90K5

    90K5 1/2 ton status

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    The wiring seems to be allright. It is possible its an internal problem like a bad rod bearing that is causong the noise? If so, what would be makign the check light come on? I think i'm gonna do a compression test and decide if its worth putting new bearings in, if thats the problem. This engine has 156K on it, so it could still have a lot of miles left. Its been perfectly maintained by all the owners, so there's no reason it shouldn't go further...
     
  14. txbartman

    txbartman 1/2 ton status

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    Kinda of off-topic now, but I have a 20' Four Winns 200. Its a bow rider ski boat. It has a Mercruiser 5.0L v8. sucker will get up and go. Tops out at about 45 or 50 due to the deep V and its weight (about 3500#). I keep it at East Fork Harbor Marina.
     
  15. Thunder

    Thunder 3/4 ton status

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    Yes it is possible that you have a bad rod, piston or other internal engine problem. The knock sensor could be picking up the noise. The ESC trys to compensate by reducing timing, but if the noise kept going it will throw a code 43 because after reducing the ammount of advance it is still getting a low voltage signal from the knock sensor, which is picking up the engine noise.
    The knock sensor is very senisitive. The way you test onr is to hook up a timing lite, start the engine, check the timing, Then Tap on the block with a ratchet or a wernch. and see if the timing changes. If the timing changes the knock sensor is working
     
  16. 90K5

    90K5 1/2 ton status

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    my friend just got his...I think its a '90, forgot wha tbrand, 16' 2.4L Ford engine with about 150 hp...gets up to about 35-40.
     
  17. Blazer1970

    Blazer1970 1/2 ton status

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    I have heard of knock sensors picking up a worn out timing chain that was rattling around. With your mileage, something like that could be the problem. I would also pull the distributor cap and see if the bearings in the distributor are shot. This is a known problem on high mileage small blocks that could cause the type of problem you are seeing.
     
  18. 90K5

    90K5 1/2 ton status

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    I replaced the bushing in there a little while ago, so its probably OK. That sound does sound kinda like a timing chain might though...thanks
     
  19. 90K5

    90K5 1/2 ton status

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    Just took a stethescope to it under idle, because there was a similar noise coming from the front of the engine. The idler pulley sounded a little funny, may have a bad bearing. I'm gonna let it cool of, take the belt off, run it with no accessories and see if it still makes that noise...if it doesn't I'll replace the pulley, just because I want to eliminate all the possibilities. Talked to a mechanic friend, and he said the timing chain sounded good, but I really think its just tjat pulley now...maybe the vibrations from it are setting off the sensor??????
     
  20. 90K5

    90K5 1/2 ton status

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    The pullys are the source of one of the sounds...i'm gonna replace the tensioner and mayeb the idler to try to see if the problem goes away...it seems unlikely to me that vibes from the accessories would set off the knock sensor enough to keep the light on...we'll see. I can always return the pullys when I determine the sourc of the problem. It doesn't really bother me too much if I have a bad bearing on my idler pully.
     

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