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89 350TBI CHECK ENGINE LIGHT GOING CRAZY

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by RESTORE89, Jan 31, 2001.

  1. RESTORE89

    RESTORE89 1/2 ton status

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    I RECENTLY PURCHASED A 1989 BLAZER SILVERADO 1500 FROM A BUDDY WHO BOUGHT IT FROM A USED CAR LOT, AND AFTER 2 DAYS OF STRET DRIVING THE REAR END LOCKED UP, AND TORE UP THE TRANNY. HE REPLACE THE REAR END WITH A USED GM 10 BOLT LIKE WHAT WAS ALREADY THERE. THEN HE FOUND OUT THE TRANNY WAS SHOT, AND I BOUGHT THE TRUCK FROM HIM FOR 2500.00, AND TOWED IT TO THE TRANNY SHOP, AND THEY REBUILT THE 700R4. IT DOES HAVE THE TORQUE CONVERTER LOCK UP. THE NEW REAR END DOES NOT HAVE THE SAME RATIO AS THE FRONT. READING 60 MPH ON THE SPEEDO, I AM ACTUALLY TRAVELING 75MPH. I BOUGHT A CODE READER, AND HAVE REPLACED EVERY SENSOR ON THE TRUCK EXCEPT THE EXHAUST. I WAS GETTING CODES FOR A DIFFERENT SENSOR EVERYTIME I REPLACED ONE. THE LAST CODE I AM GETTING IS A 43 THE KNOCK SENSOR. I REPLACED THE SENSOR, AND AS LONG AS I DO NOT STOMP ON THE GAS OR DRIVE ABOVE 55 ON THE SPEEDO (67 ACTUALLY) THE LIGHT DOES NOT COME ON. I KEEP RESETTING BY PULLING THE COMPUTER FUSES. WOULD THE WRONG GEAR RATIO MESS UP THE SPEED SENSOR, AND MESS UP THE COMPUTER? I HAVE NEW 4.11 US GEAR RING AND PINIONS AS WELL AS A POWERTRAX LOCK RIGHT. SHOULD I PUT THE LOCKER IN THE FRONT, TO MAINTAIN GOOD STREET MANNNERS, OR WILL IT MATTER. I AM CONSIDERING DUMPINT THE TBI AND ALL THE COMPUTER STUFF, AND GOING WITH A NEW INTAKE CARB AND SINGLE WIRE HEI STYLE IGNITION SYSTEM
    THANKS IN ADVANCE
    THIS IS MY FIRST POST, BUT I HAVE BEEN READING FOR A WHILE, AND HAVE LEARNED ALOT ABOUT MY
    TRUCK
    CHRIS
    i originally posted as a code 42, but it is a code 43, and it keeps coming on, more often now, even in everyday around town driving
    <P ID="edit"><FONT SIZE=-1>Edited by RESTORE89 on 02/08/01 04:17 PM (server time).</FONT></P>
     
  2. Thunder

    Thunder 3/4 ton status

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    A code 42 does not only mean the knock sensor. It could also be the magnetic pickup coil in the distributor, or the ignition module. or the electronic spark control module (EST a thin square black box located to the right of the throttle body).
    When my magnetic pickup coil went bad in my 89k5 the check engine light use to come on at highway speeds. Then it developed a slight miss when in 4th gear under a load and gave a code 42. Replacing the pickup fixed it.
    You should get the front and rear axel ratios matched up ASAP. Putting your rig in 4X4 with different axel ratios in the front and rear will destroy your transfer case. Also I would not put a locking diff. in the front if you are using your truck for a lot of street driving. They wear out front tires fast.
    If you take off the computer/tbi stuff. Consider replacing the cam shaft also. The TBI cam is different than a Carb cam.
     
  3. KrebsATM02

    KrebsATM02 1/2 ton status

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    DON"T GET RID OF YOUR TBI!!!! For the love of god keep it. More power, better throttle response, better starts, better fuel economy, etc....

    Doug Krebs
     
  4. gokartergo

    gokartergo 3/4 ton status Staff Member Moderator

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    Yes . Get rid of your TBI. I will trade you staight across for my carb and manifold for your TBI. PLEASE, PLEASE, PLEASE, PRETTY PLEASE.

    Become one with nature............Then marinate it..
     
  5. HarryH3

    HarryH3 1 ton status Author

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    First thing you should do is stop throwing parts at it. Other problems, totally unrelated to any of the computer controlled stuff can cause all kinds of bizarre error codes.

    My neighbor had a Taurus that wouldn't run worth a damn and the computer was setting codes for the oxy sensor and throttle position sensor. Before he went and spent a lot of money on parts, we did some basic troubleshooting. Turned out that a bad ignition coil was creating a very weak spark at the plugs. This made the engine run like crapola and freaked out the computer. The computer knew something was wrong, but since it doesn't measure spark voltage it didn't know what the real problem was. The computer reports symptoms, not always the real cause.

    Look at the basic stuff first. Even a computer controlled engine needs 3 things in order to run. Fuel, spark and air. This means you need the correct fuel pressure, injectors that are not clogged, an ignition system that creates a strong spark and no vacuum leaks anywhere. Make sure all of that stuff is right before you spend a ton of your money on parts that you don't need.

    Here's another tip. BUY THE FACTORY SHOP MANUAL. Yeah, I know they cost a lot of money, but they'll save you a fortune in the long run. The diagnostic flow charts for testing and verifying circuits when there's an error code will pay for the cost of the manual. They're easy to follow and usually all you need is a basic volt/ohm meter to perform the testing. Get one and go directly to the "Emissions and Driveability" section. It really will help you learn what makes that thing work. [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A>
     
  6. fr8train

    fr8train 1/2 ton status

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    At night pull the neg. cable. from the battery. In the AM reconnect and let idle. once warm, if no check light appears, take a spin around @ normal driving speed(5-65 mph). And recheck any codes. I did this to my '88 after getting some screwed up codes. I was originally pulling the fuses and got the same codes I was getting before.
     
  7. fr8train

    fr8train 1/2 ton status

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    Oh yeah about your TBI. Read the new Petersens Four Wheel & Off-road. The Nuts and Bolts section pg. 122; TBI Performance. The retro fit between carb and TBI may cost the same( parts, labor, fuel consumption) . Sure you can get some crazy horse/tq. numbers with the die hard carb. You also have to tune the thing a lot. You can do the same with a properly built TBI, TPI, or EFI system. Get better milage, just water proof your ecm. There is a guy here who has a bad a$$ 406 TPI and it can pass any emmisions test with no prob. and still puts out the numbers. The choice is up to you, your useage, and your wallet.
     
  8. Josh

    Josh Registered Member

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    I've heard of getting codes from changing the rear ends before, only on newer cars though. If you have a VSS(vehicle speed sensor) and the engine load (map) and rpm don't mesh up they can cause a value to be out of sync in the computer tables, this will magnify at higher speeds. In any case you should match up your front and rear gears, before you break something.

    Josh
     
  9. Rebel88

    Rebel88 1/2 ton status

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    Hey RESTORE89,

    What did you do and did it take care of the problem. My light come on every once in a while when i am on the highway and go to drop into passing gear. Somebody told me it might be an O2 sensor but i have never hooked it up to a computer. Thanks.

    Later

    Have you driven OVER a Ford lately?
     
  10. RESTORE89

    RESTORE89 1/2 ton status

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    i bought a $25 engine code reader from auto zone, and plugged in to the terminal hookup under the dash, and turned on the ignition, and it flashes a series of lights, and the haynes manual tells you what the lights mean. then i just replaced the parts that were bad, but i still keep having this knock sensor reading come up. i think( not sure how much that means) it has to be the gear ratio issue with the speed sensor, but we will find out next week when i put the new gears in
    chris
     
  11. RESTORE89

    RESTORE89 1/2 ton status

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    where do i get a factory shop manual, and how much is a lot?
    thanks for the info, and i am getting my gears installed next week.
    could the gear ratio cause my problem?
    i have done a complete tune up, and all the other trouble codes have gone away, except this one.
    i have run several tanks of amoco premium unleaded, and fuel injector cleaner, just to try that, and no change
    thanks for the help
    what happened with the guy saying he was getting 500+hp from his sbc at 4200rpm
     
  12. shum1

    shum1 1/2 ton status

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    I just spent a month and about 50 bucks and I fixed the error 42 code. I have the complete diagnostic flow chart for fixing the error 42. Error 42 is not typically a knock sensor. It is the "electronic spark timing control" The most common problem is a faulty ignition module in the distributor, these can be checked at auto-zone. On mine I had a bad connection plug at the module, this caused the timing bypass circut to open. I fixed that and everything was cool for about 2 days. Finally I discovered that my "new" napa plug wires were cracked after only 2 months. I replaced my wires, cap and rotor and now the light does not come on and my truck purrs like a kitten. Replace wires and cap/rotor if you havent already. If you need more info let me know, I could fax it to you.
     
  13. 6.2Blazer

    6.2Blazer 1/2 ton status

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    The different rear axle ratio should not cause any codes. On a newer vehicle it might cause problems but on the '89s the computers weren't nearly as picky and I don't think they really even interfaced with any parameters outside of the actual engine. If this was the case, even changing tire size would cause codes. In fact, a buddy of mine just retrofitted a stock TBI and computer setup out of an '87 into his 350 powered Jeep with no problems. The only thing needed was an O2 sensor added to the exhaust.
     
  14. realsquash

    realsquash 1/2 ton status

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    No no NO, its not a gear-ratio problem! Try setting your ignition advance (i.e. distributor). Remember that you have to disconnect the bypass circuit to set the distributor... Lotsa knocking will make your engine go berzerk, so make sure it's right. It might also be a plugged cat.

    Squash
    <A target="_blank" HREF=http://www.trailrunners4x4.org/users/realsquash>http://www.trailrunners4x4.org/users/realsquash</A>
     
  15. HarryH3

    HarryH3 1 ton status Author

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    Check out <A target="_blank" HREF=http://www.helm.com>http://www.helm.com</A> for the manuals. They run from about $35 for some vehicles to $160 or so for the newer ones. Painful to pay for but they hold a wealth of information!

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A>
     
  16. bart

    bart Registered Member

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    HELM manuals for older stuff get expensive...I tried to buy ones for my '92 blazer...$435.00 complete..no kidding!

    Check out www.autopaper.com bob johnson's automotive literature...they have factory manuals for older vehicles...fyi, I got my $435 set for $150 from them..

    bart
     

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