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88 K5 Blazer

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pure country

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Jun 6, 2009
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Location
Fremont, California
I have an 88 K5, and recently I put a brand new 350 5.7 motor in it which I purchased from Jaspers motors. I also installed an edlebrock manifold, J.B.A. headers(smog legal), and a flex fan. We also put MSD coil,distributor,wires, and spark box. It has been 12 weeks, and we still can't figure out why the service engine soon light keeps coming on. The code that is regitered, is #43(timing,spark, and knock sensor). It only happens once in awhile. I can go all day with nothing, then there it is. We have changed the knock sensor,map sensor, the spark sensor, and the computer 5 times. We have also put the oringinal oem distributor back in, and disconnected the MSD box.

CAN SOMEONE OUT THERE PLEASE HELP ME AND 4 DIFFERENT MECHANICS FIGURE THIS OUT. We have ran all the electrical test, and all the wires are good. We have checked all of the grounds and they are good. We even did the code 43 diagnostic test, and it checks out, OK.

Someone must of had this problem before me, I can,t be the first one. I have been told that the edlebrock manifold is the problem. I would think that the guys at edlebrock would know if there product would work or not. If I am wrong, please tell me. I am so frustrated. We also up graded the exhaust pipes to 2 1/2 inch, not sure if this matters or not.

PLEASE HELP THANK YOU!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Also one really weird thing that happens: when the light comes on, I can put the truck into neutral(while I am still rolling down the freeway), and step on the gas pedal really hard, twice, and then put it back into drive, and the light will go off.
 
I had this happen before just after i did an intake gasket. It happened for about 3 weeks before i finally got it to stop doing it. I ended up just unplugging, cleaning connections and reconnecting every sensor up top and it finally went away. Aa friend just had the same problem and after i had him clean all connections his issue went away.

I just sent you a message via e-mail through CK5.
 
The edelbrock manifold came with two diferrent sets of gaskets, one set had the rear holes plugged, the other set they were open. Would it make a difference which set was used?
 
pure country said:
The edelbrock manifold came with two diferrent sets of gaskets, one set had the rear holes plugged, the other set they were open. Would it make a difference which set was used?
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No, but IIRC the set that has the rear water passages closed with the exception of a very small hole is what comes factory on the TBI engines.
 
Someone told me that the manifold is not compatable with the TBI (edelbrock). Do you suggest that I change all of the connectors, or what should I use to clean them?
 
Hey, what part of Femont are you from? You are the guy I met through Alan at Guarenteed Muffler. You told me to change my gears , and driven gears to 40 teeth, remember? I have the blue blazer that you liked.
 
pure country said:
Hey, what part of Femont are you from? You are the guy I met through Alan at Guarenteed Muffler. You told me to change my gears , and driven gears to 40 teeth, remember? I have the blue blazer that you liked.
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HaHa, small world. Before i had a chance to ask you if you knew of this site i or you were gone. :doah:

I just seen Alan the other day and he said my suggestion about the driven gear and housing worked perfectly to correct your speedo. :thumb:
 
have you checked your timing the correct way? Have you checked electrical wires/plugs running to it for breaks/grounding out spots? Have you tested for vacuum leaks(carb cleaner spray)? I know you've taken/talked to mechanics however go back to simple methods.
 
Intake has nothing to do with knock. Knock is a vibration sensed in your engine block that is a warning that your fuel mixture is pre-detonating but I'm sure you probably know this already.

Have you tried running premium or plus gas and seeing if it goes away? How about adding a octane booster? Was the truck formerly a 305? Cause if so the knock sensor needs to be changed out for a 350.

Sounds to me like jasper shaved some heads a little too far to save a warped core they got. I've heard bad things about Jasper. The whole shaved head thing would bump your compression ration requiring a higher octane fuel. IF the problem persists after all else fails pull the heads and put thicker head gaskets on if you NEED to run regular 87 octane.

And you saying that if you put it in neutral and rev it it clears makes me thing your actually detonating. When you put it in neutral you remove the load from the motor stopping the detonating.

I would figure it out before you crack a piston in half.


PS: As said above make sure you set base timing to 4-6* WITH THE LIMP MODE WIRE UNPLUGGED.
 
I'm sure i'll be helping in fixing his problem. I'll bet that the engine wasn't designed for TBI and has the wrong cam in it. I also know the shop who installed the engine and have seen this rig before and helped with a different issue already.
 
I know gm used 2 different type knock sensors. I think one used an external esc (electronic spark control) unit outside the computer, like on my old '89.

I wonder if you have the correct knock sensor...:confused:
 
yes it did, and I just finished cleaning all the connectors on top. Thank you for the tip on the speedo. Fremont chevy has been working to fix the other problem that Alan and his mechanic created, so far no luck.
 
motor was always a 350. Didn't have this problem until the new motor went in. Checked the compression, it was lowest 160, and highest 170. The average was 165.
 
4X4HIGH said:
I'm sure i'll be helping in fixing his problem. I'll bet that the engine wasn't designed for TBI and has the wrong cam in it. I also know the shop who installed the engine and have seen this rig before and helped with a different issue already.
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A different cam in a TBI truck will not cause a knock. I have an RV cam in my tbi truck and it runs just like it should once it takes its fuel curve readings from the o2 once it warms up.

Still putting my money that something is decked causing a high compression ratio.
 
Stomis said:
A different cam in a TBI truck will not cause a knock. I have an RV cam in my tbi truck and it runs just like it should once it takes its fuel curve readings from the o2 once it warms up.

Still putting my money that something is decked causing a high compression ratio.
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No one said anything about a knock. His truck is pulling a code 43 which is ESC (electronic spark control). I was just stating that most "mail order" engine shops supply engines for a carbed vehicle and he "might" not have the correct cam for TBI.
 
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