2001 Jimmy 4X4 4WD 2000RPM P0336 w tach error

Tiny
EDWARD HIGDON
  • MEMBER
  • 2001 GMC JIMMY
I have a 2001 GMC Jimmy 4x4 (T15) with a 4.3L v6 auto 149,000 miles. Just replaced the lower intake manifold gasket the other week, so had to remove the distributor (relocated by scratch marks in same location it was). When the throttle is goosed it pops like the timing is off, but if I advance timing by the distributor 1 gear, it wont run and the other way, it wont even idle. The truck is throwing P0336 code referring to CKP sensor 'A' circuit problem but it only throws the code if the engine reaches above 2000 RPMs for three ignition cycles in a row. It also begins running rough and the tach jumps up and down above 2000 RPMs. I backprobed the CKP and CMP sensors, replaced the CKP and distributor (CMP built in, but did dist because the shaft was a little worn) and it made no difference. Found no problems in the wiring. When I run the computer on it, the ECM is picking up up to 12,000 RPM spikes, but it has no problems as long as it stays below 1900RPMs.
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Friday, November 16th, 2007 AT 6:43 PM

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Tiny
PEAR69
  • MEMBER
There is a proceedure to re-install the distributer but first- Edward- answer these questions:
When you took the distributer out, did you bump-or-disturb-or-rotate--the engine in any way? Even a little?
What class is the OBD2 scan tool you are using?
I assume you have a scan tool.

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Friday, November 16th, 2007 AT 7:30 PM
Tiny
EDWARD HIGDON
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No disturbance to the dist, less somebody wanted to clown around and did so while nobody was near it. Snap-on Modis (borrowed from work). Cross-referenced the timing off of All-Data and it's as close to right as possible by adjustments at distributor.
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Friday, November 16th, 2007 AT 7:45 PM
Tiny
PEAR69
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Ok, can the snap-on modis tell you where number one cylinder is firing? Meaning at what degree before or after top dead center(TDC).
If not bring no. 1 cyl. Up to top dead center on the compression stroke. Take the dis. Cap off. Notice where the rotor is pointing. There is a 6 and 8 stamped on the base of the distributer LOOK CLOSE.
The rotor should be pointing to the 6. The 8 is for an 8 cylinder.
This will get you close but you still have to take the truck to someone who can check the timing with a scan tool. The timing is very sensitive with these trucks and must be set by a scan tool to within + or - 2 degrees. A timing light will not work because the computer automaticly advances the timing'
Also if you change the crank position sensor you must do a crank relearn procedure--not sure if the snap-on modis does this either. Let me know how you make out.
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Friday, November 16th, 2007 AT 8:47 PM
Tiny
EDWARD HIGDON
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Cant find anything in modis about loc number 1 cyl is firing. Setting time as was said, truck wont start. 1 tooth off from where it was too far advanced. Now, a rattle is noticed at 2000 rpms under load also and motor giving same response as before. Cam retard @ idle is -2 degrees but jumps @ 2000 rpms n up to -23 degrees. Hmmm. Need a better, more user friendly scanner.
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Monday, November 19th, 2007 AT 6:41 AM
Tiny
PEAR69
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Don't forget about the crank relearn procudure. When your truck left the factory the computer was programed to your truck and your truck only. During the first start up, and I mean when the guy or girl in the factory first turned the key, your computer went through a learning process. One of the things it learned is the distance your crank position sensor is from the reluctor ring (that's the thing on the crank that tells the computer where the crank is). This measurment is in the thousandths of an inch. Sometimes you get lucky and it's right on but more times than not it's off a thousandth or two. I am pretty confident that you did not get lucky and you must do the crank relearn proceedure. The -23 degrees is correct. That is the advance that the computer runs the engine at. You will get that reading, as long as the motor starts, no matter how many teeth you are off. The computer sets the advance you cannot just turn the distributer or set the distributer off one tooth anymore. It's not like the old days--you know before computers controlled every aspect of timing advance and retard---- To check where the cam is actually at you must use a level 2 scan tool like the GM tech 2. I know the scan tool you are using is very expensive but I'm not familar enough with it to say that it can do a cam timing check or a crank relearn procedure.

I want to add if your scan tool cannot tell you where no. 1 cylinder is firing or it cannot do crank relearn proceedure it's either not a level 2 obd2 scanner or you don't have the right software to do these necessary proceedures. Let me know how you make out. Good Luck
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Tuesday, November 20th, 2007 AT 12:19 AM
Tiny
EDWARD HIGDON
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I did perform the crank relearn procedure after r&r the crank sensor, though I cant do so at the moment because the excessively jumping tach. The computer says the motor, when it first starts bouncing @ 2000 RPMs, is spiking up to 12,000 RPMs. I reset the time to TDC yesterday and tested the ICM and went through all the wiring again to check for pinched wires, etc. No luck yet. Will look around for level 2 scanner to see what can be done.
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Tuesday, November 20th, 2007 AT 6:45 AM
Tiny
PEAR69
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Hang on, I just thought of something. Sorry I didn't think of this sooner--Check the gear on the distributer. Look for worn teeth. The gears from the factory are brass, they wear out causing all kinds of problems. It may be a shot in the dark but I have seen this before.

Oh mylanta! Did you say 12000rpm? That's way past the red line! Does it realy sound like it's running that high or is that just a computer glitch. 12000rpm is amazingly high for a stock motor--it won't last long at that rpm. I think formula one race cars run at 10000rpm. For safety sake--wear a flack jacket and an astronaut full face helmet when working on a stock motor that runs at 12000rpm. LOL
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Tuesday, November 20th, 2007 AT 2:11 PM

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