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Old 03-23-2003, 02:25 PM   #1
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Default Crank Position Sensor .... misfires ....

I have been trying to track down a crazy misfiring problem for about 2 weeks now. I was wondering what I should check for to make sure the crank position sensor is working correctly? About the only thing left in my tracking down of the misfire problem is the crank sensor and the pcm, so I would appreciate it if someone could help me on this one....I really do not want to replace a pcm <img border="0" title="" alt="[Frown]" src="gr_sad.gif" />

Any other thoughts on the misfire could be helpful too!!! I have check about everything else though.
Joe
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Old 03-23-2003, 03:17 PM   #2
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Default Re: Crank Position Sensor .... misfires ....

Help me out guys!!! <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />

Someone out there has to know!
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Old 03-23-2003, 04:58 PM   #3
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Default Re: Crank Position Sensor .... misfires ....

A friend of mine is having the same issues. We replaced the crank position sensor and the issue is still there. We are going to take to Chevy dealership and switch PCM's and see if that cures the issue. Keep us posted if you track yours down. Good luck!

John
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Old 03-23-2003, 05:49 PM   #4
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Default Re: Crank Position Sensor .... misfires ....

Well, I have a new Crank sensor on the way. Whether it is bad or not I do not know, but I figured for $40 it could not hurt to get it changed. It will be here Tuesday, so if my problem is not fixed by Tuesday the only option I have left if the chevy dealer too <img border="0" title="" alt="[Frown]" src="gr_sad.gif" /> <img border="0" title="" alt="[Frown]" src="gr_sad.gif" /> <img border="0" title="" alt="[Frown]" src="gr_sad.gif" />

I have replaced all plugs and wires, and fuel filter. I already checked all ignition coils for correct firing voltage....I have also checked about every other sensor related to air intake and plug firing. My misfire is odd, in the sense that it will run fine for the first two minutes or so when the engine is cold. When the engine gets a little warm, it suddenly starts a random misfire that almost makes the engine stall at times. I know it is not a loose wire because it will do this when the car is sitting still and just idling.

Anyone else have any ideas before I have to take it to Chevy Tuesday? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
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Old 03-23-2003, 06:45 PM   #5
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Default Re: Crank Position Sensor .... misfires ....

It doesn't sound like a crank sensor problem but it also doesn't sound like a problem that can be chased down without some diagnostic equipment. I.E. scan tool etc. <img border="0" title="" alt="[Frown]" src="gr_sad.gif" />
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Old 03-23-2003, 07:16 PM   #6
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Default Re: Crank Position Sensor .... misfires ....

I consider myself an expert on crank sensor stuff.

If you car shuts off while making a pass you better check the wires to the crank sensor, they run thru that cluster by the passenger side headers, #4 and #6.

On a different note, I think that most floating misfires are due to plugs foiling out and an overly rich condition at idle. Can also be related to a cam, but only big cams.

I'd take a MAF-T and run out the base 5% and see if the misfire goes away.
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Old 03-23-2003, 07:48 PM   #7
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Default Re: Crank Position Sensor .... misfires ....

My friends does the same thing. Idles fine when cold, but every cylinder misfires after it warms up. The car stumbled horribly on the dyno and that was when we knew we needed to check it. Autotap showed every cylinder misfiring at random. If you get a chance, shoot me an email after the dealership and let me know what the verdict was. I would appreciate it! Thanks.

John
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Old 03-23-2003, 09:40 PM   #8
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Default Re: Crank Position Sensor .... misfires ....

Is there any way that I can lean it out without a MAF-T? i.e...using a resistor or something just to see if this helps the problem. Another thing that I do not understand is that I keep getting a code indicating that bank 2 is running lean, but I can smell an awful lot of gasoline fumes in the exhaust.... <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> I also changed the O2 sensors, so I know that they are in good condition.

This misfire is unnoticeable when the motor is cold, this is what I do not understand. Once the motor is warm, it basically wants to shut itself down because of the misfires....Could this be related to any of the AIR, EGR, etc....?

I have the stock cam in the car, so I am pretty sure this is not the issue....

I will get an email to you, John02SS, once I figure out what is wrong with it.
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Old 03-24-2003, 11:33 AM   #9
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Default Re: Crank Position Sensor .... misfires ....

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by chino_man279:
<strong> Is there any way that I can lean it out without a MAF-T? i.e...using a resistor or something just to see if this helps the problem. Another thing that I do not understand is that I keep getting a code indicating that bank 2 is running lean, but I can smell an awful lot of gasoline fumes in the exhaust.... <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> I also changed the O2 sensors, so I know that they are in good condition.

This misfire is unnoticeable when the motor is cold, this is what I do not understand. Once the motor is warm, it basically wants to shut itself down because of the misfires....Could this be related to any of the AIR, EGR, etc....?

I have the stock cam in the car, so I am pretty sure this is not the issue....

I will get an email to you, John02SS, once I figure out what is wrong with it. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I had a friend who had the same problem and codes, lean bank2, and misfires about a month after he installed a t1 cam, his car ran like crap right off idle, but after about a month he finally tracked down a single bad spark plug. the computer was showing random misfires, and running lean for some reason, but found out he had one bad plug. he replaced it and everything went away, he did finally catch the misfires while underload and found them to single out #2 cylinder. not saying this is your problem, but it is hard to detected bad plugs some times without trying a known good plug.
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Old 03-27-2003, 07:04 PM   #10
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Default Re: Crank Position Sensor .... misfires ....

Those of you who were interested in my outcome of the misfire problem....

I could not track it down after all this time, 2 and a half weeks, so I took the car to Chevy today. It will be in the shop to be looked at first thing in the morning.... <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> I will let you guys know the outcome when I get out of work tomorrow....In the meantime keep the ideas coming. I always like input, so I know whether the dealer is messin' with me or not... <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />

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Old 03-29-2003, 03:51 PM   #11
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Default Re: Crank Position Sensor .... misfires ....

Where you getting missfire codes for those cylinders?? Did they do a leak down test on the all the cylinders to find this? If you do have a blown head gasket it is your culprit. Interupting air pump? I'd worry about the head gasket first. Maybe he was giving you the engine is a air pump speech?
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Old 03-29-2003, 10:53 PM   #12
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Default Re: Crank Position Sensor .... misfires ....

This explaination sounds reasonable about the head gasket problem. I'm not so sure about the AIR pump explaination. By the way, did you take your car to Frank Beck Chevrolet?
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Old 03-30-2003, 12:14 AM   #13
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Default Re: Crank Position Sensor .... misfires ....

Well, I called the dealer yesterday afternoon and the Service Tech explained to me that my problem is related to a blown head gasket between cylinders #1 and #3.....Does this sound reasonable to you guys that this could somehow lead to a misfire problem?

He tried to explain to me that it was interrupting the normal actions of the AIR pump.....Just wondering if you guys think I have other problems. If I have other problems I am just going to drop a new motor in it...382

Thanks,
Joe
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Old 03-30-2003, 08:32 PM   #14
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Default Re: Crank Position Sensor .... misfires ....

I am getting a misfire as well in my car. It just started a few weeks ago and is really pissing me off. I am putting a data logger on it Monday to hopefully figure out the problem. <img border="0" title="" alt="[Mad]" src="gr_images/icons/mad.gif" />

I have changed plugs, wire and checked them twice. A/F was good on the dyno a little while back, then it starting doing this. I hear loud tick when it is idling in gear and the RPM's drop. I hope I do not have a blown head gasket. Well, if I do, I guess it is time for some heads. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

<small>[ March 30, 2003, 08:33 PM: Message edited by: TransAm2002 ]</small>
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Old 03-30-2003, 10:18 PM   #15
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Default Re: Crank Position Sensor .... misfires ....

Yes, I was getting a misfire on Cylinder number 3. I am not surprised that the head gasket is blown though. The oil looks pretty rough and it is fresh... <img border="0" title="" alt="[Frown]" src="gr_sad.gif" />

The tech did not say that it was directly related to the AIR pump, sorry if I caused confusion...damn emissions things anyways, they go crazy from anything. As for the leak down test I am not sure what exactly was done. I just questioned enough to figure out the head gasket was blown. I am going to get the heads ported now and put my 382/427 project off for now. <img border="0" title="" alt="[Frown]" src="gr_sad.gif" />

Anyone know where to get a good head gasket? How much?


01redws6ta--I did take the car to Frank Beck...do you work there?


I guess I will get a new head gasket put on and see if this solves the problem. <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> I guess at the very least I am going to get ported heads out of it a little earlier than planned, but I guess having more power can never happen soon enough <img border="0" alt="[evil]" title="" src="graemlins/gr_devil.gif" /> <img border="0" alt="[evil]" title="" src="graemlins/gr_devil.gif" />

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Old 01-30-2011, 03:17 PM   #16
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I am having the same problem as soon as my 96 TA warms up its starts missfireing. i have changed everything from the ignition syatem to the air intake system, crank sensors, mass air flow sensor, what is the problem someone give me a clue please?
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Old 01-30-2011, 03:25 PM   #17
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Quote:
Originally Posted by 9transam6 View Post
I am having the same problem as soon as my 96 TA warms up its starts missfireing. i have changed everything from the ignition syatem to the air intake system, crank sensors, mass air flow sensor, what is the problem someone give me a clue please?
This is an 8 year old thread man, you might be better off starting your own thread.
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Old 01-30-2011, 08:41 PM   #18
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Originally Posted by uLs1a View Post
This is an 8 year old thread man, you might be better off starting your own thread.
That's got to be a record!
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Old 01-31-2011, 01:23 AM   #19
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Im just proud someone actually used the search tool
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Old 02-15-2015, 04:14 AM   #20
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Super old thread! LOL but what the heck.

It is possible that these random misfires could be from a crank sensor problem. More specifically, it could be a problem with the reluctor wheel on the crank, not the sensor itself. If the thrust bearing clearance gets screwed up, the crank can walk a bit and change the distance between the sensor and the reluctor wheel.

We just ran into this on an LS2. The converter wasn't properly shimmed, and that caused the thrust bearing to get wiped out. The excess thrust caused the crank sensor to read wrong.

When I scoped it with my Picoscope, it would occasionally miss one or two, sometimes three teeth. Oddly, always the same teeth. And every time there was a missing tooth, we would get a misfiring coil.

We caught this by backprobing the crank sensor signal wire, and using a low-amp clamp on the coil power circuit, so we could see all 8 coils firing and compare those waveforms to the crank sensor waveform.

By the way, the car would start and idle fine. But if you free revved it to 2000 RPM, it would start missing on Cyl 1, 8, and I think 5.
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