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1999 996 Rough Idle P1340


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Hey! Anyone ever get a P1340 on their 996? The car has a rough idle but otherwise runs fine. I cleared all the codes and then did a test drive. Rough idle at lights. The light did not come back on but it had P1340 and P1125 in the system. Anyone with any thoughts?

Thanks.

y

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p1340 is cam in bank 1 out of sync--is that what your OBD reported? Have you had any work done that involved the tensioners recently (IMS bearing)? Maybe cam chain or cam chain tensioner wear can store this code? You didn't specify whether the rough idle was a new condition... if it was, did it exhibit sudden onset?

...j

Edited by j_beede
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Yes that is what my OBD reported. Using Durametric software. Another shop originally diagnosed the car as having a bad dual-mass clutch disc... after replacing spark plugs with no improvement in symptom. So the guy had the clutch done... which of course it didn't need.

Rough idle started up all by itself.

Chain wear.... hmmmm. How to assess that....

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On my audi a6 2.7t ..... I got this code, It turned out to be the cam seal on the cam that has the has the hall sensor on it was leaking oil, the oil got into the sensor and messed it up. I know its a diffrent engine but I feel it could be relivent.... Mine also ran fine and idled a but ruff.

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P1340 indicates that the cam allocation value (read timing) exceeded the upper limit on Bank #1. If you have the Durametric software, you can check the cam deviation values, they should be less than +/- 6 and steady at an idle; if they are, the engine is sound and the cams where they belong. If the values exceed +/- 6 degrees, I'd first stop using the car until someone with the knowledge and tooling can look at the cam timing. If the cam deviation values are swinging back and forth at an idle, you have something very loose in the cam drive, possibly including the IMS bearing. If that is the case, consider your self very lucky, most engines do not live long enough in this condition to be observed doing this, but it is still salvageable as long as it is not run until it is fixed...............

Edited by JFP in PA
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Okay current codes: P1340 and P1125 oxygen sensing adaptation.

At idle the Camshaft position 1 deviation is 25/crk it never changes either at idle or 2000 rpms.

It feels like a misfire at 2000 rpm but no misfire codes are popping up.

This rough idle issue has been happening since end of April. I suspect if it was IMS failure it wouldn't have made it this far.

Any other ideas?

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I do not understand the value you posted, you should be able to see cam shaft deviation values in degrees, the values should be between +/- 6 degrees (often something like -3.8 or + 1.5); if it is reading "25" degrees of crankshaft, you have jumped time...................

Edited by JFP in PA
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To be sure we are looking at the same values, this is what I was referring to on an M96 in a Boxster, which I think is a bit different view than you posted (sorry for the link, but RennTech would not permit me to post it for some reason):

screen shot

I think the view I am used to gives a better view of what the cams are doing, and you can clearly see the cam deviation values I was referring to. According to the OEM service manuals, these deviation values should not be outside +/- 6 degrees, unless something has come adrift in the cam drive. An additional thing you should look at it to trigger the VarioCam system using the software, just to be sure one of the solenoids isn't sticking.

Edited by JFP in PA
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Okay, a couple of adds.

First, I can only see Camshaft 1 position deviation in my list of 'available actual values'. I checked again this morning, still 25 degrees and it never moves.

Second, I don't see a way to trigger the VarioCam, when I clicked on drive link "adjust camshaft" the whole thing froze up.

SO, we pulled cam end plugs. Exhaust cam is perfectly lined up. Intake cam doesn't have marks going all the way across it, but the cams are tied together so it doesn't make sense that one of the cams would be off and not both.

Also, when I checked codes again this morning I did have misfires on 1,2, and 3.

Any more input?

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I'd still want to know why you are seeing 25 degrees of cam deviation, I have never seen that before.........................

Both the intake and exhaust cams should have a straight notch in the ends, used by the fixture to hold the cams while working on the engine; these notches should line up on both cams if everything is correct.

Edited by JFP in PA
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Okay actuated both variocam solenoids. Car reacted to activation for both. Still showing 25 degrees.

The intake cam has a notch at one end but not both ends like the exhaust cam does. This is a 5-chain car if that makes a difference.

The only thing I can think of is that the intake cam is out of time due to a worn chain pad????

What is strange is that with the engine off the active screen reads 25 degrees as well and when you turn engine on it doesn't change. Almost as if it isn't reading it correctly at all. Where does it pull data from?

y

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Here are some "stream of conscious thoughts" in no particular order or dependencies, some of which were mentioned previously.

1.) The chain skipped a tooth somewhere and your timing is off. Simply re-time, check timing again, then start the engine and enjoy the "fun" paddle. If you can't successfully re-time it might require additional engine dismantling, starting with the cam covers according to procedure. This is greatly simplified with the engine out of car.

2.) One of the flanges on the end of the cam has been bent somehow and the cam position sensor is reporting an erroneous value (say for instance if it was bent whilst installing/removing/handling the cam shaft). In this case the timing is OK, just the CPS or flange is wrong.

3.) A cam position sensor (and/or wiring) has gone bad, even though there are no codes being thrown.

4.) DME is faulty and needs to be re-flashed.

"The intake cam has a notch at one end but not both ends like the exhaust cam does. This is a 5-chain car if that makes a difference."

TDC looks like this, with the 1-3 intake cam pointing out (near the AOS).

IMG_3417.JPG

Edited by logray
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  • 3 weeks later...

Thanks for your stream of conscious thoughts! I am finally getting back to this one. My laptop died but it's back up and running.

As to 3) I just decided to change it to make sure it was not the problem and as I suspected it didn't not change anything.

As to 1) how or why does the chain skip? What would cause that if the engine has not been taken apart?

As to 2) how would a cam bend if the engine hadn't been pulled apart? Have you seen this happen?

As to 4) How can I tell if DME is the problem and needs to be reflashed? Short of taking it to the dealership is there a way to check it? I have the durametric software.

Finally, is there a way to set timing without removing the engine?

Thanks!

y

Here are some "stream of conscious thoughts" in no particular order or dependencies, some of which were mentioned previously.

1.) The chain skipped a tooth somewhere and your timing is off. Simply re-time, check timing again, then start the engine and enjoy the "fun" paddle. If you can't successfully re-time it might require additional engine dismantling, starting with the cam covers according to procedure. This is greatly simplified with the engine out of car.

2.) One of the flanges on the end of the cam has been bent somehow and the cam position sensor is reporting an erroneous value (say for instance if it was bent whilst installing/removing/handling the cam shaft). In this case the timing is OK, just the CPS or flange is wrong.

3.) A cam position sensor (and/or wiring) has gone bad, even though there are no codes being thrown.

4.) DME is faulty and needs to be re-flashed.

"The intake cam has a notch at one end but not both ends like the exhaust cam does. This is a 5-chain car if that makes a difference."

TDC looks like this, with the 1-3 intake cam pointing out (near the AOS).

IMG_3417.JPG

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If the cam time has actually moved, it is both "not a good thing", and somewhat complicated to correct. Can it be done in the car? Yes, depending upon why it jumped, and in any case is a nightmare to do. One of the common causes of strange cam timing issues is a wobbling IMS bearing; typically the beginning of the "death dance". The cam deviation values should be rock steady at idle, as in the posting above; if they are not, it is usually the IMS on the way out.

Cams do not bend, they break; the VarioCam flange bends, throwing off the cam position sensor. This can be a relatively simple repair.

camshaft1.jpg?t=1309381549

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Okay so just to confirm:

1) My screen shows 25 degrees, so it's off, by a lot it seems.

2) Likely nothing is bent, ie, cams. The reluctor wheel that the cam sensor uses to sense timing appears to line up correctly, we are checking this with motor in car. Is that wheel what you are referring to as VarioCam flange?

3) My cam deviation value on bank 1 is 25 degrees and does not waiver so it is probably not the IMS

4) IMS is cause for strange cam timing issues, but my timing deviation value does not move

SO, what else might have caused it to get out of time?

Here's my concern, I pull the engine, find the timing off, reset timing... but don't correct what caused it so it will likely happen again.... right?

Before I pull out this motor I want to be absolutely sure I've exhausted all other options.

Thanks so much for your help!

If the cam time has actually moved, it is both "not a good thing", and somewhat complicated to correct. Can it be done in the car? Yes, depending upon why it jumped, and in any case is a nightmare to do. One of the common causes of strange cam timing issues is a wobbling IMS bearing; typically the beginning of the "death dance". The cam deviation values should be rock steady at idle, as in the posting above; if they are not, it is usually the IMS on the way out.

Cams do not bend, they break; the VarioCam flange bends, throwing off the cam position sensor. This can be a relatively simple repair.

camshaft1.jpg?t=1309381549

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The software system is reading the cam position sensors vs. the crank position sensor to determine the cam positions. I'd be looking at the VarioCam reluctor, the cam sensor on that side and the VarioCam solenoid on the same side. With the Durametric system, you can trigger the VarioCam solenoid with the engine idling, and should see the cam angle jump when you do; if it does not change, it could be at least part of your issue, as it may be stuck in one position. These, along with visually checking the cam slots can be done with the engine in the car. If the cam has mechanically jumped time, it would probably be easier to pull the engine to correct the issue, although it has been done in the car, albeit with difficulty.

When the rear IMS bearing starts to get loose and wobble, the cam drive chains go slack, causing the "death dance" in the cam deviation values. Eventually, if the IMS does not totally fail, the chains get loose enough to start jumping time. Unfortunately, this entire process often only lasts a second or two before pistons start bending or breaking valves, totaling the engine (the M96/97 is an "interference" engine and cannot tolerate too much change in the cam angles before disaster strikes).

Edited by JFP in PA
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That's one problem I'm having. I can't trigger the variocam solenoid while running the cam angle deviation graph with Durametric software I can only do them as separate functions. I called Durametric and they said it was my laptop not using a dual core processor. So this afternoon I dragged out a new computer with dual core processor and guess what.... still didn't work! I can hear the idle change when I do activate bank 1 and bank 1 but I can't see what is happening.

At this point I'm stuck because Durametric won't be available until Monday again.

Do you think this could be a DME needing re-flash? Although that seems odd since it's a '99 with 109,000 miles on it. One would think if that was the problem it would have shown itself long before now.

So I'm still stuck.

The software system is reading the cam position sensors vs. the crank position sensor to determine the cam positions. I'd be looking at the VarioCam reluctor, the cam sensor on that side and the VarioCam solenoid on the same side. With the Durametric system, you can trigger the VarioCam solenoid with the engine idling, and should see the cam angle jump when you do; if it does not change, it could be at least part of your issue, as it may be stuck in one position. These, along with visually checking the cam slots can be done with the engine in the car. If the cam has mechanically jumped time, it would probably be easier to pull the engine to correct the issue, although it has been done in the car, albeit with difficulty.

When the rear IMS bearing starts to get loose and wobble, the cam drive chains go slack, causing the "death dance" in the cam deviation values. Eventually, if the IMS does not totally fail, the chains get loose enough to start jumping time. Unfortunately, this entire process often only lasts a second or two before pistons start bending or breaking valves, totaling the engine (the M96/97 is an "interference" engine and cannot tolerate too much change in the cam angles before disaster strikes).

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