Update on cam variation- need the experts!

[Gary_d]

First thing is, yes the car is off the road and garaged until fixed at this point.

I had a problem with bank 1 throwing a 1531 code. Durametric told me the solenoid wasn't working. Cleaned the wiring contacts and that seemed to fix that problem. I've been running a steady -6 on both sides (in spec), but bank 1 would still throw the code now and then.
I took a 20 mile run the other day with the laptop hooked up (had to pick up the wife), and both banks held a steady -6 for the first mile, then bank 1 changed to -4 and held. Unhooked the Durametric for her to ride, by the time I got home I had the CEL on again, same code.

Today I hooked it up again and went for an errand. Bank 1 started out at -4. About 2 miles into the run it had changed to +12. Stopped, did my shopping and refired the car. Now the variation showed +18, definitely where the code was coming from. That held steady all the way home (2 miles).

The question is, how would it change from a -6 to a -4 then a +18? If the chains were jumping time, wouldn't it keep heading in the same direction - or +?
Only happens on bank 1 too, bank 2 is still a steady -6 (omits the intermediate shaft shifting).

[JFP in PA]

Year of the car would be helpful. Are you sure you didn't see the VarioCam try to cut in? May be time to check the cam position sensor on that bank; if the timing really moved that much (+18), something would have to be seriously wrong........

[Gary_d]

It's a 1997 2.5.
That's what I thought, if the timing moved that much I should have serious problems. Car ran fine though, no roughness or change to power.
What should I see when the vario kicks in? Whenever I check it, no matter what revs or load, it runs rock steady at -6. Well it was until I spotted this. Could it be as simple as the sensor screwing up?

[JFP in PA]

You should see over 20 degrees of change at higher RPM as yours would be the single stage VarioCam. I'd look at the cam position sensor on that bank.

[Gary_d]

Thanks JFP, I'll check them both. Is there a way to bench test it?

[JFP in PA]

Durametric system can switch them on and off at idle.

[Gary_d]

I don't see a choice on the Durametric for toggling the cam sensors. I have been toggling the 'cam timing' buttons, but I assumed they were testing the solenoids. Is that actually the sensors being tested? If so, they both seem to be OK.

When I tested again today, bank 1 started out at +18, right where it was yesterday. I toggled the cam timing buttons though, and then went back to actual values. I watched the variance for bank 1 drop a number at a time until it settled back to -6 where all of this started. Now it seems to be staying there.

Watching the values for ignition timing, there's a marked change like JFP said it would. Ran it through the revs and got about 29 degrees.

One other possible fluke I found is with the tensioners. The one for the intermediate shaft has 1 ring as it should. However, both of the other ones are smooth. I also don't have the 2 rings cast into the head on bank1. When I did the IMS, I'm pretty sure I checked that tensioner had the 2 rings on the shaft even though they weren't on the head. Couldn't have mixed the two as I never removed the one for bank2.

Still think it's the cam sensor?

[JFP in PA]

Depending upon the Durametric version, it should be in the drive modes section.

[Gary_d]

I've tried it on both versions, 5 and 6. The closest I find is called "camshaft adjustment", I'll assume that's the one. Both banks have a very definite drop when I try it.

[jb92563]

Any correlation to moisture?

Corrosion and wet connections to the sensors is another possibility since corrosion could vary the resistance of the sensors seen by the computer...

[Gary_d]

Originally Posted by jb92563

Any correlation to moisture?

Corrosion and wet connections to the sensors is another possibility since corrosion could vary the resistance of the sensors seen by the computer...

Doesn't seem to correlate with moisture, but when I was doing a visual on the sensors to check the wiring, I notice a ground lug behind the AOS that looks pretty crusty. That's the side I'm having problems with, you could be onto something. I'm going to attack those next.

[JFP in PA]

Originally Posted by Gary_d

I've tried it on both versions, 5 and 6. The closest I find is called "camshaft adjustment", I'll assume that's the one. Both banks have a very definite drop when I try it.

Sounds like you found it.

[Gary_d]

So that means they're both working?

[JFP in PA]

If both sides cause an idle drop, they are working.