2004 DHS - P0106 Code - Replaced MAP - Still not getting good vacuum

[jwm_tech]

Hello all, I am new to the forum and a first time poster. I have read through some of the other posts and found a lot of good information from the members, but did not find anything related to the problem I'm experiencing. (I could have missed something though)

Problem vehicle -- 2004 DHS - 133,000 miles.

Here's the rundown of what's going on. My dad was driving, just drove 45 miles home, checked his mail, put it in reverse to back into the driveway, and he says it suddenly started running like crap. Running very rough, will not idle well, and hard brake pedal. He drove it again the next morning, and said it took a while to start and died several times along the way.

I got there and pulled the codes...P0106 & P0300. I get relieved/excited, MAP sensor replacement is about as easy as it gets. I checked for proper 5 volt reference and ground. Everything looked good, so off to the parts store. I quickly replaced the sensor, cranked it up, and..............same crap!! I hooked my meter to the signal wire to read the voltage and plugged up the scanner to read the kPa, both signals showed the same fluctuations but showed very low vacuum. The voltage reading stayed around 4.5 while running (@ idle through 3500 rpms) and the kPa stayed between 92 and 100, except when throttling down after a rev when the reading would very briefly go to about 3.5 volts and 86 kPa.

I cleared the codes before starting again after replacing the MAP sensor. When I pulled them again after running and troubleshooting a little more, I also got a P0016.

Something is obviously preventing the engine from creating a vacuum. I checked all around the intake manifold for vacuum leaks, almost expecting a ruptured plenum coupler, but found nothing. Then I blocked off the brake booster in case it had an internal leak, still no change. And I didn't get an EGR code, but I checked to make sure it wasn't stuck open anyway. It was working as intended. None of the PCV, fuel regulator, or any other vacuum components had any leaks whatsoever.

I continued to wonder where else air could be escaping, and thought about a stuck/bent valve or jumped timing. I ran a compression test and 2, 4, 6, & 8 came back around 140.........1, 3, 5, & 7 came back @ 0, the needle didn't even move. The only thing I can think is that the bank 1 timing chain either gradually jumped a little at a time, or just completely broke and caused at least 1 valve on each of the bank 1 cylinders to be bent or left in a open position by the cam (then bent ..).

Is there any other failure that could cause a whole bank of cylinders to have 0 compression? I know I can take off the valve cover and look at the cams, but honestly I'm tired, it's getting late, and I am going to get a borescope for my phone tomorrow to look in the cylinders and/or through a vent in the valve cover to see if the cams are spinning.

Thanks in advance for any feedback or guidance!!

[KHE]

I think you're on the right track with the compression test. The fact that cylinders 1,3,5 & 7 have 0 psi compression definitely indicates a problem - possibly a timing chain. If you can snake a bore scope in one of the PVC or vent lines and turn the balancer pulley with a wrench, you should be able to see if the cams are rotating. If they are not rotating, then pull the front cover and inspect the timing chain,

[OldCadTech]

Camshaft, exhaust and intake valves are what 1, 3, 5, & 7 all have in common. You're painfully on the right track, interference head and bent valves, equal zero compression.

Sorry the news isn't better.....

[barczy01]

I have had the chain tensioners problems like this one brought to me to diagnosis and fix. Your on the right track and you probably have a totally collapsed chain tensioner and the bank has jumped time. I have had one jump so bad that the engine bent all the intake valves on that bank. Use the ac delco tensioners on rockauto. The chinese ones on ebay no offense are JUNK!

[jwm_tech]

Thanks for all of the feedback and suggestions. I was glad to see that knowledgeable technicians agreed that I was on the right track, even though deep down I really wished someone would have just told to me to check the imaginary Bank 1 intake bleeder valve. That would have been so much easier than what really needs to happen. Unfortunately, I was not able to check to valves or cams with the borescope before my Dad decided to suddenly have the car taken to a mechanic shop. In his defense, he knew that once it was possible that it needed significant work I would not be able to get it done for him in a timely manner as I have a pretty full list of things that require my attention for the next few months. Hopefully the mechanic will take good care of the car for him and also let him know what the root cause was, I feel like I need closure on this because I wasn't able to fully complete my diagnosis.

Anyway, thanks again for the advice and guidance. My wife has a 2012 SRX, so I'm sure this won't be my last post.

--Til next time.

[OldCadTech]

If you can, drop a post and let us know the outcome