Hi. Hello everyone. I'm happy owner of 07 Acadia for a almost two years now and have been reading acadia and this forums for a while now. It helped a lot to fix all my issues. But now, I become a happy owner of 2010 Enclave. And there is few issues I was unable to understand and hence resolve, so I'd like to try to call for a forums wisdom. Also it may help future generations of readers after all
Thanks in advance guys!
So what we have?
163k miles 2010 Enclave. Stalling engine, timing chain codes, no data stream from CAM sensors.
Bought used as is with some engine issues. It seems that last few years under the last owner was quite rough. Oil was dark black and there was just 2.5 quarts of it in the engine when I drained it to change.
The main problem - engine starts, when starting there is a bit of a strange noise (My 07 Acadia sounds a bit different when starts) for just half-second, but then it's running good for... 30-90 seconds. And then just shuts off. Without any special effects like strange sounds, dash lights, revs going up or down. Just like if you shut it off with key. Quietly, peacefully and smoothly revs just drop to zero all of a sudden. Ignition stays on after that. I can start it up again like normal. Sometimes it goes for a minute or two, but not too long overall. I am able to drive it for a few minutes. But it tends to stall again when I stop. Also sometimes there is big hesitation happening when accelerating or just cruising. I'm not sure if "hesitation" is correct word, but I'll explain. So it accelerates pretty good, but then all of a sudden for just a mere moment (less then a second) it kinda loses power almost it looks like it's going to stall, but then it "wakes" up and continues as normal. If that happens, it only happens once during the acceleration event. It's not like it is doing this multiple time in any given minute. Also few times it died even while cruising at small speed (like 5-10 mph).
Of course there was check engine light and I happen to have pretty good OBD2 scanner (Autel AP200 (or Walmart's version - HyperTough HT200) - can't recommend it enough, for just 40-70 bucks it gives you MOST of the functions of dealer level tools). So after initial check I saw a LOT of different stored issues. But mostly it was related to the low battery voltage occurring historically. Like window motor calibrations etc. And there was P0008 and P0009 (engine position systems), as well as P0016 and P0017 (intake/exhaust CAM sensors bank 1) errors in regard to the engine. That got me alarmed. I reset everything to start from scratch and obviously after few runs MIL light came once again, and there was the same set of engine errors (no other errors though). So... starting to dig the forum. Yes, first thing everybody is talking about is timing chain issues and replacement. Ouch. But not so fast - there is good chance that the problem is with just sensors themselves. Very good evidence for this comes from the OBD2 live data - everything regarding CAM sensors is dead - no signals, no data, no nothing. Also they are much cheaper and comparably easier to change so I decided to go this way first. Spoiler alert - unfortunately it's not the end and it's more complicated.
What I have done so far?
Cleaned throttle body and MAF, changed CAM sensors. Discovered some other weird issues. It's much better, but still not right.
Ordered all 4 CAM sensors. While waiting for them - changed air filter (I changed oil and oil filter first thing in the first day). Cleaned MAF sensor and throttle body. But, when I tried to adapt/relearn it via OBD2 I noticed very odd behavior. With ignition on, but engine not running when commanded manually any degree from the scan tool it goes there, but sometimes it seems like it just loses power and it flaps back to neutral state by it's internal spring. This happens for a mere split second and then it goes back up to the commanded state. Also it seems to have higher then usual high pitched whining noise when commanded states higher than 30%. AFAIK such a sound usually comes from inductors when they are overloaded/don't have enough voltage/too much amps - hmmm, that's strange. Since I have 07 Acadia too I checked behavior there (handy, isn't it?
) - maybe it's supposed to act like that? And no, it was acting as expected - commanded 50% - it stays all the time at 50% open. Indefinitely. Command to 100% - stays like that for as long as you command that state. And there is high pitch noise, but to much lesser extent. Next step I removed throttle body from Acadia cleaning it along the way and connected it to Buick, and yes - i triple checked, they are identical and interchangeable. Aaaand, moment of truth - is it bad throttle body (easy-peasy fix) or something else (e.g. wiring, PCM, gods mood etc). And unfortunately it's something else because known good TB acted the same weird way on the Buick. Summertime sadness
Here is the video of it acting. Sorry, it's on another language, but I basically describe all of the above in it. July 17, 2022
Ok, so it's clearly something wrong with either wiring, engine PCM (ECM, ECU) or something else. Since I already had sensors on order decided to give it a try too. It took some time (and some hard words) to get to them, but finally I changed all of them with a new ones. What I noticed on this step - one of old sensors had marks/scuffs on it. It seems something mechanical actually hit it inside the engine. So timing chain might be real issue? Here is the photos: 3 new items by Tim Yoshi
Ok, so... what new sensors gave us? Hm... actually more questions than answers. With new CAM sensors it started fine, and worked for the whopping 6 minutes idling. I don't know if it subjective or if it was for real, but it seemed like idling become even better, smoother. Partly it could be because of cleaned throttle body and MAF sensor. But here comes tricky part:
1) It again died when I decided to give it a ride right after I started to move. summertime sadness intensifies
Overall I it drove around the neighborhood for a good 30-40 minutes, sometimes stopping for a few minutes, sometimes accelerating hard. During that time it died just
5 times (including the first one after 6 minute idle) and had that "one-time stutter" during acceleration two or three times. So the problem is still there, but it's MUUUUUCH better now. But... it's actually weird, because of the next part.
2) OBD2 tool still does not see any data coming from the CAM sensors, as if I haven't changed them at all. And it still throws the same (P0008, P0009, P0016 and P0017) errors sometimes. But why then it become much better - dying 10 times less frequently - if computer still does not see any data as if like nothing changed?
What I suspect?
So I'm quite puzzled now. I said that already - that's why I decided to ask for the forum crowd wisdom.
As of now I can suspect:
1) Somewhat bad ECM (PCM, ECU - engine computer) or wiring. I checked all of the connectors when I changed the CAM sensors, but all of them looked perfect inside. Also I checked ECM connectors - they are MASSIVE but they also look perfect. Checked ground where I can see it - it looks surprisingly good given the age of the car. Also I checked voltage (on the main positive wire near the distribution box and body ground) with multimeter when car is idling and with engine shut off - nothing weird. Voltage stays more or less flat.
1.a) maybe something wrong with some of the connectors, but it's unlikely since all of the look good, and problem seems to be to wide and distributed to be linked to some one connector. Except maybe for the main PCM harness, but I checked it and it looks good.
2) Actually timing chain issues. I certainly have some electric gremlins, but it seems that it's possible that there is real timing chain issue ON TOP of the electrical problems.
What I plan to do next?
So far I'm leaning towards ordering a new PCM. It's just
176 bucks with free shipping. And it's a breeze to change it - just two clips holding it in place and two main connectors. And it's super easily accessible. It should come pre-flashed with the latest firmware and my car's VIN. So the only thing left is to bind my old keys. It's actually should be quite easy, albeit it's a long process - you have to turn on the ignition and wait 10 minutes. Then turn off. Rinse and repeat 3 times.
If that doesn't help, at least we'll need to see where it leads us - will the TB odd behavior be fixed? Will data stream from the CAM sensors return? If answer to all of the questions will be "NO", then likely there is something with wiring or something else. I don't know where to dig next in that case. If the answers will be "YES", but issue will persist, then it's likely chain. I'd like to avoid doing the timing chain work, but if it's inevitable, then, I guess I'll have to do it anyways. Few days of good weather, some stock of spare hard language and likely I'll be able to change it, not having any spare parts left along the way hopefully
So the grand question to you guys
- what do you thing of all of that long story? Am I missing something? Any ideas? Any advice?