Baja Turbo Shaking at higher RPMs. Why?

[deanrocker]

My '06 Baja Turbo MT is behaving like I'm shifting prematurely (which I'm not). In going from either 3rd to 4th gear, or 4th to 5th, there is a "shaking" and "rumbling" very similar to when one shifts prior to the recommended time. I am a zillion percent confident it is not due to my shifting habits. In fact, oftentimes when I get to 4th gear, it will shift perfectly and smoothly. It is while holding this RPM that it will start shaking. Same thing happens in 4th to 5th gear. When I take my foot off the gas, the vehicle does NOT shake. So that makes me think it has nothing to do with the tire balancing.
A couple of other potentially unrelated facts: 1. My cruise control throws a check engine light whenever it is locked in and I go up a hill. It's like the cruise needing more gas throws the check engine light on, and the cruise light begins flashing and kicks off. Of course, I pull the negative terminal to clear the code, and then I typically run into some stalling issues as the computer doesn't like the battery being disconnected. I don't know if this is irrelevant or not. This problem did not exist prior to the most recent battery terminal pull. Perhaps the computer did not re-learn proper timing for shifts or how to maintain when higher RPMs are being "held"??? I'm just guessing as I have no clue. That's why I'm here!
Any suggestions are appreciated. I just changed the oil a week ago. Not sure last time other fluids were changed. Thanks for reading.

[deanrocker]

NOTE: I can't get CEL checked because COVid19 regs are prohibiting O'Reilley's, Advance and AutoZone from performing these tests. I don't really want to buy a testing kit, either.

[ZUBAJA]

If you're getting a CEL, there is obviously something wrong that the ECM is seeing. At MINIMUM, you should pull and check your plugs. The first time I got a CEL on one of our Subies (02 Forester), I took it to Autozone and had them scan it. The code was for a misfire in #2. It turned out to be the plug was now missing it's center electrode. I bought a set of plugs, put them in, and took it back and had them clear the code (I know you can't do that right now). After that, I bought an OBDII code scanner. It was around 60.00. Money well spent. It has served me well and I don't have to go off to AZ any time I have a CEL. If you have any of these vehicles with OBDII, it is wise to have at least an inexpensive scanner, as many of them are getting up there in mileage. As I understand it, there are even adapters and apps for smartphones to do this. Dennis

[kamesama980]

your description of the issue makes zero sense. no offense, it's just you're describing qualitatively and we need quantitatively. Several places you just use goofy terms and phrases I have to read 3x to get what you're saying. As an enthusiast and fairly experienced tech there are several different symptoms from "shifting early".

When are you shifting for each gear? what RPM? how much throttle are you giving it in those gears and at what RPM? I've been riding with people saying "I'm not shifting early" upshifting a 4 cyl honda at 1800 rpm with 5 ppl in the car.

Your cruise control can't throw a check engine light and doesn't "lock in". you set a target speed and when you go uphill and it tries to maintain speed, the CEL turns on. (side note, most CELs will disable cruise to inspire you to take it in for service)

When you pull the negative cable to cut power to the ECM to clear the code, you also clear the throttle learning. the ECM has to learn the limits of the electronic throttle each time which is why it stalls out on you. Stop cutting power to clear the code.

Given the symptoms, I'm guessing boost leak. under vacuum (low throttle) it doesn't leak but with rising load (more throttle), as the manifold pressure crosses 0 (gauge/14.5psi absolute) it blows open the leak causing a misfire and flashing CEL and disabling the cruise. On the other hand, it could also be the turbo inlet hose degrading and only leaking in (significantly) as load rises. Sure would be nice to see the fuel trims and freeze frame data but you wipe it along with the codes and the throttle learning every time you pull the power. Could also be crummy/worn out plugs and it's blowing the spark out under load.

What to do:
-check the spark plugs. While you're at it, look over the coils and boots for damage.
-check the intake plumbing for leaks from the airbox to the heads.

for shame! Either buy an OBD2 scanner for yourself or take it to a shop. only half kidding tho

[deanrocker]

Thanks for feedback.
I bought the Autolink AL329 at Walmart. When driving yesterday my check engine kicked on as I was rumbling along at 55 mph. Error code is P0457. Vacuum leak. Recommendation is to change gas cap. I will do this, but I'll be shocked if it's that simple.
If my post is unclear, please ask me specifically what you would like to know. I will read the scanner manual to see if I can pull freeze frame and fuel trim data.
Disregard info about cruise control. It's irrelevant that most the time cel comes on is when I'm cruising at 65 or so and hit a hill. Source of cel kicking on is tied to engine requiring more power, right?
I will inspect hoses as recommended. Haven't changed plugs on this since I purchased it a year ago. My son did it for me, I think. Hope they're easy to get to.
Thanks. I'll let you know what I find. Your input is appreciated.

[kamesama980]

P0457 is for the evap system, highly unlikely to cause the engine to misfire/shaking.