Baja Turbo jerking on acceleration.

[seawevil]

Hey everyone. I’ve been having a problem with my Baja that I can’t seem to solve. The car seems to stop and start accelerating rapidly which causes it to jerk back and forth violently whenever I do a sudden acceleration to cross an intersection or to merge into the highway. It will do it as long as I’m holding the accelerator down and will stop once I let go. I’ve tried changing the coil packs, spark plugs, cv axles, turbocharger, throttle body & a handful of other parts that looked worn that I felt would have to do but the problem continues. It seems to be worse when it’s hot outside and the worse part is that it doesn’t do it all the time. Sometimes the car runs absolutely perfect, but then other times it feels a bit sluggish & is usually when I start having the problem. I would honestly appreciate any help and thank you in advance.

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[Guacamole]

Could be several things but start with the easiest.
1. Are you using 91+ Octane fuel? Turbos need high-octane fuel to correctly operate.
2. Have you checked/replaced the vacuum hoses in case of a leak?
3. Is the car throwing any codes? If it is, it might be an 02 sensor going bad.
4. Is the car a manual? If it is, the clutch might be slipping.
Also, about what RPM does it start doing the lurching?

[anarchy1024]

You mentioned the spark plugs, but did you also do the spark plug cables? Mine had a similar problem where it would jerk under hard acceleration, but otherwise ran perfectly. For me, it went away after changing the cables.

[seawevil]

Could be several things but start with the easiest.
1. Are you using 91+ Octane fuel? Turbos need high-octane fuel to correctly operate.
2. Have you checked/replaced the vacuum hoses in case of a leak?
3. Is the car throwing any codes? If it is, it might be an 02 sensor going bad.
4. Is the car a manual? If it is, the clutch might be slipping.
Also, about what RPM does it start doing the lurching?

1. Yes & always.
2. I discovered a torn hose which I replaced a while back and it got rid of a small evap leak code I had. Have been trying to look for more vacuum leaks but have found none so far.
3. I occasionally get a p0420 code which I’ve already replaced both o2 sensors with new ones and the rear front cat with a used one. When I replaced the cat, the light went away for a couple months but then came back just a few days ago. O2 sensors did little to no difference.
4. Automatic, usually when the rpms rapidly reach 2-3 it’ll start stalling.


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[seawevil]

You mentioned the spark plugs, but did you also do the spark plug cables? Mine had a similar problem where it would jerk under hard acceleration, but otherwise ran perfectly. For me, it went away after changing the cables.

Mine is a Turbo model so it doesn’t really have an ignition wire set. It has a coil on plug system which I’ve already replaced all of the coils & I actually replaced a harness connector that was broken. I was so sure that was my problem but it still persists.


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[anarchy1024]

Ah, okay, my bad. My friend's car also has a similar problem where it does that. Supposedly the wires to one of the sensors (I think crank position in his case) is loose or something, so the ECU loses that signal and cuts the fuel/ignition until it returns.

But I'd think the Baja would throw a code if that was the case...

[seawevil]

Ah, okay, my bad. My friend's car also has a similar problem where it does that. Supposedly the wires to one of the sensors (I think crank position in his case) is loose or something, so the ECU loses that signal and cuts the fuel/ignition until it returns.

But I'd think the Baja would throw a code if that was the case...

I would think so too. I’m honestly praying to God to get a code with the proper problem.


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[seawevil]

Bump.


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[w.rohr]

Does it do it more when the AC is on? Do you have a scan tool that does real time scanning, if so check the temps also check pending fault codes. I had a problem where I would lose power with the AC on at low RPM, tried IAC valve new ecu probably a mile of vacuum hose... turned out to be the spark plug wires I bought had a small crack on one of the boots. My friend found it spraying water on it in the dark. but hey its always nice to have new part I guess

[walfredo]

Sounds like a MAF issue.

Had the exact same thing on my GTI and discovered that the air intake tube was cracked after the MAF causing an influx of unmetered air.

You said you have a recurring 0420 code and you replaced both o2 sensors. That would indicate a bad cat (which is why the code keeps coming back), although that wouldn't necessarily cause any abnormal running issues, just a CEL, foul smell and bad gas mileage.

The other possibility is you have a fueling issue, which is causing/caused your catalytic converter to go bad and could be causing your jerking issue (although if you had a fueling issue one would assume you would have other codes being thrown).

And lastly, it could be that the 0420 code and your jerking issue are completely unrelated.

My guess is on the MAF (or an air/vaccuum leak post-MAF), and would get that diagnosed.

[seawevil]

This might be a little out of left field, but I had similar issues with my old 1990 VW Vanagon Syncro 4WD once (same drive train as a Subaru, roughly, only backwards). Turns out I had a slow leak in both rear tires and the constant differential rotation between front and back would heat the fluid in the viscous coupling up just short of "grabbing" temperature. Then, when accelerating, the load shifting to the rear due to inertia was just enough to shift the effective difference in rolling diameter between front and rear to cause the viscous coupling to intermittently lock up and cause the vehicle to buck and jerk. It's dumb sounding, but I gotta ask, are all your tires aired up equally?

Thanks for the advice man. I actually do have a tire that's losing air every so often but the problem existed beforehand. I'm trying to get it fixed either way.


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[seawevil]

Sounds like a MAF issue.

Had the exact same thing on my GTI and discovered that the air intake tube was cracked after the MAF causing an influx of unmetered air.

You said you have a recurring 0420 code and you replaced both o2 sensors. That would indicate a bad cat (which is why the code keeps coming back), although that wouldn't necessarily cause any abnormal running issues, just a CEL, foul smell and bad gas mileage.

The other possibility is you have a fueling issue, which is causing/caused your catalytic converter to go bad and could be causing your jerking issue (although if you had a fueling issue one would assume you would have other codes being thrown).

And lastly, it could be that the 0420 code and your jerking issue are completely unrelated.

My guess is on the MAF (or an air/vaccuum leak post-MAF), and would get that diagnosed.

Any idea on how I could check the MAF myself?


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[walfredo]

1) The most likely issue is a boost/vacuum leak. Check all vacuum lines and air intake tubing (including all intercooler/boost lines, turbo intake connection, everything and anything after the MAF - follow the trail of the air as it goes past the MAF, into the turbo, out the turbo, into the intercooler and then into the engine) - you are looking for any connection that is loose, cracked, disconnected that would allow unmetered air into the engine. This includes intake manifold vacuum lines.

2) the non-technical way of checking your MAF is to unplug it while the car is running, if the car starts running rough, or dies, your MAF is working. If you have a multi-meter there are better and more professional ways to check it (youtube is your friend). Make sure you clear any engine codes afterwards, because doing this will likely trip a MAF code.

In my opinion, if your MAF was bad you would have major driveability issues all the time, and that doesnt sound like your symptoms. In my case, with the GTI, my air intake tube after the MAF was disconnected, my car would buck very badly while it was in boost. It would drive normally at all other times (while I was in vacuum).

If it is the case that unmetered air is making its way into your engine, you need to stay out of the boost. Why? Unmetered air will cause you to run lean, and running lean while in boost is not good (yes the ECU can compensate, but only so much). I would be careful.

Also, as mentioned earlier, a bad upstream air fuel sensor (wrongly called an O2 sensor) could also be the culprit. It would likely throw a check engine light though...