Mercedes-Benz Forum banner

Acceleration Problems. CPS, MAF Sensor? Tune Up?

6597 Views 14 Replies 7 Participants Last post by  DO_Doc
Well I bought an 04' Crossfire in December (3.2L, Automatic) and have had a lingering problem that no one seems to have an answer to. Keep in mind I have no warranty or the money to just blindly start replacing a bunch of parts. It just rolled over to 40K miles, so I'm hoping it must be something small I can fix myself.

First off, it seems I get much lower gas millage than normal 320 owners. No matter how I drive it, I never get no more than 250 miles to a tank which I'm guessing is around 16mpg. This is mainly city miles but still my driving style or more interstate trips doesn't effect it. The car always cranks fine, and early in the morning it seems to run best with no abnormal activity. During the day is a pretty huge decrease in performance. Some days I feel like I'm pulling a trailer it's so bad. I live in FL so of course the hot temps will make a difference , but I've never been in a car where it's been so effected.

Basically, when it's hot like this, the car acts up worse. When giving the car slight steady gas, it feels like it misses, or goes in and out of gear. You can watch the RPMs go up and down slightly and you can hear the engine going up and down (passengers can easily hear and feel this happening). It just kind of lurches forward. I used to think it did it worse around 40MPH going to 50, but really it'll do it whenever. When you put it in sport shift and leave it in a certain gear, it still does it, but not really at high RPMs. Under heavier acceleration it's pretty bad. Sport shift is also very rough in my car, and does a lot of hard shifting and knocking, I never really use it. It seems to act up much more when I do.

I can't believe with the millage the transmission would be bad already (or at least the TCM on it). It sounds more like it could be the MAF, but I don't know if the spark plugs could be bad as well. As much searching as I've done no one has really had the same symptoms as me, except for one I read and he had a bad crank position sensor. My car has never stalled on me before.

Anyway, any help at all would be GREATLY appreciated. I'm just looking for some positive answers before dropping $$$.
See less See more
1 - 1 of 15 Posts
Of course on-board diagnostic information would be helpful to look at. I guess you did not notice a check-engine-light, or otherwise you would have mentioned it.

You mentioned that no one is able to help so far. Just curious as to what kind of help you have had so far.

First thing in the morning when you first drive the car, you mentioned that the car runs normally. To confirm, you are implying that none of the symptoms that you are complaining about are present early in the morning, right?

When it rains, or when the relative humidity is high (damp), does it get worse?

Can you take one spark plug out and post a picture of the tip end of the plug including the make and model of the plug?

A cheap test that you can do, if you can get the symptoms to show up after it gets dark, is to look for arcing on the high voltage side of your ignition system. Have the coils, spark plug wires exposed. After having gotten the symptoms to show up, drive into a dark place and shut off the engine. Have your eyes accustomed to the darkness and startup the engine. Go and look for little sparks or tiny streaks of light indicating leakage to ground. This should be more apparent when the weather is more damp, should the cause of the fault is high voltage leakage.
See less See more
1 - 1 of 15 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.