Flickspeed

Hello,

I own a 2002 W203 C320 Automatic.

The car is normal early in the morning when cold. But after driving and having the car parked for about 30 minutes in cold weather, right after ignition the car starts jerking and vibrating on the spot, it is more in Reverse and Drive compared to P and N. As soon as I drive away the problem fixes itself.

I had the MAF checked out - was ok.
I had the EGR cleaned now is ok.

There are no malfunction codes in star or anywhere.

But the problem remains.

1 of the spark plugs was inspected visually and seemed ok.

Now we are thinking its either the injectors that need cleaning or the spark plugs need changing.

Again the car is ok when cold in the morning. Just after some rest 30m to 1h in cold weather it starts acting up right after ignition.

All filters (fuel/air/oil) are replaced.

ECU connectors had some green on them but cleaned with wurth substance twice now!

Not sure what to do next, change the spark plugs or clean the injectors...

Problem is it is a used car and we don't know when the spark plugs where changed.

neurodave

Have you ruled out motor mounts? Maybe fuel pump having issues sending fuel? It could honestly be a lot of things. I say do spark plugs and wires, just for your own sake.

Flickspeed

Engine mounts are not great but not as bad to be a cause of such violant downward and upward jerking is what the specialists told me. Plus it doesn't do any of that in other situations.

I will go ahead with the spark plugs and update.

This was being investigated but seemed ok. I will change the spark plugs since I don't have any maintenance records on when they were changed.

Any thoughts on having the injectors cleaned? Car may have been parked for a long time and I was told the heads tend to dry up or something..

Glyn M Ruck

Are you absolutely sure that there are no stored codes below CEL threshold? Like Misfires eg. 301, 304 etc.?

What you are describing is that the car runs normally under open loop enriched conditions but not fully warmed up closed loop.

The MAF & throttle body are the first suspects if plugs, wires & coils are OK. If not you should have misfires below theshold recorded.

Clean MAF
Clean throttle body including tracks under black plastic cover.
CPS might also be dodgy. Next time it does this hot throw cold water over the CPS.
Does your temperature gauge work properly. Just checking that the ECU is getting proper temperature information.
Check fuel pressure at the Schrader valve on the front fuel rail. s/b >3.8bar or 55psi while cranking.

Good Luck!

Flickspeed

I was told that is not recommended to clean a Bosch MAF as there is a very big chance of damaging/frying the MAF in case it is a Bosch.

Fuel Pressure checked out fine but the car was not having the systems at the time. Every time I go to the center I am unable to get the symptoms there possibly due to the warm climate inside there...

I am thinking CPS too maybe, but wouldn't it show that on star? What is the role of CPS? Temperatures checked out fine on star.

KSKarl

If the symptoms are less in P or N, it's because the engine doesn't have a load. Shifting to D lowers engine RPM, and the engine shakes at lower RPM. If you don't know how old the plugs are, replace them. Next clean the throttle.

Flickspeed

I replaced the spark plugs yesterday. One of the pipes or whatever you call that thing which goes on top of the spark plug was also replaced because it was leaking electricity. Lets see if this solves the problem. I definitely felt the engine working smoother and more power but haven't had the chance to ignite the car after rest in cold.

Glyn M Ruck

CPS frequently does not show up on a Star.

It is there so the engine knows where TDC is for ignition timing & so that you can't engage the starter if the engine is running.

Flickspeed

After having done the above, the car still has the problem after having rested for 30 minutes to 1 hour in the cold. And there is no problem in the morning when super cold after initial ignition. Weird...

I am doing more work tomorrow:

Instead of having to change automatic transmission oil I am replacing it with manual tomorrow (don't like auto). Will also replace engine mounts and check all rotating rubber parts along the way from the engine to the rear axle. If you are curious the whole job will cost me 150 usd and the price of engine mounts as well as a 1 for 1 exchange of my auto for a 6 speed manual gearbox set.

I am guesstimating a more than 15% decrease in fuel consumption and more than 15% gain in power after it's done? Is that something to expect on a 2001 automatic transmission with bad oil?

otosan

in my case,

it was a bad gas in the tank,

a bit too late to fillin up one time, causing some dirt/rust in the tank to goin up, clogging injector,

filled up the tank with shell v power, and put 1 bottle of gas treatment for precaution and the issue is gone,

well, it back after some period, but further investigation found my valve cover was leaking and letting oil get into the plugs, turning few of them bad,

replaced gasket, replaced plugs, and it all good...

Flickspeed

The spark plugs had 0 oil on them. Regarding fuel, I've been using above mentioned cleaning fuel... so not sure... I think I am still going to go ahead and clean the injectors if the problem doesn't go away after gearbox change and further investigation down along that path.

Glyn M Ruck

Are you sure it's not storing any codes? Could still be a MAF issue.

Flickspeed

No codes. It was checked with xentry diagnostics.

I have finished the switch to manual... will see if that changes anything.

All metal/rubber parts from the transmission to the back are ok.

Flickspeed

Ever since switching the car to manual transmission I am having a different effect from the issue. Instead of very severe vibrations I got less vibrations but also a very poor and late response from applying the throttle in the first 5-20 seconds after the car had rested in cold for about 30 minutes to 1 hour.. Once everything warms up the car is back to normal...

I highly doubt it is the CPS because I got no problems ever in the early morning when everything is cold and no problems on the road at low revs or high revs.

I will probably do 1 more test on star and then test with a different MAF.

My current fuel consumption is 12.5L in mixed mode. Engine is a 3.2L. I am guessing it is not too bad considering it is winter. But this issue is giving me headaches.

jtwillia2

I had a similar problem and after removing the throttle body and thoroughly cleaning the internals, as Glyn suggested above, it went away. I actually made a thread about that here. Sometimes this is even caused by a tiny amount of oil residue where the throttle body butterfly flap is, which can easily and quickly be cleaned. I now do that with every oil change.

Ironically, the problem recently returned but this time it was the alternator dropping voltage, so I replaced the alternator last week.

Also might not be a bad idea to run a bottle of Chevron Techron.