I have a 2005 C230 Kompressor coupe with about 135,000 miles on it. This is the first time I have had any problems with the car. The car doesn't overheat, no leaks anywhere and in good shape. My problems started when the car wouldn't accelerate on the highway and the check engine light was on all the time. A shop that I trust said it is probably the mass air flow sensor. So, even though the MAF did not look bad I replaced the mass air flow sensor and both O2 sensors (post and pre-cat) but the car still did not run very well (limp mode). I took it to the shop and they said the codes read the catalytic converter had to be replaced. Logic tells me that if the O2 sensors were bad, sending false data to the computer and/or the MAF sensor was bad, then fuel could have trashed the catalytic converter. So I replaced the catalytic converter. The battery happened to go bad, this was the original battery, so I put a new battery in it too. I saved a lot of money by doing all the work myself but this is getting to be an expensive project and I need to see it through.

The check engine light is not on any longer and the car idles fine in the driveway. I bought a code reader and connected it. I saw the error codes from before I started the work. Before I started the car, I cleared the codes and wanted to start from scratch. It now says there are "no error codes found". The motor starts up fine and idles ok, but when I put it in gear and start down the road it is like there is little power. I take it out on the road and the car still acts like it doesn't want to move just like before I replaced the parts. My code reader is capable of displaying real time data, trending PID, saving and printing. So I left my code reader connected as I was driving. A lot of data and still no error codes come up, but I don't know how to decipher the information on the screen as the car is running. Except for the obvious readings like RPM, speed, and various temperatures, I really don't know what I am looking at but I saved it and ran PID trends. I still don't know what it means. I need help but I don't want to keep depositing $1000 into this car.

 

Wouldn't any issues out of the norm show up as an emission error? I would like to know how to interpret the run data, thinking that might point me in the right direction where to look or what to check. Any ideas on where I might get normal run/idle parameters for % air, fuel, temps...?

 

I would drive it and wait for codes to show up, then take it from there with a grain of salt. And what I mean by the is the codes aren't then end all be all reason for some things. The dealer service manuals have procedures that are run based on a thrown code and the procedures will finish the troubleshooting/diagnosis of the issue.

Mine is an '03 with just under 110K miles. Not saying this is what's going on with your car, but am passing along to help with the troubleshooting. I recently had similar issues where sometimes the car just wouldn't move when I got on the gas.. This would happen after I had driven for a short distance, and I could pull over, turn the car off and restart, and the issue would go away for a while. No codes for a long time but after a while finally threw one which indicated the sensor in the throttle pedal. I replaced the throttle (gas pedal) assembly and all was good for a while, then the same thing started happening again. Eventually it threw a code which indicated the speed sensor in the transmission conductor plate. I drove it around like that a little too long and the car eventually went into limp mode and stuck itself into 2nd gear. I bought the parts and was going to replace myself, but then read several cases where others had done the same but in the end had to take it to a shop with a scanner/code reader that could reach into the transmission computer to clear things there. So I took the parts to a transmission place and 3 hours/$360 later had a perfectly running car again. I'm thinking if I had replaced the stuff before it went into limp mode I might have been OK, but once it goes into limp mode you need to go in and clear the tranny computer. I even disconnected the battery for ~half-hour to try to get it out of limp mode but no go...

 

I just completed a compression check and all cylinders seemed to be fine; 1=120 psi, 2=122 psi, 3=120 psi, 4=120 psi. I would almost wonder if there was something wrong with the gauge except for the one 2 psi difference. I did notice the well on 1 & 2 had oil up to the top of the spark plug. I think this probably come from me previously adding oil at some point, but I think this could have an issue

 

Have you ever checked the fuel pressure? 2 PSI variation is no big deal. I you have 2 adjacent cylinders that are abnormally low then there is an issue, but I don't see that here..

 

Thanks, I will check it out.

 

I know you don't want to hear it but I would get it checked with STAR.

 

STAR won't check your fuel pressure. I would do the fuel pressure first then if all is well then do the STAR. Do this at an Indy place and it'll cost you half of what the dealer will charge. (Mine here is SoCal was $50)

 

It will however tell you is there is a fault in the delivery system.


I suggest the Star scan over shotgunning money at parts. I like to see it and the determine what I am going to spend money on next. I once spent 1100 dollars to replace my conductor plate and it turned out i had a dead battery. I would have know that if I looked at the report first and saw the 7 low voltage errors.

 

STAR sounds like a good possibility, and I think anything I can do myself before going to a shop would be beneficial.

I drove the car about 10 miles today. It has some acceleration, which is better, but still not good enough and the check engine light is back. Driving it did generate some codes I did not have before; P0171, P0300, P302, P0303 & P0304. This I expect would be due to some electrical connections since these codes were not preset before. At least I don't have the cat converter, MAF and O2 sensor codes any longer. I feel I need to check all possible options before replacing any parts.

Thanks for all the help so far.

 

almost identical problems as mine. I think if the MAF does not fix it, I'm just gonna flip for a STAR scanner.

 

I know that my previous statement doesn't help, but once I figure out what the resolution is I'll try and pass it along. If u read the post I just put up it will give you a similar run down of what going on with my 203 and how my experience has transpired so far....

 

The oil there is usually the valve cover o-ring not sealing and allows the oil to pass into the plug cavity. The plugs soaked in oil might be trash. I'd replace them.

Like other advice, you should take a run with a STAR tester before you BOAT (Break out another thousand.)

 

Just found out the problem with my C230. Turns out the vacuum is being robbed by a bad brake booster vacuum hose.

 

Nice. How did you figure that out?