Poor accelration - Page 2 - PeachParts Mercedes-Benz Forum

lsmalley · #16 08-28-2014, 01:30 AM

Quote:

Originally Posted by Skippy

That code would make me tend to think the sensor was bad out of the box (It happens.) or there's a problem with the wiring.

As for checking the throttle linkage, remove the air filter and whatever else you need to see the throttle butterfly, then floor the pedal while a helper looks to see if it goes fully open.

I've had the error code 17 before switching the O2 sensor and also before the acceleration problem. When you say to see if the butterfly goes fully open do you mean the plate that is connected to the fuel distributor CIS or the actual throttle body? And if it doesn't open fully how do I fix it?

MBeige · #17 08-28-2014, 02:04 AM

I had a similar problem with the EHA. Replaced with new and all was well.

If not the EHA, look at various sensors (O2 sensor, potentiometer, temp sensor, etc) it takes signals from and go upstream from there.

Did you install the correct O2 sensor?

lsmalley · #18 08-28-2014, 02:19 AM

yes, the correct oxygen sensor is installed. what is the potentiometer? and where is it located?

MBeige · #19 08-28-2014, 02:35 AM

Quote:

Originally Posted by lsmalley

yes, the correct oxygen sensor is installed. what is the potentiometer? and where is it located?

Potentiometer is on the throttle body housing, sensing position of butterfly valve and sends signals to ECU accordingly.

lsmalley · #20 08-28-2014, 03:46 AM

Ok so I'll pick one up from the junk yard tomorrow to test? Would that cause the poor acceleration symptoms though, a failed potentiometer?

Skippy · #21 08-28-2014, 08:08 AM

Quote:

Originally Posted by lsmalley

I've had the error code 17 before switching the O2 sensor and also before the acceleration problem. When you say to see if the butterfly goes fully open do you mean the plate that is connected to the fuel distributor CIS or the actual throttle body? And if it doesn't open fully how do I fix it?

I was referring to the actual throttle body. If it doesn't go fully open when the pedal is floored, then there's a problem with the linkage. This may be due to broken or misassembled parts, or could just be an adjustment. You'll have to look things over to find the problem if it's that.

Quote:

Originally Posted by MBeige

Potentiometer is on the throttle body housing, sensing position of butterfly valve and sends signals to ECU accordingly.

That sounds like what we called a throttle position sensor (TPS) in mechanic school.

Quote:

Originally Posted by lsmalley

Ok so I'll pick one up from the junk yard tomorrow to test? Would that cause the poor acceleration symptoms though, a failed potentiometer?

Maybe. On an OBDII car a failed TPS would at least set a code and a check engine light. What else it does depends on the programming of the fuel injection system. I have no direct experience or specific knowledge relating to your year and model of car.

400Eric · #22 08-28-2014, 01:43 PM

There was a recall a long time ago regarding W124/M103 throttle linkages/cables/cable mounts. Surprisingly, a decent number of cars never made it in for the fix. Benzer1, my 89, was one of them. I found out about it and called my local dealer, they were happy to honor the recall, despite the fact that it was so old. They were also happy to check for me to see if there were any other outstanding recalls on any of my other Benzers (I had three at the time).

You should call and find out if you have an outstanding recall. Now I know that yours is a W201 but I seem to remember that it was an M103 thing and not platform specific. Either way, it doesn't hurt to inquire anyways! I recently found out that my 850 Volvo has an outstanding recall for a problem that has the potential to lead to a fuel tank leak!

Having said all this, I still predict that this throttle stuff ISN'T the cause of your trouble. I'm monitoring your thread so that I too can find out what is!

This smells like lack of fuel to me. Did you check fuel pressure? You do know that these CIS-E cars require very high pressure correct? I don't remember the exact number but I think it's in the 65 pound range.

Another possibility is that the old cat's guts might still be blocking exhaust gas flow somewhere downstream in the system. Hey, it happens! I have an old muffler sitting in my side yard right now that has a big old chunk of cat guts blocking it's exit!

Yet another possibility is that your "new" cat is bunk. I've seen cut open cats that looked "fine" from the entry view and the exit view but they were still melted and blocked internally in the middle and that wasn't visible until the cat was literally cut open!

Regards,
Eric

lsmalley · #23 08-30-2014, 08:09 AM

Well the slow acceleration problem has been resolved in exchange for an extremely high idle. I swapped out the TPS and while I had it off I shot a bit of carb cleaner into the fuel injector ports (not the fuel injectors) to see if there was something causing valves to stick, then I shot a bit of Lucas fuel injector cleaner into the ports for some lubrication. When I buttoned everthing back up I cranked the engine and the idle was extremely high so I tampered with the fuel-air mixture by turning it clockwise and the idle got higher, so I backed off and turned it ccw and it lowered. However, I don't have a duty cycle reader I was using my digital voltometer to check the mixture. I know my fuel-air mixture toggles between 5.5 - 6.1 volts (per the BOSCH KE3-JETRONIC MIXTURE ADJUSTMENT) this method is exceptable to gauge the duty cycle. Anyways, I turned it ccw until I was stopped at .11 volts, but when I shut the car off and tried to restart it it would not turnover. I then turned it cw again to bring the volts back up to where I was at before and it fired up with a really high idle again so I pulled the plug on the IACV and that brought the idle down some, then I turned it ccw again and got it to idle at 1100 rpm. What I did notice is that if I put it back the way it was and reconnect the iacv, if I similate a vacuum leak the idle drops down to normal depending on how much of a leak I create. Anyone care to shed some light on this?

400Eric · #24 09-01-2014, 12:27 AM

Quote:

Originally Posted by lsmalley

I swapped out the TPS

With a new one or with a used one?

lsmalley · #25 09-01-2014, 12:35 AM

Used. I got 2 and got no change.

MBeige · #26 09-01-2014, 02:08 AM

Was the idle adjustment screw more or less in the same position between the old TPS and replacement TPS?

Did you clean the vacuum ports on the replacement TPS before buttoning it up? Was the lever arm on the TPS adjusted the same way as the replacement TPS? Did you replace the TPS gasket to prevent any leaks?

Questions asked because these may affect idle speed.