400E won't accelerate
 

I have a 1992 400E that stumbles if I try to accelerate too fast....almost like the ASR is coming on. Idles perfectly most of the time but sometimes is does hesitate. If I try to accelerate slowly it will come up to speed with the odd hesitation. If I try any harder it does stumble, as I said, like the anti-skid is activating. GETS WORSE AS THE CAR WARMS UP. I have had the Electronic Throttle Actuator off and the wires are all perfect...no cracking at all. Another interesting thing is that it will accelerate smoothly if I use the cruise to move the speed up and down.
I did get a DTC code 17 for the Crankshaft Position Sensor, also got a misfire on #4 but cleared OK and hasn't returned, Code 17 does come back. ( I have a Snap On MT2500 scanner).. I have checked the resistance on the crankshaft wire and it seems to be within the limits. So....any ideas??

A friend of mine has a similiar problem on his 420e, so Im not sure if it applies to you, but it was purely a vacuum line issue. Im not sure how many of his lines were damaged but its definitely worth looking into.

Yeah....I though it may be that too. Right now I'm trying to get the crank sensor out.....what a night mare. The sensor case is stuck in the engine. No idea how I am going to get that out. No room to move.

I have a similar issue right now. It occurred after changing the oil. I may have disconnected vacuum line when I was mucking about.

I will check all the vacuum line...again. But I need to replace the sensor now that I got the old one out. Will let you know.

My car is doing the same as we speak.. I'm not driving it because I feel like its unsafe. Is a non ASR but its acting like its doing the limp home mode. I don't drive my car really much maybe 1 or 2 times a week so i don't know if that has anything to do with it. (replaced cap rotor and plugs 6 months ago) I'm going to give it an oil change this weekend and also check all my vacuum lines.. will report back of my findings

So I replaced the crank position sensor and that didn't help ! If I run the RPM upto about 2000 in park it starts to cut out, then catches again, cut out, runs, etc.....on/off/on/off......not the fuel pumps, the wiring harness, the MAF or any of the computers 'cause I changed them all except the base module. I see on the scanner that the Safety Fuel Shut Off is on then off. Where is that and how can I test it?? Very annoying. Got someone who will take it ASIS for $3K.....think it may just become his headache.

Brian,
In this economy if someone wants to give you 3 big ones, take it and run. If you want to keep it, I'd hook up a vacuum gauge and check vacuum at idle and 2000 ripums. If vacuum isn't higher at 200 than idle you have a restricted cat. This is just one test.

Also you said crank sensor won't come out. Did you remove 5mm allen screw?

Looks like it is the safety fuel shut off circuit in the electronic accelerator. I took it out and will open it up tomorrow. There is a switch that shuts the fuel off if the computer thinks the throttle valve is open further than the pedal position when the cruise is off. Restores the injectors at 1100 RPM, hence the surge. Cut out at 2000 +- then restores at 1000 +-. So we'll see what we got inside there tomorrow. Sure don't want to spend $800 for a re-built one. Pretty sure I can make it work....one way or the other.

Before you throw parts at it, make sure the inputs switches are working properly. If the computer thinks the throttle is open too far, make sure the throttle position sensor is working properly. Make sure all the connections are good. May be you can bypass the cut out circuit with a jumper wire to make sure that circuit is failing.

Fixed
 

Turned out the ETA was the main problem. Got a good reman. from Beckmann. Also needed a CPS. BUY an O.E. from the stealer.

Hello Brain, My 1992 400E has the same problem, can you tell me what is the ETA and where is it located?
Thank you
it has been so desperate to find out this problem for some time.

The ETA is Electronic Throttle Control. Mass air sensor sits right on top of it, that is right in the middle of the engine. It's got the screen over it. The ETA is the big aluminium colored part under the mass air and has the throttle linkage attached to it. Wiring harness on these fail, same as the engine harness. Could also be the main engine harness for that matter !! When that harness starts to act up it will short out injectors and cause poor driveability (plus a pile of other issues). You should replace that if it is still the original and you want to keep the car (and you should....great car). Guaranteed that harness is crispy and just looking for an excuse the act up........so don't touch it or move it or upset it in any way. Poor acceleration on that car could be a couple of things, other than the harness. If it has poor acceleration because of a misfire it is probably a distributor or if it just won't build up RPM it may be a clogged "cat". If it was intermittant, car drove and worked fine one day with no problem then all of a sudden started to act up then it is probably the ETA. If you haven't had the problem diagnosed using the 38 pin diagnostic connector that may be a place to start. There are a few possible causes....it could be the ignition module for example, but find a good local independent that will have the commuter hook-up for that car. He needs the correct "break out box" and the knowledge to use it. Don't let them near the car if they don't have the hook up and a scanner to read it. If they start throwing parts at it because ..." oh, we know what that is..." without a positive indication of a problem then it will cost you BIG money.
Good luck.

i also am having this problem, although my car is a 88 300ce, when cold it seems to drive fine, but as the car warms up it starts to misfire and wont rev past 2000rpms.

what was the end solution?

that's a different engine....M103... I think. Look at your crank position sensor or cam position sensor. Could also be the ignition control module !