400E Problems - Very annoying

[90free400e]

ok I just modified the intake, which i have done 3 times and hasnt ever caused any problems. Here is the problem, and it gets very very annoying, but doesnt seem to affect drivability.
The engine starts fine and idles fine. But as soon as I get over 30 mph, and when I have the gas pedal in (accelerating, maintaining speed etc) the engine starts to feel like it is stuttering. It seems like the same feeling as when u moderately accelerate, then let off, then do the same thing over and over again fairly fast. It doesnt seem to happen when i am really accelerating with the gas all the way in, but it may be jsut because I cant feel it. This only happens when the gas pedal is in. As soon as i let off the gas pedal the problem stops. Could this be a problem with the throttle cable, or throttle actuator? Or is this a Misfire problem. Any help would be greatly appreciated. Thanks.

[brewtoo]

How did you modify the intake?

[90free400e]

basically just made a cold air intake. Tubes off of the two openings behind the headlights, removed the flat air filters, put cone filters on the end of the tube, removed foglights for direct airflow. The thing is ive been driving them like this for 25,000 miles, only thing i did was build a box around them so that cold air would stay in and hot air wouldnt enter.

[euronatura]

I am by no means any expert but could it be fuel starvation? I read on another thread about cold air intake. Cold air more dense therefore more fuel can be burned therefore you get more power. Could it be too much air and not enough fuel?

Iggy

[90free400e]

there is a chance that I could be running lean, but i dought that i am since the car is equipped with a Knock Sensor and makes fuel curve adjustments every 3 secs. Im not sure if tehre is a point that it stops adding fuel though

[y2kimmel]

I you removed the tubes before the front headlights for the cold air intake, did you remember to somehow move/reinstall the air intake temp. sensor so that it's in the intake airstream? The temp sensor sits in the black plastic housing right behind the headlights. If you didn't, the air temp inside the engine bay is what the computer will use to make its adjustments, even though the true intake air temp is much colder.

if you've done this - then I'd look at the O2 sensor. It doesn't sound like a fuel delivery problem, which would manifest itself more at heavy throttles.

Best of Luck.

Troy
1995 E420 75k

[psfred]

Also make sure you don't have a vacuum leak anywhere past the air flow sensor, or you will have lean running problems with a warm engine.

Peter

[manny]

Originally posted by 90free400e
there is a chance that I could be running lean, but i dought that i am since the car is equipped with a Knock Sensor and makes fuel curve adjustments every 3 secs. Im not sure if tehre is a point that it stops adding fuel though

F.W.I.W. Knocksensors control ignition timing, NOT fuel.

[90free400e]

first off. I dont think i did reinstall the temp sensor. Thanks alot for pointing that out ill def go try to find it. Second. ur right about the knock sensor. I got ignition timing and fuel mixed up. Thanks again for the help ill update u guys on what happens

[zeronero]

Can you post some pictures of your intake?

[90free400e]

sure ill try and put new pics up by tonight

[joelpdavis]

Not sure if this applies to the 400E, but my W140 S500 has a similar problem and the Throttle accuation module is the culprit. Additionally, it could be the wiring harness that ultimately controls this module.

Try this: Use the cruise control at 30mph and see if you get the same results. If you don't, I'd suspect something in the throttle area. I believe (but could be wrong) that the cruise control has it's own system to open the throttle body.

Joel

[90free400e]

i know the throttle actuator is having problems, because I brought it in when the engine had been cutting off every once in a while, and the cruise control didnt work. The cruise control runs off of the throttle actuator, so if it isnt working it is a sign that the T/A is shot. Also, the ECU isnt storing any data codes like it should be, so what you guys are saying could be correct. Thanks for the info and help.

[amg280]

Hey.

I have somewhat similar problems with my 400. It sounds like ignition is being retarded to cut engine power. Honestly it could be SOO SOO many different culprits on this motor.

The ignition control module on the fender has an input that comes from the transmission on this car. It comes from the overload protection sensor on the tranny. This sensor can go bad. Mine did. Whenever i would punch it, or get it on it a little, my car would just lose power, like someone was switching off my ignition. The sensor controls when to dump the engine power. It does this at redline shifts to promote faster shifts and less wear on the clutches. It works well, when it works right.

Also, could be a bad wiring harness. I doubt it has anything to do with fuel.

Does your car have ASR (i hope not).

Right now I cant even drive my car on the highway over 70mph. the car goes into limp home mode and Kills my gas pedal all because my rear tires are more wore down that the front. Pretty nice engineering there huh??

-Andy

[90free400e]

nope it doesnt have ASR. So you are having the same problem with your car? If you get it fixed or find the problem please let me know. Thanks for the help