On my 2004 e320 sport sedan, when starting from a stop car seems to want to stall out until i pump the gas a few times to get going, also when coming to a stop car shakes like it wants to stall out. Fuel pump and inline filter recently changed but problem still there.? Any help greatly appreciated

 

Try this:

 

thank you, I’ll give it a try

 

Start with the fuel system that was recently worked on. Are you getting air pulled in? Seems like I remember there being a crossover pipe from one side of the fuel tank to the other that often gets messed up during replacement. Pumping the gas is a pointless endeavor in a fuel injected system; there's no accelerator pump on a carb that isn't present.
Oh, and... Codes?

 

Sounds like a MAF issue. You can either clean it or replace it. Or maybe your airbox ain't sitting firm enough so you are getting extra air that MAF is trying hard time to read. The very first suggestion about ECU reset may help in some cases, worth a try at least.

 

Thanks Winer, haven’t been out lately with this quaranteen problem, however tried the tranny reset but that didn’t help, gonna check the MAF today. Sounds like that might be the problem. Hopefully you’re right. Thanks for the response.

 

Problem seem to occur when it’s real hot outside and down here in south Florida we’ve had some real hot afternoons, doesn’t seem to be as bad in the AM when it’s a bit cooler. Might just be coincidental though. However cleaning the MAF sounds like a likely culprit.

 

I have 2004 E320 with 190K miles, I have only owned about a year. I had similar problems where pedal response seemed to be delayed, and ran rough when engine was cold, once warmed up it seemed to run smoother, but pedal response was still not good. I cleaned MAF, and things improved somewhat, but pedal response still seemed a little delayed... I installed a new MAF, and problem got worse (CEL light with code for MAF, I don't remember what the code was). I cleaned the old MAF again, and put the old one back on, and everything seemed resolved (good throttle response, ran smoother when cold, even seemed like more power)...

In hind sight, I'm not sure my problem was completely associated to a dirty/faulty MAF. Instead, I think I may have been sucking in a small amount of un-metered air, possibly somewhere around the 90 degree elbow that the MAF attaches to (underneath the MAF), or other vacum leak. My recommendation would be clean the MAF as others have stated, but also check and clean the gasket for the MAF and make sure it gets seated properly, and make sure the 90 degree elbow going into the engine is seated properly, and look for any other possible places you could be getting in un-metered air.

Here is a pretty decent video on removing the MAF and showing the gasket etc.:
Unclipping and re-clipping the plastic collar around the MAF was difficult for me (I thought I was going to break it), but after removing it a couple of times, I have gotten better at it...

Side note: mine still runs a little rough when cold. It idles fine, it just seems a slightly rough when accelerating when cold, barely noticeable, more like a car that has been sitting for a several days (this isn't our daily drive, and actually does sit for 4 or 5 days at a time without being driven, but not sure that is a factor). I have replaced the plugs and wires (not coils), air filters, and I have run Techron fuel injection cleaner, but it still seems a just slightly rough when accelerating cold (when warm, its fine). I have wondered if I still have a little air sneaking in somewhere, but I haven't been able to find it; or maybe this is just the way mine runs when cold (it does have 190K on it)...

Hope this helps.

Lee

 

Thanks Lee for your response. Although my problem seems to be opposite of yours ( I run better cool than hot) I’m going to tackle the.MAF on Monday and hopefully that will solve the problem.

 

@vincris you may be right, however I was referring to the engine being cold (i.e. not at operating temp), and I assumed you were referring to hot days vs cool days where the environmental air going into the engine is hot... Not sure it matters, but I still think both of our problems are/were related to un-metered air getting into the engine OR faulty readings from the Mass Air Flow sensor, and the engine is trying to adjust the mixture with faulty information on how much air is getting into the engine (either due to air leak or faulty/dirty MAF)... Hopefully pulling your MAF and cleaning it will resolve the issue (keep an eye for any vacuum leaks). Keep us posted and good luck!

Lee

 

Winner, seems like you hit the nail on the head. After further inspection I found that when the vechicle was recently serviced the mechanic failed to replace the engine cover properly so that the top of the MAF was not properly seated tightly with the top seal under the engine cover. When I pushed down slightly at the rear of the engine cover I could feel the cover engage with the top of the MAF and the problem was solved. Thank you to you and the other responders to my question. This forum continues to be helpful to all MB owners and I’m greatful for that.