[chojinchef]

Have read a number of threads, usually with suggestions but not any posted results.

1999 S420 147k (yes I drive it, ALOT) usually average 3000-4000 per month.

On Monday I was headed to airport. Very happy as I just had upper and lower ball joints done, got rid of the horrible second set of Lemfoerder coil springs and a spiffy new set of 255/45 18 Michelin Pilot Sports installed. Was enjoying the smooth responsive 1 hour trek to airport.

When I arrived at airport, got myself into garage and was headed up to the upper levels to park for the couple days I was to be away. Upon entering the first incline the car stalled while driving. Couldn't get it started. So of course a dozen culprits flash through my mind. Would turn over, but a second or two it would die again.

I went looking for the parking office to garner some assistance. Found no one.

Returned ten minutes later, tried again and no start. Same deal.

Sitting there contemplating the business trip to Dallas, I tried again and by manipulating the pedal I could get it to start and run but if I let off it would die. At this point, I had no check engine light come up but the whole dash lit up when it stalled.

I was able to 'power brake' it into a nearby parking spot, and I decided to get in my flight and deal with it when I got back.

Last night, I decided I had to at least get it out of the airport garage because no tow truck could load within the garage. Once I got going, I kept going knowing my route had good phone service if I needed to call AAA.

Keeping the RPMs up, I made it home. It died in driveway. Did notice that the MPG gauge needle was swaying back and forth between 15 and 35 the whole way home, but otherwise no issues with power once accelerating.

This morning, I set out to do a precursory inspection of the items I felt could cause this. First checked the basics - K&N filters clean (recharged a month ago), no obvious vacuum leaks, fuel pump humming away with key on and still no check engine light. Ok, I thought, now to get into it.

I removed MAF and gave that a cleaning. It looked clean, but I did it anyway. Looked at throttle body and it too was clean. Looked inside plenum and it looked good. MAF gasket was whole and showed no cracks. Couple new clamps and I reassembled. Checking torx bolts on throttle body for proper seating and tried to start. Same issue.

Thinking there MUST be a massive vacuum leak, I rechecked all the lines. Broke the plastic of the front most line and replaced it. Then thinking that maybe I had a brake booster failing, I disconnected it, plugged holes and tried starting. No difference.

At this point I got a check engine light.

Now I am awaiting a friend of my mechanic to stop in tomorrow night to read code (mechanic just had stints put in and is out of commission for a bit) but I am wondering if there is something else for me to check?

Plugs have 10k and two I pulled looked good. Suppose I could pull all of them and make sure. I religiously use Techron every 5k. Fuel tank over half full.

As of a few moments ago when I needed to move the car to get my Zetec powered Vanagon out of driveway to use tomorrow the MPG needle is pegged all way to left.

When I get car going, and manipulate the pedal, I notice no skipping or misfires, but I could be wrong (frequently am according to wife)

What am I missing here?

Pre owned CLS550 at dealership this morning is looking better every moment.

 

[Chono123]

MAF COULD be the culprit, mine looked very clean too but it was the reason my car kept stalling at stops. Bought the MAF for 370 with my mechanic friend's discount and paid 30 for the install. No problems since. What you have sounds the same as mine. Here is what happened for me and I had to change the MAF even though it looked "clean".

- Upon starting, it would stall out maybe 1-3 times while in parking.
- While driving it would tug as if switching gears, because air or fuel wasn't going through was my guess.
- No check engine lights until later.

If you ruled out the MAF, then I'm sorry I can't think of anything else. Good luck.

 

[chojinchef]

Maybe I will grab a used MAF to test theory from Eddie.

Really hate throwing parts at a car to 'rule out' probable issues.

 

[tackleberry]

Take it to autozone for a code check. Dont do anything until you get those.

Then, if you susoext maf unplug it then drive. See if anything improves

 

[W140 Heavy]

reads like an "idle air circuit" problem. When you're off idle the car is fine. but when you are on idle the car acts as if it is starving for air. The 140 MB's may not have an idle air control valve but the '87 420 SEL sure did.

 

[Chono123]

W140_Heavy has the right idea, the MAF sensor controls how much air to give or take away, and what was happening with mine was it wasn't giving it enough so it used to stall until I changed the MAF. Good luck sir!

 

[tackleberry]

Like I said....remove plug from maf and drive. See if it works. If car runs normally than you found your problem.

 

[95Scoupe]

You might check the number on your MAF. I have a perfectly good used one that you're welcome to test with.

 

[Benzonline]

Sounds like it could be a MAF for sure....hope that it is as its an easy fix!!

 

[chojinchef]

Just got back from another business trip.

Plugged the car into my OBD wiz software and found one stored and three pending codes. The pending codes were a P0100, P0455 and a P700.

The P0100 is a MAF code, but pending status seems to me to refer to something that was tripped and is now awaiting to drop off? Could be from trying the disconnect of the MAF?

P0455 is evap system leak. Think I need a new gas cap.

P0700 is TCM code for transmission.

The one stored code is a P1580, which refers to
P1580 - Mercedes-Benz
Type Powertrain - Manufacturer Controlled DTC - Manufacturer Controlled
Description. Throttle motor, TPM/ISC - circuit malfunction
Location Bank 1
Cause. Wiring, throttle motor, ECM

This would lead me away from MAF.

Mechanic friend asked me to wiggle the harness, to make sure it was not harness related. Was not aware that later W140s had issues with harness after the 94-95 harness debacle but he stated the had issues through 2002. Made no difference with any movement of harness.

Cleared codes and now trying to get codes to reappear.

Still have no idle to speak of.

Am I looking at new throttle body to remedy the issue?

LP

 

[chojinchef]

Tackleberry- I did remove plug from MAF. Made it worse as i could not even manipulate the pedal to force an idle with it off. Can't really drive it, unless I drop into gear at 1500 or 2000 rpm, it dies

When I did pull the plug off MAF, codes P1580 and P0100 reappeared.

OBD software is reading data from MAF. Have no basis of comparison to determine if draw is appropriate or not.

 

[tackleberry]

Have you reset everything then see what comes back.

If it is your eta its big bucks. But.....I do have one in my garage. Shoot me a part number off yours and ill see if it matches.

You also could rebuild your eta. Write up is on this site.

 

[chojinchef]

I have done the reset. Everything is same.

Going back to basics. Rechecked vacuum, harness connectors, re-checked OBD data, cable connector. Sitting in car, trying to think and I noticed one of fuel pumps is on the louder side?

That could cause my issue, couldn't it? Fuel gauge lent out, awaiting return tomorrow to check output of pumps. But if the positive pressure is waning while the suction pump is doing its thing, I am just starving the poor girl.

 

[tackleberry]

I'd check the harness. Both of your codes are from the same physical location.

 

[chojinchef]

Agree on base location of both codes. But they only popped up when I disconnected the MAF. I couldn't get any codes otherwise. Purge valve popped a code when I pulled that.

Harness is tight, wire sheathing is in great condition in the various places I checked. TBA is later style. I have one here from earlier model (back up for my E420).

 

[tackleberry]

P0455 is a serious leak in evap. Gas cap usually won't trip this. My guess is your evap is causing all your problems.
Keep in mind only codes you need to worry about are the ones that appear when all components are plugged in and appear after system resets.

 

[Sinned420]

Does your OBD scanner have live data? My e38 recently had MAF issue, it never threw any codes until I unplugged it (as expected). The MAF was just malfunctioning and the live data would show air volume being normal, but randomly will read 0 and the engine would either stall or hesitate and then suddenly the air volume would be back to normal.

I recommend the test with a working MAF (what concerns me is you mentioning K&N filters and those are known to destroy MAFs).

 

[eddie a]

Agree on base location of both codes. But they only popped up when I disconnected the MAF. I couldn't get any codes otherwise. Purge valve popped a code when I pulled that.

Harness is tight, wire sheathing is in great condition in the various places I checked. TBA is later style. I have one here from earlier model (back up for my E420).

I have the ETA you need, call me or email me at hotmail..you can come to the shop and try it before you pay for it if you want...let me know, ttyl

 

[chojinchef]

I have the ETA you need, call me or email me at hotmail..you can come to the shop and try it before you pay for it if you want...let me know, ttyl

Eddie. Do you have a known working MAF I can test with? I need to rule out some of these variables.

Really thought I was past all this crap. Suspension all new, new motor mounts, new flex disks, new tires to get it to ride smooth as silk and now virtually untraceable engine part issues. Wife wants me to get rid of it and get a newer GL.

When my Zetec powered VW bus is more reliable, I can't question her logic.:surrender:

 

[chojinchef]

So, what I have done to rule out variables.

Pulled plugs, all are dry and non fouled. They have less than 10k, so I left them. Also local FLAPS did not have plugs for me. That rules out coil issue, plug issues or wires and pretty much rules out spark problems. Battery is a year old and has been tested as good this morning. Checked major grounds and cleaned them up even though they were in fine shape.

Put a different fuel pump in yesterday to ensure I had pressure. (Sandy prevented me from getting my fuel pressure gauge back yet.) and awaiting a new fuel filter to arrive just to rule out fuel delivery issue in total.

That leaves me with the electronics. I can start it and have it idle if I depress the pedal while starting. Problem there is in cold starts I have more opportunity for issues. It will now idle somewhat.

Took it for a ride around the block this morning. Hesitant. Brought it back, it remained idling for ten minutes. Shut it down. Tried to restart and it lit up the BAS /ASR light while it forced a bouncing idle around 1000-1200. Shut it down, restarted and all was as if it did not happen?

Then thought it had to be a gremlin in the harness. There wasn't a centimeter of the engine harness I did not wiggle and twist to try and elicit a reaction on the car. No difference.

Now I seem to be left with the MAF or TBA. OBD software does have real time data, and I did not observe any figures that seemed out of line. However, it is a non Mercedes software and could be reading incorrectly.

Anyone have any ideas? Will try a known working MAF and Eddies offered a TBA to try. From there, I have no direction as of yet.

Was not aware of K&N filters causing issues. Curious.