I have a 1998 MB E320 that has recently developed problems.
When the "Check Engine" light initally came on, I took it to a local shop and had the "codes" read.
It told me Mass Airflow Sensor fault, and misfires on Cylinders 4, 5, and 6.
Since it was due, i replaced the plugs with new Bosche Platnium 4 plugs. (no small feat on the drivers side I tell you)
Immediately after that, I replaced the MAS... No problem.

After all was said and done, I pulled both posts from the battery as suggested and waited the 60 seconds.

reconnected the bat and let it sit for 5 min.... turned on the key and let is sit for another minute.


When I started the car it idled like a dream... EVERYTHING IS FIXED!.... not.

now the car will not accelerate through 2000 rpm without a pronounced stutter, almost a stall.
It doesn't matter if it's sitting in the driveway in park, or driving through the neighborhood under a load.

there are currently no engine lights, and no faults.... I'm at a loss.

Where do I look next ?

 

hey,, check the crank shaft positon sensor which is located at the back of the engine were the gear box meets the engine. replace it and see what happens. goodluck with the problem. Paulie

 

Did you use an OE MAF (=Bosch).
Sure its for the right engine? The sensors all look the same but have different characteristcs.
Was it new or ex. eBay etc?
Bosch units have the Bosch and Mercedes Part No.s printed on them
Try fitting the old MAF again and see if this clears your problem.

I prefer to use OE equipment. Doing so removes the possibilty of the non OE part causing n unexpected problem.
A post last week had a problem with these plugs (new set gave misfire on a couple of cylinders but this showed up as a DTC).
I'm sure a lot of other people swear by them however so its a personally point of view (backed by MB of course)

As you say its strange that the diagnostics aren't picking up the 2000 rpm "stutter" = misfire.

Just possibly this is for the following reason.
Your CEL came on most probably due to a P0173 DTC which is the MAF out of spec at startup. If this is not the case what was the DTC that caused the problem since this MAY be significant and indicate the real cause of the ongoing problem.

The new MAF MAY have cleared the original DTC which caused the CEL to illuminate but on the other hand it may have been cleared by the reset.

If the original DTC was cleared by the new MAF, and if the new MAF has the wrong characteristics, the engine may go Lean at 2000 rpm. If it is going Lean it may require a number of cycles before the diagnostics decide to illuminate the CEL.

Just as a point of interest engine speed is limited at rest (something like 3000 revs) to prevent damage to the engine.

Don't know what sort of scanner you are using and whether you can see Pending as well as Current DTC's etc. Even if the light is not on the diagnostics (with a good scanner) may be recording a problem.

If none of this helps I'm also at a loss.

Good luck,

Keep us posted.

Stuart

 

Stuart..................

I purchased a OE MAF complete with Bosche and MB p/n intact... it was a rebuilt from AutoZone.
(((Strange, but the engine characteristics seem the same with the new MAF and without one at all.)))
putting the old MAF back in the engine re-creates the same super rough idle and lack of throttle as it originally did.(also sometimes causes the engine to die... NEVER allows the car in gear, the engine lugs and dies almost immediately)

I may have mis-characterized the "stutter".. it's not so much a miss, as it is a stall.... the car revs ok up to about 2k then dies as though it's starving for fuel until I get off the throttle at which point it revs down to normal idle just fine.


I'm off to the AutoZone to borrow their scanner again this morning to attempt to diag any pending DTCs.

maybe I'll try to drive the car there in order to prompt any pending DTCs in the process.

I will keep posting the progress of this fiasco....

Please, if anyone else can remember seeing/hearing anything similar or have any other ideas, I'd be glad to entertain them.

 

I would suggest you try this or check this before spending anymore money. Remove the spark plugs you've just installed and observe what on them. Wipe them off, use a little di-electric grease on the threads and reseat them. Remove the rubber boot from the coil pack and observe into both ends, there may be moisture in there. If the moisture is not apparent, blow them out anyway. Observe into the electrode end of the coil pack, take a cotton swab and swab it out to ensure that there is no moisture in there. Take a swab and apply a thin layer of di-electric grease to the electrode, re-attach the rubber boot to it; swab the end that the boot re-attaches to the spark plug. BTW, do this for every cylinders that was mentioned. I would suggest that it do it for all of them.

Please don't write-off this suggestion before trying it. It can only help you to rule this out as a possible cause, and it doesn't cost you anything but time and effort, but your cash (for now), you can still keep in your pocket.

Do what Snanceki said; "re-install the old MAS, and see what trouble codes re-appear." If this doesn't work, then re-install the new MAS. If this doesn't do it, then you can check those other items that has been suggested. But, if this does work, then you take the new MAS back to AutoZone, and get your refund. That's what were trying to do, save you money!

Hope this helps you. Let us know.

 

Ok... here's the latest.

I've finally broken down and bought a code reader... and Actron CP9145.


Note above I have already tried the MAF swap this morning.

I have (without resetting the codes) hooked up the code reader and get the following codes.

P0100 MAF circut malfunction
P0110 IAT Circut malfunction.


these both seem to point in the same direction... back to the MAF.

I will, however pull the plug wires and use the di-electirc grease. (bought some of that at AutoZone when I got the code reader... I'm making these people rich)


more postings as they develop....

keep the ideas comming, I don't want to spend any more $$ on this set of wheels than I have to.

 

No need to spend any money YET.

Is the plug and wiring to the MAF OK? Inspect it carefully.

Both codes are MAF specific so it looks like a MAF/plug problem. Codes are MAF cicuit and Air Intake Temp. Common factor the MAF as you state.

What happens if you clear the DTC's and reconnect firstly the new MAF, and then reclear and connect the old MAF.
Does the P1100/P0100 code reappear? with just the new MAF or both?

Please confirm that you do not have the CEL on.

Stuart

 

but why wouldn't there be a CEL and a misfire code?

Stuart

 

Rebuilt = Not OE. I'm suspicious.
Where is the part number. On the sensor itself or the body (4" approx dia cylindrical housing) into which the sensor goes?

the codes you have read. These may have been left over from the previous old MAF. You need to reset and rea again.

Stuart

 

the numbers for the MAF were read from the housing, not from the sensor.

I am off this morning to reset the system and start from scratch.... I will look into the part numbers on the sensor while the system is unplugged and let you know about that...

Additionally I do NOT have a CEL on the display, and there is no missfire code.