JAD

I have a 99 ML 430 with 45,000 miles and the check engine light came on. Its still under warranty so I took it to the dealer. They said 2 codes caused the problem, MAF which they are replacing free and spark plugs which would cost me $450 (a maintenance item)! The car has driven just fine, no weakness or shaking. How hard is it to replace the plugs (the car doesn't even feel like it needs it)? I am not going to pay $450 to get plugs changed if I can do it myself.

When driving the car, the engine performance feels fine so I was curious why the light came on. Certainly isn't misfiring or stalling or running weak....Could any damage occur if I don't replace the plugs? Thanks.

BillM

The MAFS is usually the main culprit of the CEL along with the gas cap. The plugs are suppose to be rated to 100k. I have heard others say the plugs are a pain to get to but, $450 sounds a bit high. Keep us posted.

JAD

Picked up the car this evening. The engine seems to be running a little bit smoother, more refined but not more powerful. Loss of power never seemed to be a problem. The car seems to be running very well, I'm very skeptical about replacing the spark plugs at 45k. Anybody else?

azinn

Dealer replaced my plugs along with the MAF under warranty on my '00 ML430 last week at 46,000 miles. SA said plugs need to be replaced when MAF is bad, I guess they get dirty. Truck seemed to run okay to me.

JAD

Hmmm...that's strange, they replaced your plugs under warranty? The dealer told me they weren't covered because that was a maintenance item, not a warranty item. That pisses me off!

allan911

The CEL keeps coming on on my wife's 1998 ML320. What exactly is the MAF? One time, the gas cap was ont tight, and the SEL light came on. NOw, something periodically causes the ML to go into "limp home mode" even when the SEL is not on. does anyone have a clue what might cause the CEL to come on, or what might cause the ML to go into limp home mode (with CEL out)? thanks

azinn

My truck had to be flatbeded to the dealer twice last summer when it went into the limp mode. They ended up replacing the valve body shift plate which includes the speed sensors. Total cost for this was $706.36, which was covered under warranty. The MAF is the Mass Airflow Sensor. Mine was replaced under warranty along with the spark plugs for a total of $613.20. Hopefully I've got all the bugs out of this beast before the warranty runs out in November or 4000 miles.

ghitos73

Q: What is a Mass Airflow Sensor?

A: Mass Airflow sensors contain a thin-film, thermally isolated bridge structure containing heater and temperature sensing elements. The bridge structure provides a sensitive and fast response to the flow of air or other gas over the chip

I experienced similar problems (shaking truck, limp home mode, etc.) on my 98 ML320. I tried the cheap stuff first (Fuel additive, spark plug replacement) since my ML was no longer under warranty. Changing the spark plugs were a definite pain in the rear! I ended up damaging one spark plug wire in the process (set me back $70). Anyway, I bought an ODB-II Code Reader and managed to isolate the problem to a bad MAF sensor. It was a simple fix that you can do it yourself. In fact, I did it at the dealers lot. I paid $293 for a new one from the dealer.

• 12/12/02, 60480 miles.
Replaced Mass Air Flow Sensor.
p/n: 112-094-00-48

• 11/30/02, 59979 miles
Replaced spark plugs w/ Bosch Platinum +4.

jjcast

I had a 2000 ML320, check engine light was on all the time. I never did get a decent explanation as to why. I refused to spend a dime on the vehicle though. Finally got so fed up with the problems, in shop every 6 weeks, i had MBUSA take the beast back and terminate my lease. I have had an E320 with no problems and now have a 2002 c320 wagon which is a cool little car.

sorry for your troubles...i think its just the MLs are terrible

Callahann

I have a '00 430, it's the worst vehicle I have ever had. I just spent another $800 for a B service and an O2 sensor. This makes about the 13th time to the dealer for something wrong/broken, but first out of warranty. Just not very good vehicles, too many things go wrong.

allan911

ghitos73. I wanted to thank you for the tip on the MAF sensor. I ordered one from a Mercedes parts wholesaler in California (I'll have to post the name later). the price was $198 delivered to my door in Ohio. It was a Bosch replacement part for the Mercedes MAF. It took literally 5 minutes to change out and re-set the computer. the perfromance is back, the ML hasn't run this good in a LONG TIME. I am hoping that the plugs do not need replaced, but this same parts place has replacement plugs for less than $6 each. BTW, the CEL is off, hopefully for good, or until I can sell this SUV and buy an MDX.

thanks
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allan911

Well, I finally don't have any more headaches regarding our ML320. We got rid of it yesterday and now own an Acura MDX. Rides MUCH better, it is faster, much nicer inside with much more room even in the 3rd row of seats. The last Honda product we owned never went back to the dealer once the entire time we owned it (8 years). The Mercedes went back for warantee and non-warantee work 13 times in 5 years. oh well, live and learn

Popeye430

I have a '99 ML 430, the CEL is always on in mine too. I took it in and they said I had a cracked crankshaft pulley, needed ne MAF, and new spark plugs. These were the original plugs, and I have 93,000 miles (mostly highway), the price for the plugs was $365, $450 is high, maybe its a dealer thing idk, and the new MAF and pulley was $600+. I love my ML and how it performs, but the quality and the ride aren't typical for Mercedes. It does have its problems but its still a good vehicle.