Can any one tell me what code 10 Voltage at air mass meter to high or low means. Is the sensor bad or wire harness no good. I got 10 blinks on the self diognostic plug by the battery which is 16 pin plug (obd I). The car rough idles when you release the accelerator for a few seconds and smooths out and hesitates between 2000 to 3000 RPM over 3000RPM accelerates fine. Any suggestions is appreciated. thank you.

 

Not very familiar with OBD1. However you definition is very similar to OBDII P0170/3 which is the classic signature for the MAF requiring cleaning or replacement.

The MAF determines Air Flow which is a key input to the fuelling computer. The voltage at "startup" (Ignition ON, engine not running) is compared against set criteria and if out of spec signals a fault.
Two main parameters are measured. In OBDII there are different code signatures for these two checks. maybe in OBDI they gave the same code due to a simpler code structure.
1. Resistance of the MAF at ignition on. If incorrect it signals that the MAF cannot be operating correctly. Self Diagnosis check.
2. What "offset" correction is applied to the voltage coming from the MAF with the engine running in order to position the O2 sensor output within a specified range. (i.e. Correct mixture).
If this correction value is out of spec it signals a fault somewhere in the fuelling system which includes not only the MAF, but the Injectors, O2 sensors, ECu etc etc.

Next step. Clean the MAF and see if this "magically" corrects matters. If not a replacement MAF sensor moves up the list but you need to rule out O2 sensor and other possibilites first before reaching for your pocket book.

Is the Service History of the car up to date. Plugs, filter, etc etc.

Stuart

 

Thank youStuart for the advise, I've owended thecar for 8 yearshad 40k mi.now at 145kreplaced the spark plugs every 30k miles, air filter every 15k mi. O2 sensor every 50k, according to the manual.The car started hesitating 10 days ago. Time for tuneup. Ordered spark plugs, wires, air filter, and O2 sensor. The next day CHECK ENGINE LIGHT came on, first time in 8yr.Parts arrived after a week replaced parts except O2 sensor still in transit, will replace over the weekend. I cleaned the sensor, still the same.I'm planing on ordering MAF sensor, not cheap, but wasn't sure the way the code was written. Again thank you for your help.

Thanks

Phil

 

Looks like the car has been regularly serviced.

I'd have given the MAF a clean first before ordering a new one but so long as no one has messed around with things and all has been OK for 8 years the MAF is high on the list of potential causes.

As I stated the MAF works in conjunction with feedback from the O2 sensors so I would have had a look at the voltage coming off the O2 sensors before replacing expensive parts. However measuring the voltage of the O2 sensors is not quite as striaghtforward as it seems since the signal is cycling.

Lower on the list of possibilities is the throttle actuator since this also plays a part in the amount of fuel going into the engine and these do corrode over time or even mechanically wear the electrical resitance away which senses throttle position. I do note however that the problem occurs at small throttle angle which of course is where such wear takes place.

Finally is the insulation on the engine wiring harness in good shape. High ambient temps in the USA seem to cause degradation problems.

there are of course numerous other possibilities like sticking injector, faulty coil(s) etc but you need to eliminate MAF and O2 sensor first if everything else has been serviced regularly. 145k you are into worn out (replaceable) component territory.

Good luck,

Stuart

 

After replacing the O2 sensor, ( I ordered before the Engine light came on) the car was running the same. Cleaned the MAF whith MAF CLEANER, same problem. Ordered the MAF sensor on Ebay for $100 compered to $430 @ dealer. Replaced the MAF, problem solved, light has'nt come on, the car runs like the day I got it. Thank you Stuart for the advise.

Thanks
Phil

 

UPDATE ON THE (CEL)
AFTER REPLACING THE MAF THE CAR WAS FINE FOR ABOUT 10 DAYS AND THE (CEL) CAME ON AGAIN IT APEARED ALL THE PROBLEM WAS BAD ENGINE WIREING HARNESS IT WAS IN BAD SHAPE SURPRISED IT STILL RAN. MERCEDESSHOP.COM HAD THE BEST DEAL $852. REPLACED IT MY SELF IN ABOUT 3HRS. ITS BEEN OVER A MONTH AND NO (CEL) THE CAR RUNS GREAT.


THANKS