06 SL500 P0100 P1346 MAF and Knock sensors help needed!
 

Hi,
I have a 96 sl500 w/91k miles that I am having some problems with. Car stumbles and almost dies at idle intermittently. Took the car to a friend who read the codes and P0100 ( MAF ) and P1346 ( knock sensor) came up. I am going to test voltage (67/68) , ground wire test, and make sure that the wires/connection are good and that the culprit is the actual MAF sensor ( 400.00) and I can replace that. The stange thing is my friend alert me to a cold tick/knocking noise that I never heard before. Start the car cold and there is this intermittent driver side engine tick.knock noise that kinda comes and goes and then is gone. It is not constant, has no pattern ( as if something that is sticking and comes/goes). I am trying to find the source with my headphone noise stethescope but haven't pin pointed it yet...

Only when cold, and you have a to wait a few minutes for it to show up if it will. Car can stumble during this time. Once car is warm - no noise

Questions
1. Is this just a bad MAF and the engine set the knock sensor by the end trying to retard to timing upon stumble and this code is nothing to worry about ?
2. I am trying to isolate the noise - if it were serious - i would think it would be there all the time and the engine would have locked up by now
3. I also saw a service bulletion for "short, loud, rattling noise during cold start" - problem "oil filter return valve leaky" thoughts on this one ?
4. I read all the notes on timing chain, lifters etc..haven't be able to isolate where the noise exactly is yet.

Any wisdom from the forum - greatly appreciated.
tx
Tom

RE: 06 SL500 P0100 P1346 MAF and Knock sensors help needed!
 

sorry - it is indeed a 96. I wish i had an o6 as the title says :-)

RE: 06 SL500 P0100 P1346 MAF and Knock sensors help needed!
 

do you have acceleration problems during cold start, if so bad sensor. your knock sensor is going to throw a code if the engine is misfiring. your engine is going to misfire if your mas air flow sensor is faulty. quick diag step. let your vehicle sit overnight, unplug the mass air flow and start the car. the stumble should disapear. have your replaced your maf yet. bad maf's are common problem with all mercedes. as far as the tick goes, alot of people hear a ticking noise coming from the evap purge control valve. it pulses to let fumes back into the fuel tank. it is a black solenoid that is about the size of a pill bottle. it is located on the left front fender.

RE: 06 SL500 P0100 P1346 MAF and Knock sensors help needed!
 

Thanks for the msg. I have solved the stumbling problem - based on passing the voltage test at the maf - i took a chance that the maf was defective , changed it and the car runs fine now. 400.00 fix. The tick noise i have not solved. I thought it was the belt tensioner pulley bearing - but replaced that (20.00) and it is still there. Now i notice that I can really make the tick lounder by putting the car in gear with the brakes on ( as to load the engine). Will do more probing this am. Not sure if it is an accessory pump off the belt ( will disconnect belt and test) or if there is sometime inside the engine that is causing the knocking noise.

Only does it when cold and then clear up after 10 mins..Noise sounds like at the front of the engine. Having a ahrd time pin pointing it with my steth..

any other thoughts ?