Unclejake Posted November 3, 2011 Share Posted November 3, 2011 1996 E320 Mercedes. 225,000kms. Her car. I usually don't drive it but we have had it six years. It has been well serviced until recently, has had a new AFM around a year ago but has a very noisy drive belt or pulley. Voltages seem very good. Evidently for 'some time' (months?) the engine has backfired under full load and has not had the crisp power it used to. I managed to replicate the problem a few nights ago and it does miss/surge under heavy throttle loads and there is a muted, irregular pop from the exhaust. Under light throttle around town the car drives fine (until today). Recently it has been running too warm. Probably around 110-115 degrees C. This problem is a few weeks old. I drove it and using the temp gauge I couldn't be certain the thermostat was opening. I removed the thermostat innards and evidently the temperature is fine again. It hasn't gotten hot for me the couple of times I have driven it, but I don't drive it far. I pulled the thermostat out about two weeks ago. The car has sat idle for two days. The last time the wife drove it she said it smelt funny. I think that was Tuesday. I waterblasted the engine bay on Monday and the car ran fine after that. Today the nanny went to drive it and she had trouble getting it started. This is a new problem. It isn't clear if it was turning over or not, but after several minutes she got it running but after several hundred meters she said it started surging, the brake pedal was very hard and the car was vibrating. She parked it. I got there this evening and started the car immediately, but it did not seem to be running on six cylinders. I drove it to my workshop and was over powered by the stench of sulphur from the exhaust. It did not smell like this on Monday. I whipped out two sparkplugs and they were both dry and a good colour, but one electrode was eroded a bit. They looked serviceable but well worn. I didn't remove any more plugs as that seems to require the coils to be removed and I CBF I didn't have much time so I put it back together and the engine ran a bit better, but is definitely still missing and lacks power. There is no visible catalytic convertor light on the dash when the ignition is switched on. Either the bulb is blown or it does not have a cat warning light. Forward of the muffler there is something that looks like a cat convertor. There is a probe in it. Thoughts? Quote Link to comment Share on other sites More sharing options...
andy Posted November 3, 2011 Share Posted November 3, 2011 Disclaimer. I know next too FA about these engines but.... about 12 months ago my wifes Estima (01) had very simular issues minus the temp and backfire. It got progressivly worse. Toyota plugged it in and said it was the oxygen sensors and asked for a massive pile of money. Further probing and they admitted that their gear couldnt isolate the sensors. I took it to a sparky and had him check them and he said they were sweet. A bit of googling later and I decided to check the mass airflow sensor. It is a small probe and was caked in crap. I cleaned it with some air flow sensor cleaner (smelt like contact cleaner) and it ran perfect. It actually had more power than it had ever had in all the time weve had it. Andy. Quote Link to comment Share on other sites More sharing options...
Unclejake Posted November 3, 2011 Author Share Posted November 3, 2011 Is the MAF (?) going to be found in the induction piping prior to the plenum? If so they I took that out tonight and it was a tiny bit oily so I gave it a squirt of brakeclean Quote Link to comment Share on other sites More sharing options...
NaN Posted November 3, 2011 Share Posted November 3, 2011 Knock sensor (or knock, could be big ends or pre-ignition due to excessive coking). The ECU retards timing on knock until it thinks the knock is gone. Hence backfire and timing change. and loss of power. ? - I'm raising this, cos the initial problem sounds alot like the cars ECU is retarding the timing for some reason. Quote Link to comment Share on other sites More sharing options...
Unclejake Posted November 3, 2011 Author Share Posted November 3, 2011 It certainly did feel like it was retarding drastically. There is no hint of audible bearing knock though, and these engines are very long lived (it is the earlier straight six) so if it is a knock sensor it seems likely the sensor is poked (rather than the core engine). Would that explain the exhaust stench though? Andy - did your wife's car stink of sulphur? Quote Link to comment Share on other sites More sharing options...
NaN Posted November 3, 2011 Share Posted November 3, 2011 yeah it would. Extreme retardation would result in the timing not matching the fuel input, non burn = massive fuel stench. if no audible knock. I would try unplugging the faulty sensor, rather than replacing it. If motor will not start, assume ECU will not operate without it. (or a separate issue). Likely, possibility. Quote Link to comment Share on other sites More sharing options...
andy Posted November 3, 2011 Share Posted November 3, 2011 It certainly did feel like it was retarding drastically. There is no hint of audible bearing knock though, and these engines are very long lived (it is the earlier straight six) so if it is a knock sensor it seems likely the sensor is poked (rather than the core engine).Would that explain the exhaust stench though? Andy - did your wife's car stink of sulphur? yes it did. I thought maybe the catalytic converter had given up and I was smelling some form of breakdown. The airflow sensor was a small probe hanging in the throttle body. Have you tried it since cleaning it? The estima also had what I would call a massive flat spot and no response when stabbing the throttle. Andy. Quote Link to comment Share on other sites More sharing options...
Unclejake Posted November 3, 2011 Author Share Posted November 3, 2011 Interesting. After cleaning something that looked a bit like a lightbulb (with no glass) in the intake tract the car ran better. That was earlier tonight and before my first post. I just this moment took it for stone cold a burn and it is missing/vibrating at idle, but will rev to 5,000rpm in first and second gears. I only went 200 meters. Quote Link to comment Share on other sites More sharing options...
andy Posted November 3, 2011 Share Posted November 3, 2011 Interesting. After cleaning something that looked a bit like a lightbulb (with no glass) in the intake tract the car ran better. I just this moment took it for stone cold a burn and it is missing at idle, but will rev to 5,000rpm in first and second. I only went 200 meters. sounds like the right sensor. Keep spraying everything with contact cleaner until its fixed Quote Link to comment Share on other sites More sharing options...
Unclejake Posted November 3, 2011 Author Share Posted November 3, 2011 LOL. You could be onto it. I have basically sold the car and the dude (OS GC) is coming on Sunday. He knows it has issues and no money has changed hands yet. Today's incident had me thinking that I would have to back out of the deal and send the thing to the wreckers (which had been my earlier plan). If the MAF is the culprit then perhaps he is about to get a bargain.... or a huge MAF invoice. Quote Link to comment Share on other sites More sharing options...
Unclejake Posted November 3, 2011 Author Share Posted November 3, 2011 OK. Here is the thing I cleaned. Google says it is an Air Temperature Sensor. Does that mean I have to go find another sensor? I know what an Air Flow Meter looks like (a big thing the same diameter as the air intake hose after the air filter)... or does the MAF live inside the AFM? Quote Link to comment Share on other sites More sharing options...
andy Posted November 3, 2011 Share Posted November 3, 2011 my memory is average at best but yeah I think there were two sensors, an air temp and an air flow. It did look like that though. Someone on here should know better than me. The good news for you is that the sensors as pictured mean you would not have to buy a complete throttle body... maybe. Quote Link to comment Share on other sites More sharing options...
andy Posted November 3, 2011 Share Posted November 3, 2011 http://www.benzworld.org/forums/w210-e- ... -e320.html http://www.benzworld.org/forums/w210-e- ... aning.html Quote Link to comment Share on other sites More sharing options...
NaN Posted November 3, 2011 Share Posted November 3, 2011 Nissan quoted me $750 for a maf. The car is worth 3k. That doesnt add up. I did some research ... http://www.anythingelectronic.co.nz/front.asp <-- these guys will fix a maf for $150. Most Mafs' work by heating a wire, the air flowing over the wire cools the wire, changing the resistance, which is what the ECU measures in determining flow, thus fuel consumption. The wire degrades from the date of manufacture, not use. Older the car, more likely it needs a new wire in the MAF or AFM. I forget which. NOTE: this information relates to NISSAN Airflow meter No: 22680 2J200 other models may differ in operation, and repair needs. Apparently alot of manufacturer's use bosch parts so there are commonalities, but they all approached the difficulties of accurately measuring airflow in different methods at various points in time. Quote Link to comment Share on other sites More sharing options...
Unclejake Posted November 3, 2011 Author Share Posted November 3, 2011 Thanks guys. We paid around $850 for a new aftermarket Mercedes Air Flow Meter (I am almost certain that was what it was called) around 10,000kms/1.5 years ago. From the look of Google and the link Andy has supplied it seems that the MAF lives inside the AFM. Do I have that right? Quote Link to comment Share on other sites More sharing options...
NaN Posted November 3, 2011 Share Posted November 3, 2011 there you go, they can fix it. http://www.anythingelectronic.co.nz/rep ... low&menu=1 I bet it costs $150 to fix, and $16 postage each way. I spoke to the company owner on the phone at some length, since we're both electrically inclined I picked his brain on the topic, very knowledgeable, very nice, honest man. I'd say he does great work, and has a fast turn around (he reckons about two days from memory) Quote Link to comment Share on other sites More sharing options...
andy Posted November 3, 2011 Share Posted November 3, 2011 I just edited in another link with a PDF. Good pics. Quote Link to comment Share on other sites More sharing options...
Unclejake Posted November 3, 2011 Author Share Posted November 3, 2011 Thanks again gents. Based on all those pictures and links I have not touched the MAF yet, but is it fairly new. I will take it out for a look tomorrow night. If It is buggered I will be a little disappointed in Mercedes Benz as it was they who fitted the new one not that long ago. Of course it may still be a knock sensor... or something else (like rooted spark plugs) Quote Link to comment Share on other sites More sharing options...
Yowzer Posted November 3, 2011 Share Posted November 3, 2011 I think some weird form of air flow sensor is effectively a heated temp sensor, and calculates the air flow based on the temperature drop of the sensor as the air flows over it? Or something like that? That sounds like the MAF thing you are describing, which would explain why the car runs like crap when it's covered in gunk. [edit] already answered. Quote Link to comment Share on other sites More sharing options...
NaN Posted November 3, 2011 Share Posted November 3, 2011 actually, it's oxidisation over the metal which buggers it. So, even if you got a new one recently it was probably rubbish already if it was made years and years ago. The themo-reactive metal oxidizes and the sensor is stuffed. Oil certainly will effect it, but if you have to clean it no touchy-touchy!. Spend the money on the CRC maf cleaner, spray only the reactive metal, if you 'must' wipe it down do it by spraying the cleaner into a cup or similar and use cotton buds (ear cleaner thingy's), most of the time the cleaner just helps for a month or so. Customers tend to come back and just pay the money for a new maf. (usually on a tow truck) Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.