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Discussion Starter #1 (Edited)
Hello all...I need some wisdom from someone/everyone on what to do next!

Here is what is happening...

10 days ago I was attempting to pass someone and just as I got up to about 60mph...the CEL came on and the car jerked (like a standard does when you downshift by mistake) and then started to sputter and felt like it was going to die. I immediately pulled over and turned the car off. I then turned it back on and it started perfectly and sounded/ran fine...however the CEL was still on. I turned around and headed back home...as long as I kept it under 40-45mph...it did fine, but if I pushed it, it would do like it did the first time.

The next day I took it to Autozone and had them check the codes...it said
P0305 (2 times)...misfire on cylinder 5. As I was leaving Autozone it would not start. It finally did after about 6 tries. I brought the car back home and my fiancé tried swapping coils on cylinder 5 and 4...thinking if that was it...the codes would follow. We drove (slowly) back to Autozone and had them check the codes again. This time it said P0305, P0306, P0302, P0300 and P0335. SO...we went home and started doing our research. The next day I ordered a CPS, new plugs and new wires from autohausaz.com.

Saturday my fiancé replaced the CPS, plugs and wires. He drove it around the block, the CEL was still on and again it tried to die if he pushed it over 60mph. At that point we knew we needed help. Monday I took the car to a Mercedes Mechanic that I have used before (maintenance/oil changes) and who comes highly recommended by my other MB friends. He had the car for an hour and called to tell me it needed a MAF and a breather hose. I told him okay, lets do it and he said it would be ready by the end of the day. Well...4:30 rolled around and he had not called, so I called him. He was very short with me and said it would not be until Tuesday afternoon sometime.

When he called Tuesday afternoon he said...we have a problem. I asked what...he said they replaced the MAF...nothing...they replaced the coils...nothing...it is still throwing out the P0305 code. They thought maybe it was the catalyst...nope...it was clean...he even said that this particular engine, when it has trouble is usually very mucky and full of sludge and oil...mine is clean. They ran a compression test on cylinder 5 and it is losing pressure at 3500. He said its either a broken valve spring or wristpin. I asked what all that meant...he said, it means its time to get rid of it, trade it, do something...but it was not worth fixing. It would probably need a new block and they run $12000. Yes, that’s right $12000!!!!! After I pulled myself up off the floor, I asked him to call my fiancé and relay that information to him.

We went and picked up the car this morning. Again the tech said they believe its either the valve spring or the wristpin and either way its very costly. My fiancé is not convinced. He thinks that if its a valve spring...it can be fixed and it wont cost an arm and leg. He was a mechanic on nuclear subs in the Navy and is mechanically savvy. He knows his way around cars...and thinks we can do this with some guidance…IF THAT IS WHAT IT IS. But is it worth it? I am so confused!! Does either of these things sound plausible? Has anyone had this experience? New engines are so high...so are rebuilt ones! This car has had many little problems...but this...this is BIG! The CEL is off now and it runs good as long as you don’t push it. Please...some guidance would be greatly appreciated!!
Thank you!

My Car: 2003 C320 sedan with 83000 miles
Bought almost 2yrs ago from a dealership (not MB) with 52000 miles on it. It was a leased car from NY they purchased at auction. I asked about their extended warranties...they said "no need...these cars run forever!" I am still paying on the car.
 

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My two cents worth, but why would a wrist-pin or a valve spring require a block change! I'd ask that question. And I do not understand how a wrist-pin could cause anything like this! Wrist-pins can float in the piston or be constrained with circlips, some are press fits. But there is not much that can go wrong with a wrist-pin. I remember in days of old they could work loose and score the cylinder, you might get blow-by, noises, rattles, but not what you are describing. And I have not heard of such a thing on a modern engine anyway.

And the valve spring! That's a puzzler too unless there is valve bounce at high rpms or something similar, the valve not closing properly due to some failure or setting error - but this would not require a block change!

Does the problem happen only at speed? In other words when it happens the engine is at some set rpm, supposing you were in a lower gear and travelling slower, but at the same rpm; does the same thing happen?

My last C230, a 1999 model, had an issue where the engine would just die. EVERYTHING would cut out and it would roll to a stop. The engine would then restart well enough and it would be fine for a few more hours or days. This was unrelated to rpm, speed or load, and I took it to the MBZ dealer who diagnosed an electronic part - I have the name of it at home but not here I am sorry to say. Replacement was not cheap, $1200, but the problem - and it sure was a problem - went away. I actually sold it soon after this but I think it was fixed.

If the engine turns over smoothly, has power when you floor-it, does not belch or make rude noises and does not push out clouds of smoke - but then cuts out and splutters like you describe at high rpm under load, I would suggest it is not a mechanical problem but more likely an electrical one.

And I would suggest a trustworthy dealer, someone who has experience in some of these odder problems.

Hope this helps...

Lawrence
 

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Discussion Starter #4
Thanks Lawrence!

That’s exactly what my fiancé said...new block?...why?? It bothers me that they even said it though...almost insistent...I cant help but wonder if they saw something else and are not telling me. They only charged me for the replaced breather hose and the diagnostic check on the Star Diagnostic Computer. I was afraid they were going to charge me for all the other parts they tried (MAF & Coils) and/or the time they spent with it, but they didn’t. It may have been all my tears that kept them from doing that!!

The only time it really acts up and tries to die is when you punch it...like I was doing when I was trying to pass the other car. If you slowly accelerate...it seems to do okay until you get to about 45mph...then it starts to run real hard. I have driven it up to 60mph like that and it did not die, but boy it did not feel right. It seems to shift gears smoothly and I had not noticed it doing anything at a certain rpm. The faster you go, the worse it feels and sounds and if you punch it...forget it...you are toast!

My fiancé did say the same thing though...this car has had a lot of electrical bugs...his thought was this may be just another one. Now...I need to figure it out. As much as I hate it...I think I will just have to bring it to MB.

Thank you again,
Nikie
 

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OK, how would a weak valve spring or broken piston lose compression. If the piston wristpin broke, I would imagine that it would make noise and eventually throw a bearing which also makes noise. So find a mechanic that knows how to really do a compression test to isolate if it's a head or cylinder leak, it's very possible but it's a different test. My guess is you probably blew a head gastket, not common but more plausible than the other 2 guesses. Also, check the radiator for oil, check the oil for water contamination, sure signs of a blown head gastket but not necessarily the only ones.

But lets say he did the compression test wrong and that's not the problem. Many times, the problem is a weak fuel injector. Works fine at low RPM but can't put out enough fuel for high loads so you get a misfire on that cylinder. If you know how to do it, swap the fuel injector with another one and see if it follows that cylinder, just like you did with the sparkplugs. BTW, your C320 is not a nuclear sub, I don't see how the two relate.

Lastly, say it is some catistrophic engine failure and neither of what you described is catistrophic and would certainly cost less than $12K to fix unless you are trying to fix inside a nuclear sub using govt sanctioned $1,000 wrenches and hammers. You can go to a salvage yard and get 3.2L for a few grand, maybe $2K (check Potamac Salavage in Maryland or getparts.us for a search of salvage yards). Then putting it in shouldn't be more than $1-2K or a weekend with an engine hoist and determination.
 

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Discussion Starter #6
Thanks! You made me laugh...I needed that!

I am going to try the fuel injector swap and see what that does. AND if that does not work, find someone that can do a good compression test. I will let you know what I find!

Thank you all again!!
 

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All of these ideas are pretty much what I was thinking earlier - and it is definitely an electronic issue…for fun – put it in park or neutral and rev the engine and listen…if it is not making any horrific mechanical sounds then it is electronic…My dad and I built a fuel injector cleaning station because – as commented on – this is a common area for trouble…especially if the car sits or if it is being fed bad fuel…the pintle can get gelled or the screens can get plugged and you need to back flush them and clean them. Speaking of bad fuel – when was your main fuel filter changed last? I have seen people never change the filter, and then the pre-pump filter can get clogged too…One of my favorite family fixes was a relative never changed the filters…then one day the car acted very much like your car is now…my father and pulled the injectors first – and what do you know – they all looked like sand and dirt had completely filled them up! So we disconnected the fuel line and pulled the gas from the rail to the filter out and it was filled with rubbish! A full clean up and the car ran a-okay! Another option could be that the TPS or throttle position sensor is not happy and when you peg it the resistance is not where it should be so what is happening is the air coming into the throttle body is not matching the position the valve is at and not metering against the amount of o2 in the exhaust – car gets upset and goes to limp mode…I would track down the electrical bug…
Jake
 

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I read this forum all the time but I had to chime-in when I saw your problem. We used to have an ML320 which I believe is the same engine as yout C320. Our car had the same problem, with the same mis-fire codes. The most obvious solution was to replace the MAF. I called the dealer and they wanted something like $4-500 for one. I got one at Autozone for $160. The one from Autozone was clearly a refurbished one, I could see screw driver marks on it from when it was pried off of its orginal engine. Also, the sensors weren't very clean inside. I went ahead and installed it but it did not fix the issue. The car still ran bad and I got those misfire codes again. I did the same thisgs you did, changed the coils, breather hoses, etc.

I finally gave in and took the car to the dealer. Knowing that the MAF was replaced, they were stumped at first, too. Eventually, they replaced the MAF again but with a new MB part. The car ran fine after that. If I were you, I'd just take it to the dealer. It may cost you to get it fixed but at least you'll get the problem solved.

Oh, and one more thing...I was so pissed at Autozone. I had to escalate all the way to the district manager to get they to take their defective part back.
 

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First, a MAF doesn't generally cause misfire codes on just one one cylinder and it would have accompaning codes to show a fuel trim error. Secondly, even if it was a MAF error, you can simply disconnect the MAF, unplug it and the car will run fine and obviously, this car does not run fine. When you a get a misfire code in just one cylinder, you have to ignore items that affect multiple cylinders like fuel pressure, o2, CPS and MAF sensors, and focus on what can cause a misfire on one cylinder. On the M112 motor, each cylinder has 2 spark plugs, so the odds of a spark plug problem are rare unless both are bat but heck, changing plugs is the easiest cheapest thing you can do so people try that first. But first you must analyze the plug and compare it to the other cylinders and see if there's oil on the plug that may show oil blowing by rings or coolant stains getting into the combustion camber through a blown head gasket. Also, fuel injectors are always suspect as they get weak or clogged with age. Seriously, if it's not the injector, then a complete compression test needs to be done. That means disabling the fuel pump (remove fuel pump fuse), remove all plugs, and take a compression reading on all 3 cylinders on that bank by turning the engine over a few times, then redoing by pouring a spoon of oil in each cylinder, if the compression goes up after adding oil, then it's the rings or piston, if it stays the same it's the valves if it's low on two adjacent cylinders it's the head gasket but it can still be the head gasket even if one cylinder is weak. Then you pull that head and see, it will be obvious if a head gasket is blown or a valve is burnt/cracked/broken/bent/sticking. It's certainly not fun and you have to find a mechanic that does more than just oil changes and tune ups. But at best it's a blown head gasket, at worst it's a cracked block, in between is a burnt or bent valve, cracked cam, hole/crack in piston.
 

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Discussion Starter #10
Thank you to everyone! This is a lot of good information!

First...we already replaced the fuel filter...that did nothing to change the problem.
Second...yes, when you place the car in park and rev the engine...it sounds and behaves perfectly.
Third...they did replace the MAF with a MB part and it did not change anything. They said the same thing...its just ONE cylinder that is throwing a code now, so that cant be it.
Lastly...we are going to try the fuel injector and see if it’s the culprit. We are also going to try a compression test. Thank you Buellwinkle for the step by step!

Also, my fiancé asked me to find out what the torque specs are for the rocker arm and the valve cover AND if the fuel injectors are a "bank" or "sequential". I am not even going to pretend to fully understand what he is asking for but I have looked everywhere I know to and can’t find them. If you can help me with that information...I would be most grateful!

Thank you again!
Nikie
 

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i thought you said you already tried a compression test.

really you need to find a different mechanic. a misfire on 1 cylinder isnt hard to figure out. you have a coil, wire, injector and plug. if all those were replaced and problem still remains, do a compression and leak down test. if both are good, something is wrong with your wiring or you have a bad ME.
 

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Discussion Starter #12
Yes, they did a compression test at the shop, but they also said I needed a new $12000 block...so we are not convinced that it was done properly.

Wiring...what wiring? What is an ME?

Okay...let me tell you what happened last night after we swapped the fuel injector on five w/the fuel injector on four. I cranked the car and it sputtered at first, but then started. My fiancé told me its because he had to drain the fuel rail and there was air, but that was fine now. We drove it around the block and I was able to punch it w/out it jerking...but it sounded like it was "stuck" in gear...like it would not shift properly. I got up to about 60mph with the RPMS going really high, then the CEL came on and was FLASHING. Once I let off of the gas ...it stumbled and started to choke...like it was running out of gas, once I stopped...it died. I turned it back on and it went back to normal. The CEL stayed on.

This morning I took it to AutoZone, hoping that the code for cylinder misfire on four is what it would say...no such luck. It said misfires on 5, 4, 2 and all cylinders. My heart sank. So I thought...because it hesitated to start after swapping the fuel injectors that perhaps that would make all the cylinders misfire. Don’t know...but it sounded good to me...so I asked him to clear the codes and let me drive it around the block and see if I could get the CEL to come back on and then we can check the codes again. He did and I took off around the block. I tried and tried to push it...I got it up to 60mph and it did nothing other than sound "stuck" in the wrong gear. So I pushed it again and got up to 70mph...the RPMS were through the roof...the needle was all to close to the "red zone"...and the CEL came back on...flashing. I had to slow down to stop at a light and the car sputtered and then died. I turned it off, then on and the CEL was gone. So I turned around and headed back to AutoZone and punched it again...just as I needed to slow down to pull in...the CEL came back on (flashing). They ran the codes again and it said misfires on 5, 2, and all. I am stumped!!!! I had him clear the codes again and drove it back to work. It runs okay...but its idling high...like it needs to shift. Any new suggestions?

Oh...and the right tail light would not work last night or this morning...but the malfunction message went away after I left AutoZone!! Good GRIEF!!

Could all this be electrical? I read a post that mentioned the same symptoms and it was a clogged CAT or head failure.

I am so exhausted with all this... I don’t know what to do next....

Thank you!
 

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Hi ... Could be a exhaust issue ... Could be a few things ... That is the hard part of helping and getting help online - it is so good to see, hear and run the vehicle to try and figure it out ...

Anyway - In my experience this may have an issue with the transmission ... Why are the RPMs so high and why is it not shifting? I have pulled out a few tranny pans to see clogged filters and bad fluid that gets into the shift bodies and what happens is that those solenoids do not shift smooth so they go to mechanical override which shifts at the “last second” to move the gear up or down to save the mechanicals…

Transmission load and shifting is tied to vehicle speed and air (O2) consumption – this is relative to the vacuum the car is making … if you have a vacuum leak or an issue in the management of information being handed to the transmission from the engine this could cause the ECU to try and compensate by reacting to fuel trims on all cylinders as it frantically looks to be back into its calibrated parabola for speed, load, fuel and air …

I would maybe do something as simple as hook a vacuum gauge up to the car,
Jake
 

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you need to clear the codes and drive it again, if it still misses on 5 then swap the coils, plugs and wires, they said it lost compression at 3500? you dont check compression with the engine running, it either has good compression or it dosent, have them check it again and do cylinder leakdown, check fuel pressure and delivery, if all that passes then wiring, or the ME (motor electronics), seriously the only times i have seen these engines fail is from SEVERE lack of maintence, even then the blocks are almost bullet proof, i saw a e320 come in running rough and noisy, they hadnt changed the oil in 30,000 miles, it melted one of the camshafts to the hear and broke it, the valves hit the pistons and bent, keep in mind IT DROVE IN!!! we tore it apart, replaced both heads, cams, valves and springs, put new pistons in the origional block with new rings and it ran fine, the crank and rod bearings were fine but we replaced them also, i could tell you storys all day about the durablilty of these engines,
 

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if you decide to take a look at the valve springs, the valve cover bolts just have to be snug, dont pinch the gasket, rocker bridge torque is 15nm plus 90 degrees twice, start at the center and work your way out, get all the bolts snug first (you will be fighting the valve springs that want to open), then go to 15nm, then turn them all 90 degrees, then another 90, these engines also do good with being assembled poorley, most guys just use an electric impact wrench to assemble them so dont be scared, you can remove the bridges with out setting up the engine for timing just dont turn it over with the bridge off, also does it make any noise? broken engine parts make horrible noise,
 

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Discussion Starter #16
Okay...here is what is happening now.
Last Friday we took all the fuel injectors off and cleaned them...drove it and the check engine light came on flashing again when we punched it. It does okay, so long as you don’t push it. It almost sounds/feels like the timing is off...like it is idling too high. We went to AutoZone Saturday morning and we got all the same codes...misfire on cylinder 5, 2, 6, and all cylinders.

So...we went home and I made an appt. to bring it to MB on Wednesday. I am TERRIFIED of what this is going to cost me!!!

Just for grins, I went by AutoZone this morning to see if there was anything new, any new codes. AND THERE WAS...now it says P0171 and P0174 ON TOP OF the usual misfires on 5, 2, 4, 6 and all cylinders.

From what I read, those codes could mean the MAF or O2 sensors are bad or there is a vacuum leak. When I took the car to the first MB Repair shop, they put a new MAF on it and replaced a breather hose and that STILL did not fix the problem. I can only imagine what MB is going to say it is....
 

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Assuming he did the vent hose correctly and put in a genuine MB MAF, there could be the carbon build up problem (hence the compression test issues). Also, whatever caused the MAF to get contaminated is still present, check for excessive dust or oil in the new MAF. Also, who knows about the cam leaking problem. When oil gets in the harness it may damage other sensors like it does the O2 sensor.
 

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Actually, the cam sensors leaking is an MB thing. What makes it a M271 thing to us is that the way they are positioned, they leak into the harness. You just don't see people replacing it much on the V6 because the leaking is just that, a leak, cam position sensor still functions. Also, it maybe possible that if the cam sensor is out of sync with the crank position sensor, it may offset the timing of the valves enough to show up on a compression leak down test. Part of that variable timing stuff many cars come with now.
 

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Okay - Thanks...In the spring I will take a look at the front of my engine and see how the cam sensors look...on that note - My buddy just came over and told me his car is acting a lot like this C320 (his is a Ford)...but it tested out as a cam sensor...
Jake
 
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