Pizzaguy is not ill, he has merely embarked on a long term payment plan for that lifetime of McDonald's Big Macs and large fries

 

I won't comment on Mark's addiction to Big Macs, but I will chime in and say you have several things going wrong at the same time on your car and 180 has touched upon most of them. Crankshaft Position Sensor causes hard starting and the shuttering. Map Sensor can as well. Air pump is usually a bad relay in the RCM. I doubt your plugs are bad at all, but it is nearing time to change them. Good luck. There are "how too's" on doing all this yourself. Just use the search feature and plug in what you want to replace.

 

I just read this entire thread and I have to commend the OP on his very detailed and well stated description of the problem and his constant updating of what he is doing and what the results are after every step.

Then .... I saw the tags for the thread .... "potatoes"???

Hilarious!!

 

You bet - when I'm on here I'm reading about other folks' issues with their cars and learning everything I can. It seems each different thread has an ounce of extra information too.

I'm just in a problem where I have no internet at my house and my dad's apartment has internet when it wants to.

Anyway, on the way home from lunch yesterday the CEL flashed while I was passing a semi on the interstate. Three cylinders had misfired and that low pitched exhaust shudder returned. I had my obd2 plugged in and it started recording. I backed off and let the semi go by, threw it into neutral and shut the key off, waited a second and started the car again with the key. I then drove home the rest of the way happily.

I read about the PCM having corroded connections so I pulled it out, checked it but I don't think I knew well enough what I was looking for so i put it back in.

I might go tool shopping tomorrow to get a fuel pressure gauge and some flexible ratchets/extensions so I can check out the fuel flow and possibly change the fuel filter too.

I almost forgot to add, while I was at the gas station i pulled the engine cover off and was wiggling some wires and connections. On injector 4 the Rpms stuttered for a moment but I couldn't get it to do it again. I also unplugged maf connector and the rpm dropped for a second just like it does occasionally. The fan then kicked on and was increasing speed rapidly so I shut it off and put everything back together. Again I didn't know what I was looking for in the electrical connector but I will pull the maf elbow out once I have the right tools, clean her up a bit.

 

Well, you are on the right track to find your problem. The maf, cps, are a good start since it seems to be electrical in nature. Vacuum leaks, would result in it doing it all the time. The little cars have so many electronics, sensors, monitoring it's every move, that voltage can be affected in many ways. Battery being weak, corrosion, or loose connections. Good luck. The fellers above are steering you in the right direction. Back to my yard work, and big rig polishing.

 

I finally got my CPS in last night. I noticed the sensor that was in the car had a part number ending in 171, and had both Bosch and Mercedes part numbers on it. The new one had no MB part number but the Bosch number ended in 170.

So after struggling getting the bolt back in, it fell into the depths of hell (into the heat shield). I spent an hour using picks to pry it out and I couldn't find my darn extending magnet I have just for situations like this. So I spent another hour running into problems with components in the way of taking the two retaining bolts out of the bellhousing.. But I eventually got it!

Not a single symptom on the first 12 minute trip, on the way back it missed again maybe three times (which is ultimately minimal) and no CEL. I see improvement but I feel it's only a matter of time before it grows unbearable again. I'll research coil pack testing and plug wire testing to see if I can do that on my own. And maybe rent a fuel pressure set from Autozone.

I feel optimistic though, I'm getting closer to having this finished and having my beauty back.

I thank y'all so much for your input to get me back on the road, this is invaluable to me. I don't think I've had a bigger smile on my face since I got the car in the first place.

 

Just got home from the same road test again. Absolutely zero symptoms. My peace of mind is returning.. Again, I thank everyone for the wealth of knowledge and advice that is here for people without many options to use. Fingers crossed and hope not to jinx myself, lol.

 

UPDATE:
So I picked the car up the following weekend and paid the 300 something $$$ charge for the service. They changed out my fuel filter with a MANN brand filter and reconnected hoses and in the write-up it shows that the EGR valve had in fact blown off; however I am uncertain if that is actually true because they did not have to replace any related parts. It said that the fuel pressure was low, so upon checking the filter they found it had a torn or broken diaphram causing it to pump gasoline into the charcoal canister? So they drained the canister. I have yet to review the house routing personally to verify the accuracy of that statement, but it would make sense because the pump almost always shuts off several times while filling the tank. I filled the tank from empty later that evening and the pump didn't trip until the tank was genuinely full. No symptoms anymore apart from a slight miss at idle and occasional hardstarts, usually at cold. Never have to turn the key more than once for the car to start any more though. So practically, a fuel filter change and draining the charcoal canister has gotten ridden of the majority of my issues, I am going to change out the driver's bank spark plugs this week and see if the remaining miss goes away. Loving my car again. Thanks for the help y'all!
END UPDATE


So the problem came back, drove on it for a few days but was taking off from a stop sign when the car missed hard and I heard a loud snap, and it stalled. Started right back up but could hear a massive air leak somewhere, and the car was idling rough. Limped it home too disappointed to even look at it and last weekend I had it towed to a dealership specializing in European vehicles.

They found a hose had blown off the charcoal canister presumably due to a backfire, which I assume must account for the air leak. Also, the canister was full of gas they said? Anyway, they replaced the fuel filter with the Mann part, and say there is "still a little hesitation" but I can not get to the dealership until Friday or Saturday to see if there's any improvement. They also said there was a camshaft position sensor code stored which is bad news because I replaced that last year sometime. It could be due to the connector I broke because I was in a hurry at the time, but I have yet to look in to it.

I'll go ahead and replace the last 6 plugs on the driver's side when I get it back home and see what happens, but I'm not feeling optimistic today. Can't believe that replacing the crank sensor made all the issues disappear for a few weeks all to suddenly come back at once.

 

I hope this isn't a dumb idea, but have you thought about changing the plug wires? I have seen (on a couple of different cars; I'm new to Crossfires) where old, 'bad' plug wires will cause a motor to misfire. Sorry for your misfortune - I hope you can find and fix the problem soon.

 

That is on my list of things to do when my babe hits 100K, I'm at around 95K right now. The main issue was resolved, although now I have a slight miss at idle and occasional hard starts with a slight miss as well. But the car drives and under load during driving operation the car is fine.

I'll definitely be changing all my plug wires when I go to finish the plugs, and she's probably going in for a coolant flush soon as well (I don't drink my city water, so why should my car, right?).

 

I'm glad to hear your main issue was resolved. Do you mind if I ask what fixed it?

 

I haven't seen it in your posts but did you change the Nass Air flow or MAP in the intake?

These are classic symptoms of a dirty sensor. I think about $140 for the part, easy to change out.

 

I had the car towed to a shop that replace the fuel filter, claiming there was a leaking diaphragm that was allowing fuel to be pumped into the vapor canister, which was full of gas. So they drained that too. Makes sense to me because sometimes the tank would not fill and kept shutting the pump off, but since the repairs it no longer has.

As for the MAF, I unplugged the connector and it made the car run like **** for a moment. I otherwise haven't inspected it.