alexio senchez

Hi all,

this is lengthly but, If you've had a similar issue before, I'd appreciate some advice. Searching around this forum and others, I see this is not a rare issue, but what's rare is the OP coming back to post what fixed the problem.

2001 e430 4Matic
101k miles
well maintained and lovingly driven

The car was running perfectly, but was very low on fuel (less than a gallon in the tank) when I refueled at Shell (93 octane of course). A few seconds after starting the car, I felt an abnormal vibration throughout the whole car as if there's a misfire. As I begin to drive, the CEL comes on. The car drives with noticeably less power than normal, but still enough power for ample for city driving.

I got home to scan the codes and got the following:
P0307
P0115
P0130
P0150
P0300
P0307 (yes same code twice).

I cleared the codes, drove 1 minute and the CEL came on again. I scanned the codes again and got this:
P0307
P0300
P0307 (yes same code twice... again)

So far, here is a list of everything I've tried, yet the issue still persists:
- new plugs for cylinder 7 (old plugs didn't show anything abnormal)
- new coil
- new injector for cylinder 7
- tried swapping cables for plugs
- new fuel filter (Mann)
- checked fuel pressure, normal around 60 psi
- new MAF (OEM Bosch item)
- drained out entire tank of suspected bad fuel
- refilled with 5 gallons of fresh 93 octane along with two bottles of Techron fuel treatment. Drove about 10 miles.
- disconnected battery for 1 hour
- reconnected battery, performed ECU reset

Here's how the car behaves currently:
- After resetting the codes, the car starts up perfectly and seems to idle normally
- If, after resetting codes, I keep the car in park and just rev, no CELs and the revving seems to be normal (I can rev all the way to redline and I don't feel any hesitation in the engine).
- If, i drive in reverse, the CEL comes on after a few seconds of backing-up (even during slow backing-up without foot on gas)
- If I shift into drive and get going, the car seems to drive normally (may be slightly low on power, but that may be in my head) up until it shifts into 3rd gear before 2k RPM, then the CEL comes on and I feel loss of power.
- I can keep resetting the CEL, but doing any of the above will cause the CEL to come back like clockwork.
- Overall, even with the CEL on, I can still drive the car normally. It definitely feels underpowered, but it has enough go to cruise normally on the freeway.

After all this, I am still getting P0307 and P0300. I am now suspecting o2 sensor(s) and/or cats. Come to think of it, my MPG has been around 17mpg mixed driving lately, and I drive gently most of the time. 17mpg seems a bit low, so perhaps this issue was slowly building up and only showing symptoms as poor MPG. I know the car was well-maintained by the previous owner but he did not retain all records, and the records I have don't show that cats, o2 sensors, and plugs have been ever changed. Perhaps, at 101k miles now, its time to look into it.

What still gnaws at me is that the car ran perfectly up until a gas fill-up, then almost immediately after starting the car, these issues began. How weird is that?

Before I dedicate time and resources to look at o2 sensors and cats, is there anything else that's worth looking at?


Alex

fabbrisd1

You have been quite diligent in your work so far - compliments - with the extent of what you have done so far :

1) One good suggestion is to check your front and rears cats - as suggested on the other forum:

1) Front cats - at operating temperature take a IR thermometer - exit temp at the back of each front cat "should" be much higher than entrance temp

2) Rear Cats - do rubber mallet test to see if chunks blown from front cat may be blocking that rear cat/can

The other thing you might check is Engine Mounts - your mounts are fluid-filled and over time the ALWAYS fail - and it has been known when under acceleration (forward or reverse - the vibration of the engine hitting on failed mount can cause misfire in the ignition system - and/or add to premature cat failure/blockage because of the added vibration transferred back thru the exhaust system.

I mention this since you mention "idle" - in park or neutral does not seem to trigger your symptoms based on your description - but when engine is put into gear - yes, that's when the engine mounts are called upon to do their job once the drivetrain has been engaged (again either forward or reverse) by the torque created between the engine and drivetain.

Note China replacement mounts are sh*t - Sachs Boge and/or Lemfoerder are factory OE mounts.

alexio senchez

fabbrisd1,

thanks for the advice. Currently I am focusing on the o2 sensors based on my experience driving around the past few days (explained below). Also, engine mounts is a great suggestion that I didn't think of, but mine were replaced with OEM parts about 6 months ago.

Here's an update of what I've been up to the past couple of days -
Yesterday I drove the car about 20 miles total, to and from work. My hope is that if I stop resetting the codes and add on some miles, new codes will appear (hoping to get the o2 sensor P0130 & P0150 codes that were there at the beginning but never came back after the first reset).
Here's what I observed:
- I drove 10 miles to work, the CEL was on, the car felt under-powered but ran fine on the freeway with enough power to easily go 80mph+ and pass others with ease. No bogging, hesitation, or delay when accelerating (leading me to believe the cats are fine).
- Once I arrived at work, I scanned the codes and code P0300 went away on its own. Now its only showing code P0307, twice.
- After work, it was late, the roads were clear, so I decided to give the old girl an Italian tune-up (your grandpa would approve). I hooned this pig like it was a stolen Civic - I doubt this car was ever driven like this. I took her to redline consistently and she took it like a pro, shifting perfectly, responsive throttle, albeit still under-powered. On the freeway she'd go past 100mph easily and willing to do more.
- After said hooning, I got home, scanned the codes and still only P0307.
- Today was a similar day minus the hooning, the car performed fine as a daily driver, CEL still on with code P0307, and feels under-powered.
- At idle (around 600 rpm) I can feel that its not a smooth idle, but its not horrible - most people wouldn't know the difference. The engine mounts are good, replaced 6 months ago with OEM parts.
- MPG average during the past couple of days and 40 miles is about 19MPG which seems normal considering last night's spirited driving.

So, with all of that being said, I literally can feel that the car breathes and exhausts like it should so the issue is not with the cats. There is a sensor somewhere causing the P0307 code (I suspect an o2 sensor), which in turn puts my engine in pseudo-limp mode.

At some point during the next week I'll be getting to the upper two o2 sensors, I might as well do both banks but I'll start with cylinder 7 side first to see if it will fix my CEL. I haven't decided if I want to mess with this myself or have my mechanic do it, I'm waiting for him to send me a quote. If I do it myself I'll need to buy a few tools that will make the process easier.

Please keep your ideas and advice coming, I read it all and consider it. I hope the information in this thread will be beneficial to others in the future who dare and stand up to German engineering (David and Goliath type of thing).


Alex

fabbrisd1

Again - respect - you are quite thorough - from my side I have not seen a O2 sensor trip PO307 - I have seen a loose or failed motor mount trigger PO307 under acceleration - just what I have seen since per your report on the ignition side - plug/coil/etc you seem to have covered that side.

Keep the beat !

alexio senchez

All,

checking back in with the final resolution.

Firstly, I want to thank everyone here for taking the time to help me troubleshoot. Some of your suggestions steered me away from replacing unnecessary parts.

So, I kept driving the car daily with the P0307 code on in hopes that after some time I will get more codes that will help me narrow down the issue (I was expecting an o2 sensor code to show up). After a few hundred miles of driving, nothing changed so I gave up and took the car to a local MB specialist who's worked on it before (Peter at Silver Star Motors in Vienna VA).

They looked for the issue and their conclusion was that the overall combustion cycle in the car was bad, most likely due to the fact that at 102k miles the car's plugs and wires were still original. They replaced the plugs and wires for all cylinders and put on a new coil for cylinder 7. Then they flashed the codes. Fixed. The car runs great now - I've driven it for the past week with no issues.

Had I taken it to an MB specialist right away, I would have saved some money and time, but I was stuck on thinking that my issue was somehow related to suspected bad fuel, since the car started misfiring immediately after a fill up. Perhaps it WAS bad fuel and it was the final straw for the car's tired plugs and wires?

I hope this post will help someone else in the future who has a similar issue. The moral of the story: engine misfire codes are a bit generic and its difficult to pinpoint the exact cause of the problem so, before wasting too much time and money troubleshooting, take it to a reputable MB specialist for a diagnosis. Chances are they'll know exactly what the issue is cause they've seen it before.


Alex

kajtek1

Thanks for sharing final conclusion Alexio.
Would you mind to share how much it cost you?
Dealer dropped 3 new parts at the same time. When it got the job done, chances are some of those parts have been replaced with no need.
Unfortunately even simple things can get complicated on those cars.
I unknowingly drove the car for some time, reaching over 160k miles of factory plugs. No symptoms, so even your plugs at 102 k were due, I don't think they were the problem.
Fact is that we might never know.

alexio senchez

The cost at Silver Star Motors for diagnosis, plugs, wires, one coil, and labor was $1100. The parts were all OEM. I'd imagine this is close to what the dealer would take.

The price is on the high side, but in my situation time was more important than money. If I were to do the work myself, it would be another few weeks until I'd have the time.

I think in my situation the plugs and wires were the problem, since replacing them solved the problem. The car now runs smoother and gets better MPG.

Alex

livetodrive

The bad cylinder 7 coil was likely giving you the trouble. I had the same problem with one coil and replaced it. The plugs were due anyway at 100k. I replaced the plugs and wires myself at 100K, using Bosch OEM parts. I'm happy your car is running well now. I hope mine, or should I say my ex-car, is also doing well. I sold it last October.