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Craig finally buys a 300SE, but it’s not all plain sailing …

As readers will know, I’ve been on the lookout for a 300SE for a while now. In fact, one of the first cars I wrote up for GCFSB was a 300SE, which should tell you something. After a couple of false starts, I finally have a W126 I can call my own.

I found it on Craigslist while looking for cars to write up for the site. It stood out because it was in exactly the spec I’d been looking for. It was a 1989, a Gen II car with the more modern looking leather seats and updated exterior side cladding. It was in a great color combination, nautical blue over mushroom cream leather. And, unusually for a 1989 six cylinder, it was equipped with a passenger side airbag and upgraded Bose sound system, options that are more commonly found on the V8s. It also had only 116k miles on it, and was priced fairly. Unfortunately, it was located in Austin, TX, while I’m in Washington, DC.

After a lengthy back and forth with the seller, apparently an enthusiast who assured me it was in excellent running condition, I decided to buy it sight unseen and have it shipped to me. After a couple of weeks of delays on the shipping company’s end (I went with the cheapest option, and it showed), the car finally arrived. At first I was thrilled. It looked great.

But my excitement soon turned to disappointment as the hauler tried unload it. The car wouldn’t start. To be more precise, the car would start with a puff of black smoke out the back and die immediately. It did eventually start on the fourth or fifth try. It then ran rough for a minute or two, like it was misfiring, then smoothed out. My heart sank.

We eventually got it off the transporter and I gingerly began driving it, uncertain what the problem was. On acceleration from low RPM there was a definite hesitation and the car felt sluggish, slower than the other 300s I had driven before. The economy gauge on the dash also wouldn’t peg left on idle, as I know it should. In fact, at startup it was nearly in the middle. I’ve had a Mercedes with the M103 engine before and I knew this could be caused by vacuum leaks or problems with the CIS-E fuel injection system. So it was off to a mechanic for diagnosis.

Mechanic 1 said that there was a vacuum leak inside the fuel distributor and that I needed to buy a new one. He said I could take my chances with a cheap one from eBay, or he could get me a re-manufactured unit for $600. I had never been to this shop before. I only went there because my preferred mechanic couldn’t fit me in for another week. I wasn’t sure I could trust him. So I held out for a second opinion.

A week later mechanic 2, a Benz specialist to which I used to take my 190E, said the fuel distributor was fine. He said that the car was running rich – which would explain the poor starting and running and condition – because the 02 sensor had failed and the duty cycle was stuck at 90%. So the first line of attack was to install a new 02 sensor.

Unfortunately, even with the new sensor onboard he couldn’t dial in the fuel mixture correctly, though he was able to lean it out considerably. Cold starts were still hard but the car was running much better than before.

Suspecting a short or another sensor problem somewhere, he eventually diagnosed a broken fuel injection ECU/ECM, the black box behind the carpet in the front passenger footwell. Reading the threads on the forums, I gather that the ECU provides pre-programmed settings for the air/fuel mixture on cold starts before the 02 sensor reaches operating temperature and takes over. Apparently ECUs rarely fail, but when they do, they produce symptoms like the ones I had been experiencing.

I ordered a used ECU from eBay that matched the part number on my old unit. Once it arrived, I put it in myself (it’s as easy as changing a battery) and crossed my fingers. The car started from cold on the first turn of the key and settled into a smooth idle. Success! I took it back to mechanic 2 for a final adjustment of the fuel mixture, and then took the car for an emissions inspection. It passed with flying colors.

Now that it’s finally running properly, I love it. The interior, in mint condition, is a very comfortable and relaxing place to be. I look forward to doing long distance trips in it with my wife, who approves of the passenger airbag. All the electrical accessories work, including the heat, A/C and original Becker radio. The nautical blue exterior really is gorgeous and I’ve received numerous compliments from strangers in the short time I’ve been driving it. There are a few blemishes in the paint, some small scratches here and there, but that’s about it. I’ll probably have it gone over with a dual action buffer at some point.

Some people complain about the 300SE/L being too slow, but I think the performance is fine for what it is. It pulls quickly enough in city traffic and cruises admirably on the highway. The handling is also nowhere near as boat-like as I feared it would be. I think this is where the short wheelbase SE really excels over the long wheelbase SELs. I do miss the E34 525i which this car replaces – it was admittedly a much more spritely car to drive. In an ideal world, I would have kept both.

I texted the seller in the vain hope he might offer me some money back. He had, after all, assured me that it needed no repairs. I’ve received no reply, and I suppose his silence speaks volumes. I think I learned a valuable lesson here. I will probably never buy another car sight unseen again. Not unless it’s from someone I know I can trust. I will also not be going back to mechanic 1.

– Craig


  1. Victor Gaines
    Victor Gaines May 10, 2017

    Craig, I tried to buy a similar car from Private Collection Motors in California that I think you touted a few months ago (Blue-black). I got as far as a agreed upon price and a PPI (I live in New York) when the seller abruptly decided not to sell. It took multiple phone calls to get them to even admit they weren’t interested in selling anymore. Very aggravating. A month later I found a 560sel that had been in Connecticut all its life and was in amazing condition. A real unicorn. After all the advice I’d gotten to look only in California. Totally agree with you. You gotta see these cars in person.
    The car drives like no other I’ve experienced. Like a big old Cadillac from the sixties except more precise and powerful when you want it to be. Love it. Victor

  2. pmichaelg
    pmichaelg May 10, 2017

    Congrats – it looks beautiful!! I’d say you made out pretty well all things considered.

    As for lessons learned, another option is to have someone local to the car be your eyes and ears. Usually you can find plenty of willing folks on the boards to help out like this. It is obviously not as good as a personal inspection but at least you don’t have to fly all over.

    That… or… pick it up and road trip it home!!

  3. Carter
    Carter May 10, 2017

    Congratulations on the new purchase! A lovely car in a lovely color for sure.

    My sight unseen trip to get the M3 was slightly less eventful, but still full of half-truths. “I just replaced the rear tires, so no worry” meant “at some point in its life, this car received at least one new tire”.

    Hopefully that’s the end of the surprises!

  4. Woodie Man
    Woodie Man May 10, 2017

    Having had a similar experience buying a car sight unseen, I,ve come to the obvious but ugly realization that trusting anyone in a long distance auto purchase is a fools errand. We all know this inherently but wanting it to be otherwise is not the same as reality. People tend to be dishonest . Period. After all, the ECU on his Benz didn’t fail on the car carrier.

  5. GWG
    GWG May 10, 2017

    Congrats, looks absolutely gorgeous! I have the same in black / palomino with 48k miles. I actually missed a couple of things despite a PPI when I bought mine (these cars seem to drive fantastically even with some things not working) – had to invest a little more than budgeted upfront but it’s been nothing short of perfect since. And definitely agree on the fantastic ride quality for road trips combined with very tight handling. Check the front suspension bushings – if those are worn, a replacement changes the ride immensely.

    I also really like the M103 (also have it in my r107), it could be a little torquier in town but at anything over 25mph it’s perfect for the car’s cruising nature.

  6. BrianZ
    BrianZ May 10, 2017

    Congrats. I always admired these cars back when they were new. Buying sight unseen is always risky, seems like you did okay. I love the color combination.

  7. MrMan
    MrMan May 10, 2017

    Your adventure was a joy to read. Glad you got it sorted out. My last four cars have been destination purchases where I fly out and drive her home.

  8. Bushwick Bob
    Bushwick Bob May 10, 2017

    Having just done the same thing (buying sight unseen from an “enthusiast”) and having gotten myself in to a similar situation, I feel for you. Sounds like the story has a happy ending, which gives me some hope.

    I had a pristine 300se for a while. I appreciate the looks and lines of that body. However what made me part with it was the transmission. I couldn’t get over the way it revved on the highway and the forced second-gear start.

    One thing that really helps a 126 are urethane bushings and a beefier rear sway bar – I got mine from Fiend Motorsports in Texas. Not sure they’re still around, but maybe there’s another supplier now.

  9. Doug
    Doug May 10, 2017

    That’s sharp.

  10. audifan
    audifan May 11, 2017

    Congrats on your purchase. This car can be enjoyed for many years to come. We’ve been driving our 1990 420 SEL for the last 10 years and 50 k trouble free miles.
    I’ve been looking for a 300 SE for a while too, but anything in white or with a grey, beige or palomino interior is not my cup of tea. I’ll keep looking in Japan for a car with red, green or brown cloth interior.

  11. Dan Crouch
    Dan Crouch May 11, 2017

    Congratulations on the purchase and nice story to go with. Glad to hear it’s purring now 🙂


  12. Christian
    Christian May 12, 2017

    Excellent. I have a 420SEL that has been very reliable over the past 3 years. I bought it as an airport car since I didn’t want to leave my other cars at the mercy of airport parking lots. I’ve put maybe 8,000 miles over the past 3 years and it has been fun. Really needs a paint job, but I am afraid if I do that….then I won’t want to leave it at the airport!

  13. Michael Lenoch
    Michael Lenoch May 13, 2017

    I think you mean “…mechanic 2, a Benz specialist to whom I used to take my 190E” since, presumably, said mechanic is a person.

  14. Craig
    Craig May 13, 2017

    Thanks for the compliments all.

    @Victor Gaines: I’m sorry to hear about your experience with PCM. I spoke briefly with them about that car, and the salesman even sent me images of receipts for work they had done on it. But your interaction with them sounds really iffy. Thanks for letting us know. Since you scored a great 560 elsewhere, it sounds like things turned out well anyway!

    @GWG: Thanks for the note about the bushings, good to know. Now that I’ve driven it some more, I notice a bit of a rattle coming form the front end when driving over bumps in the city (DC’s roads are horrendous). I checked the tires and they were over-inflated (according to the PSI figures inside the fuel door), though I haven’t driven it again to see if that makes a difference. I suspect some parts may need a little refreshing – control arms etc – so that will probably be the next investment.

    @BUSHWICK BOB: I had never heard about the rear swaybar upgrade, thanks for the tip. I agree that the weakspot with the W126 + M103 combination is the gearing of the transmission. It sits at 3500 RPM at 70MPH, just like my old 190E 2.6 in fact. The cabin is well insulated from engine noise, so I don’t find it “buzzy,” which is a complaint I’ve heard before. But it does mean that the gas mileage suffers. The second gear start doesn’t really bother me: I drive like a pensioner most of the time anyway 😉

    @Michael Lenoch, you are right, of course! Thanks for catching that.

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