Okay, so this issue has been going on for less than a week...

Last Friday (7/13), I was stopped in traffic for at least 5 minutes, and all of a sudden, my car started shaking noticeably, and revved "raggedly" when I raised the rpms. In other words the shaking persisted throughout the rpm range, and increased in frequency as a function of engine speed. This was regardless of whether the car was in gear (moving) or in neutral. After less than a minute, this behaviour stopped, and the car drove normally until later that evening, when it repeated the performance for about two minutes--again during low-speed city driving.

Then the car drove normally for the next several hundred miles, until Sunday (I drive a lot), when the phenomenon occurred that evening, and has continued persistently through today (Wednesday).

I've driven the car every day to work like this, and it hasn't gotten worse, but obviously I can't live with this consistently. It seems like the car is missing/misfiring--running rough and significantly down on power, although I can still go 80 mph comfortably (during which time the shaking is not very noticeable, I guess because of the higher rpm being turned). Stepping on the gas is met with a far LESS response than usual, as the car takes its time to get up to speed.

The car has 183K on it now, and I don't know when a tuneup was done last. I had the oil changed less than 3,000 miles ago, and I have used premium 93 octane gas since I bought this vehicle. Friends suggested I need a tuneup, as perhaps a spark plug or spark plug wire has gone bad. This Friday I'm planning to buy a new set of spark plug wires (at $80-100) and install new spark plugs.

Is that a good start? Is there another common issue I'm unaware of? What else could be causing this? Obviously I could tackle every possible cause for thousands of $$$$ (not feasable for me!!), so what are the most LIKELY (and easiest to address) suspects?

 

I had a similar problem, though only on start up. Check the OVP.

 

bad gas

 

Unless he pulled the R1/16 I doubt it would be bad gas.

 

not unlikely tho, if he got it from a station that watered it down... its happened to me before. im not positive it was watered down, but the gas wasnt right. well see how he runs next tank

 

Could be water in the gas, or your friends could be right and you need a "tune up". Tune up = plugs and wires.

 

You won't do any harm, and you may do some good, if you put some injector cleaner through. The one I've used for some years, and which cleared a cool-running problem in an Audi overnight, is the VW/Audi product G 001 700 03. It also boosts octane level. It's been noted as a factor explaining the very low emissions levels from my cars at their annual official tests (MOT tests).

 

Your kind replies alerted me that I left some info. out of my initial post.

Regarding gas--only Premium--93 octane--has been burned since I bought the car. And I have always filled up at reputable stations--usually Shell. And the issue has persisted on what is now my 3rd tank of gas since the problem came on in its initial stages. The poor performance is consistent, and doesn't get slightly better or slightly worse as I'm driving. With the exception of my car's initial "indecision" last weekend about whether it wanted to manifest this problem or not, it's been running consistently poorly, as if some component just went bad and has stayed bad.

Additionally, I've already been adding STP fuel injection/carburator cleaner (the kind commonly available at gas stations) during most fill-ups, well before this issue started.

To add--there are no "check engine" or other warning lights on, so I'm not thinking it's emissions [O2 sensor] related. And the car runs cool (usually no more than 80 degrees C) as it always has, so I'm not yet buying the blown head/head gasket theory some of my friends are scaring me with. No white smoke out the tailpipe either.

I'm planning to change the spark plugs and spark plug wires tomorrow evening. Will let you know the result, if any

 

It almost HAS to be plugs and/or wires. I just hope you have a catalytic converter left after driving this long with a misfire.

 

Oh, man--really?? And I have an emission test due 9/5/07!! Well, we'll see.

It's been 1 week since the problem first showed itself, and 6 days since the car started doing the misfire consistently. And I drove every one of those days.

Well, new plugs/wires should be going in this evening...

 

Put in 6 new Bosch Platinum spark plugs this afternoon. Friend looked at the spark plug wires, which appeared to be fine, so I didn't replace those.

The car runs almost exactly the same. Still the very rough idle. Engine may be a little smoother when revved in neutral, but that could also be my imagination.

Any other ideas? Fuel filter? Clogged injector? BAD injector? Fuel pump?

 

Find out which cylinder is missing by disconnecting the wires one at a time. The one that doesn't change the way it runs is the culprit. The wires may look good, but watch it running the dark and see if the wire on the problem cylinder is arching to ground. If the wire is good, then it's the injector gone bad (plugged up). I think you could pull the injector out and watch it to see if it sprays when running. Also, you could move the injector to another cylinder and see if the misfire follows. That would tell you for sure if it's an injector. Driving with a bad injector will not hurt the cat.

 

I took the 300E to an M-B specialist this morning (he has a lift in his home's garage and massive experience working on these cars) and he diagnosed the problem pretty thoroughly. Spark plugs, of course, are new--and he used some kind of electronic sensing tool to check all the spark plug wires; they are OK as well.

He did exactly what you said to do (pulling off the spark plug wires one by one with the engine running), and determined that one cylinder--the second one back from the front of the engine--has NO compression at all. He used a compression gauge to test this. His hypothesis is that either the lifter for this particular cylinder "collapsed," or a valve--he presumes this to be the intake valve--is not fuctioning. He actually used a scope to look around inside through the spark plug hole--it was pretty cool.

Even so, a 100% accurate assessment cannot be done until he takes apart the top of the engine. I'm planning to leave the car with him on Wednesday. Until then, I have no choice but to continue driving...

 

Wow, that's extremely rare; I never would have believed it. These engines rarely have mechanical issues, even when you detonate a pile of dynamite on the manifold (it's been done). A simple way to check compression is to crank the engine with no spark and listen for a cyclic 6 pulse pattern from the starter. If you hear 5 pulses- spin, 5 pulses- spin, then you have one cylinder with no, or very little compression.

Keep us informed. I would think a collapsed lifter would make some serious racket and your complaint would be that the engine sounds like it's going to come apart. A cracked piston or broken rings would usually cause some smoke. I would suspect a burned valve. This would cause a misfire with no other symptoms. I'm on the edge of my seat...

 

Yeah, this guy seems to be very good, and that's exactly what he did--disconnected the distributor wire and had me crank the engine. The result was "5 pulses- spin, 5 pulses- spin" just as you said.

I neglect to mention that my car has a sizable exhaust leak from the center exhaust link (just behind the cat) so the rough engine running is quite noticeable because of that. However, there are NO abnormal noises (other than the rough idle) coming from the engine itself.

As I noted earlier, he actually used a fiber optic scope (I think that's what it's called) to look around INSIDE the cylinder, and specifically commented that the piston looked OK, with no pitting, holes or cracks. And there's no smoke from anywhere.

I was reassured to hear your comments about the durability of these engines. Believe me, although I like M-B's I'm more of a BMW enthusiast. And I think I'd actually prefer a Lexus LS 400 (even 1st gen.) over a W140 S-Class, especially for the sake of reliability/efficiency. But faced with having to get a car quickly and very cheap, I bought a 300E because of their reputation for durability. Yesterday the mechanic told me he's worked on one 300E with over 400K miles and another with 320K (mine has 184K now). That was nice to hear. So hopefully if I can iron out this situation, the car will be good to me while I save my money for something a bit newer.

And I'm on the edge of my seat, too! I really appreciate your theories/suggestions--it does help alleviate some of the suspense...

 

OK, I picked the car up today, and the verdict is apparently that the exhaust valve on that #2 cylinder is bad. A piece of the valve is missing or something.

The mechanic quoted me $2,500 to rectify this, and added that it's not worth it in this case (duh!).

Really??? This costs $2,500? Hell, I could get a new engine for that much, and a used one for a lot less (I won't though--remember I only paid $1700 for the car).

By his advice I can drive the car around on 5 cylinders for a while (no specific time period was given) without causing any damage. The piston might eventually develop holes or pits and the car could start to smoke, but right now there's no damage to the piston.

Now I'm really irritated because the car is significantly down on power and runs pretty rough at anything below highway speeds. Driving this car around for the next year (approximately how long it'll take me to save money to get a better car) doesn't seem like too appealing a proposition--if the engine even lasts that long. I'm kind of upset this had to happen to my car given all the older 300E's I see driving around with more miles than mine where the engines are still solid. Not that I've had the car that long (only since Memorial Day), but I've already changed the oil TWICE, use premium gas, and don't drive abusively. Not too happy right now. Do I need to spend **$2,500** to rectify this???

 

I'm sure we all feel your pain. That is a MAJOR bummer! I would get a 2nd quote.

 

I stopped by a gas station today that previously had worked on my car (they have above-average experience with Mercedes [there are a lot of M-B's in my area]).

I ran the issue by the guy there, and he said $1,500-1,700 to replace the head to rectify the problem, but agreed that it could easily run up to over $2,000. He asked if the car ever overheated [NO] or if I ran it without oil [NO]. I guess this just happened out of the blue. Like the other mechanic, he advocated engine replacement as the more cost-effective solution.

Now I'm on the fence. I have no other car to drive. A year (possibly less) of driving the car in its current condition could buy me enough time to get a newer Benz, BMW or Lexus. Hopefully I won't destroy the car in the interim. I wasn't going to invest any money in this fair-condition-at-best 300E (it was to be just a temporary measure) but now I feel kind of bad for it and have begun considering a "new" used engine if I could get one for $1,000 INSTALLED--$1,500 is the most I would spend. The money would take away from my savings for a newer, nicer car, but would probably assure me another 100,000 or more miles of reliable driving if invested in this car.

The gas station guy quoted me as little as $500 for a used engine and $400-500 to install. The other mechanic advised $800-900 minimum for a used engine and $550 to install.

Should I save for this engine, or just put money aside and push my luck without addressing the misfiring issue? The guy at the gas station said I could eventually break my crankshaft.

And if I WAS to get a used engine, what kind of miles could I expect to be on it for the price? I'm about to run a search on junkyarddog.com now...

 

It will probably run a long time like it is. I've never actually seen a car stop running all together because of a burned valve. Why would the crankshaft break? Never heard of that. I can't think how the valve would be missing a piece, but I can see it getting burned. What happens is a piece of carbon sticks to it and keeps it from sealing completely. The hot exhaust gas leaking past eventually burns a path in the valve where the carbon is stuck.

If I were in your situation, I would just drive it as long as it will be driven, putting as little $$$ in it as possible. I spend too much time on this forum, and I've realized that these cars are a money PIT! There are so many other things waiting to go wrong with your car that it would scare you to death. Has your transmission been replaced? They die all the time. Suspension components, too. They entire car needs to be rebuilt every 150,000 miles, or it will cost you $2,000 a year to replace things one by one. This is what I've read, anyway.

I'm finding out that these cars are only worth about $2500, even in good condition. People know what money pits they are so they won't pay anything for them. I paid WAY too much for mine so my situation is worse than yours.

 

Hmmmmm....
Thanks for your candid response. Well, you've also got an '06 X3, so at least there's that as a backup... When I was shopping back in May I saw a '95 E320 listed for $2800, but even that was out of my range, not to mention the low price sounded fishy. Yesterday I saw an '88 735i w/180K for $1750--wish I'd bought something like that instead as I simply feel more comfortable with BMWs. But you're right! Even though I have yet to see a 300E with less than 200K under $2,000 (mine had 179K for $1700), I've seen so many pristine late-80's 300E's with LOW original miles--100K-130K--for only about $1K more than I paid for my car (all under 3 grand). At least I had four near-perfect W203 16" 7-spoke (C240/C320) rims (on bald tires) thrown in with the purchase of my car. So deducting the value of those I only paid like $1300-1500 for my car.

I was told by the seller that the transmission WAS replaced and currently has about 60K on it. My car has leaked transmission fluid ever since I got it, but it shifts all right. I just dump in more fluid once in a while.

Btw I found a number of used engines with 120-140K on them on eBay in the $350-500 range. When you figure $200 for shipping and another $500 to install, I'd be looking at mininum $1,050 total investment. Do you think it's worth it? I guess I could just drive the car continuously until I do blow up the engine (if that'll even happen) and get the new engine then if I feel like it. I'm glad you don't think the crankshaft will break. I'll keep my fingers crossed.

I went to NTB today to try to get a simple $60 alignment, and waited for an hour and 45 minutes before **I** had to go up to the counter and inquire what was going on. At that point I was told "Oh, by the way we couldn't perform an alignment because we don't have the necessary equipment, and that can only be done at the Mercedes-Benz dealership." I avoided asking how much longer they were planning to let me sit in the waiting room if I hadn't come up and asked what was going on, and instead wondered why so many generic service shops treat M-B's like the space shuttle when they're actually pretty easy to work on. I've also noticed that I appear to have "sucker/ATM" printed on my forehead when I enter one of these establishments and tell them what kind of car I have. I guess even a 20 year-old, $1700 Mercedes still carries a stigma with these people which encourages them to either chicken out on servicing my car or try to d**k me around. Sorry for the rant. I didn't notice this attitude with my BMW's as much, though.

Well, I'll keep rolling and may be back here crying again if something else happens. Thanks for your thoughts and advice, though--it's much appreciated!

 

^ What jerks! Yes, I too have noticed that taking an MB to a place that sees Fords and Hondas all day tends to lead to disappointment. Walmart did a stellar job with my tires, but that's about it. If you look in the Walmart oil filter catalog, it goes from Mazda to Mercury. It has BMW, Jaguar, Lada (not even sold here) and others but NO Mercedes.

Anyway, If your Tranny has been replaced then that changes things a bit. BTW, the fluid NEEDS to be changed religiously every 30,000 miles so yours probably is due. That should solve the leak as well, assuming it is the pan gasket. They seem to start leaking about the time it's due for a fluid change.

If the suspension is good, body is OK, and you are alright with the car the way used to be when the engine ran well (didn't your AC evap spring a leak?) then putting another grand in a used engine wouldn't be a terrible thing to do. I think yours is a bit more reliable than the '93 and later models. It has less electronics. Actually, if you did that you could probably sell it for $2,000 to $2,500 if it looks good. If it were me I might go sell it and buy that 735i; That is one of my favorite Bimmers!

Off topic, but how do you think the reliability of a mid 90s BMW 5 or 7 compares to the same year E-Class? I love those cars. They seem to be priced higher for some reason, and also harder to find in good condition. They always seem to look like they belonged to a 17 year old who had no job and a lot of spare time.

 

Glad you asked! I actually had an '86 (E28) 528e that I ironically bought when I was 17 (I'm 24 now), then a 1st-gen. Acura Legend and then a 1990 (E34) 535i auto in which I covered 46,000 miles (129K-175K). I never should have sold that car--it was in near-perfect condition, unlike my 300E now. Along the way I've also driven an '89 535i, '90 525i, '95 525i, '93 740iL and '90 750iL, two '97 528i's and a '97 740iL.

If you scroll down under the W124 thread you'll find a thread (recently dug up by other members) that I actually started way back when I had my 528e (and yes, I was dumb and used my real name as my username back then). It's titled "W124 300E or E34 BMW 525i?" You should see some good comments from other members there (albeit several years old).

My PERSONAL preference now would be definitively with the 1989-1995 5-Series now that I've owned the 535i. My E-Class experience is limited to 5,300 miles so far with my own '87, plus brief time in an '86 300E and a '92 300E. I find the BMW's styling more appealing (especially the taillights), and the drive is a bit more responsive while still very solid. The 300E has that block-of-granite feel--like you could demolish anything you ran into--but in my opinion, combined with more numb steering and skinnier tires, that detracts from the more nimble back-road feel the BMW provides. I also find the interior more modern feeling and comfortable than the W124--plus the seats don't get springy and collapse down with age like Mercedes seats. There's no power-adjustable steering wheel and seat memory is optional on the 5-Series (mine didn't have it), but there are other neat features. For example you can double-lock [deadbolt] the door locks if you wish by turning the key further than usual in the outside lock, and you can also close the windows and sunroof from outside the car, again by turning the key in the door lock and holding it in the "lock" position. The driver's window is one-touch down AND up (the sunroof is one touch open/close as well). 1992 and later, all windows were one-touch down/up. Unlike the E-Class and also the newer W140 S-Classes (from my experience), there's retained accessory power even after you remove the key from the ignition, so long as no door has been opened yet. There are other subtle clues these cars are a bit more advanced than the W124--for example, turning the key in the outside door lock generates an electronic signal causing all the locks to pop up simultaneously a split-second later--there's no mechanical interaction between the key and the door lock mechanism like in the 300E.

Reliability-wise, I was very impressed with my 535i. Like the 300E, it has a timing chain rather than a belt. The steering box became loose over time (more undesirable play on center) and the radiator started leaking and eventually had to be replaced. One of the back doors became permanently locked shut when I kept habitually double-locking the doors even though I knew the lock solenoid for that door was going bad. I would've had to take the door panel off with the door still closed to fix this. I also had to get the O2 sensor replaced, and got a tune-up at the same time. The glovebox latch came off in my hand one day, but you could still open the glovebox with your finger, so I never addressed that either. These cars are also notorious for the glued-on vinyl interior door panels coming off, especially on the back doors. Over 46K miles, NOTHING mechanical ever went wrong, and NOTHING electrical failed either (save for the lock solenoid for that one back door--and it gave me plenty of warning).

The 535i is fast, too--a lot of torque (225 lb.-ft. vs. 188 lb.-ft. for a 300E--your E320 would have 229 lb.-ft. though). The 3.4-liter inline-6 pulls like a V-8, and it gets V-8 fuel economy, too (I averaged 17-18 mpg overall). It's a great highway car--AT LEAST as composed in a straight line at high speeds as a W124, if not more so. Although the V-8 540i is no worse on gas than the earlier 535i, if you're looking for better economy I'd go for a 525i--EPA 28 mpg highway w/manual trans. Early 525i's had a timing belt, but with the new M50 inline-6 introduced during MY 1991, I believe a chain was used.

Most of what I said about my car would apply to the 1988-1992 735i and 735iL (same engine). The E32 7-Series is said to be more complex, although I can't think of any electronics a 735 would have that my 535i didn't. Due to the longer wheelbase, the 7-Series feels slightly more ponderous around town and on back roads but actually remarkably similar to a 5 on the highway. Just as solid yet responsive to steering inputs for lane changes, etc. Much more athletic and confident than a W126 S-Class for sure, but with a similar amount of room and (in my opinion) greater amenities.

If you're thinking about an early V-8 BMW--1994-1995 530i, 1994-1995 540i, or 1993-1994 740i/740iL, make sure you are aware of the Nikasil block issue with some of these engines: http://www.e38.org/nikosil.html# I would also say that the 5-speed automatics found in those models are more flaky than the 4-speed automatics found in their predecessors.

This website is devoted to the E34 (1989-1995) 5-Series.
http://www.bmwe34.net/

Moving on to my car, you think that's why the tranny is leaking? That's a good idea--it can't cost too much to get the fluid changed. Like I said, the transmission shifts fine (it's now a bit befuddled by the lack of power from the misfiring engine sometimes and won't downshift as easily as I wish it would, but there's nothing wrong with the shifts themselves).

Yes, there's no A/C right now. That's OK, I'll sweat until it gets cooler in a couple months, and by next summer I should be in another car.

Don't know about the suspension. As you already know I need an alignment, and when I got the MD inspection done a couple months ago they told me I needed a "rear flex joint" to pass (among $1,100 worth of other things they came up with. The car is now registered--don't ask). With the tires properly inflated, the rear end self-steers quite a bit--walks all over the road. If I'm cruising on the highway under throttle and let off the gas abruptly, the car will yaw just as abruptly to the right enough that I need to correct by turning the wheel several inches to the left. If I don't correct but get back on the gas, the rear end will swing back over to the right and straighten the car back out. You can also feel centrifugal force swaying the rear of the car to the outside of the turn while going through a relatively sharp highway turn, especially under deceleration. VERY spooky in the rain. Could this be the "rear flex joint"?

Sorry for the long write-up, but thanks for your advice again.

 

I only know of a rear flex DISC. It acts as a drive shaft universal joint so would not cause any change in direction. Your issue sounds scary. If a domestic car did that I would say it's a broken centering bolt on a leaf spring, but with the rear suspension on the MB I don't have a clue. I would jack it up with the jack under the wheel frame (?) instead of the body, just like it's sitting on the ground, and grab the wheel and see what moves.

Thanks for your pointers on the older BMWs. I will definitely explore them when the time comes to replace the MB. At the moment I have restored my confidence a bit in my own car. I finally found the elusive source of an intermittent fuel smell. I had been smelling raw gas in the mornings until it ran for a while. On my way to work I never had time to investigate, but Sunday I started it up and in 2 minutes there was a 3 foot round puddle of gas on the driveway. It was a loose hose clamp on the fuel hose I had replaced last month. There's still the slight vibration from the driveshaft above 45 mph, but I can't find anything wrong so I'll ignore it for now. I just have to keep reminding myself this is only a $3,000 car, not what I paid for it. NEVER buy one of these from a Benz dealership.

 

The 300E is a great car....no doubt. But you need to be able to do SOME of the work yourself. The local mechanic doesn't care if you have a 2005 car or 1990 car...his shop rate is the same. I would just replace the head with a used on....or...(dare I say)...just replace the valve? Pull the head , replace the valve..you're done. It really isn't rocket science. All you need is a place to do it, some tools, a couple of friends with some common sense and an online subscription to ALLDATADIY. Try it.....isn't that hard. And the MB parts are not that expensive. It is a one day job , maybe 2....head off...take it to a machine shop and ask them to replace the bad valve (that's all...don't let them sell you a lot of unneccessary work...just do what is needed). You also get to put on a new headgasket...which that car will need eventually.

 

shdoug--
the rear flex disc is it--that's what they said was worn (not the joint--sorry). But you said it WOULDN'T cause the car to yaw in the manner I've described? I don't know, I'll ask the mechanic I took the car to earlier to diagnose it; he can look at the car hands on, you know.

And talk about scary! I'm glad your car didn't catch on fire because of the fuel leak.

How many miles are on your E320 btw? I don't know what kind of shape it's in, but the late-model W124's can be pretty expensive--$4,000-6,000 quite frequently. Of course I'd go for $6,000+ and easily get an early W210 E-Class (although I'd rather be in a 1996-1998 or so 7-Series for similar money). I think if your car's decent, you could get a hell of a lot more than $3,000.

Brian McL--
THAT'S WHAT I THOUGHT when the mechanic told me the valve was bad--I was immediately thinking (but afraid to say out loud for fear of sounding niave), "OK, so...why don't you.......just replace the valve that's...BAD??" I mean, this is not a concours winning car, nor one I plan to drive for the next 100,000 miles (it'd be nice if it lasted 20-30K). If it runs smoother until next summer because I replaced one valve, then it'd be worth a couple hundred bucks to me to have that done. How many hours do you think is involved to do that? And how much does a valve cost roughly?