Rough Running 2.6 190e
 

Hi all.

I need some help troubleshooting my rough running 190e, 2.6. In the past 15k miles it's gotten new spark plug wires, new plugs (correct copper core), new distributer, cap and rotor, new air filter, new fuel filter, new O2 sensor, and recently I replaced the coolant temp sensor and OVP. The car has 195k miles, it's a california spec car so it's got the x11 diagnostic port with LED. My exhaust recently developed a hole right before the muffler but my problems predate this. My compression is 180 to 185 across all cylinders, tested a few weeks ago.

Prior to replacing the coolant temp sensor I was having hard cold starts. I believe this is now resolved, my cold starts first thing in the morning are no problem, fires right up. Rarely do I have to crank very much. I adjusted the duty cycle to 50 after replacing the coolant temp sensor.

My problems persist, namely, rough idle in gear and poor fuel economy. I don't think the two things are related (but it's possible) because the poor fuel economy has been with me since I got the car two years ago. I get on average 230 miles to a tank. It's almost entirely smooth in park or N but it's rough in gear. Warm starts are very rough and it stalls sometimes when starting warm. The rough idle is kind of consistent in that it feels as though a cylinder is not firing or something, ie;

brr, brr, brr, shudder, brr, brr, brr, brr, brr, brr, brr, shudder, brr, brr, brr, shudder, etc

Once put in N or P however it's hardly noticeable. The latest development that I almost forgot is leaving a light with the engine warm (later in my morning commute) the engine bogs and won't accelerate, I have to nurse it a bit but once it revs up it's fine.

I am not a mechanic, I've owned this car for two years, it's my first car and I've endeavoured to do all the repairs myself. I've learned lots but I'm still very green. I'm tempted to replace the fuel injectors but I don't want to spend any more money on the car until I know what's wrong. Gas prices are high and my car is getting something like 16mpg. I could be driving a 560SEL for that kind of money!!! The valve cover is leaking as is the timing cover and I want to resolve those things as well. I'm considering resealing the valve cover, timing cover and while I'm in there, possible replacing the timing chain guide, cam seal, valve seals and guides and then the injectors. That's a lot of money however and I really want a 300TE so I'm loathe to spend more money on the 190e that I could be putting towards a TE ... if I ever find one that's not rusted.

Where do I start with the troubleshooting? I don't know anything about testing fuel pressure or injectors, I don't have the tools to do those things. Maybe they are cheap and a worthwhile investment, I'm open to suggestions. The other thing I would like to simply replace are the breather hoses going to the ICV but I'm not even sure how to get at them or what parts to order. I figure I should just replace them on principle. I would also like to test the EGR but I don't know how.

Thanks

I'm going to guess that the rough idle you feel is caused by worn engine mounts.

I would also start looking for vacuum leaks for your other performance complaints.

Also, check that the spark plug boots are properly seated on the plugs. This same thing happened to me and it ended up being that the inside of one of the spark plug boots were worn and was very loose around the plug causing it to slip off and lose contact.

Try putting a bottle of redline fuel additive in your next tank. You can find it on amazon for ten bucks or so a bottle.

When you notice a 100% improvement, change out your injectors for a good lasting repair.

Also, do you have a mity vac? If not, does your dash have an economy gauge? Vacuum leaks will cause rough idle/ stalling.

smp, the sluggish acceleration may be due to a faulty Oxygen sensor. When was it replaced last?

I have been going through the same thing you are going through with a 103.

While I haven't replaced the cold start sensor, I have done a full tune up.

I am convincing myself that the problem is old rubber under the fuel distributor... when i get time in the next couple of weeks, I will replace those.

The car is 24 years old...and I have no evidence that those hoses have been replaced.

Can't find a vacuum leak anywhere else

btw... I want a TE, too..if I can ever find one where the owner isn't too proud

Lee, count yourself lucky that you're in a place where rust-free w124 wagons live on. Up here in Toronto .. not so much. And they're all 4matics *shudder*.

I have a mityvac, but I don't really know what I'm doing with it. The next thing on my repair agenda is likely the hoses to the ICV, these seem to be a common weak spot on our old m103s and it's a cheap 'fix'.

O2 sensor was replaced about a year ago, mentioned in the OP.

Just attach the mity vac to one of the vacuum ports. you should read minimum of 12hg, 15 being ok, 17+being tight as a drum.. Needless to say this is done at idle.

Dont waste your money on things that do not need replacing. I do agree that the idle air hoses should be replaced as a maintenance item(every 15 years), but why not do it at your lesuire in the spring? It is probable that it will not solve your problem today, and they are kind of difficult to swap out.

Try a bottle of redline, its 10 bucks, and it can only do good for your car.

I don't have any gasser MBs, but I had similar issues with a Nissan with a crapped-up EGR that got stuck partially open. It ran fine on the freeway but bogged at lights and had like 1/3 of the power- so the mileage was terrible. I also had an intermittent issue with spark plug wires like lsmalley in a chevy- when the motor warmed up- the boot would work loose, causing an intermittent miss- and it would ground out on the header. Took months to find that one. Had to run it- pull the boots off one by one (and noticing the change in idle) until I noticed NO CHANGE when I pulled #7. I forced #7 boot back on, and it sprang to life- and idle went up- and then shocked the p*ss out of me because the exhaust header had burned a tiny hole in the insulator- which was arcing on the header... Best of luck.