1992 190e 2.6 M103

I'll try to keep this post balanced .. too long, people gloss over the details, too short people ask for details.

Trying to troubleshoot a rough idle. Stutter is hardly noticeable in park or neutral, stutters excessively in drive or reverse. Car starts fine cold (albeit now with the temps really low it requires some effort) and idles fine cold. It's when it warms up that the problems arise. Car drives fine once RPM is up so good on the highway, cruising, whatever. Accelerates consistently on the highway, does not bog.

Things I've done in my 2 years of ownership:

- All ignition components including non-resistor copper core plugs (have not replaced coil however)
- O2 Sensor
- Fuel filter
- Air filter
- Coolant Temp Sensor
- OVP
- I've removed the ICV and watched it click open and closed with a 9V battery so I assume it works (just a couple of days ago)
- I have sprayed carb cleaner all over the damn place underneath the airbox and I couldn't really register any change in idle. I did not spray the EGR and now I'm thinking I should have, would that be a good test?

And probably a bunch of stuff I'm forgetting. The rough idle is a stutter, not consistent rough idling and really only when warm. Lately it's progressed to stalling when putting it into gear. Idles fine in park or neutral, idles like crap in drive or reverse, sometimes stalls when shifting into D or R, sometimes stalls at lights.

If my EGR was stuck open I've read that would be a massive vacuum leak. I keep reading references to vacuum testing the motor but I don't know where to plug a vacuum gauge (I have one). My car does not have an economy gauge. I have drawn a vacuum on the hose going up from the EGR (to the check valves or whatever along the firewall) and either there is a big leak or no vacuum is supposed to be present there. What does a vacuum leak here indicate?

IF my EGR was stuck open, would it affect the cold idle as well?

What vacuum port can I use and where is it, to test my engine vacuum?

My fuel economy has always been crappy on this car.
Compression is 180-185 across all cylinders.
I have read numerous threads on rough idle and there is always a lot of conjecture and "throw parts at it" suggestions and that's not what I'm trying to do, I would like to know how to go about troubleshooting this in a systematic way by eliminating variables.

There is a faint exhaust smell in the cabin when stopped at lights, is this a clue?

Thanks

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1992 190e 2.6

I guess it's possible there could be a small leak in either the EGR itself or the tube that foes from it and any associated connections, that may cause your exhaust smell in the cabin when stopped, if theres no leak in your exhaust system. I have no idea what the vacuum value is supposed to be there.

How's the fuel injectors? If they're old they might not being spraying like they used to...

And of course check the condition of all the rubber bits, such as the hoses to/from the ICV, the boot between the air meter and the throttle body, and the other little elbows/hard lines. There's tons of stuff that could play a part in a rough idle.

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Streetside: 1987 Mercedes 300E Petrol Blue/Green
2014 Ford Mustang Grabber Blue
1999 Ford Ranger Green

Dockside: 1968 Eltro 17
1985 Silverton 34C

Take your car for a drive tonight, then pull in to your driveway and look. Make sure it's as dark as it can be. I chased a problem like this for a long time before I noticed arcing between the wires and the cylinder head. Ironically, I. Was dumping washer fluid in when I saw the spark.

Generally speaking, when it is a consistent stumble, it is fuel related. When the miss is completely random, it is usually spark related.

Keep in mind that 80's vintage cars need new spark plugs regularly.

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Eugene

10 E63 AMG
93 300te 4matic
07 BMW X3
14 Ford F-150 Fx2

Thanks. Yes, I actually did this. Drove into my garage, closed the door behind me and turned off all lights .. it was pitch black and I didn't see anything. In the two years I've owned it I've only driven 16k miles and I must have changed the plugs, wires, distributor and rotor about 10 to 12k miles ago, if not less. I had the plugs out about six weeks ago when I did the compression test and they were a light tan. My duty cycle is 50%.

That is useful information. What are the characteristics of a vacuum leak?

Also, is there any significance to the "rough in gear, smoother in park/neutral" observation?

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1992 190e 2.6

I had a similar rough in gear and smooth in neutral and it was solved with new injectors.

If you plan on keeping the car long term, I would go to auto zoo, and buy a mity vac for $30 or so bucks. You should read a minimum of 13 hg, 15hg being ideal. Make sure everything is off (climate control).

A cheap test to see if your injectors are clogged is to buy a bottle of redline fuel additive. It can be found on amazon. If you notice a significant difference, (positive) then I would do fuel filter, then new injectors. Injectors are pricey....

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Eugene

10 E63 AMG
93 300te 4matic
07 BMW X3
14 Ford F-150 Fx2

Thanks for the reply. I do have a mityvac I just don't know where on the engine to hook it up! Simple, I know, but I have to ask because I couldn't figure it out.

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1992 190e 2.6

I don't think they sell redline here in Canada. Will seafoam accomplish the same thing?

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1992 190e 2.6

No, in my opinion seafoam will make matters worse. You cant order it online?

with the air cleaner removed, there is a small vacuum line towards the rear. that one controls the climate control, and the economy gauge. Once you plug it in, and fire it up, it should give you an instant reading. 13-15hg.

The more I think about it, maybe you can try seafoam. If (perhaps when) it makes your car run worse, then you would know certainly it is fuel related, and most likely injectors.

I would still try and buy redline. That stuff is the best chit I ever used.

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Eugene

10 E63 AMG
93 300te 4matic
07 BMW X3
14 Ford F-150 Fx2

It's pretty cold up here these days so my laziness at properly troubleshooting the vacuum lines hasn't entirely been laziness, it's damn cold out in the garage! And I can't idle the car in the garage anyway. So I've made a proper effort now that I know where to hook up the mityvac, thanks Lorainfurniture.

The EGR does not hold vacuum, so I plugged it off.
I found that one of the lines going to the HVAC was not holding vacuum either. I thought, surely plugging two vacuum leaks would fix it. Sadly no, problems persist. I took some video.

The first part is just idling and shifting the transmission around to demonstrate the dropped idle and the stutter, which is hardly noticeable in the video but very pronounced in person. The oil pressure gauge is probably the thing to watch here. Second part is me flooring it from a slow crawl, major stutter doesn't want to go, threatens stalling. In fact, it stalled on me backing out of the driveway. I can floor it on the highway and it downshifts like it should and does not stutter or bog, acceleration seems normal. Third video is the vacuum state as I mess with the throttle. You can hear the engine bog and stutter much better here. I rev it slower to show that it performs normally when throttle is applied slowly. It's blurry, sorry, but it's at about 16/17 HG which I perceive to be within reasonable operating range for these motors based on what I've read around here. The engine was as warmed up as it's been getting lately (have another thread about engine temp, it's running cool).

http://www.youtube.com/watch?v=IANlAFwoEt8

So, what do I try next?
Again, all ignition components have been replaced with the exception of the coil. I don't know how to test a coil and they aren't exactly cheap so not sure how to eliminate that variable. Otherwise, the car has 195k on it and my guess is original injectors, but no idea really. Would a bad fuel pump cause this?

Pics are of the blocked off vacuum lines. The EGR is disconnected. Anyone have any idea what the red vacuum line that I disconnected is?

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1992 190e 2.6

Your vacuum is excellent. Your YouTube video is private? Can't see it.

__________________
Eugene

10 E63 AMG
93 300te 4matic
07 BMW X3
14 Ford F-150 Fx2

My bad. Should work now.

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1992 190e 2.6

I would try the redline. If you truly can't get it, let me know and I'll try and ship it to you. If I had a farm, I'd probably bet it on clogged injectors.

The theory is if you could imagine your injectors peeing instead of spraying. At idle, the combustion chamber starts filling up with fuel bc it's just not combusting well. When you gun it, you almost flood it, but once you burn out all the extra fuel it's like turbo boost and you have full power. Until the next red light.

Sound about like your symptoms?

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Eugene

10 E63 AMG
93 300te 4matic
07 BMW X3
14 Ford F-150 Fx2

Yeah, about like. Also terrible fuel economy!!! But the fuel economy has been terrible since I have owned the car. I might as well be driving one of the 8 cylinder SELs!!!

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1992 190e 2.6

Bad MPG definitely unlike an m103. I get 20+ in mixed New York driving. And thats even with all original fuel components at 235K

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Streetside: 1987 Mercedes 300E Petrol Blue/Green
2014 Ford Mustang Grabber Blue
1999 Ford Ranger Green

Dockside: 1968 Eltro 17
1985 Silverton 34C

I own a 230 E -> basically your engine with 2 less cylinders, and no EGR, and I have some problems with idle aswell. Have you looked at the crankcase ventilation? The rubber gets very loose with age, and when I bought a new one and compared it to the old hose, there was a huge difference in diameter.

I know this sounds a bit like "throw parts at it", but you can examine them beforehand. There is no sure way of telling if they need replacement, but if they feel really soft you should consider it atleast. You might however run into problems when ordering parts, even here in germany the EPC does not list all the hoses, the only way to get the part number is comparing it to the old one.

I'll update if I end up replacing the rest of the hoses in the near future.

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-1990 W124 230E; Winter car
-1985 W123 230TE; Ex-280TE, daily driver
-1976 W115 200D; Restoration project