OK gents, I have a bit of a pickle on my hands here.

I have one sick 190E 2.6 and have a busy month ahead of me at school.
This leaves me to take my car into the main dealer, which I've had a great history with. Normally, I like to try my own luck first, as I've done a few jobs on my own with great success.

I have a brutal stumble at idle, when the car has warmed up to operating temperature (82C or so). After it reaches this temperature, the check engine light comes on and the stumble will occur at idle. Hesitation upon acceleration also happens, but after you reach 2000 rpm or so the car is smooth and strong.

I'm leading towards a water pump related problem. I read through the 3 or so pages worth of threads, and the car has some of the symptoms. The serpentine belt is noisy on the car, when you put it in gear that noise becomes louder. I'm not sure if I'm seeing a little coolant or not from underneath since it is winter up here and I'm always in a lecture or lab so I never can get a good look under there. Water pump is original

The car has 219,000 km on it now. Alternator replaced 20,000 km or so ago. Head gasket 10,000 km ago (along with the idle speed sensor). I did the plugs and wires on it 30,000 km or 2 and a half years ago. All electrics operate well on the car.

Serpentine belt has been on it for 60,000 km now, I did it 4 years ago. I did the tensioner at the same time. What do you think guys? I'm wondering if it could be the coolant temperature sensor? Everything electronic on it is original.

I rarely drive it now that I've moved so close to the University, I drive the car once a week or even less, and for a maximum of half an hour (to my part-time job).

I was thinking of dropping it off at the workshop and asking them to due the water pump, accessory belt idler pulley assembly, serpentine belt and tensioner, coolant flush, oil change and to run a star diagnostic to code pull for the check engine light. That is $2K CDN worth of work (or thereabouts). I don't think I'll be able to make an RRSP contribution this year

Have I overlooked anything do you think?

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1989 300CE - 269,000 km
1994 SL600 - 59,000 km

Your 1991 car does not have OBD. The CEL is connected to the O2 sensor.

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John Shellenberg
1998 C230 "Black Betty" 240K

http://img31.exs.cx/img31/4050/tophat6.gif

You may need a new water pump, or some other belt-driven accessory at that mileage, but I don't think the water pump is causing your driveability problems.

It could be a variety of things, but the check engine light plus the stumbling after the engine has warmed up suggests that it might be an O2 sensor issue. (Among other things) Try testing your O2 sensor and see if it gives you good, snappy voltage changes. I can't remember the exact values but I think it should alternate between 0.2 and 0.8 volts once or twice a second, with a sharp voltage switch between the two.

Anthony

I agree. I don't see how a water pump could be the culprit.

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2012 E350
2006 Callaway SC560

Hi,

I cannot figure how a water pump will do that....

Does your ABS light working when you turn ignition switch ON?

When your engine is running do the ABS light come on at the same time of your Check Engine Light (Cel)?

If the Abs light come on at the same time, Check your OVP relay located behind your battery.

If you have only the CEL that come on then check O2 sensor.

Have a nice day
Max

The CEL leading to the O2 makes perfect sense. This reminds me of my last emissions test, just before my birthday. I passed by only 1 hydrocarbon.

Passing by only one hydrocarbon, after changing the oil immediately before the test, along with the engine coolant and a new set of spark plugs leads me to a new problem.

The catalytic converter. They are pricey.

What would you guys do? I'm a pretty anal retentive purist and would not consider one of those jobber type cat cons. I've replaced both mufflers recently so the underside of the car looks pretty damn good. I think I'd like to just put on another 02 and keep driving for sometime and make an RRSP contribution.

Would this be throwing money out the window? What are my options here?

Thanks a bunch,

Mike

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1989 300CE - 269,000 km
1994 SL600 - 59,000 km

PS
ABS is fine, I did the brakes (all rotors, all pads including parking brake assembly on rears) myself in May, bled all four sides through the master cylinder and with the proper spec DOT 4 MB fluid. This included the speed sensors. All the lines looked great. I left the calipers (didn't rebuild them) since they felt and continue to feel just right.

PPS

John, how many kms did you get out of your 190?

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1989 300CE - 269,000 km
1994 SL600 - 59,000 km

I bought it back AGAIN last fall, and it's sitting outside the house right now with 509,000kms on it. Engine all original, trans never done. Original shocks, but deader than Elvis and same for the springs. The AC still works and has never had any sort of repair. The rad is fairly recent, and a couple years ago the thermostat housing exploded and some repairs were required. The alternator has been rebuilt.

The engine is now smoking at start-up, so I imagine some of the top-end is getting weak, probably guides and seals. Given the value of the car at pretty much zero, it's no use spending any money on it. The list is just too long now. Top end, all suspension, etc. Still runs great, and I took i for a drive the other day just to keep things moving. Not sure what I'm going to do with it.

If I sell it, it would never pass an insurance safety inspection (suspension) and I was fortunate my own company didn't asked for it to be recertified.

The PO left some major door dings uncared for, and now it's rusting, otherwise the body is great.

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John Shellenberg
1998 C230 "Black Betty" 240K

http://img31.exs.cx/img31/4050/tophat6.gif

How old are they? I overlooked this on my car and it turned out to be the problem. The reason it baffled me so badly was the similarity to your symptom of not causing problems until warmed up. Ran fine when cold but not so fine when warmed up good.
It's cheap to check.

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1983 M-B 240D-Gone too.
1976 M-B 300D-Departed.

"Good" is the worst enemy of "Great".

I don't see why you would want to replace the cat unless the car actually failed an emissions test. I'm not sure that replacing the cat would necessarily reduce your HC by that much either. I'd just test the O2 sensor first, then replace if necessary, and see how it does the next test.

The O2 sensor does not operate when the engine is cold. Before spending a TON of money, diagnose the O2 sensor. Stop. Do not replace the catalytic converter without first examining the much-much less expensive O2 sensor.

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John Shellenberg
1998 C230 "Black Betty" 240K

http://img31.exs.cx/img31/4050/tophat6.gif