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Old 08-19-2002, 06:57 PM
Registered User
Join Date: Apr 2001
Location: Central Oregon
Posts: 91
Techron and W126 rough idle remedy

So my 85 500SEL has the common "rough idle" symptoms that is well documented in threads of this site.

I attribute my problem more to infrequent driving than anything else. She does not go out much in the winter, and I have a company car during the week (1985 with 115k - you do the math).

I have been using a bottle of Techron FI cleaner with any fillup before an extended road trip. The old girl is so appreciative and just loves the open road, that the idle problems disappear, transmission smooths out, and the ride is wonderful. But then I go back to my old routine and she starts grumbling again. This tells me that some new injectors would make a world of difference (no record of FI service in the books - 2nd owner).

My question (finally!!) is:

Would others continue with this magic elixer method, knowing I am lucky to put 5k miles on a year, or would you buck up and plan to replace injectors, seals and misc. fittings? My concern is that the persistent rough idle will make other parts wear out sooner. I know too - I would enjoy old blue even more. I am inclined to DIY (did this on my 72 280SE 4.5 with great success).

What do others think?
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Old 08-19-2002, 11:55 PM
Senior Member
Join Date: Jun 2001
Location: Northern Calif. (Fairfield Area)
Posts: 2,225
Are your washing machine and clothes drier located in the garage where you park the car?

Auto Zentral Ltd.
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Old 08-20-2002, 01:58 AM
David C Klasse's Avatar
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Join Date: Jan 2001
Location: Mission Hills in the City of San Diego
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I'm not sure if I understand... if so, then try this:

Run a (big) bottle of techron through the fuel system only when you have 3 or so gallons of gas left... then run it real low. Upon fill-up, use one more big bottle of techron... and when finished with that tank of gas, get an oil change.

Good luck!

It might just take a second application through the system.
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1993 300E 3.2L Sedan w/ close to about 300k miles
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Old 08-20-2002, 11:22 AM
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Join Date: Apr 2001
Location: Central Oregon
Posts: 91
Peter - not sure where you are heading, but I have a separate laundry room. Wish I had a utility sink in the garage though.

David - here is a more simple explanation.

It is not uncommon for my car to sit 2+ weeks at a time, even longer in the winter. In the summer I take the old girl on long golf excursions - that is when I add Techron and get immediate benefits. But then she sits for two weeks again, and the rough idle returns. I am not sure a more concentrated/larger dose will provide more benefit. I think cars in general just don't like to sit unused for extended periods of time.

So .........

If you were me, would you buck up this fall and replace the injectors, or continue with the Techron additive on a regular basis.
Of course I have several other wants/needs for the car.

Thanks again, Michael
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Old 08-20-2002, 11:41 AM
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Join Date: Jun 2001
Location: Northern Calif. (Fairfield Area)
Posts: 2,225

It took me awhile to figure out why my 560 would run rough til it ran down the road awhile. It turns out the old plug wire insulation couldn't handle the moisture produced by the clothes drier which was near by. You may be experiencing some dampness particularly if you let the car set for long periods of time. You might be due for plug wires. A new set of wires solved my problem.

Auto Zentral Ltd.
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Old 12-09-2002, 08:00 PM
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Join Date: Oct 2002
Posts: 75
When you say run rough what do you mean? Like a dead miss almost like you would have water in your gas. Mine sits alot but the miss is intermitnent. Injectors tend not to like sitting for long periods year after year. I mean 3,000 miles a year average.
1989 420SEL 105575 miles
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Old 12-09-2002, 08:14 PM
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Join Date: Jun 2001
Location: Northern Calif. (Fairfield Area)
Posts: 2,225

You need to either drive it or get rid of it. Cars, boats, RV's, etc. deterioate rapidly when not used. I have the same problem you have. I have a 1987 560SEL just setting in the driveway with the birds crapping on it. I need to get my act together with a New Years resolution and prep it for sale. It needs to go to a good home where it will be driven and enjoyed. I suggest you do the same.

Auto Zentral Ltd.
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Old 12-09-2002, 08:49 PM
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Join Date: Aug 2002
Location: Lake Powell
Posts: 25
by all means

by all means use the Techron and enjoy your car as YOU see fit . I would not concentrate it but use it as labeled. I recommend that you try to purchase the "professional version Techron" There are less powerful formulas of the same product, I find mine at the commercial counter at Checker Shucks Kragen :{ Unfortunately they are the only ones in my area who carry this version
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Old 12-09-2002, 08:55 PM
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Join Date: Dec 2002
Location: Colleyville, Texas
Posts: 2,694
Ran across this with my 560SL. I would have a miss at idle. the car ran fine but at the light it would ocasionally miss. I brought it to the dealer and they replaced some injectors and spark plug wires. It still missed. I brought it by a 2nd time. Some more injectors and resistors.
Well the 3rd time I was pretty ticked off. Especially since they just had my E300 for 3, yes 3 weeks to fix a radio problem that they didn't fix.
They had the 560SL fixed in 2 days but forgot to call me. A week after I gave them the car I called them. ( I guess I really didn't mind I was driving a E320 loaner car, puting the milage on there car not mine) Oh yea its ready It was your distrubutor cap.
The cap was corroding on the inside of the cap, at the contact points. So check this out.
To contune this weird story. I requested a refund for the $1100. charge for the 2 previous visit. I had to sign a legal release before they would give me a refund. Well of course I have changed dealers. gone back to ******** in Dallas. I went to them for 17 years and never had a problem. Switch to the closer dealer for convinience.

Well enough of this rambling. Go check your distributor cap. Then I would check the wires, then think about the injectors.

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