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Old 06-09-2003, 02:44 AM
190ebenz's Avatar
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Join Date: May 2003
Location: San Diego, CA
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Question 190E 2.6 Deceleration FUEL ISSUE

1990 190e 2.6 Deceleration ISSUES /FUEL RELATED?

having issues with my car decelerating at odd times, spiratic and odd behavior. I'll be driving any speed ..40,50,65,75mph and I let off the accelerater and the car will start to decelerate (a significant amount) by it's self, I thought it was supposed to keep rolling some? (acts like i'm breaking). When I'm going down my streets hill a nice grade, it'll stick to same RPM/MPH and won't speed up at all, like somethings holding on and slowing the car down. this is all off and on behavior.

Sometimes (spiratically) where i'm going along on the freeway or the road and it's like something kicked in cause my economy gauge goes down to (no fuel) being used and just cruises real smooth??? just like it was a new car.

This problem even persists and changes will driving steady on freeway, i'll go 70-75mph and my fuel gauge will read the middle line (50% gas output) and then once in a while act out and like go in economy mode?? The gauge moves to 0 fuel being used and then, i've regained strength and power in my car. weird......

this problem goes on often even when i'm cruising the car will be making accelerate more to get it up to speed, giving it more gas.
this all acts off and on, one day or time it'll be like a new car, next it will act like a fuel deprived car.

what's up with this? any suggestions would be greatly appreciated. I am going nutz with these issues. I do put in highest ocatne in car.

Thanks you guys your all great, I don't know what i'd do without this MBShop Forum!!!
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Old 06-09-2003, 09:57 AM
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Join Date: Sep 2002
Location: Newcastle upon Tyne, UK
Posts: 215
Sounds like a fuel/air problem. Either you've got too much air, or not enough fuel.

Too much air comes from leaks in the air ducting on the engine. Look for broken or detoriorated connections.

Too little fuel could come from a faulty fuel pump, a blocked fuel filter, an intermittent fuel pump relay.

When a similar problem happened on my 190E, it was the fuel pump.
Cheers, Neil
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Old 06-09-2003, 11:32 AM
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Join Date: Jul 2001
Location: SoCal
Posts: 1,303
Can't answer some of this, because our 2.3 does not have an 'economy' gauge. Still, the CIS injection IS designed to shut off fuel thru the injectors in most deceleration conditions. With your foot off the accelerator, engine braking would be normal.

My understanding is that the function of the microswitch behind the accelerator linkage, above the throttle body, is the one that provides the ECU with the decel fuel-cutoff signal. The ECU also balances this against engine speed and possibly other factors.

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Old 06-09-2003, 12:56 PM
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Check out this post which also discusses testing the microswitch.

190e : Decel Switch???

Good luck!
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Old 06-10-2003, 02:43 AM
190ebenz's Avatar
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Join Date: May 2003
Location: San Diego, CA
Posts: 8
Throttle Microswitch changed.....and now...

Thanks Neilg, sbourg, azhari

Neil G - I checked around today up and down through the engine hoses seem to be okay and all in tact. no problems in that department. Fuel pump? any way of feeling that or knowing?

Sbourg, Azhari - I just popped for the new $20 dollar part because I did some checking and found that my microswitch wasn't always making the right connection weird! That seemed to have helped some. Thanks!

Still seems as though i am receiving a little bit of lagg from the car, seems like something just not talking. Any other switch or function which i should check? Throttle linkage setup seems fine, going back to default when i left off accelerator and making good contact with the throttle microswitch.

I just wish I had the one amazing cruising experience return back to me, just drove so smooth and had so much power, it was there for 5 minutes or soo..until traffic caught up. Now it's gone, never again have I had that. Fuel Filter/Wires/plugs (copper) changed.

Anything else I should checkout?

thanks again!

190e 2.6 1990 - 179,529 mi, auto 4 speed trans
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Old 06-10-2003, 05:42 AM
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Location: Newcastle upon Tyne, UK
Posts: 215
The fuel pump runs all the time that the engine is running and you can hear it if you stand at the rear of the car. A pump in good condition may be almost silent, or produce a little 'sizzle'. As it deteriorates, the noise usually gets louder and harsher. However noisy fuel pumps can often go on for a long time without causing a problem, so you can't be certain,

In theory, a fuel pressure test can be carried out, but that will only tell you that the pump is working at the time you test it.

When I had the problem on my 190 I figured that the cost of replacement ( about $140 for the pump and $40 for the fuel filter) was less than I had already paid for a Bosch technician to fail to diagnose the problem. I was fortunate that this worked for me.
Cheers, Neil
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