16v flat spot, plus it feels like it is a turbo - PeachParts Mercedes-Benz Forum

pentoman · #1 12-31-2005, 11:51 AM

The more I drive my 1990 2.5 16v, the more I'm convinced there's something not quite right.

If you go full throttle from low rpm, it accelerates well, up to around 3000-4000 rpm, where it makes lots of noise but acceleration does not increase, until it hits the cam at ~4500 and takes off.

Additionally, and probably related, there's a definite throttle lag/poor response. I have to drive it like a turbo, putting your foot down early in anticipation of the power coming in about 1/2 - 3/4 second later. It's not a big deal but for what should certainly be a sharp normally aspirated engine is not right.

ideas?

I've had the mixture adjusted correctly (though I still have a high warm idle). The OVP is fine but I might replace it anyway because it may be causing me an ASD problem.

Russell

P.S. I have checked, nobody has put a turbo on it

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yhliem · #2 12-31-2005, 01:27 PM

but if it did, check your O2 sensor.

pentoman · #3 12-31-2005, 01:56 PM

Quote:

Originally Posted by yhliem

but if it did, check your O2 sensor.

Funny you should say that.. look at the other thread I just posted:

thread clicky.

Not sure if my car has/is supposed to have an O2 sensor. Since I've got the wires I should probably assume it should do and find out where it's at. Or to save me time, does anyone know if all 16v's have oxygen sensors?

Russell

happy new year from England by the way

yhliem · #4 01-01-2006, 02:40 AM

I can't speak for Euro spec versions, but I know for a fact that all North American spec versions were equipped with O2 sensors. European 16vs were available with or without catalytic converters and I don't know if this applied to O2 sensors as well.

That being said, the picture in your other thread suggests to me that your car should be equipped with an O2 sensor. These are generally located under the passenger seat updraft of the catalytic converter.

A faulty O2 sensor, or lack thereof can result in all kinds of drivability issues.

pentoman · #5 01-01-2006, 07:59 AM

How can you identify whether your car should have a lambda sensor then? Would it be a KAT model as opposed to EZL (and where would I find out what I have?)? Or do EZL cars still have the lambda sensor?

There must be a very obvious way to tell...

thanks for the help so far,

Russell

pentoman · #6 01-21-2006, 09:38 AM

Thanks all.

I suppose a good idea with this sort of problem might be, to remove the OVP and see what happens! In my case, no change to the engine's running. This means the OVP is not doing anything, so many electrical and important functions (eg cold starting) will not be operating and my engine is not running as its proper self.

Whilst tracing an ASD diff problem, I have realised the OVP relay is faulty (well either that or one of the wires to it is).

I did a wiring bypass (bridged pins 87E and 87L with the OVP still in there if anyone cares) and solved the problem. At the same time, my idle became more normal and the poor response *seems* to have gone (only had a 5 minute test drive though).

So I need to either replace my OVP or find out what powers it if it is not the OVP. I'm fairly confident it is.

Not only that, my ABS was working properly so I had thought the OVP was fine. Apparently not the case in these twin-fuse ASD equipped 190Es.

Thanks all that helped, I hope this information helps someone else out there!!

Russell

mctwin2kman · #7 01-23-2006, 10:03 AM

Yeah these OVP's can wreak havoc on the more advanced 190's! My lil 1986 only has a single fuse OVP and no ABS or any other traction altering frills. So no nice ABS or ASD lights to light and let me know of junk OVP. Hope the new one fixes it.