16 vlv surging on deacceleration!!! - PeachParts Mercedes-Benz Forum

Potomac Pat · #1 09-03-2002, 01:14 PM

I am encountering a rather strange problem. Regardless of what gear that I am in when my car deaccelerates and the tach is @ 3000 rpm the car surges and jumps. Then when around 2800 it stops. It is weird b/c it is only happens @ the 3000 mark. Any ideas on this one guys?

Potomac Pat · #2 09-04-2002, 01:57 PM

Maybe the EHA is losing current? What about the throttle switch? Any ideas?

Hurshi · #3 10-06-2002, 11:15 AM

Hey Potomac,
what you are exolaining is exactly what is happening to my car too. The rpm surges while engine revving down at 3000 rpm even at a stop. I was thinking the idle control relay could be causing this because it is the only thing that can make the car rev up (my guess).
My car started doing this after I replaced the fuel pump relay. Did you change it too?
The OVP can also be a problem. Once I pulled it out when the car was idling and the car surged to 3000 rpm for 2 seconds and settled back to normal.

My car is 1989 230E. Please let me know if you discover something new about this.

yhliem · #4 10-08-2002, 02:31 AM

Pat,

the problem you are encountering is common with 16v. incidentally so is the idle problem that people have been asking about. the one where a 16v does not idle smoothly but hunts between 800 and 1000 rpm for the idle point.

From what I have been able to find out, the root cause is the KE-jetronic injection system. The K system is a piece of work. If I'm not mistaken, many VWs use that system. The problem comes when Bosch too a mechanical system and piggybacked electronics onto it in an effort to gain fuel efficiency, reduce emissions and get more power out of the engines.

With the purely mechanical systems, you could adjust the settings yourself, but you'd sacrifice some efficiency when conditions were not equal to those for which you made the adjustments. In essence the electronics are meant to make the system self-adjusting so that it can compensate for the varying conditions that engines are exposed to and therefore spend more time operating within "optimal" specs.

The problem occurs when the system starts to fight itself. ie. at one point the air-fuel is too lean, so it sets itself richer. until it get's a little too rich, so it starts to lean itself out until it gets too lean, then it adjusts back the other way...and you can see where it's going. either the required adustment is less than the smallest increment of adjustment possible by the system or there's a feedback lag so that the system cannot react in time to control the adjustments.

the upshot of this is that with the 16 in particular (not sure about the euro versions, but I know this to be true of the NA models) they are TOTALLY inconsistent when it comes to how well the engine runs. Some cars never experience idle hunt or surging, while with others it's a chronic problem.

I've spoken with several MB techs in the area that own or have owned 16vs and the consensus is that "these cars never ran properly from day 1. unless you were lucky."

mine hunts and surges too, but the way i look at it is that it's the nature of the beast. yeah, it's a PITA, but hey a Lamborghini Countach is a fast sexy car, but DAY-UM is it ever a ***** to parallel park!

Potomac Pat · #5 10-09-2002, 04:59 PM

Well just as an update. I have gone over the entire system as best as possible.

I started by checking/inspecting the fuel system. I replaced the inline tank filter, the fuel filter/accumulator & pump assemblies. Problem still apparent. At this point I checked the current to the EHA. I wasn't all that happy w/ the results, so I replaced it w/ a new unit. No change

I was getting frustrated as hell, b/c I have already dropped over $4k into the car.

From that point, I looked at the possibility of having a defective O2 sensor. Again, swapped it out w/ a new unit. While doing this I said WTF & changed out the KE control unit as well. Still experiencing a hesitation !!!

From this point I am wondering if the poteniometer on the airflow meter has a flat-spot in it. Or if the internal workings of the fuel distributor are fuc*** up. I have check for all possible degradated wire connections and/or possible vacuum leaks. NOTHING !!!!

I love my 16-vlv and just got done swapping a 93 sportline interior into it and aside from the surging issue, it's GREAT !!!!
BUT I HAVE ABOUT HAD IT !!!

Hurshi · #6 10-25-2002, 02:32 PM

I read a post about how cleaning the idle control valve smoothens up the idle and decided to clean my car's idle control valve. I took it out and cleaned it with an injector cleaner (gas additive) then put it back. After I put it back I forgot to attach the wires coming to it. The car started out and test driving showed no surging at all. Then I noticed that the idle speed rpm was about 1100. After I reconnected the wire to to idle control valve the idle came down but the car started surging again. Then I understood that there is something wrong with the valve or the control module.
Then I decided to find out if the idle control valve or the idle control module causing the surge. I connected a voltmeter to the valve and saw that the valve get about 12volts when the ignition is turned on and for 2 seconds after car is started. The the voltage comes down to about 0 volts. When I push gas and the engine hits over 3000 rpm the idle control module supplies 12volts to the idle control valve which makes it stay open and causes surging.
I am now wondering why is the idle control module is supplying voltage when the rpm are about 3000. I don't even know where the idle control module is located and where does it connect to. Can someone help me out with the information about its location and pins please?

Hurshi · #7 10-25-2002, 02:42 PM

Hey Mr. Potomac Pat

Why don't you try disconnecting the idle control valve and tell us what happened. I hope that it is not the bad idle control module causing this. Heard that the control module is a very expensive thing about $1000-2000 depending new or old.

#8 10-25-2002, 04:43 PM

Sounds like you really like the car. Too bad it's got this mechanical defect though. I wonder what it would sell for if you got rid of it?

Hurshi · #9 10-26-2002, 01:01 PM

I like the car because it looks nice. People stare at my car as to something they have never seen and girl beg me to give them a ride! That is why I don't want to get rid of it. It has been rebuild and has a nice new interior, new headlights and grill, new trunk and taillights. It has alloy wheels and a Becker CD player stereo with a pioneer amplifier! Here is a picture.

#10 11-05-2002, 11:29 AM

I am also having problems with surging on deacceleration. Mine happens when I am in gear, below 4k rpms, and have taken my foot off of the gas pedal. Another symptom that I believe was related was that there was a delay of about a half an inch from when i started pressing the giggle pedal to when anything happened.

I was about to wade into the KE system, but first I checked the throttle linkage on the side of the fuel distributor. As it turned out, two things appeared to be happening. First, the linkage had worn to the point that it was causing that half inch delay. In addition, the wearing had occured in such a way that it was not allowing the fuel cutoff switch to engage completely when I took my foot off the gas! This was what I think was causing my surging, the switch was making occasional contact, but not all of the time. Further investigation revealed that the switch was occasionally sticking also.

The parts are ordered, switch and most of the linkage came to 60 odd dollars. I'll update this post after this weekend.

Potomac Pat · #11 11-05-2002, 03:45 PM

PLease keep us posted !!

#12 11-13-2002, 07:12 PM

Sorry about the time it is taking me to install the linkage, classes hit a bit hard these past weeks. The car is in the shop right now, getting its tensioner updated. I'll install the linkage probably over thanksgiving, and let youguys know what happens.

dan

#13 01-14-2003, 03:45 PM

I had the dreaded tensioner update done, and let this thread slip my mind. Apologies all around. First, if you have a 190-16v you'd like to keep, get the damn update! No joke, i dodged a huge bullet! You should most likely get the tensioner and the gears replaced replaced as well...mine were badly worn.

Now then. I installed the parts, i.e. the two parts of the upper linkage and the throttle-switch. There still seems to be too much play in the throttle linkage! Perhaps the problem is further down, i'm not sure. As to the surging, it is alot better as the new switch doesn't stick, but I would say that it isn't fixed! After looking at the problem, I am still not convinced it, the surging, is anything more than a faultyswitch/wiring or throttle linkage adjustment. I am going to leave for a year or so to go out west two days from now, I'll post if I track down the problem!

Dan

Potomac Pat · #14 01-15-2003, 08:39 AM

I have given up on my car.

No, not really !

I have changed everything under the hood directly related to the CIS and the ignition system, etc, etc.................

Tonight I am heading down to RC Imports and hopefully Rick & Theraz can help me solve my issues. I'll keep everyone posted.

yhliem · #15 01-15-2003, 09:33 AM

Quote:

Originally posted by Potomac Pat
I have given up on my car.

No, not really !

I have changed everything under the hood directly related to the CIS and the ignition system, etc, etc.................

Tonight I am heading down to RC Imports and hopefully Rick & Theraz can help me solve my issues. I'll keep everyone posted.

*L* i keep telling you, Pat: it's the nature of the beast. :p

you could spend your life's fortune trying to fix it and chances are, you won't be able to