Stalling - OVP?? - PeachParts Mercedes-Benz Forum

tinypanzer · #1 04-07-2009, 07:38 PM

I've been dealing with an intermittent stall for a while now. It first showed up about 6 months ago, then went away completely. Now it's back, and seems to be happening more frequently.

It always happens when I am braking and at or near a complete stop. It also happens as I slow down to make a hard turn.

The last time it happened, I observed the instrument lights.

The Battery, Brake, and ABS lights were on.

Am I right in thinking this is an OVP issue?

I have brand new distributor cap and rotor and plugs. The wires are newish. The motor runs like a swiss watch other than this stalling issue. Idle is smooth and stable. The car always starts right back up after the stall and runs fine.

Ideas?

babymog · #2 04-07-2009, 08:04 PM

Battery brake and ABS lights indicate low voltage. Possibly a failing ignition switch?

tinypanzer · #3 04-07-2009, 08:44 PM

Really? That's about the last thing I would have suspected......

BTW the car is a w126 1990 300SE.

Gilly · #4 04-07-2009, 08:49 PM

I'd be thinking more in terms of the idle control valve, although even a failure with the idle system could be the OVP.

Gilly

MDE3 · #5 04-08-2009, 09:23 AM

Water in gas tank...more common than you might suspect...Do the symptoms get a little better after driving for a while?(the water will eventually mix with the fuel after continued driving, and the symptoms might improve..until you park and let the water settle out).

Water sinks to the bottom of the tank below the stand pipe..however if enough gets in it can be right at the level of the stand pipe, and so everytime you come to a stop, it sloshes into the fuel intake and causes rough idle or a stall and occasional rough starting...adding a little isopropylene might help..but typically if there is a lot of water, it will require constant use of this for a while..another solution is syphoning the bottom of the tank...may need a weight on the hose to get it to sit on the bottom. Have had this happen.

mak · #6 04-08-2009, 11:16 AM

my 300se /90 had developed the stalling problem too . i assumed it was a ignition fault so i replaced all the ignition consumables and only then was i able to narrow down to the fuel pump relay . removed the relay and resoldered all the joints . no more stalling problem.
OVP failure becomes obvious as the cold start RMP's stay low and difficult starting .had that too once.
mak
300se /W126

david s poole · #7 04-08-2009, 11:32 AM

when you take your foot off the gas the mixture goes lean and the voltage drops from the o2 sensor down to nearly zero.this triggers the ecu to send a milliamp signal to the eha [between 20-40]which will richen the mixture[until the voltage rises at the o2 sensor]and maintain idle.maybe this will help.

ds190 · #8 04-08-2009, 11:53 AM

I had symptoms like that with my 91 300TE when it had about 105K miles on the original OVP but after new ignition everything. New OVP, problems gone. I cut open the old OVP- you would not believe how much dirt gets in there, which becomes crud and rust.

If your car has the original OVP, I rec replacing it for $85.

whunter · #9 04-08-2009, 02:33 PM

Quote:

Originally Posted by tinypanzer

I've been dealing with an intermittent stall for a while now. It first showed up about 6 months ago, then went away completely. Now it's back, and seems to be happening more frequently.

It always happens when I am braking and at or near a complete stop. It also happens as I slow down to make a hard turn.

The last time it happened, I observed the instrument lights.

The Battery, Brake, and ABS lights were on.

Am I right in thinking this is an OVP issue?

I have brand new distributor cap and rotor and plugs. The wires are newish. The motor runs like a swiss watch other than this stalling issue. Idle is smooth and stable. The car always starts right back up after the stall and runs fine.

Ideas?

How old is the battery?

I would first suspect a brake/turn stall to be a sulfated battery = sludge inside battery sloshes up short circuits battery plates and draws full alternator capacity = drops voltage below minimum required by computer.

With the common OVP issues, it is still a good idea to upgrade to the newest level...

Have a great day.

ps2cho · #10 04-08-2009, 03:03 PM

ABS light on generally indicates OVP. Stalling sounds exactly the same as my TE experienced. Would stall randomly, but start up okay right after.
Has happened to both my 300TE and 260E. Check the fuse before replacing it.

You may also want to look into the voltage regulator that is attached to the alternator.

tinypanzer · #11 04-09-2009, 05:25 PM

Hi all, and thank you all for your responses. The thing stalled again yesterday, and this time it had a different set of symptoms. Perhaps this will shed light on the culprit.

First off, Whunter, thanks for your reply. I don't think the battery is to blame, it is about 6 months old. However, I have a charger that tests for sulfation so I will hook it up and see what it says.

It stalled on me this time during a straight ahead stop at a traffic light. When it stalled this time, the instrument cluster lights were totally different than last time. Last time it was the Battery, brake, and ABS lights that came on. This time, it was the battery, brake, brake pad, coolant, oil level, and ABS lights that came on.

Later that night, it almost stalled as I came to a stoplight but didn't. When that happened, the Check Engine light flickered for a millisecond and then went out.

Does this help pinpoint a culprit at all?

Thanks so much for your help!

tinypanzer · #12 04-09-2009, 06:51 PM

Well, I just went ahead and ordered one. I guess we'll see soon enough if it was the problem.

Thanks again for all your advice.

tinypanzer · #13 04-10-2009, 05:27 PM

Well, the plot thickens. I am beginning to doubt my OVP diagnosis. I haven't put a new one in yet, but the problem is starting to act much more like a vacuum leak, idle air valve issue, or fuel pressure issue.

My idle, which has been smooth until now has become rough when the car is in drive. If I pop it into neutral, it idles a little low - around 650-700 rpm. If I put it in gear, it wants to drop to around 500 where it burps and bogs.

This is the first time I've gotten a symptom that won't go away, so at least I will be able to diagnose it easier.

While poking around last night, I found yet another problem - torn EGR diaphragm. I doubt this is my issue since the EGR shouldn't be opening at low RPM. I plugged the supply line, and it made very little if any difference in my problem.

I have a few parts on hand that I haven't installed yet - an O2 sensor and a fuel filter. I also have the idle air hose. I'm going to slap them in over the weekend to see if any difference is made.

David S. Poole - Thanks for the info on how that signal is sent. Do you think it is possible that the O2 sensor could be to blame?

I guess I'll find out anyway this weekend.

If anybody has any suggestions for places to look, I'd sure be grateful.

Thanks!

gschira · #14 04-11-2009, 09:13 PM

Can anyone tell me where the OVP is located on a '88 300 SE? Maybe include a pic?
Thanx........

Ivanerrol · #15 04-11-2009, 10:00 PM

T.P have you cleaned out your IACV yet?

If you haven't, remove it and clean out the business end with carby cleaner.
If the vacuum hoses attached to it are hard and brittle, replace them while you are there.