96 C36- random sputtering and stalling- I searched..

[RANDY P]

Hello- have a 96 C36 (M104.941) that basically started losing power and stalling randomly, and when it stalls I can fire it back up and it will run, then stall again sometimes. Totally erratic sometimes it's ok for a few minutes hot, sometimes just dies. It will fire back up and sometimes run for a minute, sometimes just immediately die.

When the problem surfaces the car lurches forward, idle will hunt, then lose power and just stall.

Tach doesn't SEEM to lose signal, if it cuts out it's as if I lifted the accelerator and took my foot off the gas. As I coasted I noticed the RPM's were still registering on the tach,

car has exactly 150K miles, just completed a 3kmile road trip on brand new

-bosch OEM plugs

-coil boots

-new front 02 sensor

- brand new KAE OVP relay (I read the posts, could they really be THAT bad out of the box)

- new Fuel pump relay (switched it out since I got free shipping by ordering it and it was cheap)

- NO CODES AT ALL, no funny lights, nothing.

the problem surfaced last week, did searching and determined the OVP relay must be the problem, henceforth the replacement.

Car ran flawlessly for about 50 miles after the OVP / fuel relay swap so I thought I got it then it came back.

I've had a bad MAF and it caused the car to surge and hiccup but never die, could a crankshaft position sensor cause these issues? It will fire up immediately after stalling, sometimes running for a minute, sometimes not?

Please help.

[mbdoc]

The overvoltage relay is the MOST likely cause, buy an OE Stribel relay.

[RANDY P]

I let the car cool off yesterday, it was basically cold. Drove it, and everything was absolutely peachy until we got to operating temp and then I parked it for 5 minutes and let it heat soak.

sure enough, after a few of those I let it idle and it just died. Restarted, made it a few miles, pulled up to light and instant stall. No warning.

Pulls cleanly through rev range when it's running, no sign of low fuel pressure, and what would be MAF symptoms are gone, just drops dead at lights.

Checked battery voltage it's sitting at 12.5 off, and 13.5 at idle when I checked it, no signs of under or overcharging.

Considering the behavior is exactly the same with the "new" relay vs. the old I'm hesitant to think the OVP has gone bad after 50 miles.

Ordered CPS and we'll see what happens.

[RANDY P]

OK- just swapped out the CPS on this thing. What a PITA.

for the record, I needed the following

1) 5MM 3/8 drive MALE ALLEN socket. Yes, it's an allen head on this car. Obviously, a socket wrench too.

IT IS NOT A E8 TORX LIKE COMMONLY REPORTED ON THE ML320 AND LATER CARS.

2)- 24" extension 3/8" drive (NOTE: 1/4" drive is too small to try the drop the extension into the socket trick below, just my opinion)

3)- a fairly stiff 3/8" flex joint. One that does not flop around as you move it.

4) 10MM combination wrench to loosen harness attached to starter.

Jack and jackstands (Please don't be stupid and get underneath a car just supported by a jack)

You will be working under the approximate area of the starter on the driver's side, behind the front left wheel.

Loosen 10MM bolt holding harness to starter body, take out bolt and move harness out of way.

Fight, wrestle, cuss, cry and pray to wedge your hand in the area around the starter till you feel a plastic plug approx 5/8" in diameter. Right next to that, you will feel the 5MM allen head bolt, it's between the plastic plug and the firewall. Due to space this is torture, its one of THOSE types of repair jobs.

Cram the 5MM allen socket into the bolt holding the sensor in place, beware, this is NOT a pleasant task, you will be fumbling things around and you could easily spend 30 minutes trying to get this step done. Once it's in there it will basically be touching the firewall at an angle, so spend a few minutes getting that situated in there then go to the top of the engine.

Flash a light down in that area around the starter and you will see your socket. Attach the 3/8" drive universal to your extension, carefully lower it down in there and pray you get it attached to the allen socket you have placed in the bolt. This is why you need a fairly stiff joint to accomplish this.

Once you have the allen in place it's pretty secure so you can give it a knock or two and it'll be ok. just do your best to get the universal joint into the socket, and press down to latch the extension and joint to the allen socket.

Sounds hokey, but I was able to both loosen the bolt this way, and reattach the socket to tighten it with this method, easily hitting the mark both times.

Pull the sucker straight out, unplug the harness, and install is reverse. It takes a while, not terribly difficult, but trying for sure. If you have very large hands, well I'm sorry.

If you have big hands, take it to a shop, your best bet.

As for the sensor that came out, it was sitting at 1040 ohms cold, and when boiled for a just a minute went to 1255 ohms and spiked at 1400 ohms after a few minutes.

Like a dummy I didnt measure the resistance of the new sensor I was in a hurry to get this over with.

However, it's been 45 minutes of heat soak, idling, and loading this engine and NOT ONE STALL SO FAR.

I think I got it this time.

crossing fingers

Tags, M104 CPS crankshaft position sensor C36 reference sensor changing CPS sensor.

[RANDY P]

Great...

Problem came back, been about 100 miles +1 really fresh tank of gas and now with occasional surging.

The only other thing is I filled up at the same gas station as before this problem surfaced. Filled up this AM, drove 20 miles, parked car, came back out 44 minutes later- instant stall.

Poured Heet in the tank, problem went away for a bit. Parked it for 4 hrs. while I took a nap and came back out and blamo- instant stalling.

Took car out and drove it bucking and surging and wanting to die, in 1st gear and feathering / pounding the throttle to keep it running (admittedly cuz I was pretty pissed).

I GOT A CODE THIS TIME. P0101 + P0170 - Maf and fuel trim - probably p0170 was a result of bad readings I figure.

Took M.B. Doc's advice and went and bought a new OVP from Fletcher Jones in LV (Lowell in parts is a cool guy, and gave me ONE HELL OF A DEAL)

Still doing it, surging at idle now, so ordered new BOSCH MAF (existing one is USED Bosch) and reset codes.

any other suggestions?

The only positive thing is that at least there are no other obvious failures that will happen since I've nailed all the other potential problems and they are due to occur anyhow, so assuming the MAF is faulty (which seems entirely possible) then I'll be OK with this.

I'm having a great time with this too FYI. I seriously thought bout taking my shotgun to this thing in the driveway or fixin to drive it off a cliff somewhere in the desert.

rjp

[mbdoc]

P0 170 is indicative of either a fuel pressure issue, vacuum leak, or bad MASS air flow sensor.

[RANDY P]

Originally Posted by M.B.DOC

P0 170 is indicative of either a fuel pressure issue, vacuum leak, or bad MASS air flow sensor.

Good morning,

leaning towards the MAF- the worst thing about this issue is the problem is intermittent. Sometimes it runs killer. It was freaking out the moment I started it after letting it sit for a few hours. You can force it to stay running if you keep your foot in it.

When it started acting up again I was forcing the car to stay running, and it got to the point where I worked through the bucking - and that's when the codes came up. I was hoping it would straight up die and stay dead so I can find it that way.

As for the MAF on the car, it came off a crashed 95 and is definitely at that time where it's probably time to quit on me anyhow.

I checked the FPR and no sign of diaphragm leakage, all the lines on the motor and the clamps and all lines appear to be tight and clean.

rjp

[RANDY P]

Brand New Bosch Maf in place.

Man, serious increase in both off idle TQ and top end pull is apparent. I keep triggering the ASR all the time from the light all of a sudden. Idle is pretty damn steady in D at 600RPM +50, and one other nice benefit.

The car when sitting hot when restarted would hiccup and surge between 500 and 1K RPM for a minute until you held the gas up or just drove away.

NO MORE of that from what I can tell...

50 miles, parked for dinner then drove home not one hiccup.

Crossing fingers, again

rjp

[BongC36]

Hi Randy, did the MAF replacement solve your problems? My C36 is also experiencing these pesky intermittent surging

[RANDY P]

Originally Posted by BongC36

Hi Randy, did the MAF replacement solve your problems? My C36 is also experiencing these pesky intermittent surging

Yes it did. Not a single hiccup.

Just did 9 hr round trip drive and lots of miles in town since then. I can't believe how much power I picked up too.

Salamat!

rjp

[Cysquatch]

Originally Posted by RANDY P

OK- just swapped out the CPS on this thing. What a PITA.

for the record, I needed the following

1) 5MM 3/8 drive MALE ALLEN socket. Yes, it's an allen head on this car. Obviously, a socket wrench too.

IT IS NOT A E8 TORX LIKE COMMONLY REPORTED ON THE ML320 AND LATER CARS.

2)- 24" extension 3/8" drive (NOTE: 1/4" drive is too small to try the drop the extension into the socket trick below, just my opinion)

3)- a fairly stiff 3/8" flex joint. One that does not flop around as you move it.

4) 10MM combination wrench to loosen harness attached to starter.

Jack and jackstands (Please don't be stupid and get underneath a car just supported by a jack)

You will be working under the approximate area of the starter on the driver's side, behind the front left wheel.

Loosen 10MM bolt holding harness to starter body, take out bolt and move harness out of way.

Fight, wrestle, cuss, cry and pray to wedge your hand in the area around the starter till you feel a plastic plug approx 5/8" in diameter. Right next to that, you will feel the 5MM allen head bolt, it's between the plastic plug and the firewall. Due to space this is torture, its one of THOSE types of repair jobs.

Cram the 5MM allen socket into the bolt holding the sensor in place, beware, this is NOT a pleasant task, you will be fumbling things around and you could easily spend 30 minutes trying to get this step done. Once it's in there it will basically be touching the firewall at an angle, so spend a few minutes getting that situated in there then go to the top of the engine.

Flash a light down in that area around the starter and you will see your socket. Attach the 3/8" drive universal to your extension, carefully lower it down in there and pray you get it attached to the allen socket you have placed in the bolt. This is why you need a fairly stiff joint to accomplish this.

Once you have the allen in place it's pretty secure so you can give it a knock or two and it'll be ok. just do your best to get the universal joint into the socket, and press down to latch the extension and joint to the allen socket.

Sounds hokey, but I was able to both loosen the bolt this way, and reattach the socket to tighten it with this method, easily hitting the mark both times.

Pull the sucker straight out, unplug the harness, and install is reverse. It takes a while, not terribly difficult, but trying for sure. If you have very large hands, well I'm sorry.

If you have big hands, take it to a shop, your best bet.

As for the sensor that came out, it was sitting at 1040 ohms cold, and when boiled for a just a minute went to 1255 ohms and spiked at 1400 ohms after a few minutes.

Like a dummy I didnt measure the resistance of the new sensor I was in a hurry to get this over with.

However, it's been 45 minutes of heat soak, idling, and loading this engine and NOT ONE STALL SO FAR.

I think I got it this time.

crossing fingers

Tags, M104 CPS crankshaft position sensor C36 reference sensor changing CPS sensor.

What about using a 5mm allen wrench and swap it out from under, bypassing the extension/flex joint from above? Too tight? Lemme know. I'm about to do this job on a 1996 C280. Is the location the same as the C36? Oh yea, this is sinlab from mbworld. =)