My 92 300CE is driving me nuts, most times it starts fine, but has high idle, 1200 rpm and then other times its hard starting and and won't stay running, when its doing the hard starting thing it almost sounds like its out of time as it stops cranking like its locking up and then starts cranking again, walk away from it for awhile and then it starts fine and will run fine for days and then for no reason it starts acting up again, anybody know what's going on?? Thanks Wayne

What are you running for fuel? What type of spark plugs are you running and when were they replaced last?

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I don't think its low octane gas or plugs as it doesn't do it all the time, I'm thinking cam sensor or maybe fuel pump relay, do you know if the cam sensor is bad will it make it crank funny?? Or maybe the distrubtor cap is cracked, and its cross firing? hell I don't even know if they have distrubtor caps?? it cranks like a cylinder is firing before the piston is at the top causing it to lock up, but keep in mind that 50% of the time it starts and runs fine.

Which engine, CSI injection + distributor or HFI management?

RayH

Ohhhh goodness, sounds exactly like my issue....currently replacing EHA valve since it was leaking...I already replaced the OVP and O2 as well.

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TC
Current stable:
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- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth

Hi Ray, its a 92 3.0 gas, I'm sending a photo of the motor, I don't see a distrubator anywhere, unless their hiding it as they are good at that, its probabley in the gas tank they put everything else in there, I'm not used to these gas models, I always run diesels, I bought this one to resell, never again.

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Let me know how you make out and if you get it fixed, what is the EHA valve??

Engine is M104.98, CSI, same as on my 1991 300CE.

Distributor cap is under black shield with the Mercedes star.

Camshaft position sensor is just behind the right edge of this black plastic shield with the Mercedes logo. Check the connection. My sensor was nearly in two pieces when I changed it. It made no noticeable change to the car though after I changed it.

EHA valve is on the side of the fuel distributor. You have a different engine and different fuel injection system, I'm not sure if the two both have an EHA valve. Mine was leaking really bad anyways (to the point where it was undriveable) but exhibited almost the exact same symptoms as you've described. I needed to be replaced regardless as to whether its the cause of the running issues or not.

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TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth

Distributor yes, under black shield.

Camshaft position sensor, yes again, I trashed mine and had to replace it. Made no difference.

You have the M104.980 like mine.

Whatever your problems, eliminate HT problems like distributor rotor, cap, leads and plugs (cheap copper plugs, NOT exotic platinum etc. and certainly not resistor plugs. Only buy HT components of the highest quality - MB original then possibly Beru and Bosch.

Also, eliminate ALL inlet leaks. Any vacuum leak into the metered part of the circuit (after the mechanical MAF) is metered by the MAF and if it leaks the 'brain' will try to compensate for something random and erratic. You'll suffer grimly trying to set up the system if it's leaking.

Then go from there.

Er.

That's it for now.

RayH

PS: Crankshaft position sensor is at the back, lower, right hand side of the engine, by the flywheel, under the oil filter. Another potential cause of problems. I had to have mine replaced for me as I'm to fat and lazy to get under the thing.

Right, that's a CIS M104, only had them for a few years, kind of an oddball now.
If you really don't know the state of tune then it might be time to at least look at the plugs, cap and rotor. I am not saying to start replacing parts, but start with the basics. Again if you don't know about the air filter, fuel filter and like that, again you need to maintain these cars. See if it has the proper plugs.

I was not getting at "low octane" when I asked that. What I remember from these days was there were some engines that would start and run better on MID grade rather than HIGH grade, seems wrong I know but I know we fixed a few hard-starting cars by having them try the midgrade fuel, something you could try.

Cam position sensor, now you have me thinking: In more recent times the cam position sensor is used by the fuel injection system. Crank sensor is for ignition timing. Being a CIS car, there should be no cam position sensor (not a sequential injection engine). You have a SOLENOID connection I believe as it does have variable cam timing (on/off, not really "variable", just 2 positions, not advanced ((off)) or advanced ((On))). That connector is on the side of the upper timing chain cover, drivers side. I may be all wrong, but I think the CIS cars did have this, I know the SFI cars did.

Now I suppose it could be that the advance could be getting stuck mechanically (lack of maintenance ie oil changes making it gummy?) into the advanced setting and might cause a starting problem if it did.

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To the couple guys who have said they have replaced the cam position sensor, I wonder what it even has one for, unless the ECU is monitoring it to check if the advance is working. Hmmmmm. Shouldn't need it on a CIS car.

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OK fellas, You all gave me alot of good information to go on and I thank you very much, now at least I have some idea what to look for, wish me luck

EHA valve is a little black box on the side of the fuel distributor closest to the fire wall.

It is a big ticket item and not readily available. There are 2 green "O" rings that are cheap.

Make sure it is plugged in. After I had work at a shop, they forgot to plug it in and the car ran crappy.

The "crappy" mode is called fixed operating mode. the engne will even run with the ECM unplugged in this mode. It is a sort of "non-tailored" mode where the engine will run but not well. Runs better warm, runs bad when cold and warming up. They figure if this is a fail safe mode that it makes the most sense to have it run (sort of) well when warmed up.

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