300 ce intermed. miss - PeachParts Mercedes-Benz Forum

voz1 · #1 07-02-2002, 12:03 AM

quick run down. 92 300ce wife blew bypass hose under intake and overheated blowing the head gasket. Sent head out, new guides seals and valve job. While I had the top apart did timing chain. Also new cap and rotor. Put car back together and it ran better then ever. After one week car developed a dead miss on cylinder #3. rang out wire (all under 2 ohms) changed plugs (only 1 wk old) still missed. Did compression test thought maybe a guide slipped and was holding valve open...160 all cylinder. removed all injectors and had them test and cleaned removed fuel regulator for testing. Was told the regulator was holding pressure and popping open around 80 lbs but an exact pressure was unknown. Put it all back together changed fuel filter and now the miss is intermittent. On the highway I can feel the cylinder come to life and now sometimes it will idel without missing. I also put in techtronic (some sort of supper duper fuel system cleaner) I've been advised to run the tank of gas w/cleaner and see if miss works it self out. I dont have much faith in quick fixes from a can..... any advise would sure be welcomed.. thanks for reading thru my saga and a great 4th of July to all !!! ed

Gilly · #2 07-02-2002, 01:10 AM

Hmmmmm
Well, you could try swapping the #3 injector to a different cyl and see if it follows the injector. I assume the injector seals were replaced, but you could carefully spray some carb clean at the injector seal area to try to find a vacuum leak there. As far as a secondary ignition problem, ideally you should get it in a failed state while on a ignition scope. Did you use good quality cap and rotor?
The fuel injection cleaner is called Techron, made by Chevron, and yes it's pretty good stuff.
Gilly

voz1 · #3 07-02-2002, 05:47 AM

the cap & rotor was purchased from M.B. However I had'nt thought about a leak around the injectors. I will persue that ave also this problem came on very sudden. That is why I was thinking some sort of clog. Also do you think I can add the cleaner in a stronger dose? Say on bottle to maybe 1/2 or 1/4 tank of fuel? I'm also using Amoco premium fuel. Thanks Ed

Gilly · #4 07-02-2002, 09:42 AM

Ed:
I'm not sure if running a higher concentration of Techron would be either beneficial or harmful. Thing that bothers me is that the injectors are said to have been removed cleaned and inspected, so if that's the case, why even worry about the cleaner? Kind of double-talk to me.
I'm trying to remember now if the 92 CE was CIS injection or SFI injection, do the fuel injectors have seperate steel lines from a fuel distributor, which is CIS, or a long fuel bar over the injectors and an electrical connector to each injector, which is an SFI system, either LH or HFM. If it's LH or HFM, it could be the dreaded bad wiring harness problem.
Gilly

engatwork · #5 07-02-2002, 09:52 AM

Gilly - after replacing the head gasket on my '95 E320 I have a very, very slight miss at idle only and the fuel mileage is suffering a little bit. I did not replace the seals on the fuel injectors and will probably replace them over the next week or so. During the test with the carb cleaner what exactly should I be looking for? Do I just spray the injectors down with it idling? The wiring harness has been changed and I'm pretty sure it is not an ignition "miss" because it is not severe enough. You can barely feel it.
thanks

Gilly · #6 07-02-2002, 10:13 AM

Jim:
Just direct the spray at the base of the injectors, at the seal area. It's best if the engine is fairly cool, as the stuff is flammable. You're listening for an idle fluctuation, and it will seem to idle a little smoother, as you are inducing something flammable into the engine through the vacuum leak, rather than just air.
Gilly

suginami · #7 07-02-2002, 12:20 PM

I believe 1990-1992's 300CE's have the DOHC 3.0 liter M104 engine, KE-5 CIS.

Gilly · #8 07-02-2002, 12:29 PM

Yeah, I knew it was a 104 for sure, the 300SL and 300CE both got it in 1990. Originally it was the CIS motor, I'm unsure exactly when they went to the SFI system. It would make a big difference in diagnosis.
Gilly

suginami · #9 07-02-2002, 01:18 PM

Well, I believe 1993 300CE / 1993 300E (3.2) was the first year they got the HFM fully electronic with integrated ignition.

Gilly · #10 07-02-2002, 02:33 PM

You are probably right about the 1993 being the model year it changed from CIS. I believe LH preceded HFM, the only true difference being the mass airflow sensor itself, hotwire vs hotfilm.
The ignition did not become integrated into the fuel injection computer until ME engine management systems.
Gilly

voz1 · #11 07-02-2002, 11:46 PM

it was the mechanical injection system. The reason I'm trying to work with the cleaner is I feel the fuel distributor (for lack of a better term) may have some sort of blockage. I understand there are some sort of check valves inside but any dismanteling scares the hell out of me. I was careful not to mix up the injector because I wasnt sure if they where tuned per cylinder(I see a differt number on the brass end on the injector) I thought that may have been sized like carb jets. Next step will be to follow your advise and swap out an injector. I will also swap plug suppressor ends or better yet just replace the one on troubled #3. The car does seem to be getting better but very slowly I've clocked on 200 miles with cleaner in tank. Thanks again for your replies you guys have been great......Ed

endeavor · #12 07-09-2002, 05:33 PM

I have a similar miss in my 1990 300CE (104.980 motor).
I have exhausted all my efforts, replacing ignition components, fuel distributor, fuel injectors, idle stabilizer valve, all new vacuum lines/new tees etc.
My engine miss is much less. It is more noticeable when I accelerate from a complete stop. if I accelerate slowly, the miss is not there. I found that by decreasing the spark plug gap from 0.030 to 0.025 makes the miss go away until the gap widens.
I also replaced the camshaft adjuster as the oil was leaking through the electrical connectors.
The only thing I have not checked is the fuel pressure regulator or check the fuel pressure. Quite not sure how to do it, have to refer to MB manuals.
The miss appears to be more with warm engine and when the car is under load and it is erratic, kinda comes and goes.
Any ideas?? my e-mail is bshah@satx.rr.com