96 E320 Cold Start issues. Stalling under throttle, misfiring, low idle, etc...

[RichPugh]

I've spent hours of searching these forums for my specific symptoms but only came across a few different threads with similar symptoms.

One day driving home, my car felt as it if was running on 5 cylinders (misfiring while driving). I pulled off, shut the car off, restarted it and the misfire was gone. CEL was on./ Later I checked the code(s) and came up with a Cyl 6 misfire code only.

Since this happened, on cold starts (any cold start, not just overnights) the car idles very low and if I naturally press the throttle pedal to try to raise the rpm, it dies, sometimes taking several times to restart but usually will restart the next try with the same problems.

It doesnt have anything close to a warm-up or cold start high idle like I think I remember it having. If I feather very lightly the throttle, it will raise the rpm. If I hold the throttle at half way while starting the car, the engine will sputter exactly as if it was misfiring up until aprox 2k rpm and then it smooths out. No smoke. No puffs. Not too bad fuel smell except when it dies and may take a few trys to start.

I am going to replace the plugs tomorrow. Car has 128k on it. I dont know much history... not sure if the MAF was replaced. This has been happening for several months but typically is worse under 50 degrees. Started in early winter. I am hoping I can pull the plugs and coils and clean it all up while I replace the plugs and clear codes and reset battery (disconnect for 10 min, reconnect). Any ideas?

-Rich

[Check Codes]

That's a lot to digest.

Since you apparently don't know the history of the car either, I'd suggest replacing the connectors at the coil when you do the plugs and since the wires are off check them for resistance. (I'm not sure what the spec should be, but all the wires should be similar.) And with the plugs out, do a compression check as well.

Have you inspected/replaced all vacuum lines, hoses, check valves and connections? Pulled and cleaned the EGR valve and checked the diaphragm (visually and whether it holds vacuum)? I think a vacuum leak near the back cylinder culd account for all of your symptoms, so be sure to spend some time checking carefully.

Take care and enjoy the ride,
Greg

[Kobus]

Wiring harness on the 1996 disintegrating? Or was the 96 no longer affected?

[RichPugh]

I think I'll take a look at the plugs and plug connectors, check for vacuum leaks and probably bite the bullet and end up taking it to MITCH CARR'S benz repair shop down near DC. it's got a few more issues like hesitation under heavy throttle (probably fuel filter related), still runs warm after replacing leaking water pump and thermostat (probably fan clutch) and I could be talked into a trans service if I decide to keep the car.

[RichPugh]

Ended up being/needing K40 relay, coolant temp sensor and brake lamp switch. Also decided to do the fuel filter, oil and filter change, replace the battery (wrong Pep Boys battery in there when I bought it) and I'm gonna do the plugs, air/pollen filter and sell this baby off LOL.