Cam Timing
 

I have a 400E, 119 motor, 140k, that has not been running right for quite a while. It idles rough, runs OK, but doesn't have as much power as it should. Basically everything is new on the car, wiring harness, spark plugs, wires, caps, rotors, coils, fuel pressure regulator, injectors (cleaned) and the problem persists. The problem has been traced by my mechanic, with diagnostic equipment, to one bank of cylinders, the passenger side. This would point to a distributor or problem or electrical problem on that side. But a new backing plate and rotor did nothing. He now thinks it's a cam timing problem of some sort. It just started up one day with the problem - ran fine the day before - there was no trauma of any kind. My question is this - what could cause cam timing to get out of whack like that? Or what else might the problem be? Thank you.

How about the throttle slide? I have seen them cause similar symptoms, and it is a common point of failure on the 400E's.

Jonathan

Are you getting any engine codes?

The M119 has an electromagnetic camshaft advancer - they adjust around 3000 rpm to deliver extra power (On my E420 it feels like a turbo coming on at 3000 rpm). There are wires that attach to one on each cam bank. I would say that perhaps a connection has come loose on the passenger bank, but this would probably trip a Check Engine light.

The Throttle Actuator is a much more common problem (I've never heard of a camshaft advancer problem on this board). And at 140k miles, much more likely if it's never been replaced before.

For your sake I hope it's not the actuator - I think they run around $1000 just for the part.

No engine codes. All the wires are connected because the wiring harness was just installed. Throttle actuator has been replaced - although I suppose it could still be the problem, but mechanic seems to think it's a one bank of cylinders problem. What's a throttle slide? Thanks.

Throttle slide = throttle actuator. Double check to make sure that you've got good contact on those camshaft advancers. Unplug, lightly wire brush, reconnect.

Troy
1995 E420 94k

It turns out the cam was off by a tooth. Upper chain guide had broken and the one side skipped a tooth. It happened without any apparent calamity. And the chain is stretched a bit so it's time for a new chain and upper guides. Disaster avoided again.

i'm glad I'm replacing my chain guides and cam oiler tubes next weekend. Hoepfully I'll avoid this. I'm sure this is not a cheap repair 9but cheaper than having the chain snap!).

Troy
1995 E420 94k

I'm thinking replacing the guides is the first and most important thing to do - even before the tensioner. Broken guides seem to be the source of the problems, more so than bad tensioner or chain. In 92 the oil tubes are metal and pretty much bulletproof.

chain/guide replacement
 

y2kimmel

I've got to do the same thing on my 95S420. Take lots of pictures for me will ya, and post on the board. I'm sure lots of us shade tree mechanics could use the pointers.

Ron

Check out the "DIY" section at the top of the page - it has a great article on replacing the oiler tubes, and is what I plan to use to help me fix my car.

Troy
1995 E420