Hey guys. My '88 760 GLE has had this problem for the better part of a year now. I'm really looking for suggestions on what is up. Here's what it does. The problem is worse after it has warmed up, but still does it when cold. Say I'm sitting at a stoplight, it will be idling just fine and smooth, then the RPM will drop a bit, and the whole engine will start shaking a little. RPM will smooth out for a bit, then do the same thing again. Then, when accelerating, I can actually feel the power cutting in and out. Just like a surging feel. I can even feel it throughout the whole car, sputtering and whatnot. Like I said it's been doing this for almost a year and hasn't gotten any better or worse, and I've been pretty hard on it. Very hard to describe. A few things I've changed. Spark plugs in late '07, plug wires in early '08, fuel filter in spring '08. I do have a bad valve cover gasket. I'm out of things to check. Here's a couple of vidoes. Best one is the one of the exhaust where you can hear the sputters. The one of the engine is to show the shaking, but you can't really see it all that well.

http://smg.photobucket.com/albums/v2...nt=exhaust.flv
http://smg.photobucket.com/albums/v2...ent=engine.flv

 

Was that smoke coming out or was it the camera hazing up from the heat?

Did you clean the throttle body and idle motor?
Did you test the o2 to make sure it is sweeping?

 

It was just the heat from the exhaust. And no to both questions. Can't say I really know how to do either.

Thank you, tech.

 

Just remove and clean the throttle body it is held on with 3 nuts. The idle motor is under the intake. It is a cylinder looking thing.

For the O2 sensor there is 2 plugs for the sensor. One should have 2 wires and the other is a single wire. Pull the boot back on the single wire. Clap a positive lead from a meter to it. Then put the other one on ground. Then start the car and let it warm up some. Read the meter and make sure it sweeps between 0 and 12 volts.

 

Hey tech, thanks a bunch. I'll try these things later.

Appreciate it.

 

No problem glad to help.

 

K, here's a few things I had done. Pulled each plug wire from distributor one at a time. Checked resistance of each injector, all were ok. Unhooked cat. Checked fuel pressure regulator, seemed fine. Wiped down throttle body. Monitored O2 voltage - stayed 6v when wide open, .5 and under when off the gas right after wide open.

Still runs bad.

 

At a steady idle it should sweep from 0 to 12 volts at all times when at idle.

 

Well, someone else who has worked with cars quite a bit told me it is the coil goin bad, so I thought it seemed pretty logical, and replaced it. But it is still doing the same thing so I checked the voltage on the O2s at idle and it never even reached 1 volt.

 

Unplug the wire(Single one) check voltage only with the key on. You should have a 5 volt refrence.
But it should sweep. Maybe the sensor is bad.

 

Ok, I just checked it KOEO, and it has 0.1 Volts coming from the sensor, and 0.5 volts coming from the car's harness.

 

That looks like 1/2 volt is there a chance the meter is in the wrong range?
If you don't have a 5 volt refrence then something is wrong in the harness or ECM.

Also make sure there isn't any fuses blown. I know on the 240 there is a fuse tied into the O2 system but not sure on the 760.

 

Before I head back out there, I was just going to say that I checked the battery voltage before I went to the wire, just to make sure I had a good ground and that it was in the right range. BRB

 

Back, and every fuse and circuit breaker in the car is good.

 

Maybe there is a signal problem from the ECM.
You should have 5 volts from that wire coming from the computer.

 

Would you happen to have a wiring diagram for the main connector on the ECM?

I'm searching on ShopKey5 but I am coming up with nothing.

 

I will look in the morning and see what I can find.
Sorry getting late and have to finish up with the kids.

 

Well, I've pretty much ran out of ideas. I'm kind of leaning toward ECM. I'm going to do a compression test today. Thanks for the help again.

 

Sorry my diagrams don't go back that far.
I wish I had more answers for you.
It is possible the ECU went bad. Not really common but possible.

 

I was doing the compression test, and 5 of the cylinders read ~105 PSI but on the 5th cylinder the tester came apart and left the adapter in the spark plug hole, so I put some thread locker on the hose and screwed it back in and hopefully it will bring it out when it dries.