Bosch KE problem
 

This one is puzzling.

'88 300E: I tightened the clamp on the heater hose at the left rear of the cylinder head. I don't think it had anything to do with my problem, but maybe there is cabling or a sensor there that was disturbed, although I have checked everything in that area thoroughly. I think the following problem occurred only coincidental with this action.

When leaving the office yesterday, the car ran fine for about a half mile. I turned a corner and began to accelerate. It would not make power, but when I gave it about 7/8 throttle it came alive like crazy. It kept doing this for a mile or so of stop and go, slow and accelerate driving.

I then stopped for a few minutes, started it up again and it did the same stuff for a little while. It then seemed to level out after driving for awhile and was fine for eighty miles while on the highway.

This morning it was not bad until about 15 miles from home. The cruise control was set and I noticed the power falling off and the cruise control was progressively putting down the throttle.

I began manually managing the throttle and it required me to FLOOR it for it to make power. Once I matted the throttle the power would come on like crazy, no weak cylinders here.

After about six or eight miles at highway speed it would level out and cruise normally. Every time I would come to a light or have to seriously slow down, it would go through this all over again and make no power at cruise. I would have to FLOOR the throttle for it to make power. When it finally makes power it comes on like you flipped an electric switch, all of a sudden.

Once I got to the office the idle was getting a little rough.

So, to summarize, until it has leveled off on a long highway for six or eight miles, it will not make cruise power, it will only make power if you floor it.

Thanks for any help anyone might offer,

Steve,

Thanks very much for your response and thoughts.

I may have additional reason to suspect secondary ignition. We began with rain and dampness yesterday.

I will begin the pursuit of the culprit in the morning.

Thanks a bunch,
Larry

Steve,

Thanks very much for your response and thoughts.

I may have additional reason to suspect secondary ignition. We began with rain and dampness yesterday.

I will begin the pursuit of the culprit in the morning.

Thanks a bunch,
Larry

Big field here. I'm not sure you have a KE problem, but if you did I would expect a big air leak. Its not likely to be fuel pressure as it would have no reason to improve with full throttle.

It could easily be secondary ignition. The problem can occur two ways. One is that at a certain required voltage the spark finds a lower resistant path to ground shunting the needed spark. The rotor is a common cause of this type event. The second way is that available voltage is reduced (by a bad coil) causing a threshold where required voltage exceeds the current capabilities.

The reason either of these events can fit your senario is that idling is a minimum voltage requirement. Low rpm loading is probably the highest voltage requirement, which drops as timing increases and load is reduced with higher rpms.

Plugged cats probably fall under the same concept as fuel pressure: they shouldn't improve with rpm.

KE electronic control could go wild (not likely) and can be eliminated from consideration by just unplugging the EHA connection after warmed up. Car should run just fine with The EHA unplugged when warm.

Uh OH,
 

Larry, any error lights in the dash to accompany this?

No error lights. I am looking to get back my duty cycle meter, so I can check for an error code at the ECM box. There are several errors that are indicated by the duty cycle at pin 3. I don't expect this turn anything up, but I will check.

I think the ignition system is a good possibility. It's about due for some preventive maintenance attention anyway.

Have a great day,

Larry:

Check the idle control valve hoses. One of mine was loose it was so hard, and if seriously adrift, you will have screwy response to throttle. I once left a hose off on my old Audi Fox, and had exactly the same problem -- would only run if floored.

I don't think you will have the other problem I had with the Fox -- ice accreation in the venturi in cold weather. Fuel control flap would rise until the car would only run at full throttle -- trailed black smoke behind. Cured by disconnecting the blowby hose.

Peter

Well, this morning I pulled the cap and rotor and they were indeed in pretty sad shape. I ordered these parts then flushed the heater core radiator and as much of the cooling system as I could and put the new heater hose on.

I replaced the plugs and air filter. I think I will at least put an ohmmeter to the coil and pull the air cleaner and check the idle control hoses as suggested.

Thanks for the responses. I will keep everyone informed regarding the outcome.

Have a great day,

It may have appeared in the post above that I thought that replacing the plugs and air filter would cure my problem. I had bought these parts a few weeks ago and they were due.

I checked the coil with an ohmmeter and it reads as it should. I expect that means the coil is probably okay.

I removed the air filter and checked all vacuum connections and everything looks good.

I will post mid week with the results of the rotor/cap.

Thanks for the help,

Larry,

I hope you find the problem before Mon. Morning when I take mine in. I am experiencing the same problem and have been for short period of time. I cant take it anymore, I changed my rotor button, cap and plugs. This problem is driving me nuts. I must give in and take her to a tech with proper tools to diagnose her.
:)

FYI,

God didn't take nails in his hands, his son Jesus Christ did.

Have a great day,

Larry,

The holy trinity...God in three forms the father son and the holy ghost. But yes it was Jesus that took the nails for us all.


Have you found the problem yet?

No, I've ordered a cap and rotor and checked a few other things. The cap and rotor should be in Tuesday, so I won't know anything before then.

Good luck,

Larry,

I have found my problem luckily before throwing in the towel and taking her to the shop. My coolant temp. sensor had become unplugged just enough to make contact intermittently. After plugging it back in Sadie is driving great .................

Good luck,

I put on the cap and rotor last night. If it ever ran any better, I can't remember when that was.

Thanks Steve for the response. I'm quite sure I would've headed the wrong direction without your response.

Have a great day,

It's BAAaaack! We had really damp weather set in again, and this problem has come back. Rereading this thread has been worthwhile as a diary of the problem and recommendations.

I am responding to my own thread here to bump it to the top.

It's funny how this toggle switch type throttle condition requires the throttle to be bottomed out, not 1/8" or 1/4" from the floor, but ABSOLUTELY on the floor for it to just slam in the power. It jerks hard when it comes in at full throttle.

I guess I will recheck the thermal sensors and maybe disconnect the EHA as Steve suggested. This one is frustrating.

Thanks for any help you can offer. If I don't get any responses to this thread, I will post a new one to get attention.

Have a great day,

Bumping it to the top to go along with my new thread regarding this recurring problem.

Please see the new thread.

Thanks,

Larry,

If you have time, could you post the steps in replacing the distributor cap and rotor? Is this a simple DIY type thing?

Thanks,

glenmore
1991 300CE 116m

Replacing the dist. cap and rotor is as simple as falling off a log.

Grab the rubber cover on both sides sort of toward the bottom and expand both sides out to release the tabs. Pull up and forward and it's out of the way.

Loosen the three screws holding the cap in place and pull it forward and lift up. If you are only replacing the rotor, you can just fold it out of the way. If you're replacing the cap, pull all six plug wires loose from the plugs and lift the plastic loom from the top of the valve cover, remove the coil wire and take the wires, loom and cap to the bench. Lay the new cap next to it and move the spark plug wires one by one to the new cap. Now it is ready to go back in the reverse order.

Using an Allen loosen the screws holding the rotor in place and pull it forward. Reverse the order to replace the rotor.

Once the rotor is in place, put the cap back on and hook up the plug wires to the plugs and snap the loom back on the valve cover. Hook up the coil wire and screw the three dist cap screws back in place.

This isn't much different than any dist cap and rotor except for its position and lack of a distributor as we used to know it.

Good luck,

I would add that on my 300SEL, the bottom screw for the distributor cap was tricky to get in and out. I ended up using a hex bit socket with a universal joint adapter. It would also help to have small hands and good direct lighting.

Another possibility would be to remove the fan blade for more access room, but I didn't take the time to figure out how that's done.

I seem to remember that the three screws take a 5mm hex bit.