jmotavalli

I have a 1989 300TE wagon with 220,000 miles. It runs very well for its age and mileage, but has a rough idle. I'm told it's the fuel distributor. I bought a used item and had it installed, and that made the problem much better. But it's still somewhat rough. It doesn't stall, but seems to want to be in neutral or park at stoplights. Idling in drive is around 500 rpm, too low. In neutral it goes up to 800 rpm and stays there. Is there some way of getting around an $800 rebuilt fuel distributor? Under way, the wagon runs perfectly.

dolucasi

I heard that for rebuilding a KE-JET FD you should go to CIS flowtec for this.
You ship them yours and they ship you either yours rebuilt or another one they rebuilt. Ask them. I believe their prices are in the $600 range but check with them.
I believe they maybe the pre eminent experts. However I do know know where you reside and if outside north america that could be an issue.

https://cisflowtech.com/

However, I'm not sure your conclusion is correct about a rough idle being an FD problem. There are so many other things involved in a rough idle. FD could be just one culprit/suspect of many. Ignition is probably more of a suspect than FD. But we do not know your maintenance history.
Also, show us your rough idle with a video if you can. Can you see the rpm meter moving at all?

What is the build date of your car (what month in 88 or 89)

jmotavalli

Thanks for this information, which I will follow through on. Can you be more specific about what the ignition problem might be and what can be done about it? I'll check on the build date--not sure where that tag is and how to translate it.

Jim Motavalli

dolucasi

Let's first check out your build date. It is on the tag/plate by the driver side door. It lists other spec's like weight, etc.

dolucasi

Lower door by the seat. This says 01/89

dolucasi

Lower door by the seat. This says 01/89

jmotavalli

The build date is 8/88. Model 124T. VIN # EA90D1KF086380. Does this make it an '88 instead of an '89?

jmotavalli

Here's the build tag for my car

dolucasi

OK, so you have an '89, built in late '88 with the old style camshaft and rockers. And if they are originals at 220kmiles most likely they are shot.
Mine lasted less than 170k miles with regular oil changes. It is also a function of how hard the car rpm's are pushed, mine was not at all.

First thing I would do before anything is open up the valve cover end check the camshaft lobes on cylinder #1 and #6. Those go first.
If I can find the photo's I'll send you my example.

Hopefully yours look OK but I doubt it. Also check to see if the modified oil drippers were swapped in by the dealer. They did that at ~60K miles for me. That prolongs the life.
You will either see a V shaped washer in the middle to hold down the ripper or an extra screw in the middle.

I would first take care of this before anything else.

dolucasi

Here is the modified dripper. Notice the V shaped washer and the center bolt. I put both in for good measure.

Cliff Johnson

Problem solved! Tried idle control valve, egr valve, vacuum lines, etc. Turns out it was the throttle body assembly... went into LimpHome mode... and when changed, idles like a sewing machine!

dolucasi

Yours is a different engine and fuel injection system entirely. I had a '95 E320 as well in the past. It has electronic fuel injection as opposed to the OP's engine which is Mechanical.
Entirely different beasts with different kind of problems.

- Cheers!

jmotavalli

This could be the problem, a worn camshaft, but the car had a top-end rebuild not that long before I obtained it. The guy who did that work said he thought the cam was ok then, and a subsequent mechanic who went over the car also said he thought the cam was in good condition. If it helps, the condition is worse when the car is warmed up.

dolucasi

It is entirely possible that during the top end rebuild they changed out the camshaft and rockers for the new style and more hardened steep. I changed mine out from a pristine JY find 5-6 years ago. Only cost me $68 + my labor.

Since you are sure your valve train is fine we can dive into diagnostics.

(1) Can you describe your rough idle? Is it that the rpm's randomly change by something that feels like a miss?
(2) Do you get this as the car is warming up at higher rpm or does it only show up after the car has warmed up?
(3) Does the idle roughness go away when you turn on the AC?
(4) Does the idle roughness go away when the aux fan is on?

Perhaps answer these questions itemized like I have asked them.

- Cheers!

dolucasi

Looks like you already answered #2, Worse at warm engine. Let's change that question to: What is your rpm's when this is happening? Does the gear being in neutral versus park or drive make a difference?

jmotavalli

1) It bounces around a bit, maybe like a six-cylinder engine running on five cylinders. It doesn't stall just sitting in park.
2) It starts doing the rough idle fairly soon after the engine is started, but not immediately.
3) The AC doesn't affect it.
4) I will have to see about the aux fan. How do I turn that on, or is it automatic? I haven't actually driven the car much because of its condition.

And, yes, the RPMs go up from 600 to 800 when in park or neutral, and it's less likely to stall.

dolucasi

Sounds like it is seriously "rough" idle, not just an annoyance. What happens when you unplug the IACV connector after the car warms up?

jmotavalli

Not sure what the IACV connector is--a bit more explanation. It's at a mechanic now, who says it's not getting spark on number five cylinder. Perhaps that's my problem all along--running on five cylinders. It would seem to explain it.

dolucasi

Hmmm, lesson learned. An M103 with a cylinder not firing would run horribly. Your original description in the post just mentions "a rough idle and everything else is fine"

IACV is your idle air control valve. It is hidden under the air filter box. Info for future use.

Hopefully your mechanic will fix yours up, could be a distributor cap or spark plug wire problem. Helps to have an in line spark detector. Can be purchased at your regular auto stores for $12.
Let us know if you have other issues.

- Cheers

jmotavalli

Thanks for this. I hope it turns out to be just an errant cylinder. It was running a bit better than "horribly," though the idle was pretty horrible.