I'm considering an '87 w/ 261k miles that the owner says has a very rough idle below 1,500 rpms. He says that one over that level, it runs smoothly as can be. The car averages ~27-30 mpg and he says it passed a recent compression check as running strong along with the injection pump.

His mechanic has stated that it is a vacume problem, but probably not the actual pump. Other than than cosmetics, this seems to be the only major problem. the only unworking thing is a rear window doesn't roll down. AC, locks, rears suspension, etc. all in good shape.

Any guess what might be the rough idle cause? How much would something like that cost to fix? Just looking for ballpark figures to see if the car is worth the effort.

Its a possibility that it is sucking in some air on one of the fuel lines between the IP and the injector. I looked at a 190D that did that. Saw fuel on the top of the IP. One or more fuel starved cyliders can cause that. Also check the condition of the motor mounts. Do your own compression test to be sure as well.

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Common rough idle causes on the 603 engine can be searched in the archieves, things to consider though:
1.Fuel filters, when were they last replaced, could be clogged or partially clogged only flowing under high load rpm conditions.
2. injectors could be bad one or a few of them, they could also be loos and not fully seated. When the compression test was done, did the mechanic replace the injector seat seals? They should always be replaced whenever the injector is removed.
3. Check the condition of the motor mounts, these sometimes look like bells, if the cup edge is less than 1.5 in. from the frame it is likely shot and transmitting a lot of engine vibration to the chassis. Replacement mounts are gel-filled and will cure many rough idle feel in the car.
4. Was the injection pump timing checked or adjusted, could be off.

Barring any metallic grinding sounds or clanks indicating mechanical issues, the rough idle is likely due to poor or obstructed or leaking fuel delivery and or IP or cam timing,more likely the IP. There are several other possible causes and a search of this archieves will yield a lot of info on the topic.

Good luck

__________________
Stable Mates:
1987 300TD 310K mi (Hans)
2008 Jeep Grand Cherokee OM642 165k mi (Benzrokee)

Thanks for the quick answers, i appreciate it.

I forgot to mention that he said in it's current state that you have to be careful in stop and start traffic to throttle the car down gradually, as just taking your foot of the gas quickly can cause it to stall.

Don't know if this sheds any more light on the issue, but I will talk to him again thsi afternoon and get more details. He has said that he will let me talk directly to his mechanic if I need more info. I will also see how long ago the comrpession check and injectors were checked.

I would check all filters, including the air filters as well. Sounds blockage somewhere.

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Check to make sure the fuel shut-off lever is fully in the upright position when the engine is running. I used to have idle problems with my original injection pump, which had a fuel shut-off lever that would bounce around and sat lower than other pumps I've observed. The idle would clear up a bit when I pulled the lever up fully.

Another thing you might consider would be replacing the delivery valve seals and o-rings.

Well guys, as is usual, whenever I think about something long enough, I usually find it not worth doing.

I think I may pass on this car for a couple of reasons:

1) The rough idle may only be filters, fluids, adjustment, but if it is the vacume pump or more the $4k value price becomes significantly more. I'm not confident it will make the drive from the Denver area to Los Angeles.

2) The car is not in the cosmetic condition I'm looking for. There are a few rust spots that the owners says were badly filled in and painted over. So, that would be something needs to be eventually done, possibly just paint matching at this point. But, could mean a completely new paint job. Also, the dark blue Tex-Mex interior is not a real favorite of mine.

So, suddenly a $4k value becomes a $6-7k+ moderate deal or worse. At that price range, I can simply wait a little longer and buy one in better condition with more complete repair documentation.

Is the vacuum pump really that expensive to replace?

__________________
87 300D - Running on Veggie oil; 260,000 plus miles; Original #14 head