I have a 93 Monoco Diplomat. Took it to the shop for a once over. They ran engine diagnostics and fixed some electrical issues with the transmission cooling fan. I have three problems; Once the engine is heated up and have run it down the interstate, it wants to idol rough. It has not stalled, but seems like it wants to. 2) The turbo works 98% of the time, but occasionally on initial start of acceleration, the turbo does not work. I take my foot off the accelerator, re-accelerate and the turbo then works. 3) I have some dash lights that are not working and the windshield wipers are not working. I have the checked the fuses and everything seems to be fine. I have direct wired the wipers and they work fine, I would just like for it to work as intended. Any advice would be appreciated. I only have experience with the F53 chasis, the diesel is a whole new animal for me. Thanks Mark

Perhaps you have a bad temperature sensor causing the idle problem. Could the exhaust brake be stuck closed and you think it's the turbo? There is very high temp oil for the exhaust brake or wire it open to see if the problem still occurs. Use a meter or test light to track down the electrical issue.

Were ALL your fuel filters changed?? A dirty fuel filter can cause rough idle.Is there any smoke from your exhaust when you accelerate? White or black?Exhaust brake is a good place to look also. Check the vacuum line going to it. Make sure it's good. With a 21 yr old coach, I'd just get a few feet of hose from NAPA and start replacing whatever I could find. The EB should be lubricated anyway. Use the proper lube. PacBrake makes the best, IMHO.If you wired your wipers direct, make sure you put an in-line fuse in that circuit so there's no surprises later.Wiring ages same as any rubber or plastic. The wiring coating splits as the wire bounces going down the road. I bought a pack of 1000 zip ties when I bought my coach and zip tied whatever wiring I could find about every 12 inches or so. This prevents many of the wires from breaking from vibration.Buy and learn how to use a meter if you don't already know...BOL....Dennis

I would have thought the shop would have found the bad temperature sensor. You may have something with the exhaust break. We were mentioning yesterday that it felt like the breaks were on, but could not detect that they were. Now to find the exhaust break. I'm green when it comes to the diesel chasis'.

Any time a diesel doesn't run right, the first thing to do is change the fuel filters. You might give that a try.

Look at the engine exhaust - manifold then turbo then ex brake which is a flapper valve designed to close the exhaust causing the engine to become a air compressor. It works with no pedal depression and electronics that will shift the tranny to the lowest allowed gear consistent with your speed. Be aware that on a steep grade if your speed increases the tranny will up shift protecting the engine and giving you even less braking.

New to me 93 Monoco Diplomat - 1st Diesel | Good Sam Community

Executive45
Explorer III
Sep 20, 2014
Were ALL your fuel filters changed?? A dirty fuel filter can cause rough idle.
Is there any smoke from your exhaust when you accelerate? White or black?
Exhaust brake is a good place to look also. Check the vacuum line going to it. Make sure it's good. With a 21 yr old coach, I'd just get a few feet of hose from NAPA and start replacing whatever I could find. The EB should be lubricated anyway. Use the proper lube. PacBrake makes the best, IMHO.
If you wired your wipers direct, make sure you put an in-line fuse in that circuit so there's no surprises later.
Wiring ages same as any rubber or plastic. The wiring coating splits as the wire bounces going down the road. I bought a pack of 1000 zip ties when I bought my coach and zip tied whatever wiring I could find about every 12 inches or so. This prevents many of the wires from breaking from vibration.
Buy and learn how to use a meter if you don't already know...BOL....Dennis
CA_Traveler
Explorer III
Sep 20, 2014
Perhaps you have a bad temperature sensor causing the idle problem. Could the exhaust brake be stuck closed and you think it's the turbo? There is very high temp oil for the exhaust brake or wire it open to see if the problem still occurs. Use a meter or test light to track down the electrical issue.

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