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Old 02-23-2023, 10:13 PM   #1
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Brand: Thor Motor Coach
Model: Miramar 37.1
State: California
Posts: 2,460
THOR #12698
2022 Miramar 37.1 engine misfire issue

We traded in our 2018 Thor Siesta 24SS this past March(2022) and bought a 2022 Thor Miramar 37.1. We have put on about 5,000 miles on it. During our last trip(1200 miles) a small dash light came on at least three times and went off on it's own(about 1200 mile trip). It never went into limp mode. I checked the Ford manual and it listed the fault as the electronic throttle control. When we returned home, I dropped it off at my dealership to address two water leaks and once it was repaired, I contacted a Ford Truck Service Center in Fontana and drove it to that facility to look at the dash light issue. It has been at that facility for just over 9 days. Their tech has been in contact with Ford directly since they discovered an error code that indicates a misfire condition. They have been directed to check the spark plug wires, coil pack wires, plugs and the firmware in the coach's computer to be sure it is the updated firmware program. I know I have heard that others have had the same issue with the spark plug wires(faulty wires/plugs). The coach never seemed unusual and drove great with the trips we have already taken in it. I am glad we came across with this issue now since we have scheduled out our summer with the coach to go from California to Florida and all points in between.

Is there anything else the Ford Truck Center should be looking at for those that have had this same issue?

Paul

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Old 02-24-2023, 01:01 AM   #2
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Brand: Thor Motor Coach
Model: Hurricane 29M
State: Texas
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THOR #11781
Nothing to add about your issues, but when I took my coach to a Ford Truck Center for the front end alignment they had troubles. They called me and said they were in touch with Ford for technical assistance. The Ford tech folks put them in the right direction and we ended up having our steering box replaced. So to me, your dealer being in touch with higher ups is a good thing.
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Old 02-24-2023, 02:23 AM   #3
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Brand: Thor Motor Coach
Model: ACE 27.1
State: Florida
Posts: 14,129
THOR #7035
Quote:
Originally Posted by paulwadley View Post
We traded in our 2018 Thor Siesta 24SS this past March(2022) and bought a 2022 Thor Miramar 37.1. We have put on about 5,000 miles on it. During our last trip(1200 miles) a small dash light came on at least three times and went off on it's own(about 1200 mile trip). It never went into limp mode. I checked the Ford manual and it listed the fault as the electronic throttle control. When we returned home, I dropped it off at my dealership to address two water leaks and once it was repaired, I contacted a Ford Truck Service Center in Fontana and drove it to that facility to look at the dash light issue. It has been at that facility for just over 9 days. Their tech has been in contact with Ford directly since they discovered an error code that indicates a misfire condition. They have been directed to check the spark plug wires, coil pack wires, plugs and the firmware in the coach's computer to be sure it is the updated firmware program. I know I have heard that others have had the same issue with the spark plug wires(faulty wires/plugs). The coach never seemed unusual and drove great with the trips we have already taken in it. I am glad we came across with this issue now since we have scheduled out our summer with the coach to go from California to Florida and all points in between.

Is there anything else the Ford Truck Center should be looking at for those that have had this same issue?

Paul
Probably not. I'm sure the first thing they did was connect to the OBDII port to read all codes and run diagnostics. They're probably waiting on new plug wires unless their availability has gotten much better that it was.
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Old 02-24-2023, 01:18 PM   #4
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Brand: Thor Motor Coach
Model: Miramar 34.4
State: Iowa
Posts: 794
THOR #4488
I had a similar problem with my 2016 Miramar. I purchased a reader to plug in and also clear the code. The message was identical to yours. After a little research I found it was due to excessive RPM's caused by allowing the transmission to downshift in the tow mode. I started being more attentive to upcoming hills and speeding up before getting to them... Not just relying on the cruise control.

I haven't had an issue since doing this for the last 4 years.
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Old 02-24-2023, 02:38 PM   #5
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Model: ACE 27.1
State: Florida
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THOR #7035
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Originally Posted by Miramar Owner View Post
I had a similar problem with my 2016 Miramar. I purchased a reader to plug in and also clear the code. The message was identical to yours. After a little research I found it was due to excessive RPM's caused by allowing the transmission to downshift in the tow mode. I started being more attentive to upcoming hills and speeding up before getting to them... Not just relying on the cruise control.

I haven't had an issue since doing this for the last 4 years.
You have the V10.

The OP has the newer V8.

Probably not the same problem.
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Old 02-24-2023, 03:47 PM   #6
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Model: Vegas 25.1
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We've had coil pack failures on both the V10 in our RV and the V8 in my F150. If it is a single cylinder failure the OBD tester should identify it. If it shows random it's a tossup.
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Old 02-24-2023, 04:33 PM   #7
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Model: ACE 33.1
State: Nevada
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THOR #21278
When he did our first cross country road trip in our 2021 ACE 33.1 (V8 engine), we had a CEL while on the road. Prior to our trip, I came across a posting here about a Ford TSB regarding the spark plug wires failing. I purchased 8 of the NEW wires (different part #) just as a precaution. I mentioned "NEW PART #" because when I went to ford to purchase replacement wires (8x), they ran my VIN #, they wanted to order the SAME part number as the problematic ones. I insisted in ordering what the Part # listed on the TSB. I found a mobile mechanic on the road when the engine gave us the CEL. He replaced ALL of the wires, not just the 2 that gave me the misfire codes. Never had a problem since.

Maybe try replacing the spark plug wires and see if that fixe the problem?
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Old 03-02-2023, 11:50 PM   #8
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Brand: Thor Motor Coach
Model: Miramar 37.1
State: California
Posts: 2,460
THOR #12698
I picked up my 2022 Thor Miramar 37.1 this morning from the Ford Truck Center in Fontana California. After several days of driving it around and scanning the computer, they contacted Ford directly with the engine fault codes to direct them in determining the misfire. Cylinder #3 had the misfire. The spark plug, wire assembly(ignition) were replaced along with some blue wire and blue plug. They drove it around after clearing the fault codes(P0496,P0731,P0732 and P0303). Once they removed spark plug #3, they found signs of carbon tracking and the wire failed under a load. Both were replaced and drove it around with no fault codes returning. It is now up and running again. All of the work was covered by Ford under my 3 yr/36000 mile warranty.

Paul
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