[Brian]

TPS – Throttle Position Sensor?

[Archived]

thank you. I will add your comment to the list. It has cost in excess of 20G’s and no repair shop has found the answer. I would rejoice if it was a simple fix! What is wrong with today’s mechanics?

A second thought: While driving without cruise control, holding the throttle in a depressed position to maintain speed, the turbo will drop out when descending a slight grade. The throttle position has not changed or been let up yet the turbo still drops out…???

[victor]

Where do u live at I might be able to help

[Archived]

Sorry you’ve spent so much money on thjs problem when the complete
system could have done away, never to trouble you again for less than
half that amount (although that’s not for everyone). Since you are in this deep how many miles are on the
coach and has the actuator on the turbo been replaced?

Of course it could be something simple like the throttle position sensor
but l hope those things would have been checked by the previous
technicians.

Ken

[William]

Royale 399,

Please post the name and location of the Detroit shop that is taking your money. We know from previous posts most shops are good, but we also know some are not so good. When I read your post my first thought is how to go about getting your money back because of all the needless expense you were subject to. That shop likely should throw in the towel.

I am nowhere near an engine expert, but based solely on your description the problem is not mechanical but is associated with the electronic engine controls. Yet the shop has been taking your money to replace mechanical parts.

I don’t think taking a hard look at the TPS is a bad idea and I did not see where the turbo boost sensor was considered as part of the issue. Both simple replacements, and both will control whether you get boost or not.

What Ken mentioned is something everyone should think about. He can take a EGR engine and with the replacement of a lot of parts completely simplify the engine deleting almost all of the parts you described, replacing them with simple pre-EGR components providing you with a rock solid engine without the complexity and unreliability of the systems EGR engines have. The result is an engine that not only provides better fuel economy, cleaner operation with respect to internal sooting being eliminated, the engine provides better performance. One of our members had that done and he is very happy with the results.

[William]

Hi,

I have a couple of thoughts. First how old are the fuel filters? Next, you need to be sure you are getting fuel pressure. The turbo cannot spool up if the engne is not getting fuel. Now, with those 2 thoughts on the table, the easiest way to determine the issue is to drive the unit with a computer with the DDEC software running. While doing this when it acts up have the person operating the computer do a data capture. This records all engine parameters, if it acts up several times during the drive capture the data each time. After this return to the shop and review the data in graph form. You should see what the issue is.

You have changed a lot of things attempting to diagonise the issue. A likely culprit may be the turbo speed sensor. If it is not seeing the turbo RPM the ECU will command the turbo blades to 0 angle to increase turbo speed. When it sees the turbo speed it then increases the blade angle to provide boost.

It may be something else as well, but with the data capture you can determine what it is.

What is your coach number? How long have you had the coach?

I have the DDEC software if you are anywhere close to MD.

You did not sign your post so I do not know your name or location.

Mikee

Parliament

[Reagan]

Hello Ken,

We hail from Lake Wales, FL and spend some summer time in Bentonville, AR with our chlildren and

their families.

Bill

[William]

Hello Ken,

The bus has about 105K miles on it. Nothing has been said at any shop regarding the turbo actuator???

What has been mentioned was replaced and that was the two v-pods, and the EGR valve along with any

electrical wiring. Unfortunately when the EGR valve was being replaced the stud on the EGR Cooler was broken and although they tried to drill it out they had to replace the entire Cooler $$$.

Bill

[Andy]

Hello Jon,

Thank you for your post and of course I wish to thank all the other fellows who have stepped in.

The TPS has not been mentioned by any mechanics. I have had this bus in 5 rpair shops. The turbo sensor was the first item replaced.

We led 11 members of the Royale Coach Club from Michigan to Colorado. Our troubles began on our way to Michigan so our first repair was done at Traverse Grand Diesel. They replaced the turbo sensor after doing an engine diagnostiic. The code 39 showed up. Since the problem doesn’t show up for 30 or so miles we left MI and headed to WI. The problem showed up again about 150 miles down the road.

Arriving later in Green Bay we went to Truck Country in Kaukauna, WI. The engine diagnosis showed

code 39 S147 FMI 2 that logged 14 times. (I am re-reading the invoice right now and see that the tech tested the turbo actuator from his laptop and it tested fine in all positions…I stand corrected Ken…and there were n o leaks). After a road test the mechanic experienced the long period of no turbo boost with the throttle floored.

At this point the Charge Air Cooler was mentioned due to the smoke comming out of the tail pipe and the air leaking around it but his comment was “all” CAC’s leak. He believed the non-activation of the turbo was due to

something else which led to replacing the Barometric Sensor. This led to the v-pod’s, which didn’t solve the issue which led to the EGR valvle and then the EGR Cooler due to the broken stud.

On the road again non of the previous work solved the issure of “no trubo boost”. In MPLS we stopped

at Interstate Power Systems. They suggested replacing the Charge Air Cooler also but due to our schedule

with the Royale group we did not have time to get one shipped in. After their analysis they replaced the wire harnesses and fuel filters. They mentioned that the OEM (Prevost) might need checking and that the ECM might be the problem. We later had this replaced in Rapid City, SD Interstate Power Systems.

Finally we had the Charge air Cooler replaced at Prevost in Ft Worth Monday and drove it yesterday.

The good: Much better fuel mileage, no smoke, but same problem.

[William]

If you like, you could give us a call at American Fleet in Springfield Missouri. After we read your post, we have a few ideas/questions for you so we can help get you back on track.

[Bill]

Hello Jon,

I appreaciate your thoughts and suggestions but I although I heartily agree with the idea of throwing away all the EGR stuff I find it hard to make such a call at this point. We had 100K+ miles of great touring without any problems, now with a practically new engine I feel I am one step closer to getting the riddle solved. All the suggestions on these posts will be discussed with the next Detroilt Diesel expert I talk to. Of course this is a sarcastic comment regarding the DD experts.

Bill

---

2005 XL Thompson Coach

Rarely tow anything behind us.

Sold: 1993 Liberty that we loved for 12 years.

[Tim]

I had a somewhat similar problem on my recent trip. I had recently had major engine work done as well. The turbo would spool up then drop out. Blew large amounts of smoke and threw codes and CEM light like crazy, no power frequently. Most where EGR and Turbo codes. Because I was on the road heading back to TN I stopped at American Fleet Services in Springfield to let them look at it and also get a feel for their shop since they advertise on PC.

The shop foreman (and certified DD mechanic) immediately took me out on the road with the computer hooked up. Logged the codes and headed back. Opened up the back and started to check things out. Within 10 minutes they found the Delta 50(?) sensor off the engine laying on the the turbo tube. This sensor is the electronic brain for the EGR and somewhat the Turbo response. 15 minutes and a new sensor and the bus was like new. The previous shop failed to bolt it in place so it came off after a few hundred miles. Cost of the part $100 plus time. Very happy they did not start with all of the big stuff first.

As to the shop I liked it. Smaller, family owned and DD certified. No recent Tech school grads as mechanics. A significant part of their business is re-maning engines. Thus they have most parts on site and are used to major Detroit work. Alsp there major work is on buses. There were 6 or 7 there with two entertainer buses from Nashville when I came through. Although just one experience at Fleet, from that I would recommend them. Also if you call first they will take appointments unlike my experience at the big corporate shops.

Chris

[William]

Pumping the accelerator should have no effect helping the
engine make boost except for this possibility. The VNT portion of the turbo
could have carbon build up and that carbon is causing the vanes to drag or stick.
When you pump the throttle the ECM is asking for rapid position changes to
vanes in the turbo. This could help the vanes break free of the carbon build up
just enough for some movement. The control shaft bushing can wear causing the
shaft to bind but’s that unlikely with only 100,000 miles the on the engine.

If you have lot of black smoke coming out the exhaust under
full throttle that usually means your throttle position sensor is working correctly.
Sounds like the correct amount of fuel is
getting to the engine and just as you have said not enough air (boost
pressure). If all the things you mention have replaced/checked correctly there are
very few possibilities left. Turbo boots, turbo plumbing or the CAC has a big
leak. I don’t think pumping the accelerator would make any improvement to the boost
pressure if a leak was the cause of low boost.

I attached some pictures if anyone is curious what these parts look like.
Keep in mind these parts work in an environment that is full of
soot/carbon and regularly see temperatures over 1000 degrees. I’m amazed the
system works as well as does.

[Brady]

I am really glad you had a good experience at American Fleet and based on all that we have heard they are a great shop. Royale if you are close enough to make it to American Fleet it likely would be a good idea to do so. It appears all others have mis-diagnosed your problem and taken your money.

[Archived]

Hello Mikee,

The coach is 9 years old, 2004 chassis but 2005 Monaco Royale conversion. It has new fuel filters which were installed since the problem showed itsel. Fuel pressure was normal and computer was hooked up during a driving test. Code 39, and I believe 147 dealing with the VNT Vanes showed up. It now has 105K miles. Since all the work has been done the coach runs better, i.e. better mileage and hardly any smoking. But the turbo is still dropping out going down hill or after stopping. Shutting off the cruise control and flipping the throttle a couple times will get the turbo going.

Bill Sage

Royale 399

Lake Wales, FL