Diesel Place banner
Cancel
Create thread New Garage Forums

jumping idle, jumping rpm when driving

Jump to Latest
1 - 18 of 18 Posts

whitesmoker6.2

· Registered
Joined
·
77 Posts
Discussion starter · #1 ·
My 6.5 just started acting up on me. when it is warm, it will jump idle. when I am on the highway I could be cruising and the rpm will be around 2000, and it will jump up, or keep going up in rpm and then all the sudden it will go back to normal, or more recently I will be at a stop sign/light and the truck will go up to 3500 rpm and stay there. I can shut it off with the key and it will start back up and be normal for a while, so it isnt running or acting up off of oil. It has shut off on me twice in the past week when all of these things have happened. when the truck is going down the road and it is acting up, it will smoke black like crazy. I have checked my lift pump, that is fine. The system is primed, and no air in it, the vac. on the wastegate is working. The only thing i have left to do is try the clear line on the return. Other then that I think my injection pump is going out on me. the truck only has 80,000 on it so I would like to think my injection pump isnt bad already.

What do you guys think, anyone else have these werid prolems?
 
#2 · (Edited)
D_Tech,Dipaco,WAP pmd has been known to fail in that manner recently.
Those PMD's are all made by the same company.

Runaway engine failure is a bad symptom found only in the flight systems PMD's mentioned above.

There could be other reasons for your problem but your symptoms have been common reports here lately with those types PMD failures.

The stanadyne PMD's seem to fail in a more conventional manner eg:stalling,no start.
 
#4 ·
I'm having the same problems as you are whitesmoke. excluding the IP and PMD I'm leaning to the Accelerator Pedal Position Sensor (APPS), optic sensor or the injectors themselves. I'm excluding the IP and PMD for now as the vehicle is throwing no codes. and the PMD is New. Been working to many Hrs to play with it so I can't help you just yet.
 
#6 · (Edited)
The mounting location arguement is funny, living in AZ when the temp gets up to 120+ in the direct sunlight it doesn't matter where you mount the pmd it will always be in constant heat. as long as its under the hood it will also always be in constant heat. I dont by it for one second that the manifold is any better or worse then the bumper location. both areas have a air going over them while driving. As for my truck the pmd is new but I bought it with 173000 miles and don't know when the injectors where changed and I'm starting there. Also the way the truck is acting is the same way a gasoline motor acts with a bad Throttle Position Sensor which on a diesel it is known as the APPS so that will be my next check also.
 
#7 · (Edited)
GPK3500 said:
The mounting location arguement is funny, living in AZ when the temp gets up to 120+ in the direct sunlight it doesn't matter where you mount the pmd it will always be in constant heat. as long as its under the hood it will also always be in constant heat. I dont by it for one second that the manifold is any better or worse then the bumper location. both areas have a air going over them while driving. As for my truck the pmd is new but I bought it with 173000 miles and don't know when the injectors where changed and I'm starting there. Also the way the truck is acting is the same way a gasoline motor acts with a bad Throttle Position Sensor which on a diesel it is known as the APPS so that will be my next check also.
Click to expand...
Being in constant heat is not the problem for PMD"s,the problem arises with drastic changes in temperature.
Outside the engine compartment is going to be an environment where the PMD is going to stay at ambient temperatures.
Under the hood there is more of a temperature swing especially at shutdown when heatsoake occurs,temps can rapidly rise and spike in that environment.
BTW there are no codes for PMD failure.

Since I am not paying your bills, my opinion and yours don't have to match.
Everyone is entitled to thier own opinion and the exchange of these ideas and experiences is what makes being a part of this community great.
There is a vast amount of knowledge here and something for everyone to learn,and possibly teach.

The APP normally lights the service throttle soon light when a failure occurs,if the bulb is burnt out however you won't know from that.
There are several APP DTC's though.
 
#8 ·
You are right Racer 55 it is the PMD. Mine was purchased from SS DIESEL SUPPLY and it is fried already. Whitesmoker6.2 it is most likely the same for you stay away from SS Dieasel Supply and use a site vender. Walt from SS Diesel Supply is trying to get out of the Warranty for the PMD/FSD being its less than a year old.
 
#9 · (Edited)
Glad you found the problem but sorry to hear about the warranty issue.
I would still give serious thought to remote mounting your replacement outside the engine compartment with an extension cable and relocating the IP harness ground to it's original position.

The SS Diesel heatsink is one of the best available but Walts insistance of mounting on the intake is questionable at best.There have been many instances of ground faults when the IP harness ground is relocated to the heatsink as well.
 
#10 ·
just food for thought that the heat sink is the same from accurate diesel just a different sticker to say there name on it. plus you can get it from hdiesel.com (Huckstorf Diesel). But dealing with SSDiesel is a nightmare.
 
#12 · (Edited)
Well, 120F is a lot lower than the temp inside the hood. In the TX heat, with the hood open, the temp on the intake area goes up to 225F and it is climbing after the engine is shut down. Imagine with the hood closed at 120F outside!!! This is non-scientific, just out of my curiousity.

IIRC, the PMD is only good up to around 150F. So, outside the hood is still well below the threshold.

Now, if you live in AZ, my suggestion is to get Heath with 7 yrs warranty. I know it is pricy but I am sure you will need some replacement before 7 yrs.
 
Save
Reply Quote Like Like
#13 ·
From waht I read the new gray Stanadyne PMD is good up to 150 degrees celsius so that means it would be good up to 302 degrees Fahrenheit. Plus Stanadyne will not warranty the PMD if its mounted anywhere else but the IP.

My whole point to the mounting location is that when my truck is sitting outside all day in the AZ heat the PMD is already sitting in almost 150 degree heat in direct sunlight and that no matter where you put the PMD it will always stay in the heat from direct sunlight. then when it drops to 80 degrees at night it goes through a big drop in temperature event though it is still hot out.
 
#14 · (Edited)
A PMD mounted on a heatsink behind/under the frt bumper is never in direct sunlight,its shaded by the bumper.
The air gap between the bumper and heatsink is an insulating factor and unless your bumper is painted a dark colour and absorbing heat it should not transfer the temps you are eluding to.
Most bumpers are white or chrome and reflect radiant heat.

As I wrote in the thread linked here ambient temps are just that and when day turns to night the temp change is a gradual one unless you run over a cooler full of ice and park on it.
Under the hood the only airflow available is coming from air that has already passed through a 200+ degree rad and over an equaly hot engine that is transmitting heat into the heatsink combined with the heat generated by the PMD.
At the time of engine shut down a heatsoake occurs with the lack of any airflow when the truck is parked and all the heat inside the engine begins to radiate out of the engine on all of its surfaces,the heat is however trapped by the hood and its insulation and the already hot PMD gets hotter very quickly.

Again there is the chance that you don't agree so I won't try to force my thoughts your way after this post.
 
#15 ·
I don't want to get in a peeing match here. But the bumper itself is in direct sunlight so the heat that radiates to the other side is almost as hot when left there all day let alone the radiant heat from the black top of the parking lot is just as hot. i lived up in Northen Michigan for 22yrs and trust me there is a difference in the heat.

I am not saying its a bad spot at the bumper I am saying that no matter where you put it on the truck unless its a freezer capartment the heat will always be very hot around the pmd out here in AZ.
 
#16 ·
As I said, outside is better than inside the hood after engine shutdown. It is the better of the 2 evil. I have been to Phoenix, so I know that. Another place will be in the frame under the truck but it has radiation from the asphalt also.
 
Save
Reply Quote Like Like
#18 ·
whitesmoker6.2 said:
I know my pmd is good. I will still be chasing my problem over the weekend. hope I can find something out by monday.
Click to expand...

I thought my PMD was good too just bought it. but nothing else checked out wrong no codes, good fuel pressure, no air in fuel line, all fuel lines good, good lift pump, good OPS, good fuel solenoid relay. fuel out of the injectors. My only conclusion is PMD at this point. I finally got a answer on the return so I'm sending it back. BTW what color is your pmd black or grey?
 
1 - 18 of 18 Posts
About this Discussion
17 Replies
4 Participants
Last post:
GPK3500
Diesel Place
posts
5.3M
members
225K
Since
2003
A forum community dedicated to Chevrolet and GMC diesel truck owners and enthusiasts. Come join the discussion about duramax engines, performance, builds, modifications, classifieds, troubleshooting, maintenance, and more!
Full Forum Listing
Explore Our Forums
6.5L Diesel Engine Duramax First Generation: 2001-2004 (LB7) Duramax Second Generation: 2004.5-2005 (LLY) 6.2L Diesel Engine Fuel System, Air, Exhaust & Emissions Upgrades