Wide open throttle when put in Drive

[HHhuntitall]

I've never heard of this before, but a guy called me today, said his truck was going to full throttle when he puts in Drive. 2004 5. 9 w/auto. It overpowers the brakes eventually. They scanned it, no codes, but he read the engine load % and it went to 100% after a few seconds. WTH? Anyone gat an idea where to start? I don't normally work on autos just for this reason!!

 

[Wingate]

hhmm. . I would maybe pull the signal wire out of the ecu for the apps... see if it does it again... if it doesnt, maybe do some measurin' on the signal wire... .

 

[HHhuntitall]

The guy told me he tested the APPS with the scan tool, and it showed 0-100% when pressed. Could it be wrong?

 

[Bob4x4]

Ck the torque convertor. If it wants to lock up and drop rpm below idle the computor will try to keep it from stalling

 

[Wingate]

The guy told me he tested the APPS with the scan tool, and it showed 0-100% when pressed. Could it be wrong?

I was just wondering if there is a wiring issue that is errantly applying voltage to the throttle signal wire...

Engine speed should remain at the low idle setting if the torque convertor is applying load... the effect would be the same, the truck would try to drive thru the brakes... but engine RPM would stay at low idle. . Boost/fueling would increase to maintain low idle RPM, but RPM should not increase. . if thats the case, yes, definitely check the torque convertor l/u function.

With the scan tool on it, when you are monitoring the throttle command, does it go to 100% when you put it in D???

 

[HHhuntitall]

I was just wondering if there is a wiring issue that is errantly applying voltage to the throttle signal wire...

Engine speed should remain at the low idle setting if the torque convertor is applying load... the effect would be the same, the truck would try to drive thru the brakes... but engine RPM would stay at low idle. . Boost/fueling would increase to maintain low idle RPM, but RPM should not increase. . if thats the case, yes, definitely check the torque convertor l/u function.

With the scan tool on it, when you are monitoring the throttle command, does it go to 100% when you put it in D???

Yes... so unplugging the APPS to test, or just the input signal wire itself?

 

[59Turbo]

I've had a bad torque conv. do this. Boost and egt would go up but it would stay at idle, under 1000 rpm.

 

[cerberusiam]

Bet it seized the stator sprag and its locked hard all the time inside the TC. Might have pukes some more pieces in there also. That is about all that is going to load the engine like that unless its throttle linkage related.



TC lockup is doubtful unless the TC is junk. I guarantee if the lockup solenoid applies in gear it will just kill the engine, NOW. No revving, no pulling thru the brakes, just lurch and quit.

 

[Wingate]

Yes... so unplugging the APPS to test, or just the input signal wire itself?

I'd start by just unhooking the signal wire... then you would know that you have no input command going to the ECU from the TPS/APPS. you are probably going to get a CEL for un hooking it, just clear it after you finish testing...

 

[cerberusiam]

The guy told me he tested the APPS with the scan tool, and it showed 0-100% when pressed. Could it be wrong?

Its not the APPS or it would show up on the test and throw codes. The ECU will NOT let APPS input rev the engine over 2100 rpms with 0 wheel speed. You cannot power brake a stock truck thru the brakes. He is showing no codes and and it will eventually power thru the brakes. The ECU is simply trying to maintain idle speed outside of any other inputs. Normally they don't ever lock so hard it will pull thru the brakes but without more info on the truck its hard to tell.



Different story if he has a downloader or box, but not stock.



Easy enough to test linkage problem, just disconnect the throttle cable and TV cable at the APPS. If it still does it then its not the APPS.



If its a 4x4 put the tcase in neutral and run it thru the gears. Should see little increase in rpms with no load.



Also check and make sure it does the same thing in reverse but not in neutral. If neutral is good and all other gears pull you have your answer.

 

[HHhuntitall]

It is doing it in reverse. That was the bad news I didn't want to hear..... I was thinking it was something in the valve body... .

 

[cerberusiam]

Pretty sure the TC is toast, 2nd most common failure on the stock TC's is the sprag.



There is an over running clutch on the stator that disengages at idle rpm's so the truck can be held with the brakes. As rpms come up that sprag engages to put the power thru the input shaft and move the truck, it is essentially what gives the TC its stall speed.



When the sprag locks you have a no stall condtion and the fluid flow generated by the turbine is trying to move the truck which drops the rpms. The ECU says woops, add fuel to maintain rpm which just increases the load and rpm drop which just adds more fuel. Usually it only goes so far as the sprag is not totally seized but it sounds like it failed completely and is locked solid to the input.



If you take the truck out on the road and drive it, once it us up to speed they will work and shift perfectly. Just a bugger to stop.

 

[Mhannink]

im thinking its wiring. since the engine isnt throwing codes the computer thinks everything is normal. the comp seeing 100% load tells me that it thinks you are doing it like stepping on the gas. i would be looking at wiring, the apps, and maybe there is a communication problem inside the comp, not sure how you would test that but it could happen. if you can start it up tap into the signal wire on the apps and read the voltage in the wire when you put it in gear. if it goes to full voltage then its getting power from somewhere either a short to power probably with the trans or and internal short in the apps unit.

 

[cerberusiam]

im thinking its wiring. since the engine isnt throwing codes the computer thinks everything is normal. the comp seeing 100% load tells me that it thinks you are doing it like stepping on the gas. either a short to power probably with the trans or and internal short in the apps unit.

Can't happen. If there is a short the ECU shuts down and won't even start the truck. The APPS signal is failsafed. If it is out of range for too long it just goes to idle and turns on the CEL. Same thing if it is intermittent, CEL and limp mode.



The trans relay will kick out if anything shorts in there and you have limp mode and CEL. There is nothing in the trans harness that can effect the throttle input. If it did it would do it all the time not just in gear.



Engine load is a calculated value based on APPS position, boost, rpms, output shaft speed, and probably others. If the boost is going up and the wheel speed ain't it will read 100% load at 1000 rpms if the ECU cannot maintain idle speed at the bottom of the fueling tables.

 

[rbattelle]

im thinking its wiring.

Back in 2003-2004 there were problems with corroded PCM connectors causing all sorts of strange troubles. Have a look at the TSB:



Link to TSB



Notice a TPS error is among the symptoms.



I'm not discounting cerberusiam's diagnosis, but I'd check the PCM connectors first. They're a lot cheaper to check/repair than pulling the torque convertor.



-Ryan

 

[Mhannink]

Can't happen. If there is a short the ECU shuts down and won't even start the truck. The APPS signal is failsafed. If it is out of range for too long it just goes to idle and turns on the CEL. Same thing if it is intermittent, CEL and limp mode.



The trans relay will kick out if anything shorts in there and you have limp mode and CEL. There is nothing in the trans harness that can effect the throttle input. If it did it would do it all the time not just in gear.



Engine load is a calculated value based on APPS position, boost, rpms, output shaft speed, and probably others. If the boost is going up and the wheel speed ain't it will read 100% load at 1000 rpms if the ECU cannot maintain idle speed at the bottom of the fueling tables.

turning wrenches profesionally for the last 5 or 6 years and as a serious hobby for 12 to 15 years i have found that truely anything is really possible ive seen stuff and diaged stuff that mechanics with 30 plus years experience have never seen and probably without seeing would have said it cant happen.



the engine load is calculated but not off of many factors it looks at boost and fuel position as well as rpm. also if it does use the apps which it could its going to look at the voltage thats how it knows the postion and if the voltage is false aka short to power then it will rev the engine up and read engine load with out a code. hook up a scanner and in neutral hammer the throttle. it will say engine load is 75 plus percent if not 100. as for the computer voltage and apperage throw codes. thats how it knows if voltage or amperage is high or low it throws a code. however if you have a short to power it might not throw a code as long as voltage is correct it wont trip the comp.



i still think its an electrical problem. also again could be a internal computer problem.



not that this is related ive had a couple trucks that had electrical problems that couldnt be explained one had intermittent blower motor problems the other had the abs and brake light on and maybe the air bad light as well. 2 different model trucks however new igintion switches solved the problem. i cant really explain it but my point is look outside the box just becasue the engine has a probelm that looks realted to one thing it could be something else completely.

 

[Road Dog]

If I was guessing -- and I am -- I'd say the TC was locked creating a serious load on the engine. If the truck is 4WD then set the transfer case to N and shift the transmission into D to test. With no load the engine should just idle with the smaller load of the transmission.

 

[Mhannink]

I've never heard of this before, but a guy called me today, said his truck was going to full throttle when he puts in Drive. 2004 5. 9 w/auto. It overpowers the brakes eventually. They scanned it, no codes, but he read the engine load % and it went to 100% after a few seconds. WTH? Anyone gat an idea where to start? I don't normally work on autos just for this reason!!

quick question is it going to full load or full rpm or both?

 

[HHhuntitall]

It's only going to full load, the rpms are not spiking. It does it in forward and reverse, and is not throwing any codes. A short would throw SOMETHING, as it would eventually overheat and short the PCM or TIPM. I have seen quite a few failures in the TC and valvebody, especially after 60-100k miles. Stamped or cheap parts are typically the problem I've seen. I don't work on the auto's very often, mostly because the cost of the scanners, tools, and the vast and endless possibilities... ... That, and lack of experience with the newer autos. If it was an old 727... . no problem!! I'd have it torn out, overhauled, and put back in two days!! But the newer trannies have grown in complexity to the point you almost have to have a designated shop to tear into them. I can't keep all the new tools, along with all the new tools for the engines I have to buy, scanners, programs, parts, payroll... . "The Everest... ... the Everest never ends!!" (the Grinch)



With little description, Cerebrusiam has nailed it's characteristics. It works fine once you get down the highway, just stopping can be difficult. N works great.



I've been over it front to back last night; I can't find any bad connectors, frayed/rubbed wire loom, and I threw every sensor code there was unplugging and starting, trying to figure it out. I didn't dissconnect the APPS input wire, as the connector was difficult to seperate, and appeared "iffy" to take apart... .

 

[cerberusiam]

If it was an old 727... . no problem!!

Then I have some great news for you, a 47\48RE is nothing but a beefed up 727 with an OD on the back.



The OD is dead simple in how it works all the way thru. Follow the same procedures as you would with a 727 and you will good to go. The ATSG manuals will get you up to speed on the differences quickly.



The governor solenoid\transducer and the lokcup\OD solenoids are the only electrical parts in the trans and they are dead simple in operation. Their operation is completely controlled by the TCM. Keep things clean and its good. Shift kits are a little different but most of them detail the changes well.



In this case it probably doesn't need a rebuild if the pan looks clean. The sprag will a lot of times lock and not spit any fragments out. Swap the TC and good to go.