No start no idle

I have a 96 dodge ram 1500 5.2 auto 137000kms For the last month or so when I start it cold it will start then stall immediatly I have to keep my foot
on the gas to keep it running after a few minutes it will idle on its own and is fine warm starts are no problem. My dealership says they think the PCM loses power (they haven't figured out how or why) and when it happens the iac settings are lost. The computer will relearn the settings but loses them just as fast. Does anyone have any ideas as to why or how this can happen. This is the second PCM in this truck and the iac motor was replaced 4 months ago.
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How old is the battery?
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"spudy" < snipped-for-privacy@shaw.ca> wrote in message
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I'm guessing the battery is 4-5 years it was in the truck when I bought it 2years ago, no problem turning the engine over.
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Just because it turns the engine over doesn't make it a good battery and its age shows it to be near the end of its useful life. If you have a volt meter, have someone start it while you are checking the voltage and see what the voltage returns to when it starts (without giving it the throttle you currently are to keep it running). If the voltage is lower than 12V, you probably have a bad battery. Another quick test would be to jump start it. If it will start and idle normally cold while connected to the other vehicle, that is just about proof positive of a bad battery.
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"spudy" < snipped-for-privacy@shaw.ca> wrote in message
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Don't jump start with the donor rig running ! If the battery will start the engine and the system is charging why jump start ?
However: the battery can have problems.. and the alternator will load the engine till it stops charging after a cold start. check with T-bones checks below. The problem could be simple, like as a worn throttle cam or stop setting. There are a lot of plastic parts that ware out. Check all the vacuum pots ! might be a leak ?
TBone wrote:

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Yea, the donor rig may need to be running.

Because it may have a bad cell and while it still may have enough current to crank it, it may pull the battery down to a level that is causing the computer to not function properly.

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spudy wrote:

================== Spuds.......... a couple thoughts come to mind..........
#1 ANY Technician that is capable of understanding the data he's looking at on the scanner..for this particular vehical....would KNOW if the computer is loosing power or not....there would be no "think" about it!
#2 You CAN.....run a fused power feed to the controll module, off the battery, as a diagnostic step to see if the symptom disapears with a "known good" feed to the computer. (that's IF....the computer is loosing power)
#3 The computer should be setting a code if a power loss situation is (?) occuring.
~~QUESTIONS~~
How did the Dealer dude verify that module was loosing power? how'd he explain it to you?
Did the Dealer dude say if any codes were set... and if so...what were they?
Why was the IAC changed 4 months ago?
Why is this the 2nd PCM in this truck?....... and....does 2nd include the original one?
How much gas are you having to give it? 1/4 throttle? 1/2 throttle? 3/4 throttle? full throttle?
there are more questions........ but let's git these answered first.
There ARE several sensor inputs that WILL cause the coldstart symptom......but none that will cause the module to reset memory for the IAC....... if that's what's happening.
~:~ MarshMonster ~:~
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I never got a chance to talk to the tech guy in person Question 1 The service guy said the tech guy said the settings for the iac were being changed or lost due to a power loss at the pcm. Question 2 No codes set Question 3 Changed the iac because we were getting codes saying there was a problem with it. Question 4 I tried to get the pcm flashed in hopes it might correct the starting problem but when I took it in the tech said they couldn't perform the flash because the pcm wouldn't accept it and told me the pcm was bad. Yes only 2 pcms including the original. Question 5 Maybe 1/4 throttle just enough to keep it at idle, once it warms up a bit it will idle on its own. Got it back yesterday they thought it was a bad ground which they repared, this morning same s$#% won't stay running.
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What shape is the battery in? Has it been load tested?
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"spudy" < snipped-for-privacy@shaw.ca> wrote in message
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spudy wrote:

============Mr. Tater.........
try this.........
Go get the vehical scanned again at a different shop...... all you're after are the CODES set in the computer. A secret for you.....Almost EVERY single tranny shop out there does this at no charge.....almost..not every...though everyone I've ever come across has. Don't try to bull-crap the dude..... tell him the truth...give him the history and tell him all yer after is a list of codes......won't take 2 minutes to hook up and pull them out. Have him clear the codes with his scanner, then the next day go back and get the codes pulled again. We're after a verifiable code......not after aggrevat'n the tranny dude.....trust me....i do enough of that for both of us.
Here's where we're headed...for a loss of power to the ECM.........
THE FIRST STEP= Run a jumper wire STRAIGHT OFF THE BATTERY positive post to the bat + feed wire on the back of the controll module. Cut the OEM wire and BYPASS IT with yer JUMPER WIRE. Be sure to leave enough length on the OEM wire to work with.... don't go chopping it off and only leaving yerself an inch of wire to fool with. This is jest a FAST diagnostic step to eliminate the possibility of the Bat Pos feed circuit being the culprit to the power loss. So....leave enough wire to work with.
Keep in mind......the diagnostic steps are directly formulated to the work with the symptoms you've posted, the answers you've provided to the questions asked.....and......all this could be for nothing if the system isn't loosing power. That's the reason for getting a second opinion and pulling the codes 2 times.... we want to KNOW FOR FACT.....what codes are resetting everytime.
post yer VIN # and we'll get you a schematic.
get the codes pulled...and post the results.
buy the tranny dude a beer for his trouble..... or ...if yer in my town....a crown royal would be nice.
~:~ Marsh ~sips his coffee......dealer techs....now there's a special breed~
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spudy wrote:

============Mr. Tater.........
try this.........
Go get the vehical scanned again at a different shop...... all you're after are the CODES set in the computer. A secret for you.....Almost EVERY single tranny shop out there does this at no charge.....almost..not every...though everyone I've ever come across has. Don't try to bull-crap the dude..... tell him the truth...give him the history and tell him all yer after is a list of codes......won't take 2 minutes to hook up and pull them out. Have him clear the codes with his scanner, then the next day go back and get the codes pulled again. We're after a verifiable code......not after aggrevat'n the tranny dude.....trust me....i do enough of that for both of us.
Here's where we're headed...for a loss of power to the ECM.........
THE FIRST STEP= Run a jumper wire STRAIGHT OFF THE BATTERY positive post to the bat + feed wire on the back of the controll module. Cut the OEM wire and BYPASS IT with yer JUMPER WIRE. Be sure to leave enough length on the OEM wire to work with.... don't go chopping it off and only leaving yerself an inch of wire to fool with. This is jest a FAST diagnostic step to eliminate the possibility of the Bat Pos feed circuit being the culprit to the power loss. So....leave enough wire to work with.
Keep in mind......the diagnostic steps are directly formulated to the work with the symptoms you've posted, the answers you've provided to the questions asked.....and......all this could be for nothing if the system isn't loosing power. That's the reason for getting a second opinion and pulling the codes 2 times.... we want to KNOW FOR FACT.....what codes are resetting everytime.
post yer VIN # and we'll get you a schematic.
get the codes pulled...and post the results.
buy the tranny dude a beer for his trouble..... or ...if yer in my town....a crown royal would be nice.
~:~ Marsh ~sips his coffee......dealer techs....now there's a special breed~
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Ok spudy I had the same problem you are having just last week, on mine there were no trouble codes, brand new battery, full tank of gas, but it would not run without my foot on the gas. Now I remedied this by replacing the fuel pump now the truck starts and idles fine no problems. On mine the problem was that the fuel pump had enough wear to it that when you shut the truck off all the fuel pressure would bleed off, It takes the fuel pump a few minutes running to get the pressure back to what is needed to run the vehicle. If this does sound like something that could be wrong the easiest way to get to the pump is to loosen the bed slide it back about a foot and replace the pump only six bolts. and about 4 hours faster than dropping the tank. I also replaced the alternator and a new air filter
spudy wrote:

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Truck back in shop today no word on what they think the problem is now, just have to wait and see. The vin # is 1B7HC16YXTS690734. I'd like to try running a jumper wire from the battery to the PCM but the PCM on this truck has 3 wire harnesses going to it with each harness having around 15 wires. I have no idea which wire is the power from the battery. About the fuel pump, I only need to keep my foot on the gas on a cold start, if the truck is warm it starts fine. When I get the truck back I'll check for any stored codes.
Thanks for the ideas guys Spudy
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spudy wrote:

I'd like to try

<<SNIP>> ====================== That's why we needed the VIN #. I'll post which wire to butcher tomorrow.
Keep in mind......the diagnostic steps given are a direct result of the symptoms and facts posted.....and it's easy as sheet to fry a computer.
anywhooo..... be sure it's setting codes FIRST.....or ..... check ign. cycles in the data field.
~:~ MarshMonster ~:~
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A little late with this post but better late than never Finally got some answers, took truck to our mechanic he changed the IAC motor, truck starts and idles fine, was a defective IAC in the first place but the dealer couldn't figure it out. Any way thanks for the input from everyone and keep truckin.
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As strange as it seems replacing the battery with a really high amp rating cold crank battery will most likely fix your problem. Any terminal corrosion can also cause the problem also.
The problem is the idle servo driver chip in the PCM will reset at 6 volts and the computer don't reset until the voltage falls below 5 volts. If the PCM software was done correctly it would notice the bit set that the driver chip lost power and reset the driver but it don't. This is still a problem in the 98 models I am not sure how far back it goes.
When the starter first gets power the battery dips to a low voltage until the starter spins up. This only lasts for a few milliseconds just long enough to reset the chip driving the idle servo motor.
If builders built houses the way software engineers wrote programs then the first termite that came along would destroy the world. John

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