High Idle after hitting deep puddle

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kevaug

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Hi All
During a rainstorm with flash flooding I hit a deep puddle and now when I start my truck it idles at 1200-1500 rpms. When I am driving and press in the clutch it climbs to 3000 rpms. If the truck is rolling in neutral it again goes up to 3000 rpms until the truck stops moving then it goes back to 1200-1500 rpms.
Anybody have any idea what the problem could be?
I have new plugs. I swapped the IAC, TPS and MAP - no difference. I could not find any vacuum leaks but I cant guarantee Im good at that stuff.

Do you think something could hve been ripped off the tranny like a sensor wire or a ground wire?
Im trying to think of what could have been ruined from hitting the deep puddle.
Thanks
 

Elevated 2013

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Have you checked your air filter? If it got soaked from water getting up in it, the engine may have to speed up to be able to pull the normal amount of air to it. Just an odd possible theory. Normally I would say check your spark plug wires for arcing but we don't have any! lol
 
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kevaug

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Thanks for the responses.
I dont think any water got into the intake. I did check the air filter the next morning and it was completely dry and no water was in the bottom of the air box or air resonator box on the TB. I also took apart any electrical connector i could find and blow them out with my air compressor than used CRC electrical cleaner spray on them. Again no signs of any water on the connectors. It was a huge flash flood puddle that I hit hard and Im sure the fan sloshed some water around the engine bay but Im thinking this is more of any issue underneath the truck from the force of hitting the water.

I did notice some other symptoms while driving yesterday. Its a manual transmission and while I am in gear doing about 40 mph if I take my foot off the accelerator at around 20 mph I can feel the truck bog down then it surges up again.

In another instance when coming to a stop the idle would normally go up to 3000 rpms and then settle at 1500. yesterday for some reason a few times it wouldnt back off the 3000.

Also during the periods where I have to slow down and stop, occasionally the CEL comes on with a P0068. I personally think this is a false code.
 

Max1329

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I’m in the exact same situation if you ever figure out the answer
 

Donutsahoy

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My old 4.7 used to randomly high idle and I could never figure out why. If I revved it I could get the RPMs to go back down, really weird.
 

LoneWolf3574

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I won't profess to being an expert, however, I would check the TIPM weather seals and water infiltration (it's the large black box with all the fuses under the hood if you didn't know already). I don't know if the throttle body on 4.7L is in the same location as the 5.7L or not (toward the back of the engine), but, assuming it's toward the front of the engine, I'd look at my TPS since it is a drive by wire system like the 5.7L. Check the plug gasket and the weather seal on the cover for water infiltration, then put a little dielectric grease in the plug when you put it back together. Just my two cents, no ideas really beyond that, sorry.
 

Max1329

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So I just replaced map sensor throttle body and spark plugs and runs like new again
 

Jason G Slabaugh

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Thanks for the responses.
I dont think any water got into the intake. I did check the air filter the next morning and it was completely dry and no water was in the bottom of the air box or air resonator box on the TB. I also took apart any electrical connector i could find and blow them out with my air compressor than used CRC electrical cleaner spray on them. Again no signs of any water on the connectors. It was a huge flash flood puddle that I hit hard and Im sure the fan sloshed some water around the engine bay but Im thinking this is more of any issue underneath the truck from the force of hitting the water.

I did notice some other symptoms while driving yesterday. Its a manual transmission and while I am in gear doing about 40 mph if I take my foot off the accelerator at around 20 mph I can feel the truck bog down then it surges up again.

In another instance when coming to a stop the idle would normally go up to 3000 rpms and then settle at 1500. yesterday for some reason a few times it wouldnt back off the 3000.

Also during the periods where I have to slow down and stop, occasionally the CEL comes on with a P0068. I personally think this is a false code.
Just so you realize a p0068 code is map sensor, and could very well be your issue. Why do you think its a false code when the ECU senses a problem there? You stated you swapped your sensors, does that mean you replaced with new? Just making sure youre on the right path here ;)
 
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kevaug

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First thanks for all the great feedback - I really appreciate it.

Yes so far Ive replaced new parts- MAP, TPS, IAC and put new spark plugs in.
I havent replaced or removed the throttle body but I did clean it with some throttle body cleaner, a rag and a brush.
No change.

I say the P0068 is sort of a false code because it happens when I try and come to a stop and I keep the truck in gear as long as I can to avoid the rpms spiking to 3000 when I have to shift and it hits neutral. It only seems to set that code when I do that and strain the engine. If I put up with the high idle and drive normally it doesnt seem to set.

Maybe the sensors are good and the wiring is bad. i did use my multimeter to check out grounds, signal & reference voltages but maybe its time to start wiggling some wires and see if there is something intermittent in them.

I did look inside the TIPM the next morning and didnt notice any water infiltration and all fuses tested good.
The throttle body on my 2004 is towards the rear behind the ********* air diverter box.

I was under the truck and found one of those hard plastic lines coming off the EVAP canister that runs up along the tranny quite a ways. Its just hanging by the exhaust and seems to go nowhere. I googled it - seems to be some evap vent to the atmosphere but the end seems to be burned by the exhaust.
Does anyone know about this vent? Maybe the water snapped it off where it was secured and then it melted against exhaust and isnt working properly now.

While under the truck I also noticed something (some black part about 6 to 8 inches long bolted to the tail of the tranny. Any idea what that is?

20190527_152226.jpg

My high idle is definitely water puddle related - truck was running fine and then after puddle - BAM high idle.

Im also going to do a compression test. If that makes any sense to do?
 
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LoneWolf3574

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I won't say the EVAP line alone is the cause of your issue, but you'll definitely want to take care of that. I have dealt with something similar in the past on a car of mine. Long story short, somebody kept topping off the tank and flooded the canister to many times leading to a hard start condition after every fill-up. Yours, on the other hand, could lead to a lean condition if it is open to atmosphere and if it is, it MIGHT be pulling in some water when you go through puddles.

Sent from my LG-H830 using Tapatalk
 
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kevaug

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So the evap system melted part that is supposed to be a vent is part # 52121035AG a vacuum emission harness. But it is discontinued. I think the part that melted was supposed to look like a mushroom and I think it had some kind of valve in it.
Any ideas on how I can fix this if I cant locate the part?
 

LoneWolf3574

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So the evap system melted part that is supposed to be a vent is part # 52121035AG a vacuum emission harness. But it is discontinued. I think the part that melted was supposed to look like a mushroom and I think it had some kind of valve in it.
Any ideas on how I can fix this if I cant locate the part?
If it's JUST the evap line you can try splicing in a new section, if it's the entire assembly that needs to be replaced, I would try finding a 02-08 Ram 1500 or 2500 with a 4.7L or a 5.7L in a parts yard. Your only other option might be eBay or a recycled parts group in your state or even on a national website. I haven't had to look at mine, so I'm not positive as to what may be involved or what it physically looks like.
 
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kevaug

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I think Im barking up the wrong tree on the evap line. I looked at it today and even though it is melted I dont thnk it matters. The "mushroom" vent cap is only there to keep big foreign objects out of the evap. It appears this line I am talking about is actually an air intake or atmosphereic vent for the evap line off the evap filter off one of the canisters. So even though the "mushroom" vent cap is melted it still seems like fresh air could be sucked in without a problem or fumes expelled if needed (not really sure if its air in or air out). I did find a new "mushroom" vent cap but it wont be in until the end of the week and I dont expect to see any difference. Since its called a vent cap Im assuming air out.

I also completely removed and cleaned the throttle body and put a new gasket in. Still no change.

How would I go about troubleshooting the PCM?
If all these sensors are fine then it has to be the PCM? right?

Im going to do a compression test now to rule out a dropped valve seat or would that be giving me a different mess of problems?
 
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kevaug

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I did check the PCM connectors when I first hit the puddle/lagoon. Yesterday I started pulling the connectors off the IAC, TPS and IAT and the PCM set codes for each of them. So Im thinking the PCM is probably good.
 
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kevaug

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compression was fine, approx 130 psi in each cylinder
 
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kevaug

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So a new PCM did fix my high idle issue but now I have an ABS light flashing and setting an ABS code of 54 (Shorted Dump Coil Rear) and 55 (no code definition available on my scan tool). I did try and clear these codes with my scan tool but it was to no avail.

So I am not sure if the PCM they sent me is totally functional since as indicated before hitting the puddle my truck was perfect.

Perhaps the puddle also ruined something with my ABS and my old PCM wasnt detecting it after the puddle.

Also I ordered a 50628778AC PCM and they sent me a 50628778AD. I called their tech support and they said this was OK - they said the AD unit would be more up to date than the AC unit and I could install it no problem. Physically the AD unit is much heavier than my unit and has heat sink fins on the back - my OEM AC unit is just flat and much lighter.

I just noticed from my scan tool that the VIN # is also wrong. That surprises me since they require your VIN # to program it. Maybe they sent me someone elses unit?

I did send them an email detailing all of this.

Any suggestions? Thanks
 

LoneWolf3574

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It's been a long time since I checked the compression on a V8 (got a family and started driving cars with an I4), that sounds about right at 8.7:1 I think. Please correct me if I'm wrong.

As far as the ***AC vs the ***AD part number, those last two letters have to do with the revision of the firmware they flashed to the PCM, ***AD is more current. Physically speaking, it may be heavier because of the cooling fins on the casing. I would be more bothered by the VIN# and mileage stored in the PCM personally. I'd raise a fuss about it as it may cause a problem down the line.

The ABS module sits behind the battery on my 06 and this is known to cause issues with corrosion caused by the battery over time (leaking, off-gassing, etc). This causes, in my truck anyway, the ABS and Brake lights to come on occasionally (disconcerting as I hate any lights being on that should not be on).
 
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