Help, 03 5.7L hemi Lost idle

[MrFixIt]

Can anyone explain why I lost idle after a tune up in an 03 5.7l hemi? I replaced fuel pump/regulator, sparkplugs, airbox sensor, Throttle Body, air filter, and a couple other things. The engine sounds fine when idle it held at 800RMP or higher, but has a rough idle at 550 rpm and dies shortly thereafter. if the engine has warmed up, forget restarting it. Have looked for vacuum leaks, found the 2nd hose behind the TB was loose and the connection to the crankcase vent tube, but that is before the TB unit. Checked the wiring to and from the coils, some of the labels are missing, so placed them back to where they wanted to go. any other ideas? I'm trying to pull codes, had a front air sensor error before the tune up. any logical suggestions appreciated.

 

[Daw14]

Just to recheck that no pins were pushed back into their connections.double check wires on ecu.

 

[Rlaf75]

That's a pretty extensive tune up if you replaced the throttle body and fuel pump. Were you having this problem before you replaced everything. Sounds like you went on a fishing trip hoping to catch the lunker that was swimming around

 

[MrFixIt]

Got the truck not running from my son-in-law. He said it stopped on his way home from work. Rebuilt the motor, crank, bearings, a piston all new valves, rebuilt the lifters, blew out the oil guides, compression checked at 110 on all cylinders. Also, a couple of other hoses and water pump radiator etc. really enjoyed working on this truck, it was so easy and accessible.

 

[MrFixIt]

Just to recheck that no pins were pushed back into their connections.double check wires on ecu.

Re-checked the motor wiring connectors for bent/damaged/pinched pins or wires, saw nothing. The code is P0032 heaterO2. Not sure where to find the heaterO2 sensor or wire. Saw thread mention check #107 ground under hood, so i checked all i could find. Another thread mentioned pre-Cat O2 could be a problem; so, checked the wiring at pre-cat O2 and the red with a strip was damaged, looked like a rock strike. repaired the wire.

 

[Rlaf75]

You say lost idle. Does it start and wont stay running or will it run if you keep your foot on the gas?

 

[Daw14]

Got the truck not running from my son-in-law. He said it stopped on his way home from work. Rebuilt the motor, crank, bearings, a piston all new valves, rebuilt the lifters, blew out the oil guides, compression checked at 110 on all cylinders. Also, a couple of other hoses and water pump radiator etc. really enjoyed working on this truck, it was so easy and accessible.

Re-checked the motor wiring connectors for bent/damaged/pinched pins or wires, saw nothing. The code is P0032 heaterO2. Not sure where to find the heaterO2 sensor or wire. Saw thread mention check #107 ground under hood, so i checked all i could find. Another thread mentioned pre-Cat O2 could be a problem; so, checked the wiring at pre-cat O2 and the red with a strip was damaged, looked like a rock strike. repaired the wire.

Did it fix it ?

 

[MrFixIt]

You say lost idle. Does it start and wont stay running or will it run if you keep your foot on the gas?

Yes on both accounts. It will idle rough for about 3 min. Sometimes I can restart it with gas pedal depressed. The truck will run as long as I keep the pedal down and keep the RPMs up. Also, the engine runs without the air filter box & TB attached, holds at about 1100 RPM. That was really interesting to see. It acts like fuel mix is off. Still thinking a vacuum leak, but after operating without the TB am not sure.

 

[Rlaf75]

Yes on both accounts. It will idle rough for about 3 min. Sometimes I can restart it with gas pedal depressed. The truck will run as long as I keep the pedal down and keep the RPMs up. Also, the engine runs without the air filter box & TB attached, holds at about 1100 RPM. That was really interesting to see. It acts like fuel mix is off. Still thinking a vacuum leak, but after operating without the TB am not sure.

It runs without the throttle body on the engine?

 

[MrFixIt]

Did it fix it ?

Still not idling for more than a couple min. It is roughly 550-630rpm. Then stalls out unless I hold the pedal down, then it will keep running pretty smooth.

 

[MrFixIt]

It runs without the throttle body on the engine?

Yeah. Just a wide open hole and TB was off near the battery, not even close to connected. Impressed me. The filter box and the other chamber with a sensor in it (the two before the TB) were on the garage floor. I just want to turn over the engine to listen for a sucking or blowing intake valve. The engine came to an idle about 1050-1100 and just ran until I shut it off.

 

[MrFixIt]

Yeah. Just a wide open hole and TB was off near the battery, not even close to connected. Impressed me. The filter box and the other chamber with a sensor in it (the two before the TB) were on the garage floor. I just want to turn over the engine to listen for a sucking or blowing intake valve. The engine came to an idle about 1050-1100 and just ran until I shut it off.

I’m guessing folks have not tried that one before. I used to do that without a carb when doing compression checks. Forgot the engine gets injector fuel and guess the air mix was close enough.

 

[MrFixIt]

Yes on both accounts. It will idle rough for about 3 min. Sometimes I can restart it with gas pedal depressed. The truck will run as long as I keep the pedal down and keep the RPMs up. Also, the engine runs without the air filter box & TB attached, holds at about 1100 RPM. That was really interesting to see. It acts like fuel mix is off. Still thinking a vacuum leak, but after operating without the TB am not sure.

So, Back to the basics. Is it likely the O2 Sensor isn't reading and that drives the P0032 error code and I just need to replace that O2 sensor?

 

[MrFixIt]

Can anyone explain why I lost idle after a tune up in an 03 5.7l hemi? I replaced fuel pump/regulator, sparkplugs, airbox sensor, Throttle Body, air filter, and a couple other things. The engine sounds fine when idle it held at 800RMP or higher, but has a rough idle at 550 rpm and dies shortly thereafter. if the engine has warmed up, forget restarting it. Have looked for vacuum leaks, found the 2nd hose behind the TB was loose and the connection to the crankcase vent tube, but that is before the TB unit. Checked the wiring to and from the coils, some of the labels are missing, so placed them back to where they wanted to go. any other ideas? I'm trying to pull codes, had a front air sensor error before the tune up. any logical suggestions appreciated.

How likely is it that i just need to replace the O2 sensor at the pre-cat on the exhaust?

 

[MrFixIt]

Okay. So, the P0032 code I get must be one that only a shop can fix.

 

[Recoil]

MrFixIt, it sounds like you have more than a vacuum leak somewhere - who rebuilt the engine?

 

[Daw14]

Use only mopar brand sensors. your code says it is the 02 sensor pre cat bank 2 ,change it and inspect the wires .

 

[MrFixIt]

MrFixIt, it sounds like you have more than a vacuum leak somewhere - who rebuilt the engine?

I agree, it is possible to have a vacuum problem. Spray checks didn’t identify any. I did the rebuild. This is my hobby, I enjoy taking my time to fix vehicles. Someday, it’ll return to the road or a junkyard. I prefer to get it back on the road.

 

[MrFixIt]

So, Back to the basics. Is it likely the O2 Sensor isn't reading and that drives the P0032 error code and I just need to replace that O2 sensor?

The passenger side O2 sensor wires were damaged at a corner of the transmission. Would a short on the data sense wires back to the module cause the module to fail? If so what module should I check and where would be nice information.

 

[MrFixIt]

Can anyone explain why I lost idle after a tune up in an 03 5.7l hemi? I replaced fuel pump/regulator, sparkplugs, airbox sensor, Throttle Body, air filter, and a couple other things. The engine sounds fine when idle it held at 800RMP or higher, but has a rough idle at 550 rpm and dies shortly thereafter. if the engine has warmed up, forget restarting it. Have looked for vacuum leaks, found the 2nd hose behind the TB was loose and the connection to the crankcase vent tube, but that is before the TB unit. Checked the wiring to and from the coils, some of the labels are missing, so placed them back to where they wanted to go. any other ideas? I'm trying to pull codes, had a front air sensor error before the tune up. any logical suggestions appreciated.

Still have an idle issue: engine will run smooth above 1000 rpm, but idle has problems.
Replaced: fuel pump, O2 sensors, TB, crankshaft/bearings during a motor overhaul, cleaned oil channels and rebuilt roller lifters.
Background: swapped trucks with Son-in-Law when he said his 2003 Dodge Ram 5.7L hemi would not run. I tore motor down and found #8 connecting rod bearing was thinned out and left in the oil pan. Replaced crank, bearings, honed cylinders, replaced valves, spark plugs, many other items. Love the access through the radiator area to work on this truck, best and easiest truck I have EVER worked on.
Any ideas of what to check on these rigs? Please let me know.