Odd engine speed problem
Thread Starter
|
Registered User
Joined: Aug 2012
Posts: 2
Likes: 0
From: South Florida
Odd engine speed problem
I've got an issue with my '04 Ram 1500 that just showed up a couple of days ago...
I run the air 10 months a year - Jan-Feb is about the only time down here when its cool enough not to. Anyway, I noticed that when downshifting or coming up to a light in neutral, the engine speed has stayed elevated for a while. I thought maybe a malfunctioning TPS, but the operation returns to normal if I turn off the compressor. I first noticed this on Monday, but seemed more pronounced yesterday, to the point that I would cycle the A/C on/off in traffic.
Say, for example, I'm in 4th gear at 2000RPM. I see a light change up ahead and slip the tranny into neutral. The engine will stay at 2000 RPM until I slow to maybe 10MPH, then slowly drop down to an indicated 5-600 RPM. This can take a minute or more. If I slip into neutral and hit the compressor button, the engine drops down to idle in 2-3 seconds. On the highway, the truck will take minutes to coast down from say 2500 to 2000 RPM in 5th - its almost like having the cruise on.
I looked through the shop manual, but I see no throttle solenoid for the A/C. How is the engine speed altered by the A/C - does it work through the TPS, or is there something else I need to look at?
BTW, I hooked my OBDII tool - no codes.
Truck is a Quadcab 2WD LB with a 4.7L/5speed manual.
I run the air 10 months a year - Jan-Feb is about the only time down here when its cool enough not to. Anyway, I noticed that when downshifting or coming up to a light in neutral, the engine speed has stayed elevated for a while. I thought maybe a malfunctioning TPS, but the operation returns to normal if I turn off the compressor. I first noticed this on Monday, but seemed more pronounced yesterday, to the point that I would cycle the A/C on/off in traffic.
Say, for example, I'm in 4th gear at 2000RPM. I see a light change up ahead and slip the tranny into neutral. The engine will stay at 2000 RPM until I slow to maybe 10MPH, then slowly drop down to an indicated 5-600 RPM. This can take a minute or more. If I slip into neutral and hit the compressor button, the engine drops down to idle in 2-3 seconds. On the highway, the truck will take minutes to coast down from say 2500 to 2000 RPM in 5th - its almost like having the cruise on.
I looked through the shop manual, but I see no throttle solenoid for the A/C. How is the engine speed altered by the A/C - does it work through the TPS, or is there something else I need to look at?
BTW, I hooked my OBDII tool - no codes.
Truck is a Quadcab 2WD LB with a 4.7L/5speed manual.
Last edited by BillTS3; Aug 15, 2012 at 02:07 PM. Reason: more information