I have a new to me 2000 1500 with the 5.2/auto, 2wd, 213,000k. The prior/original owner is a friend who did NOTHING to maintain the truck. I purchased it not running for cheap and have done the following: replaced all freeze plugs/timing chain/water pump/thermostat (napa)/thermostat housing/hoses/heater core/radiator/had the trans rebuilt.

I now have the following issues:

rough/surging idle and it won't idle under about 1000 rpm. I can play with the throttle and get it to eventually drop under 1000 and it stays running but it won't go there without fiddling with the throttle pedal.

surging at cruise speed (65mph), I can't really feel it so much but can see the tach swinging a bit over about 150rpm

Code 1281 set after driving about 25 miles to work at 65mph. Temp gauge moves a bit off of 120/130 but not much. Lower radiator hose temp'd at 120, upper radiator hose 165 and heater core inlet hose 185. I pulled the 180 degree thermostat and put in hot to boiling water and it opened as it should.

Outside air temp 75 - 80 degrees.

Any thoughts?

Thanks!

 

P1281 Engine is Cold Too Long

That code is going to pop up until you put the 195 degree thermostat back in. The newer trucks are a lot more picky about it. Make sure to put in a GOOD quality thermostat. (skip the 'safety stats' though, they suck)

Check the throttle position sensor. I suspect yours is failing.... That may also be the cause of the tach bouncing on cruise control, that's the TCC locking/unlocking. That may also be caused the brake switch.

Leave the battery disconnected while you change the stat..... That may take care of several of your problems. (but, unlikely to fix the tach bounce.)

Welcome to DF!

 

Or maybe broken temp sensor (to the ecm).

Or the thermostat is installed backwards (sorry but it does happen).

 

Sounds good, thanks for the info and I'll check out the thermostat temp (believe its the 180) and the TPS sensor.

 

I'll have to rotate the alternator out of the way and check the two senders next to the thermostat and then pull the stat to make sure its not installed spring side up! Thanks for the tips!

 

The newer trucks use one temp sensor not two. As said put in a 195 stat. The 180 is to low and will throw a code on the newer trucks. There is a way to confuse the pcm in thinking it's 195 but that's a another thread.