I am sorry if this is too much info, but I have been doing a lot of forum surfing and I am sort of confused....I just bought a 1999 Ram 1500 with 140k with a MINT body. The vin shows it is a 5.9. The seller said it had an engine swap with another 5.9 at 100K due to some overheating issue, not sure if it is true or not. I know the block should be stamped near the starter, but I don't see it. Either way, here is are the issues....the temp seems to hold at around 150F. I got a new NAPA thermostat and it stops at the exact same place. I have do have heat through the heater and it runs ok, just lacks some power for the 5.9...

I have the intake with two temperature sensors, 1 by the alternator and 1 by the thermostat. The thermostat sensor is broken off, but I do not see any unused wiring....no plugs to use even if I get the sensor.

Can someone post a picture of showing the wiring for the temperature sensor near the thermostat, I see no unused connectors anywhere. The temp gauge stops at 160 and doesn't go up. I changed the thermostat, but still have the same issue. The sensor near the alternator is plugged in, so I suppose that is where it is getting the gauge info??

Second issue, the exhaust smells pretty rich and it lacks power. It does seem to start, idle and drive fine, but just has no where near the power my durango had. Could this be related to the broken sensor?
Thanks!

 

The 98 and up trucks only used one coolant temp sensor, apparently, your engine came out of an earlier model truck. (97 and older had two)

So, just to hazard a guess, they simply dropped in the donor motor, and left the intake in place, as opposed to swapping over the original. Which works... to a point. Check the back, see if there is an EGR valve back there, that won't be hooked up either. (EGR went away with the 96 model year)

In any event, I suspect your 'new' motor has a blown plenum. That would account for the loss of power. See the plenum thread stickied at the top of this forum for a wealth of information on the plenum issue.

 

Should I try to do something with the ECT near the thermostat? I obviously DON'T believe everything he told me, but supposedly the entire engine got all new gaskets before it was installed...he made a point of pointing saying "even the plenum gasket was changed, which can be an issue on the rams"...

 

The o2 sensors should throw a code if they are out of spec also, correct?

 

Don't worry about the extra sensor. At this point, its only purpose is to fill the hole in the manifold.

I would be seriously tempted to pull the throttle body, and have a look into the intake, and see if you are getting oil pooling toward the back...... plenum should be pretty clean, but, I bet it isn't....

O2 sensor have a multitude of failure modes, not all of which will set a code. You can test if they are compromising performance by simply unplugging the front O2, and see if the truck runs any better.

 

I just got a P1281 code....looks pretty clean inside the plenum.

 

P1281 Engine is Cold Too Long

Probably bad thermostat.

 

I put a new one in about a week ago, because the code was pending with the old one.
So just to clarify, you are saying I don't need to worry about the ect that is broken off beside the thermostat, since the one by the alternator is connected...correct?

 

Correct. The one that is actually plugged in should be a two-wire connector. Make sure that it is. If it's only a one wire, that will confuse the PCM, and also the gauge in the dash. (as the PCM tells the cluster what the engine temp is.)

Wouldn't be the first time someone got a bad 'new' part, right out of the box.

 

Mike, I think the temp issue and the rich exhaust/lack of power are related, especially with your too cold code.

If the PCM isn't figuring out that the engine is up to temp, it'll dump fuel into the cylinders trying to get it to temp... Hence, rich exhaust and low power.

I'll see if I can get good pics of my 01 temp sensor (which I believe is next to the thermostat housing, IIRC, and should be the same style as what your PCM is expecting) tomorrow when the sun is up.