Wacked out idle issues

[beendooben]

Having a issue with the idle on my 97 X 5.0 AWD. This morning on the way into work i heard a lil pinging. Massaged the gas a little and the trans downshifted and would not shift correctly. came to a light with the motor taching up to around 3000 rpms then went down. Stopped for a cup of coffee and when the truck was in park had a high idle up and around 3k again. Shut the truck off got the coffee started the truck again and the idle was bouncing all over the place. real low-high then mellowed out. Put the truck in gear and was fine. Got to work shut the truck off started it back up and the idle was all over the place. went to shift into gear and the idle mellowed out. the past few days the truck when cold would idle fine until it was put into reverse then the idle would raise then go down as the truck warmed up. Any ideas would be very helpful.
Thanks in advance.

 

[my98nnj]

Vacuum leak, Defective TPS - You need to do some troubleshooting. Any DTC codes stored?

 

[beendooben]

I did not get any dtc's from the computer. With it pinging it is safe to say that there is a vaccum leak that needs to be found. The TPS seems to sweep fine on the code reader but will check it with the voltmeter.

 

[my98nnj]

It's pinging, didn't catch that. Check the MAF too.

 

[imp]

Did you possibly catch up with a tankful of bad fuel? imp

 

[beendooben]

yesterday after getting home i pulled a P0125 dtc which indicates that the engine has not reached the required temperature level to enter closed-loop operation within a specified amount of time after starting the engine. I checked the fluids and low and behold, it needed coolant. I also checked the TPS with the meter and it checked out good. I got a fresh tank of fuel and was much better on the way into work this morning. I will be cleaning the MAF tomorrow and looking for vacuum leaks also. The motor has a fresh tune on it but will also check the plugs and see what is going on. I could see the low coolant giving a problem as the computer does not know what the actual temp is and would adjust to what it was getting from the temp sensor.

 

[imp]

yesterday after getting home i pulled a P0125 dtc which indicates that the engine has not reached the required temperature level to enter closed-loop operation within a specified amount of time after starting the engine. I checked the fluids and low and behold, it needed coolant. I also checked the TPS with the meter and it checked out good. I got a fresh tank of fuel and was much better on the way into work this morning. I will be cleaning the MAF tomorrow and looking for vacuum leaks also. The motor has a fresh tune on it but will also check the plugs and see what is going on. I could see the low coolant giving a problem as the computer does not know what the actual temp is and would adjust to what it was getting from the temp sensor.

Very good point here! Engine Coolant Temp. Sensor, if not immersed in liquid, will probably indicate low, since gas or vapor surrounding it are much poorer temperature conductor than liquid coolant. This would happen if the sensor is mounted high up in the system, like near the thermostat. imp