I was inspecting the plug wires yesterday and one of them is wrapped around the corner of the valve cover and does not have like any slack. It almost seems like a longer wire should be there... Anyways, I was looking at it and it is already starting to burn on the surface. It has a light brown mark where it was pushed up against the valve cover.

So I went and bought some convoluted plug wire covering to keep the heat off these wires and keep them from chafing. Could it also help keep them from "crosstalking"?

I will also do the fuel injector test but might not get to it today since I have something to do later so then I will do it tomorrow

 

I finally got a code but I don't know if it has anything to do with my engine performance problem.

I did the trick with the key to see if any codes would appear on the odometer after going for a drive even though it always says "P done". I've done this a couple times before because my CEL does not work

Today was different and it threw the code...
P 1281

I looked it up and it means "Engine cold for too long".

What are all of the things that would cause this and could any of them cause poor engine performance such as what I have previously stated?

 

Bad thermostat (stuck open) and/or engine coolant temp (ECT) sensor. Depending on the year of your truck, you may have two temp sensors, one for the gauge, one for the PCM.

 

Could either one cause poor engine performance?

 

Well, if you are always running cold, your mileage would suffer. But if the PCM thinks it's cold (actually or due to bad sensor) it will keep it in open loop mode. This, IIRC, will make run rich.

 

I think this could be what's causing me so much headache. I noticed sometimes the temp gauge doesn't reach the normal operating temp... And the truck does seem to run best while it's cold... GRRRR. I'M SUCH A BONE HEAD lol. Idk if this is it for sure but I kinda hope it is.

 

You only have one temp sensor. It should be located just to the drivers side of the thermostat housing. Beings as how you are going to change your stat, check the sensor while you are there. Make sure the connector is still good, and plugged in tight.... If things are really bad there.... The PCM thinks its -40*... and positively DUMPS fuel.....

 

I've looked into it a little bit. I'm just going to change both the sensor and the thermostat because it seems kinda a pain to get down there. What's the best way to do this? Like what needs to be removed to get down in there?

 

The sensor? I don't know. The thermostat, I actually did by just removing the air filter housing and a few misc items to get at it. There is a nubbin on the housing that I think is there for indexing the housing. It will make your life easier, when you go to put it back, if you grind that nubbin off. When you get there, you'll know what I mean. Also, drill a small (1/32" or 1/8' or so) hole in your thermostat before you install it. It will help remove the air from your system.

 

I've been doing research online about what could possibly be going on with my truck and given that I have this P 1281 code and the temp gauge almost never gets to operating temp (stays too cold) I am really starting to believe it is either the thermostat is stuck open or the ECT sensor is faulty/bad connection. Both of these cause the truck to run rich or stay in open loop. However, I am leaning towards the ECT because a bad one is known to cause a ton of engine performance problems.

I'm a busy guy plus it's getting cold here in Michigan and I am sorta limited on tools so I decided I will just take in to a shop. I will tell them about the code and just tell them to change both the thermostat AND the ECT sensor and check the ECT wire harness. Might as well since they are cheap parts and right next to each other.

Hoping it doesn't cost more than like $250 because that seems like the most a place should charge. I will probably get it done in about a week or two.

I will come back here and post the results once it's done.