Yeah... it's heading in the right direction. On the good side, it idles right (even when it's running rough) because the EGR isn't 1/2 open.

But, the saga continues... I think I'm figuring something out.

It ran rough going to work (4am, jacket weather, heavy dew). It ran rough on the way home (4pm, hot sun, humid). I just got back from a trip to the grocery store (8pm, sun down, low humidity, beautiful outside) and it ran like a top!

I'll be in the white padded cell talking to the voices in my head...

Could it be connected to the temp/humidity? It did throw the MAP code once, but hasn't returned since I replaced the vacuum fitting. If the MAP is going bad, could it screw things up without triggering a code? Is there something else that I haven't thought of that would be sensitive to the weather?

 

If the MAP isn't working it would run like total garbage. Of all the sensors on the motor, the MAP is the most important. Want to have some fun and do a little test, unplug the vacuum from the MAP and try to drive it. It won't be easy. Since the computer still isn't sensing EGR movement, it's opening it all the way up trying to get a reading. So even though it's working now, it's not working right yet. Opening up too much when not needed doesn't help how it runs.

 

I totally agree (maybe even understand) on both counts.

But why in the hell would the truck drive so well in one sort of weather, and so crappy in another if it's just the EGR?

I promise - I won't spend anymore money on a MAP sensor until after I've replaced the EGR sensor and see what happens - I'm just trying to wrap my mind around all of the options.

 

The weather is probably a coincidence. What would be more probable is that it runs great cold, but not so much warm. There is very minimal EGR function if any when cold, at idle and at wide open throttle.

 

That's exactly what doesn't add up - early morning it's cold and runs like crap. Mid afternoon it's hot and runs like crap. Late evening it's perfect outside and runs good. (the engine was hot tonight, though - I'd been playing doctor with my home-made stethoscope for quite awhile)

I'm probably trying to read too much into this - that's the problem with spending such a long time with this on my mind - my mind has wandered so far I can't find it anymore!

 

Get the sensor changed and see if you still get the lean code. Then I would suspect the fuel pump or filter.

 

This gets even more ridiculous!

Of course the sensor didn't arrive today, so I'm still driving the thing with the washboard sensation now and again. I had thought it was weather related, but it's probably not. This morning, I expected it to run rough as usual, then smooth out as I neared work - just the opposite. This afternoon, it had been doing the same thing, but again, just the opposite.

Here's where it gets worse - the old EGR valve didn't close completely. As I'm coming home, the truck starts to die every time I stop at an intersection. I get home, check to make sure no new codes came up, and just happen to look at the EGR valve - it's sitting there partially open!

The fuel pump and filter are both brand new - I replaced both (along with sending unit, wiring harness, and tank) last month.

 

Dude, you're going to make my head explode. Check when it's stuck and remove the vacuum line from the EGR. If the EGR closes all the way the new solenoid is bad, if it doesn't then the new EGR is bad, unless a big chunk of crud lodged itself in the EGR.

 

Been doing that tonight -

I took the vac line off, hoping it would close, but no.

I checked vacuum in and out of the solenoid, and it's working like it's supposed to.

I pulled the whole valve off, and looked at the bottom opening - just a touch of film in there, barely anything at all. The valve moves freely, and if you push it up just a bit, you can hear it click (metal to metal) when the spring pushes it back down. And believe me... I inspected this thing and compared it to the old one before putting it on - the bottom end of the plunger (where the exhaust tube connects) is resting in the same place (distance from the opening) as before I installed it.

Maybe the rubber plunger just rides up the shaft a bit... Hopefully the sensor gets here tomorrow so I can see if it makes a difference.

 

My sensor came in today, and I just put it on while the battery cable was disconnected to clear codes.

Started it up, drove it a bit, and it's still running like crap! Came home, pulled codes, got the 33 code again... Maybe the new EGR valve really is bad - it's still sitting about 1/8" open (from looking under the rubber plunger). It moves, but it just doesn't seem right.

I'm gonna head to the parts store with it and see if I can get it replaced.