Alright... I replaced the EGR solenoid and double checked vacuum lines to be sure none are leaking. I also put a K&N air filter in while I was at it.

Not sure if I'll get to drive tonight or not, but idling in the driveway was much better - it idled up a little higher, even when in gear.

I'll post results after driving a bit tonight or tomorrow.

 

So far so good... I've driven the truck through the day, a couple of longer trips (15-20 minutes) and a lot of stop-and-go in the city. No issues, more power, idles better at stop lights, you name it. It's like a new truck!

Until it proves me wrong, I'm going to assume I'm in the clear on this one.

Thanks again for all of the great advice!

 

Hooray! Good deal, glad it's working good now.

 

Maybe I spoke too soon... It's been running great (when the weather is great) - here's the deal:

When it's cool and dry, the truck runs fabulous.

Early morning (I go to work at 4am) with cold temp and heavy dew, it runs rough until it's up to normal temp, then it runs fabulous.

Mid afternoon when the sun is beating down and it's hot/humid, it runs rough until up to temp, then it runs fabulous.

The weather has been great lately, and I thought I had the whole thing beat, but we've had a couple of the extremes in the last day or two, and it's acted up each time.

So, I'm thinking in the back of my mind - maybe the MAP sensor is giving up, but when it acts up it's the old chugging like the EGR is not working.

I pulled codes tonight, and it's 33 and 22 - EGR and MAP. I'm gonna have to break down and replace the EGR sensor and valve. Everything else in the EGR system is new. Is the MAP something that can be taken apart and cleaned, or is it replacement only?

 

The MAP can't be cleaned, at least I never heard of anyone cleaning it. Those are both things that run on vacuum, and they should both get vacuum from the same port on the intake manifold. Check the port for vacuum and for leaks. Spray starting fluid around the port while running and see if idle picks up. I'm thinking that with the EGR not working there was enough vacuum to operate the MAP but now that the EGR is working the vacuum leak is preventing both from working properly.

 

Good point - before I buy anything, I'll check vacuum. The rubber elbow running into the MAP sensor looks iffy anyway. I need to buy quite a bit of that size rubber hose - the canister purge solenoid tubing is (I think) the same size, and it is looking ragged too.

Back on track, I'll start with a vacuum check over the weekend, and probably replace the old rubber tubing no matter what, and see what happens before I part with any more money.

Maybe I should verify... Are you thinking that the port itself (with 4 or 5 vac connectors) is leaking, or just the rubber connectors attached to it? Or do you think the leak could be somewhere else?

 

I think it may be the port. I think it threads in and if it does it could be loose. It also may be cracked or you could just have a big mess of old lines. I guess it may be possible that the port is partially clogged. If you can unscrew it, check it out. But if you spray the starting fluid it should make finding leaks easier.

 

I was hoping your were right like you usually are...

No vacuum leaks (aside from the elbow fitting on the MAP which I suspected anyway). I replaced that fitting and checked every other vacuum line and fitting that I could find in the engine bay, no other leaks. The main port on the intake is tight, no leaks, and it's not clogged.

I cleared the codes, and will see how it acts for a day or two, and check again. Hopefully the vac line is what the MAP needed at least.

If this continues, I guess I'm off to the parts store again? I don't know of anything else that I can suspect aside from the actual parts.

Here's a good question, since I never needed to look at the one on my old bronco... When you look into the holes on the side of the EGR, can you see a small portion of the metal rod that moves to open it? On mine, there's about 1/16 to 1/8 of an inch showing when the engine is off. It moves up to show more of the rod when the valve opens, but should it go all the way down to close completely, or is this normal?

 

Well, on my EGR none of the rod shows when the engine is off. It must have developed the worse MAP vacuum leak while you were checking all the lines. I like to make absolutely sure of a problem before changing such an expensive part. With the EGR not working properly it must have siezed up or is crapped up so bad it doesn't want to move right, so I suppose it's time to go ahead and change it.

 

...that's what I was afraid of. The section that is exposed looks little too shiny to have been exposed to the elements for 18 years. It acts like something is blocking it from going all the way closed. From where it rests, with vacuum it will open on up.

I probably got a chunk of crud stuck up in there while trying to clean it out. I might try one last time before buying a new one to see if I can hold it just a touch open while flooding it out with cleaner. Maybe I'll get lucky... probably not, but I have nothing to lose at this point.