I'll need to take another drive tomorrow... I didn't make it to the parts store tonight, but I did take a look at the PCV valve - nothing but trash. I put a breather filter that I had laying around in it's place, and that smoothed things up a lot just idling in the driveway. I'd like to see how it handles a longer trip.

If it still pulls the same tricks, I'm off to buy an IAC and an EGR solenoid. I'm wondering whether to get a new PCV valve or leave the breather in place.

Do you think the PCV valve could be causing all this? The idle sure seems to have smoothed out, I backed down the drive and pulled up to the house several times and it never tried to die, and the oil pressure is reading just a touch higher. But then again, without making a long enough trip to get it warmed up it's hard to say what difference (if any) it really made.

 

The breather is just as good as a PCV valve. Old cars didn't even have that, they had a tube that spit the vapors and oil on the ground. If the PCV valve rattles when you shake it it's ok. All of your idle problems are exactly what my truck does. I once smacked the IAC with a wrench and that fixed it for a while. Now it does it again and I just turn the key off to reset the IAC. The idle doesn't go low too often but goes high more regularly and I turn the key off and on to reset it all the time. The EGR shouldn't have any effect on the idle but your gas mileage will go up if it works properly. I lost 2 MPG when my EGR failed and got it back when I fixed it.

 

The old PCV was the nastiest mess I've ever seen - totally gummed up, ball wouldn't move at all, had black slime oozing out of it. I've cleaned those before with good luck, but this one created an oil slick and still had plenty of junk in there. It's in the trash now. I'll probably just leave the breather on anyway.

I can see the IAC causing idle issues, and will most likely have a new one on this weekend. Is the EGR causing the stutter, or could the clogged up PCV cause that?

 

Well the clogged PCV isn't an issue anymore, just remember that a breather isn't smog legal. Fix the rest that you know is broken and see how it runs after that. If it hasn't been tuned up in a while I would do that too, and some fuel system cleaner wouldn't hurt.

 

I changed plugs/wires, fresh oil, and tranny service right after buying it (just to be sure it was done). The seller said the coolant had been flushed over the summer, so I didn't bother (it looks new and clean). I've only had the truck about a month, so this is recent stuff.

After the fuel tank, filter, and pump were replaced a couple weeks ago, I ran some fuel system cleaner through after considering how nasty the old tank was.

The only thing tune-up wise that I think I've left out at this point is the distributor stuff, and I can't believe I overlooked it, but the air filter is due for a change. I didn't really think about it until I was pulling all the PCV stuff out tonight, and noticed the air filter is needing a change.

So I'm definitely making a parts store run tomorrow, doing some work on this thing, and then a good long drive will hopefully tell me what I've got.

 

I took it on a long series of errands around town today, and this seemed interesting - maybe will help narrow down the specific part.

It started cold and ran fine - all the way through fully warmed up, thermostat cycled several times, etc. Made my first stop, and when I came out to start it, it didn't act the same - ran like crap too - bogging down and stuttering again. From there on, through 3 or 4 more stops, it did the same thing when starting it hot.

My last stop was the parts store, and they didn't have anything in stock... I had them order in an EGR valve, EGR solenoid, and an IAC. I can take or leave any of them Monday.

Based on earlier comments about how the IAC acts up, I don't think that's the issue (but I really don't know anything at this point). Shutting off and restarting doesn't change the idle a bit. It's also idling much better now that I've cleaned the IAC out, even when it's acting up, which leads me to believe that it's now working right.

I'm not so sure about the solenoid either - seems like it would act up the same (vacuum or no vacuum) whether hot or cold. Again, maybe I'm wrong.

Based purely on a hunch, and on how similar it's acting to how my wife's van acted when the EGR went out last spring, I really think it's the valve.

Any thoughts? I'm grasping at straws here, but would really like to buy/replace one part instead of $300 worth of assorted parts if I can.

 

...changed my mind. After typing the previous post, I decided to go out while it's hot and do some more testing. Maybe I could figure this out myself instead of letting everyone else think for me?

With the engine running, I can put a separate vacuum line on the EGR valve and it'll open with vacuum. Seems to be working.

With the IAC left alone, putting vacuum on the EGR doesn't change the idle much (if at all).

With the IAC unplugged, putting vacuum on the EGR drops the idle a lot.

Based on that, I'd guess the IAC is doing its job too.

That leaves the EGR solenoid (I guess). I have strong vacuum into it, and have replaced the vac line between the solenoid and the EGR just in case the old one leaked. I still don't seem to have vacuum out of it.

Am I on the right track? Any other ideas?

 

Change the solenoid and see how it runs.

 

A little more info on the EGR. It does nothing when the truck is cold, it only works when the truck has warmed up. And according to the book, symptoms of poor EGR performance include: driveability problems such as rough idle, surge, hesitation, general poor performance and poor fuel economy.

 

The parts store will have a solenoid for me on Monday. I'm gonna pass on the EGR valve and IAC for now, hoping this is a $35 quick and easy (I guess by this time we've gone beyond quick and easy...) I guess if the solenoid doesn't cure it, I'll keep throwing money at it!

I did some more thinking, and wondered what the solenoid would do if working properly. On another car (that doesn't set an EGR code), I put vacuum on the input of the solenoid. With no electrical signal to open it, I couldn't make anything happen - like sucking or blowing into a glass bottle.

I tried that on my truck, and it makes a cute little fart sound - I'm assuming theres a baffle or diaphragm in there, and due to the sound it makes, I'm assuming that it's broken or rotted.