Once again, great advice!

I was under the same impression on the codes, but I read somewhere (I've been scouring the net all evening...) that 91 was a transition year, and could go either way. Either that's the case, or I'm hallucinating.

Here's how it went - I got the 11, pause, 33, the separator (or whatever you call it, between the hard codes and the memory codes), then the 173. Hard telling... I cleared them and we'll see what kind of silliness happens tomorrow.

I did find the IAC, but didn't pull it to see how nasty it is yet. Hopefully (weather permitting) I can mess with that tomorrow. I'll try the vacuum on the EGR too, just to be sure. Here's my findings on the solenoid - strong vacuum in, and weak vacuum out all the time. Is that typical, or should be vacuum out be zero until the throttle increases?

 

I thought it may be a transition year.
I'm not exactly sure, but I think minimal vacuum out of the EGR solenoid at idle is ok, but it should increase with an increase in throttle movement.

 

I just went outside with flashlight and vacuum tube in hand, and tried sucking on the EGR valve - it does move (seems to take a bit of suction, but it's hard to guage by mouth). The sound it made was best described as a horse trotting - knock knock, knock knock as I applied and released suction. Is that right, or is it gummed up to where it might be needing excessive vacuum to move it?

I also noticed that the vacuum connector on the EGR was pretty loose fitting. I don't have a spare on hand, so I put some sealant on it to see if that helps get good vacuum to it. The line has a good seal at the solenoid, but the EGR end seems really questionable. If that makes a difference, I'll put a new fitting on there.

It sure seems like we're getting closer to a solution. I truly owe you for the money you've saved me! I would have spent $200-300 in parts by now if you hadn't been keeping me thinking logically (and still not even thought about the IAC causing all of this!)

Back to the IAC - can that be cleaned, or is that a replacement only?

 

It's a tough call, but it sounds like the EGR is working fine. Maybe cleaning it some more would be wise, it sure wouldn't hurt. As long as the vacuum wasn't leaking, the connection should be fine. As I said before, some have cleaned the IAC but I think it's only about $30. You can try cleaning it, if that doesn't work you can just buy it later.

 

After sealing up the vacuum elbow on the EGR, the truck drove great all day today. When I got home, I pulled the IAC and cleaned it, but haven't driven it yet. Hopefully it helps. I'll keep you posted.

 

I just got back from about a 1/2 hour drive in the truck. Just driving around to see how it's running, trying to get on the highway, hit some city stoplights, climb hills, etc.

Cleaning the IAC seemed to smooth out the idle a lot, and there was no stutter or chug at all. In fact, it is running the best it has since I got it.

Obviously, I haven't re-developed a 'trusting relationship' yet, but the next few days should help if it keeps running right.

Thanks again, sean - you saved me a ton of money in parts that I didn't need and gave me perfect advice every step of the way.

 

No problem. Make sure you reset the computer again to erase the codes. Then you can check again later to see if any came back.

 

I cleared 'em - been a daily thing for quite awhile now... After driving it tomorrow, I'll see if anything comes back. Like you said before, I might still need to clean the EGR and IAC more, or just replace them. I'll wait and see how the next few days go.

 

The truck ran great this morning, then started the stutters again on the way back home.

This might help narrow it down - It did fine all the way home, until I came up on a stale green light, which changed at the last second... I stopped really quickly (on the verge of squealing tires) and the damned thing tried to die. The rest of the way home, it stuttered and tried to die at every stop light.

Checked codes, and 33 is back. Pulled the EGR and cleaned it more - I also cleaned the passage into the intake being sure to pull the crud out and not knock it in. (that was about 1/2 way blocked up) reset the codes.

Started the truck and let it idle until the rpm dropped down - it landed at about 700rpm in park, and about 550rpm putting it in gear with the brake on. Didn't even drive it - cycled through the gears and shut her off. Pulled codes and got 33 again.

Do you think it's the EGR as the code states, or does it sound more like the IAC? $75 for the IAC and $130 for the EGR... not a lot of difference in cost one at a time. Any educated guess, or should I go for broke and get both?

 

The bad idle is the IAC. Doesn't usually store a code for the IAC. With high idle, do like I said before. Without letting the truck stall, turn the key off and back on and see if the idle corrects itself. With low idle, turn the truck off and restart it. If the idle corrects itself with either of these tests, change the IAC. When you shut off the key the IAC resets itself. Whatever happened with the EGR solenoid? I would try the solenoid before changing the EGR. Depending on the cost of a new one, I'd throw the junkyard $5 for a used one.