thaddeusss

I hate to keep asking for advice, but I feel stumped.

I'm working through some bugs on my 93 pickup, the previous owner had just rebuilt the motor and left a few things unfixed.

#1 was a burned out CEL. fixed it, got an oxygen sensor and a rich mix code... all said and done it turned out that the oxygen sensor at some point had been ripped out (trail damage) and shorted wires had burned out the circuit in the ECM. fixed all that.

I was hoping the oxygen sensor issue would also fix the high idle, but it didn't.

it idles ~1200 rpm when warm. I have scoured it for a loose or broken vacuum hose (all new, connected properly) sprayed the hell out of it with fluid to find leaks (no changes anywhere) tried covering the hole for the cold-start valve (no change, I assume it's working properly and is closed when warm)

it idles smoothly and has good throttle response, but the throttle stop is barely open and the idle air screw is screwed all the way in. idle goes up if I screw it out, it also goes up when I disconnect any of the large vacuum hoses. disconnecting small hoses does nothing. I know I'm getting 'false air' but I can't find it. I'm figuring it must be a failure in some other smog control device, but I don't know where to look next.

please help.......

scope103

If you identify your motor you might get more intelligent advice.

But since you didn't, here goes.
1. check ALL the vacuum hoses shown on the sticker under the hood. If you have a 93 3VZE, there is an idle up "valve" on both the power steering pump and the A/C. That's a pretty good thing to "leave unfixed," and you may be in "idle up" all the time.
2. 1200 rpm, though, is a lot. How do you know the throttle stop is barely open? With the TPS and the damper etc., there are several screws holding the throttle plate open, each with its own purpose. Pull off the air intake from the throttle body and look at it, then start going through everything connected to the throttle plate. Remember; it could be something as simple as a cruise control cable too tight.

thaddeusss

sorry I didn't give more info.

it's a 22re. I know the throttle plate is barely open because I checked the throttle stop screw early on - if I back it off at all it sticks. plus, I looked inside and checked. that was part of the duct-tape-over-the-AAC-valve test.

I've also tested the power steering idle-up valve by unplugging the hoses and plugging the manifold ports. the a/c valve is removed and plugged.

the problem doesn't drive me too crazy because it's consistent - the idle doesn't change any except the usual cold-to-hot transition (another reason to believe the AAC is working properly) cold it runs 1700 to 1500 depending on the outside temp and it smoothly slows to 1100-1200 when warm.

TNRabbit

You're throttle body butterfly shouldn't be open AT ALL. The idle is supposed to draw through the idle screw adjustment, so there's your first problem. Fix that then adjust your idle screw for hot idle.

If the butterfly valve is sticking, it needs to be cleaned well.

thaddeusss

I think I wasn't clear. the butterfly is 'barely open' as in 'not jammed closed against the throttle body'... i.e. set according to or just under factory specs. if your butterfly closes completely, it jams, wedges, and sticks against the throttle body. that's not good. that's why there's a throttle stop screw... and yes, some (very small amount) of air is supposed to leak past it. if I look in at my butterfly, it looks like it's closed completely. but it's not, because it's not jamming

and like I said, the idle air screw is screwed all the way in. the only way to go is out, and that (even 1/2 turn) means 2500 rpm idle instead of 1200.

thaddeusss

oh yeah. and I don't have a damper dashpot, it's been removed. the cables are free, not tight. so... yes, the first thing I checked was to make sure some other idiot didn't do something to let the butterfly valve sit too far open. yay, I learned how to mekanik on motorcycles, that's the first thing I check.

thaddeusss

I spent about 3 hours on it this afternoon... went through the entire egr system and it all checks out ok, I double-checked all the hoses for possible leaks... checked all the bolts on the intake manifold for tightness, sprayed all the joints with carb cleaner... sprayed carb cleaner in an open port just to make sure I would be able to notice the change if I did hit a leak (easily). replaced the coolant temp sensor. checked the TPS.

the only new information I have is that the rear two spark plugs have a heavy buildup of white/gray/tan crud, that the front two don't. there's also a semi-loud tapping noise from that vicinity (upper rear engine area)

is there a possibility my injectors could be going bad and causing this?

thaddeusss

update...

I finally got around to pulling off the throttle body and upper plenum... holy &)&* there was so much black goo in there... when I scraped it out with a screwdriver I wiped it all on a rag and just for kicks wrapped the rag around a rod and burned it for a torch.... it kept going for half an hour!

anyway, after everything was clean and I put it back together, there was enough 'false air' to cause that obnoxious surging idle rev/die thing. however, I noticed when I was cleaning the throttle body that a good 1/16" of the edge of my throttle butterfly had been worn off against the side of the throttle body. big air gap there... I hadn't noticed it before because I couldn't see into the intake very well with all that sludge. I'm thinking that there's enough air leaking past my throttle plate to cause the problem.

anyone have a used throttle body in decent shape they want to sell me?

thaddeusss

finally fixed it....

found a used throttle body in practically new shape, with a TPS attached, for $80. problem fixed... now, with the throttle plate stopped short of jamming per FSM, if I screw the idle air in any more than 2 turns out it threatens to stall.

fuel economy is up to 20 mpg with a big lumber rack.