Ok here goes.

I needed a power steering hose.

I bought it and installed it. (no problem)

It was a nice night and not too hot so I figured I would take a look at my TBI I have a 94 silverado with a 350 TBI motor.

I looked inside the throat of the air box (one with the round stock filter element)
I noticed inside that there was a spring loaded flap, at on time it was attached to the manifold kind of a heat riser type of a deal. It was no longer connected, so I Chose to do away with the flap inside the air box, figured more airflow cant hurt.

I used a hammer and a chisel, and poped the welds on flap, and pulled it out, this left a bit of a hole, so I put a nice smooth peice of plastic over the hole and duct taped it in place.

I then took off the thing on top of the left valve cover (pcv valve?) it connects to the base of the tbi on the other end. I used a bunch of gumout, and sprayed it until it was nice and clean and moved freely.

I then with the engine running, sprayed gumout all over my throttle body, around and in the injectors etc, just basically cleaned whatever I could hit with the filter off, while the truck was running.

Well, after I did all this, I decided to take it for a test drive, and something was wrong.

It runs fine after 1000 rpms, but when in gear, if you let off the gas to coast(automatic), when it idles down the tach jumps a bit, it seems to miss and sputter. (isn't idling above 500rpm either)

If I get on the gas it runs fine, just when i let off, or try to idle it falls on its face.

I went and got super unleaded 96 octane, and a bottle of injector cleaner, put the cleaner in, filled up the tank, and let the truck run for about an hour as I washed and detailed it, still same problem.

I checked all the vacuum hoses I could find, they all seemed intact. I also plugged the vacuum line going to the (pcv valve?) thinking that that might be the culprit, it didn't make a difference, although when I pulled the line off it revved up a bit.

Sorry for the long post I just thought you all would want as much info as you could get.

#1 So, I cleaned the tbi with gumout.
#2 I cleaned the PCV valve with gumout.
#3 I removed the internal flap on the metal filter

Sorry for the crude pic,. but I wanted you to know what i was talking about.

If you guys have any ideas on what to do be sure to let me know I really hate whenmy truck doesn't run right, as soon as it gets light enough ill be out tinkering again tryen to make it run right

Thanks

 

Nothing you did should cause problems like that. If you had a vacuum leak it would idle high (like when you unplugged the PCV valve vacuum line) but a low stumbling idle sounds odd. Did you remember to plug in the Air Temp sensor (in the base of the air cleaer) when you reassembled? Did you maybe knock something else loose while you were in there?

 

Carburetor cleaner can be a little tough on TPS sensors.

Your cleaning may also have dislodged enough gum and varnish to slow down the IAC action. You may need to clean the IAC passages more thoroughly.

The higher octane fuel probably isn't going to help at all. It won't hurt anything, but isn't going to add anything either.

 

This is what I'd suggest also, they don't like getting wet, in any way, shape or form.

 

This is something else I found odd, there are no vacuum lines, or sensors on the air filter assembly at all.

I'll take the TBI off and give it a reallly good cleaning now, anyone hve any suggestions on how to fix the TPS or may it be shot now?

**edit**
whats a "IAC passage?"

Can yu tell I am a total newb when it comes to TBI

 

Ok some new specific info.

The problem rears it's head when I am about 1/8th of the way into the throttle, after that it evens out and runs like normal. It sputters, lurches and sounds like it is going to die, with very low rpm.

It also apears when I get into a it a little bit, then let off and coast, it surges, seems like it is going to die, and then the idle smooths out again.

I checked all the vacuum lines etc, everything seems in place.

Any more suggestions?

 

Disconnect the negative battery terminal for 5 minutes or so. while it's disconected unplug the connector from the throttle position sensor and spray with some contact cleaner. Reconnect battery cable and give it a try

May help,can't hurt.

 

Ok I found out the proble whooo!!

Next to the passenger side valve cover there is a little black box, one side of the box has a vacuum line coming straight from the lowe thraot of the TBI, and a two prong plug in.

On the other side there are two places for vacuum hoses. I hooked up the vacuum hose on the wrong side, this caused the terrible idle/idle down miss. (thank you so much for your suggestions)

I now have another question for you guys.

I belive this box is somehow realated to cruise control.

When I bought the truck, the side of the box with the two places for vacuum hoses was vacant, there were no lines hooked up.

They both look like a hose belongs there. I hooked a hose to the upper one, that looked like it belonged (it made the cruise work), but the lower one is still vacant, any ideas on what really belongs there?

 

That is the solenoid for the EGR valve. A vacuum line hooks to the bottom port and runs to the EGR valve. Nothing on the top

 

thanks