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Running very rich after IAC replacement.

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AlaskanDad

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Truck left me stranded last week while it was well below zero and had no way to get it home or the time to fix it myself. I limped about 100 yards to a local shop and left them the vehicle.

Mechanic replaced the fuel filter and pump, then put it back in time since it had a slight stumble. Now it ran great! Even though it still had a slight hesitation, then I remembered the IAC was cleaned a few years and should replace it anyways. So I preceded to do so this morning just before class.

Now it runs like garbage, hesitating, miss, backfiring, and runs extremely rich.

I am at a complete loss with what do now. I tried putting the old one back and resetting the computer by disconnecting the battery. Could use some assistance with this matter.

Thanks!
 
Sounds like something got knocked loose or out of place. But, as mentioned, more info please.
 
Sorry about that. Was speed typing while flying out the door for class. Had to take wife's car when she got home.

1987, GMC Jimmy w/ 5.7 TBI / 700r4 - 4wd
 
Update: Just got home from class and tried starting the truck. Gave it a little throttle since it was having issues and it made a funny pop and tons of atomized fuel came out of the throttle body filling he engine bay with a thick haze.

Now I am just dumbfounded.
 
Okay. Looked it over again and notice a hard plastic tub running from the lower front TBI down to the lower driver side just under the battery. It was cracked cleanly in half and looks like it just happened. Possible when my air filter cover fell on that side.

I would guess this is the evap system? Not sure, but would this cause my problems?

Anyways, I had some extra vacuum line lying around and used it in place. However, now all my truck does it just turn over. Should I remove my spark plugs? Curious if it is flooded now, and if this is why it wont start.

And by evap, what I really mean is Charcoal canister.
 
If its flooded, you hold the pedal to the floor and crank it a bit. Then start as normal.
 
So put the pedal on the floor and then crank it for a bit? Doesn't this just flood it further?

How long does something like this take? I am afraid to fry the starter.
 
Holding pedal to the floor while cranking is "clear flood mode" in GM EFI. I've never tried excessively, but it's NEVER started when I've done it before, so I doubt it's adding any fuel.

I don't like cranking my starter anymore than even 5 seconds, it should not take long...gasoline evaporates quickly, especially as air moves through the combustion chamber when the engine is cranking over.

Complete guess, I'd say 15 seconds total crank time (and I'd break that up into at most seven seconds of cranking a time, with a healthy wait between) before it should be cleared enough to start.

Way too many variables for there to be a set limit on how much cranking will clear a flooded engine.
 
Just tried this several times and nothing. I do not even smell fuel coming from the tail pipe like I did before.

Will not be able to check for spark or fuel until Friday. I have classes all day tomorrow.
 
Bottom of the tbi unit, pretty sure that's a main vacuum source. You crack that tube you're gonna have a bad vacuum leak.

I actually think I may have done that in the past as well because I remember I tied the two ends together with a piece of rubber hose.
 
Holding the throttle down to the floor/wide open while trying to start a flooded engine is holding the butterflies open all the way, allowing a ton more air to flow through and blow out, clear out the excess fuel. Works on carbd engines the same way.
 
My buddy who owned the truck before me said he replaced the cap and rotor a couple years back, but did not touch the electronic ignition. I am going to check and see if I am getting spark.
 
You can either check for spark, or test for injector pulse with a test light. Both will (somewhat) narrow it down to an ignition or fuel problem.
 
Okay. Fuel looks fine and is not wildly spraying anymore. However, there is no spark. I couldn't see any and felt no shock. Normally wouldn't feel for shock, but it was an accident. :doah:
 
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