UPDATE- replaced cap, rotor, plugs, wires, tps, iac and a bad vacuum line going to the throttle body. Now I have a high idle issue. It will idle around 1000 and if I apply any throttle it will hang there as if I never let up then fall back to 1000. No vacuum leaks, throttle body gasket new and good. If I unplug the iac, the idle drops to normal... no cel. Although the stumble is gone, now I have another issue to track down. Any ideas?

 

OK. So I have been granted the day off due to weather. I am going to go over all the systems and sensors that I can with the tools I have available. (quite a few)...Oh yeah and the greatest tool of all... So is it possible I have bought a bad IAC valve? How do I test that? Multimeter? Any tips, tricks, or personal experiences would be greatly appreciated!

Also wanted to say the O2 sensor that was mentioned before has been replaced and is no longer an issue. P.O. decided to just thread one into the pipe without a bung. He broke the old one off and left it. Drilled a hole behind it and ran the new one home! Gotta love Iowa....

 

Ok. So the throttle body gasket I installed looked to be bunched up around the bottom of the mating surface. I'm replacing that, again, also noticed I can see light slightly around the butterflies. Is this normal or does it show that it is worn?

 

Sounds like the t/b gasket shifted when you installed it. The throttle blades do not close completely at idle. When you replace the gasket, use some heavy grease to glue it to the surface so that it'll stay put when you install the T/B. When I bought my 96 E150 last year I "bit the bullet" and bought a code reader to help in diagnosing problems. That jury rigged O2 sensor can be a problem for the downstream sensor if it leaks. Does it have two upstream and one downstream sensors ? Mine does and I had to completely fix the leaks in the Y pipe before the downstream sensor quit acting up.

 

Yup, dead on. It was such a tight area with all of the conversion added hoses and wiring that it rolled the gasket. I actually used a set of carb studs I had laying around to mount it this time. Sliding the gasket over the studs and then the TB was much easier than any other method I tried. IDLE is just @800!!! No more stumbling (which continued after replacing the O2 sensor). I have a Blue Point code reader I picked up from a Pawn shop for $50! The guy had no idea what it was. And yes the downstream was an issue. Put on a Y-pipe assembly and new O2 downstream. There are 2 upstreams but those were new and went right back in the new assembly. My code that kept coming up was "Heated O2 Fault"

 

Mine keeps getting the same code. I've learned to ignore it. My mech friend says it's a fault in the wiring harness. Not an issue though as far as performance.