With the plenum off fuel in the runners has to be coming from the injectors 1&2. Try a paper towel in the runner to catch the fuel better, it will tend to discolor from the fuel so Even if it is evaporating you'll be able to see it.

Fuel on the middle runners is a little strange, I don't think the angle is right for it to catch for drops from the coldstart, maybe it is traveling along the surface of something else. Don't over look the pulse damper, regulator, or fuel filter lines, all very close to that area.

 

I drove the truck to work today. After it gets to operating temp the problem seems to go away. It only seems to affect it when it is cold. I'll see what happens when i drive home tonight.

 

so on the way home, first start up was slow, about 6 or so cranks before it fired up. idle started low and then rose to 1100 -1200 and stayed. any throttle input at this point chokes it up and it stumbles.

after the engine was warm and I drove it a while it ran fine, no on throttle stumbles or anything like that. ran perfect to be honest. idle steady at 700 rpm.

so it is definitely due to cold / startup.

to recap, i have pulled the CSI and it fires fine when connected straight to battery, nice mist, no drips afterwards.

i have a new CSI Timer that appears to function perfectly fine (in bench tests) i have checked the voltage to the CSI during cranking before using the max hold function on my fluke and i think it was something around 10-11 volts. i would have to recheck this, its been too long.

 

Voltage to CSI isn't relevant really, yes there are concerns about voltage drop, but it is more about how long it stays active in relation to the CSI temp switch.

Six revolution isn't that off the mark depending on the cranking rpm. Typically the faster the engine spins the more cranks before it will fire as the older ECM CPU works out the position. With my 86 on a low battery I get "whomp whomp vroom" (about two revolution), with a good charge its "Whiiir vroom" (I can't count that fast)

Regarding the "stumble". Remember if the ECU thinks the engine is cold it is running the enrichment program. When you mash the throttle (tip in) it is going to dump even more fuel which the engine can't handle until the air flow (rpm) increases. Double check the ECU temp sensor has a good ground.

 

I'll double check the grounds. Even though i have probed all sensors at the ECU and have the proper readings at e1 and "x" terminals

any chance the vafm flapper spring has weakened and the sudden throttle change is causing it to over richen the mixture?

i have two. One in the truck now is unopened/ unmodified. The other one has been opened but not changed (i opened it to look inside but never changed it)

 

 

I checked the grounds and resistance values on the ect and cold start injector again. They are fine. The ect from sensor body to battery ground is 0.01 ohms. Same on csi injector.

i did find an issue. I turned my idle adjust screw all the way in and the engine didn't stall. So looking around i found that i had looped the air line on the throttle body to the intake manifold for the power steering idle assist, creating an alternate idle bypass of sorts. I fixed that and reset my idle properly. Now i have to let the engine cool back down to see if i fixed it. (And maybe reset ignition timing).

i Also rechecked my auxiliary air valve for proper operation, it is fine.

 

Ok so hooked my data logger (fluke 87v and notepad) to the computer and logged some data going down the road. I did this after a computer reset.

i drove the truck for over 30 minutes and logged everything.

first test was the vf signal from the ecu. Obviously it had no learned value to start, cold engine etc. It read 0.4 volts the entire time until the engine warmed up and i had driven about 6 or 7 minutes. Then it started showing values other than 0.

vf signal

1. 0.4 at no throttle idl contacts closed
2. 0.4 to 0.8 at light acceleration / cruise
3. 1 - 1.2 at decent acceleration occasional spike to 2v
4. 0.4 @ WOT
5. .89 stuck throttle plate

tps signal

1. 0 @idle 12 at all throttle positions idle e2
2. Vta .55 closed 3.8 WOT
3. .65 stuck throttle

vafm vs signal

1. 5.15 to 8.00 depending on throttle
2. 5.56 stuck throttle

so what does stuck mean? Well my throttle plate is sticking open enough to draw the flapper in the vafm open, raise my idle etc but not enough to open the idle contacts in the tps.

that being said, my vf signal is showing a rich condition under most conditions (if I'm reading that correctly) after i drove 30 minutes and checked it was showing 0 v effectively. And while driving it never read 2.5 volts like one would want. My current elevation is around 2200ft.

my o2 sensor is working properly (new denso unit ) and vf signal with te1 and e1 jumped shows a fluctuation like it should.

i think i will try to find a good throttle body that has no shaft play that hopefully will not stick any.

 

That is interesting and supports other info I've seen about butterfly plate bushing tolerance issues. Neither the shaft or bushings are serviceable, but I saw a detailed post with follow-up on another site (sadly I didn't bookmark it) that solved this problem.

The guy removed the throttle body, inspected the valve spacing with a feeler gauge and determined that the throttle plate was binding against the inside of the throttle body on the tps side. His solution was to remove the throttle linkage and spring assembly, grind a steel washer down to an exact size and place it on the shaft first before putting the throttle linkage back together. This slightly pulled the throttle plate towards the linkage assembly side and restored correct throttle body function.

I've been meaning to take mine apart, measure it and make the spacer so I can post a detailed write-up with photos. Hopefully I get around to it soon, I believe many of our 22re's are suffering from this problem.