Did TBI mods and spacer today. Now truck dies upon accel from idle. please help?

[jdyates]

This might sound stupid, but did you remember to put the gasket back under the throttle body? Sounds like a massive vacuum leak to me

 

[Yeti_Owner]

Hold one : putting something together for you...

This crap better get stickied!

 

[Yeti_Owner]

x10 on JDYates's suggestion - odds are it's a vacuum leak or a disco'd sensor/ground.

Provided it isn't, though, grab your multimeter:

I couldn't find a ready-made one that pulled it all together, so I put together a quick and dirty diagnostics "How To" for you:

TPS:

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Backprobe with a high impedance voltmeter at TPS terminals A and B.
With the key ON and engine off, the voltmeter reading should be approximately 5.0 volts.
If the voltage is not as specified, either the wiring to the TPS or the ECM may be faulty. Correct any wiring or ECM faults before continuing test.
Backprobe with a high impedance voltmeter at terminals C and B.
With the key ON and engine off and the throttle closed, the TPS voltage should be approximately 0.5-1.2 volts.
Verify that the TPS voltage increases or decreases smoothly as the throttle is opened or closed. Make sure to open and close the throttle very slowly in order to detect any abnormalities in the TPS voltage reading.
If the sensor voltage is not as specified, replace the sensor.

Map

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Backprobe with a high impedance voltmeter at MAP sensor terminals A and C.
With the key ON and engine off, the voltmeter reading should be approximately 5.0 volts.
If the voltage is not as specified, either the wiring to the MAP sensor or the ECM may be faulty. Correct any wiring or ECM faults before continuing test.
Backprobe with the high impotence voltmeter at MAP sensor terminals B and A.
Verify that the sensor voltage is approximately 0.5 volts with the engine not running (at sea level).
Record MAP sensor voltage with the key ON and engine off.
Start the vehicle.
Verify that the sensor voltage is greater than 1.5 volts (above the recorded reading) at idle.
Verify that the sensor voltage increases to approximately 4.5. volts (above the recorded reading) at Wide Open Throttle (WOT).
If the sensor voltage is as specified, the sensor is functioning properly.
If the sensor voltage is not as specified, check the sensor and the sensor vacuum source for a leak or a restriction. If no leaks or restrictions are found, the sensor may be defective and should be replaced.

Coolant Temp Sensor:
(This has to be done off the truck)

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O2 Sensor:

Start the engine and bring it to normal operating temperature, then run the engine above 1200 rpm for two minutes.

Backprobe with a high impedance averaging voltmeter (set to the DC voltage scale) between the oxygen sensor (02S) and battery ground.

Verify that the 02S voltage fluctuates rapidly between 0.40-0.60 volts.

If the 02S voltage is stabilized at the middle of the specified range (approximately 0.45-0.55 volts) or if the 02S voltage fluctuates very slowly between the specified range (02S signal crosses 0.5 volts less than 5 times in ten seconds), the 02S may be faulty.

 

[jdyates]

I'm actually going to use that myself, thanks, Yeti! (Don't know your real name, lol)

But as helpful as all that is, if all OP did is mess with the throttle body, only things he'd have to have left disconnected are the IAC (he mentioned reconnecting it), the injectors, and the TPS. Has to be a vacuum leak. My truck was doing the same thing when the vacuum line that goes to the EGR solenoid broke. Ran like crap.

 

[Nobodys94]

Thanks yeti owner. Going to check all that after I do some paperwork. All gaskets are in place. I did find a cracked vacum line that goes to the fuel canister solenoid from front of tbi. replaced it and took it for a quick drive. Here is a video. sorry, its sideways. LOL

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[jdyates]

DEFINITELY double-check all the vacuum lines.

 

[Yeti_Owner]

Yah...something's pulling WAAY too much air...

Either that or it's lean...which wouldn't make sense..

Unless the TPS is disco'd or just messed up...

 

[Nobodys94]

I was cleaning of the work bench in my lil shop and found this. Its from the main body, somewhere. I removed the inj pd assembly outside on a different work bench so my area didnt smell like gas. So its either supposed to be where IAC was or somewhere on the main tbi assembly.

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I had also brain farted and left the original tbi gasket on bottom of the tbi so It was dble gasket between tbi and spacer, man the entire stock tbi gasket is soaked with gasoline now. Removed it and retightened the tbi back down.

Just wanted to post that real quick. Had to print out yeti's post so its in hand along with my meter. Will report back.

Thanks again fella's

Edit: Yesterday I was thinking to myself seems like a lean condition. I have had this issue before with carbs, but not much TBI experience.

 

[Yeti_Owner]

Edit: Yesterday I was thinking to myself seems like a lean condition. I have had this issue before with carbs, but not much TBI experience.

Ya'll got a bad accelerator pump diaphram! (Old holley joke).

Two gaskets might be an issue

As far as that washer, or whatever - I've never had the TB apart, so I'm not sure where that goes.

 

[Nobodys94]

So checked everything but coolant temp sensor. Not sure how to go about doing that? All the other sensors check out fine..

It seemed to do a little better this go around but once the truck warmed up to op temp and i went half throttle at a 10mph roll , it flat out died (even made a small pop)and was a pita to get started again. It has got to be lean, I dont see any other things it could be? The exhaust doesnt even seem to have much smell to it anymore.

Maybe weak fuel pump? Too low fuel pressure from regulator? I dont have a dang fuel pressure gauge out of all the tools I have. My truck has the inline fitting on the back of the TBI to check fuel pressure...

Shot another video. Its from a slow roll and only went 1/4 throttle. The throttle blips I did are not even half throttle. I barely even have to touch the pedal now to get it moving.

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Thanks again for all your help..