Vince's TBI woes, progressive revelations, and tbi mods.

[Vbb199]

Update

Did a voltage test on the tps
.65 at rest and 4.4v at WOT, with smooth sweep forwards and backwards, twice.

 

[gmbellew]

So i watched it on lunch with a "cold" start (99° lol) and IAC steps started at like 140 something for high idle, and slowly counted down until it was hanging around like 40-50. I was thinking anywhere between 30-50 counts was ok for IAC operation. At least thats from my tuning experiences.. preferably lower 30s

I did observe that when the idle blipped or acted weird, the counts would go up, then count back down. Nothing wild. Like shoot to high 50s or 60s.

I just picked up a new gasket kit for the tbi. Im gonna look into this FPR.

I did observe something today on the way back. I noticed at like half throttle, it was breaking up at like 2700, approaching 3000...

So i let off the throttle slightly and let it climb in RPM naturally, and it did go to 3000 without a hiccup.

Im gonna toss an extra TPS i have laying around on before i break the seal on my gasket kit.

I didnt test that things sweep with a dmm either
Maybe i should.

The IAC counts seem normal. Some folks like them on the low end to have more air through the throttle blades for better fuel delivery. IAC opens up when you are off idle. Mine are normally in the 90-100 range when cruising, and 120ish range with AC on. So blipping the throttle will open IAC. But if it was opening on its own with the idle being funny, that is different.

ALDLDroid should show you TPS voltage that the ECM sees....shouldn't need to get out the meter. Just key on and press on the skinny pedal inside the cab.

Did MAP change at all when it was acting up at higher RPM? Like sudden decrease in vacuum at steady throttle?

I'd spray around the tbi gasket and intake manifold gasket with some carbon cleaner to look for vacuum leaks before I ripped the tbi off.

I doubt the FPR is an issue unless you are having fuel pressure issues (forgot if you've checked under load) or if it is leaking fuel.

 

[Vbb199]

But if it was opening on its own with the idle being funny, that is different.

Thats what im saying, it was changing idle speeds on its own without me doing anything
Like someone cut the power to the truck and quickly put it back.

Did MAP change at all when it was acting up at higher RPM? Like sudden decrease in vacuum at steady throttle?

I didnt scan any longer while driving, but i'll take it for a spin in a minute and observe the map kPa. Perhaps capture a log and upload it? I recall watching it a month ago and i didng ever see anything offputting in the ecm data during the events

I'd spray around the tbi gasket and intake manifold gasket with some carbon cleaner to look for vacuum leaks before I ripped the tbi off.

I doubt the FPR is an issue unless you are having fuel pressure issues (forgot if you've checked under load) or if it is leaking fuel.

i bought a can of cleaner and i will be spraying around the tb, but i was thinking maybe that diaphragm in the fpr is torn, or the spring is weak/broken causing it to run rich

when i get on it and it breaks up at 3000 i smell misfires
Not raw gas, but stinky exhaust is what it smells like to me. And the blurbling exhaust notes after letting off the gas sounds like a ricer with a tune.

"blurble tunes"... ive done a few for some guys. Ya pull spark adv on decel as low as safely possible, and add copious fuel so the raw gas fumes explode in the exhaust... thats exactly what my truck sounds like on decel

 

[Vbb199]

I didnt scan any longer while driving, but i'll take it for a spin in a minute and observe the map kPa. Perhaps capture a log and upload it?

Havent had a chance to look at it closely, but here it is.

I turned it on while hot, went up the driveway, took it for a drive, manually shifting so it'd dwell in the higher R's, i turned around, came back home, revved it to 4000 or so, then shut it off and ended the log. Have a look whoever

 

[Vbb199]

No fpr damage but i noticed there was busted screens in the injector pods ..... worth a shot. Im cleaning the top end of the tb real good as we speak.

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[Vbb199]

Update 69.2:
That did nothing in terms of the weird idle jumping around lol

I then proceeded to spray carb cleaner around the blocked off egr, tbi, intake and vacuum lines and saw no change.

So whats next

 

[gmbellew]

Thats what im saying, it was changing idle speeds on its own without me doing anything
Like someone cut the power to the truck and quickly put it back.

I didnt scan any longer while driving, but i'll take it for a spin in a minute and observe the map kPa. Perhaps capture a log and upload it? I recall watching it a month ago and i didng ever see anything offputting in the ecm data during the events


i bought a can of cleaner and i will be spraying around the tb, but i was thinking maybe that diaphragm in the fpr is torn, or the spring is weak/broken causing it to run rich

when i get on it and it breaks up at 3000 i smell misfires
Not raw gas, but stinky exhaust is what it smells like to me. And the blurbling exhaust notes after letting off the gas sounds like a ricer with a tune.

"blurble tunes"... ive done a few for some guys. Ya pull spark adv on decel as low as safely possible, and add copious fuel so the raw gas fumes explode in the exhaust... thats exactly what my truck sounds like on decel

you'd think if the FPR were torn and leaking or somehow getting too much fuel, that the fuel trims would pick it up as they

Update 69.2:
That did nothing in terms of the weird idle jumping around lol

I then proceeded to spray carb cleaner around the blocked off egr, tbi, intake and vacuum lines and saw no change.

So whats next

does the voltage change at all when it acts up?

might also check the plugs/wires and also make sure no plug wires are touching ECM or ICM wires.

did you ever check the fuel pressure? although the trims looked OK in the log....

 

[Snoots]

Update

Did a voltage test on the tps
.65 at rest and 4.4v at WOT, with smooth sweep forwards and backwards, twice.

TBS should be very close to .5
A .65 is too high.

 

[gmbellew]

TBS should be very close to .5
A .65 is too high.

I think the ECM uses tps volts at start up as a baseline, and anything less than about 1.0 (maybe even higher) won't mess with the ECM. I think the benefit of being around 0.5-0.6 at idle is the tps has more of its operational range to work with.

 

[Vbb199]

you'd think if the FPR were torn and leaking or somehow getting too much fuel, that the fuel trims would pick it up as they

Yea i had a feeling that wouldnt fix anythinf but i wanted to check it off the list, thats for sure.

Does the voltage change at all when it acts up?

According to the logs ive viewed no, but occasionally i will see the tach bouncing which seems like EMI to me, but im not sure. I went down a rabbit hole as part of my problem solving by checking the coil voltage with key on /off and in "run" and deduced my ignition switch was so sloppy, key movement would change voltage +/- 1v lol. I thought that was an issue but alas, just improved the trucks operation but didnt solve my mystery.

might also check the plugs/wires and also make sure no plug wires are touching ECM or ICM wires.

Yea ignition was one of the first things i investigated because it acted like coil fade but after replacing the coil, checking all 8 plugs, and replacing the cap/rotor, nothing changed. Never actually changed the plugs, just checked them, they didnt look fouled so i said F it. Maybe i should toss a set in for giggles.

As far as potential EMI from plug wires touching sensitive electronics, theyre near them but not on them i think.

did you ever check the fuel pressure? although the trims looked OK in the log....

incoming pressure? After filter? Yes. 60psi with the ep381 that was in there, and now 15 or whatever with the stock pump thats in there. Didnt check while driving... i cant

Return pressure? I dont have the setup to tap in and check while driving.

TBS should be very close to .5
A .65 is too high.

I think the ECM uses tps volts at start up as a baseline, and anything less than about 1.0 (maybe even higher) won't mess with the ECM. I think the benefit of being around 0.5-0.6 at idle is the tps has more of its operational range to work with.

I can loosen the screws and probably adjust the tps to read .5 at rest, maybe even less. I swear i thought it used to sit on .45 when i installed it.

 

[gmbellew]

I usually just bend the table to adjust TPS voltage at idle.

if the tach is bouncing up high at low RPM it sounds like EMI. I used to have EMI so bad that it would even show up in the slow data stream. on a whim, you may check the ICM low reference to make sure it is grounding back through the ECM. I had a bad connection splice there from a previous repair that caused EMI. but I don't think that is what is causing it to fall flat at high RPM.

 

[Vbb199]

Ok so today while driving i was able to find a pattern of behaviour maybe.

Attached is a brief log of me playing with the throttle at 3000 rpm

I was able to climb beyond it with low throttle, and then the minute i gave it the beans it'd bog down and fall on its ass, back and forth like a switch. The 400 baud rate of the data stream isnt going to show it all happening instantaneously but what i did see was every time tps goes above 100%???? It bogs down

Whats that about.

 

[gmbellew]

Ok so today while driving i was able to find a pattern of behaviour maybe.

Attached is a brief log of me playing with the throttle at 3000 rpm

I was able to climb beyond it with low throttle, and then the minute i gave it the beans it'd bog down and fall on its ass, back and forth like a switch. The 400 baud rate of the data stream isnt going to show it all happening instantaneously but what i did see was every time tps goes above 100%???? It bogs down

Whats that about.

the TPS% being off is probably because of the .adx file you are using? i dont think that would affect things at the ECM. the TPS voltages look good. and MAP corresponds with TPS voltage - more throttle, less vacuum.

the only thing I can think of is a vacuum leak that only appears at heavy throttle for some reason. I had an intake gasket leak that was like that once. normal driving it was generally fine. but a big downshift and heavy throttle would often, but not every time, cause it to suck air and I'd have no power.

maybe pressure test the intake?

 

[Vbb199]

the TPS% being off is probably because of the .adx file you are using?

Yea thats what i was thinking, but its the only thing i have been able to find thats suspect.

the only thing I can think of is a vacuum leak that only appears at heavy throttle for some reason. I had an intake gasket leak that was like that once. normal driving it was generally fine. but a big downshift and heavy throttle would often, but not every time, cause it to suck air and I'd have no power.

maybe pressure test the intake?

Im beginning to think it myself because im also getting an annoying random , intermittent stumble/buck while cruising sometimes. In the past, i recall finally changing intake gaskets on other motors and the stumble went away