Any TBI troubleshooters out there?

[Chevy3+3]

I'm having a tiny problem with my'88 V30 454 tbi truck not running quite right. its hard to put my finger on. To describe it best is it feels like when trying to accelerate under normal load that my power comes & goes a little. Almost like my fuel & air mixture is changing or my timing is searching. The trucks base timing is at 6-7 degrees BTDC (computer wire unplugged). The truck idles great. Runs good but not great at WOT. The exhaust smells RICH but don't notice any black puffs from tailpipes. It never backfires but occasionally has a weird floaty hollow pop sound from tailpipes at idle. Its very faint.

To describe it best is a slight hesitation just off of idle (occasionally), somewhat sluggish come & go acceleration through midrange almost like I could have a vacuum leak. If I push the throttle more is seems to come out of the sluggish acceleration until I hold the throttle stationary again. It almost acts as if its responding to getting more air for a split second when I apply more throttle. At idle and WOT it runs the best.

I've tried a new distributer, old working distributer, 2 new Delphi fuel pumps, new fuel filter. Triple checked timing, Triple checked and cleaned all grounds, I have sprayed every possible location searching for a vacuum leak and have found none. I've checked the EGR valve and it holds vacuum. The truck doesn't display any codes or check engine light.

I'm wondering about the TPS, MAP sensor, IAC valve or EGR solenoid malfunctioning?

Any thoughts or ideas would be appreciated. Thanks in advance

[Pano]

This may help

http://www.73-87chevytrucks.com/tech...TBISystems.pdf

[Desert1957]

I can tell you on my 87 350 TBI setup needed a a reprogrammed prom for the ecm module. After an engine swap I experienced a lot of the same symptoms you are describing.

I think for my setup Just adding true dual exhaust and a performance air cleaner made the mid range too lean. The new computer prom fixed this problem for me.

My truck had more throttle response, more power , no surging and as a plus got better fuel mileage.

Might be someone on this forum who sells these. I found the guy I used off ebay.

This guy was great to deal with. Call him.

http://tbichips.com/

[Chevy3+3]

Originally Posted by Desert1957

I can tell you on my 87 350 TBI setup needed a a reprogrammed prom for the ecm module. After an engine swap I experienced a lot of the same symptoms you are describing.

I think for my setup Just adding true dual exhaust and a performance air cleaner made the mid range too lean. The new computer prom fixed this problem for me.

My truck had more throttle response, more power , no surging and as a plus got better fuel mileage.

Might be someone on this forum who sells these. I found the guy I used off ebay.

This guy was great to deal with. Call him.

http://tbichips.com/

Maybe that's part of my issue. I forgot to mention that I did switch the intake to a TBI specific Edelbrock intake when I replaced my intake gaskets. I'm not sure how that could necessarily alter the tune I need but anything is possible. I didn't notice this problem immediately after switching the intake either. Its something that has gradually started I think. The problem is also worse when my truck is warmed up or outside ambient temps are warm.

Do you recall how much you spent for a reprogrammed PROM?

[cheepin]

Why do you have your timing at 6-7 advanced with the comp disconnected? Isn't it supposed to be zero?

[Chevy3+3]

Originally Posted by cheepin

Why do you have your timing at 6-7 advanced with the comp disconnected? Isn't it supposed to be zero?

A big block is 4 degrees initial from factory. A 350 is zero

[Chrispbrown36]

Just found this tonight....it's the most information I have ever seen on how a TBI functions.
http://chevythunder.com/fuel%20injec...g%20pg%20a.htm

[Chevy3+3]

Originally Posted by Chrispbrown36

Just found this tonight....it's the most information I have ever seen on how a TBI functions.
http://chevythunder.com/fuel%20injec...g%20pg%20a.htm

Wow! That's a good read. Thanks!

[Desert1957]

Originally Posted by Chrispbrown36

Just found this tonight....it's the most information I have ever seen on how a TBI functions.
http://chevythunder.com/fuel%20injec...g%20pg%20a.htm

How much of this article crosses over to "TBI" ?

Pic at the top shows a "TPI" intake, Just curious.

[Chevy3+3]

Originally Posted by Desert1957

How much of this article crosses over to "TBI" ?

Pic at the top shows a "TPI" intake, Just curious.

I saw that also but being that most of the sponsors are the same i would assume it would be the same

[Chrispbrown36]

I skimmed through it and as far as I saw he just mentions similarities between TPI and TBI but focuses on TBI.