chasing gremlins......

[quietfly]

I have a 95 TBI hoe with 186k on the clock. Recently she's developed a low end bog, between 500 and 1400 rpm.I've been noticing it more while placing her under heavy load, for example while towing my boat at low speeds. thinking the issue was plugs or wires, i've just did a tune up that included wires , plugs, cap, rotor, map, EGR valve, EGR solenoid. When i pulled the plugs they all looked about the same, so no obvious detonation or fouling on any of them. She ran much smoother after the tune up, however still has the low end bog. my next "step" is a TBI rebuild kit, or possibly a replacement Holley TBI unit. but at 500.00 for a not guaranteed fix. i'm a bit tentative to spend the dough.

Anything i could be missing? tips, hints, comments? Let me know


-chris

 

[SunlitComet]

try dumping some Chevron Techron fuel injection cleaner in your tank before you do the whole tbi. Perhaps you injector are cloggy.

 

[Dpsthomas]

x2 , I had a similer problem a while back. I gave it a full tune up. Problem still there. Sea foamed it, cleaned the throttle body as best I could, and used injector cleaner on nearly every fill up. Problem went away.

 

[gpracer1]

Had a similar problem on my 93 but I replaced waaaay more than you did. Had an off idle hesitation as if it had a bad carb accelerator pump. Replaced everthing including map sensor, O2 sensor, entire Holley TBI, and it seems the fuel pump fixed it.(needed to replace due to bad sender anyways)

Not sure if the EGR would cause that problem, but you can check it.

 

[ncdrtyhoe]

seafoam the heck out of it! I had a 90 K5 that smoked like crazy and the o2 sensor had the CEL on and no power on low end rpm 3 tanks and 3 bottles of seafoam it was all good after that!

 

[quietfly]

i've run seafoam twice through her and not sure i want to go a third time. I'm debating if the TBI injectors could be the source. i'm thinking about :
A) replacing the injectors
B) rebuilding the TBI body
C) purchasing complete new Holley 675 CFM TBI

 

[ezdaar]

No need to rebuild the TBI unit.
Theres nuthing to rebuild unless you want to replace the regulator spring and diaphram. Look Here To make your FPR adjustable, or Buy the kit...

You can however pop the injectors out and clean the screens on them, as they tend to clog up.
You can do it with TBI on vehical. Just pop the top off and use flat blade to pop them up and out.
At base of injectors, you will see the screens, pullem off and scrub them clean with worn out tooth brush.
Rebuild kit
This is the bad boy That I have been talking about in other threads, I used multiple gaskets as I had plently laying around (also was not avalible). It makes a noticable improvement, Even on the Holly TBI unit...

About the only thing to clean on a TBI is back of blades and IAC passage.
Both can be done while on vehical. use Berrymans B-12.
Just hose down the IAC passage a few times then blast some compressed air through it. repeat a few times and it will come clean.

When you take out IAC valve, look at its tip, if its got a weird wear ring thats uneven around the plunger, replace it. That is a sign of the shaft bushing being worn out.
If the wear pattern is even around the tip, whie holding it FIrmly so it doesnt rotate. use some 4k grit paper and freshen it up. remove that wear ring but be gentle.

I currently have a 670TBI forsale, if the 2 guys fall through. Ill post it up and you can snag it..

Go ahead and finish your ingnition tune up with this control module you will notice a immidiate improvement in starting, idle and all around performance... This has been installed in ALL of my early 90's chevy/gmc's and reccomend it to all my friends.

 

[quietfly]

hey EZ thanks for the links and tips... i'm going to try cleaning the screens and modding the FPR to make it adjustable. do you really think that 21.95 spacer from CFM would make that big of a difference?

 

[ezdaar]

YESS! I dbl gasketed every single one of mine and my buddies TBI setups, both the injector pod and the TBI unit itself.. This was before nifty little items like that pod spacer was avalible.
it lifts the injector pod up and out of the throttle bores, This Doubles the amount of air that can pass between them.
Its the most benificial mods to do to a TBI unit.. Other than milling off the throttle bore horns.

Did you happen to look at the TBI baseplates they also offer?

 

[quietfly]

i looked at them, i'm just worried about spending money on it if i'm going to replace it