Hey guys, newbie here.........have a 406SB in my Blazer with a Frankensteined '90 TPI unit on top........24 lb/hr injectors, 52mm throttle body, custom chip. All this on top of a one year old rebuilt 400 with lots of goodies. OK, the motor has run great up until recently, so its not a compatibility issue, this combo ran flawlessly for months with no problems. What it does now is this - first, it does not have a good cold start personality - it runs like a poorly adjusted carb would until it goes into closed loop (2 minutes after startup apx.). Then it runs fine.......for a while. Then, after about 20 minutes of driving around town, you will notice it act like it doesn't want to accelerate........like the timing all of a sudden got retarded big time. Kicking the loud pedal makes it get moving again, but it returns by the next slowdown/takeoff again. No codes/no light coming on. Have replaced the EGR (had a history of EGR issues in the computer) and a new knock sensor. No change at all. My engine builder was 'sure' it was the EGR but if so, maybe its a bad one.

By the way, this motor and TPI was set up by a local guy here in Portland that has done literally over a hundred of these conversions..........mostly in Jags, but plenty of trucks. He is currently unavailable for this issue.

Anyone have any ideas on this? Fuel filter/EGR/voodoo? Help!!!


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'79K5 Blazer with 406TPI

 

Check your fuel injector resistance when cold and when warm, my bet is that the problem is with those when they warm up. They should all be 12-16 Ohms and if you find a couple that are like 8 Ohms hot then that's more than likely your problem.

Is the computer giving any trouble codes?

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1990 IROC 350
Mods: Too busy trying to make it run right to mod it.
Airfoil, Dynomax cat-back, MSD coil, 180 t-stat, Bald Eagle tires,
Hypertech fan switch, Accel 23# injectors, Holley module, ported plenum,
Ported Daytona Yellow stock base, Moroso valve covers, other stuff,
Streetdampr, Ruger P95DC, hot wife, new oil filter, !cats, !TBC, !AIR.
18.0 @ 85MPH since I'm one big-a$$ MF
"It's better to have and not need than to need and not have."

 

Oh, and WELCOME ABOARD .