Car runs great exept when at minimal throttle, like you would give it when slowly accelerating from a stop light.

Stumbles and hesitates. Today started the rumblings of a possible backfire. Nothing major but definate loss of power for as long as 3 or 4 seconds. Give it more accelerator peddle and the car recovers. Can happen when cold or hot..but normally 2-5 minutes after the car is started.

Can't recall exactly when this started happening but I've done continious modifications to the motor since last year so I'm not sure of the exact culprit. Just wondering if anybody has had the same problem.

Thanks!

Marty

I've got the same problem in my chevelle. Im running a 350 with a tpi, using the commander 950 ecu. The other board i post at said that its a lean miss. I havent been able to get ahold of a laptop to get my engine tuned perfectly, so im just being easy on it. Hope it helps yah out
Chris

Hesitation (and even a slight backfire) at throttle tip-in isn't uncommon with a TPI. There are ways to minimize the phenomenon, however.

Start with a clean throttle body and IAC. Make sure the TPS voltage is no lower than 0.50VDC. With the engine fully warmed, perform the throttle minimum air position adjustment procedure, but set the minimum position RPM to the higher end of the scale, like 525-575 RPM. Reset the TPS voltage if necessary.

This procedure still allows the IAC to control idle RPM, but causes some of the idle air to flow around the throttle plates instead of strictly through the IAC air passages. If there is little or no throttle opening, the air in the plenum just behind the throttle plates is basically static, and will need more time to begin moving when the throttle plates are opened.

A dirty, sticky, or poorly calibrated PCV valve can also contribute to the hesitation and lean tip-in phenomenon.