Frequently Asked Questions

1985 TPI systems had an ECM and other electronic components that were only used for that year and a 1985 TPI ECM will not work with our 60102/60202 harness.. The intake parts can be used if converted to an '86-'89 or '90-'92 control system. The early TPI units from 1986 through 1989, have a MAF or Mass Air Flow sensor to measure the amount of air entering the engine. The early TPI also has a 9th injector to inject extra fuel during cold starting. The late TPI units from 1990-1992, use a MAP or Manifold Absolute Pressure sensor, which uses vacuum to help calculate the amount of fuel needed. The late TPI units do not have a ninth injector. Instead, they inject extra fuel from all eight injectors during cold starting. Our TBI and TPI harnesses also plug into a 700R4 automatic transmission. The TBI and the early TPI systems use a 2-pulse speed sensor and the '90-'92 TPI and LT1 use a 4-pulse speed sensor.

Yes, as long as it is not too radical. MAF and MAP systems use vacuum for fuel pressure regulation. The late style TPI uses a MAP sensor, which measures engine vacuum. A cam other than stock lowers vacuum, which could cause the MAP sensor to assume the throttle is open. It would inject extra fuel to compensate, creating a fuel-rich, rough running condition. An adjustable fuel pressure regulator or custom after-market chip may be required with either type of system using a non-stock cam.  Give our tech line a call for information on what to do with your specific application.

First, You would use a 60103 or 60203 Painless Wiring, speed density TPI harness. Change the computer to the late style unit with a non-VATS PROM, remove the MAF sensor and add a MAP sensor. Next, change the knock sensor and eliminate the electronic spark control module. Change the speed sensor from a two-pulse to a four-pulse sensor. The manifold, injectors, and most other sensors are the same. If you have a ninth injector on the manifold, it would not be connected.

Replace the fuel pump and add a return fuel line. Install an oxygen sensor adapter in the exhaust system. Replace or modify the alternator and AC compressor brackets. A different style air cleaner is required. A different ignition distributor is required. Throttle linkage, wiring and other small parts will need to be replaced or reworked.

Chevrolet had three basic TPI systems, other than the LT-1. The '85 TPI, which used the same intake manifold system as in '86-'89, but had its own ECM and other electrical parts that were only used that year, '86-'89 mass airflow (MAF), and '90-'92 speed density (MAP). Painless does not have a '85 TPI kit, and our 60102 and 60202 TPI harnesses WILL NOT WORK with a '85 TPI ECM, but the intake from a '85 TPI can be used with a later harness and components. The '90-'92 MAP system is a little easier to install and has a cleaner appearance because a MAF sensor doesn't have to be mounted in front of the intake like on a '86-'89 system. The '90-'92 MAP TPI systems are the ones you see with the air cleaner attached directly to the front of the intake. Driveability is the same for both systems when installed correctly. As for which year to use, the best advice is to go with the system you have the parts for.

PROM is short for Programmable Read Only Memory. They are also called a chip. The prom is inside a bolt-on cover on the engine computer and it contains specific information as to the engine and vehicle combination. Factory PROMs have different information depending on transmission type, gear ratio, accessories, and other things. Early GM TBI computers also have a removable Calpack in addition to the PROM. Aftermarket companies like Hypertech and others can custom make a chip just for your specific application. If you've made any internal changes to your engine, a custom chip is recommended.

You also need to change to a MAP-style knock sensor. A MAF-style knock sensor will hook up to a MAP system but it sets the code 42. See our parts list in the instruction manual for the correct part number.