I've been through the wringer.......
I restored a non molested 1989 Formula 350 TPI for my Brother a couple years ago. Recently he brought it to me with a new problem.
It has an intermittent stutter and is running rich.
Also the TCC does not engage but the cruise works fine.
Transmission shifts properly. TV cable is set properly. Trans filter and fluid replaced.
There is no check engine light. It does not suffer from a lack of power. At WOT is runs like a bat from Hell. Here is a list of what I have replaced just to be sure.
New Distributor with all new components.
New plugs (AC delco gapped correctly)
Wires. There was no arc. with the old wires, just wanted to be sure by replacing them.
New Ignition coil.
I swapped the ECM with PROM from my own 1988 350 TPI GTA. The result was the same stutter on the Formula.
I added an additional ground cable from the Ignition coil mount to the firewall. The OEM braided ground strap is in excellent condition along with the battery to chassis ground as well as the battery to engine ground.
PCV is not clogged. There is no vacuum leak on either hose.
The voltage at the ECM battery terminals as well as the grounds are good.
The alternator is charging correctly and the battery is new.
All sensors have been tested and check out good i.g. MAF,TPS,IAC,CTS,IMT, etc.
TPS, IAC and base timing have all been re calibrated. There was no change when the EST was disconnected.
There is no change when the vehicle warms up. Cold or hot makes no difference.
Fuel pressure holds steady @ 41 PSI after key is off. I followed the troubleshooting chart and determined the injector o-rings are good.
FPR diaphragm and spring replaced, checked .
Vacuum tested after check valve and holds steady. All vacuum lines are good and not collapsing under vacuum (not soft).
Injectors replaced with Bosch type 2 and all ohm out within tolerance when cold and heat saturated.
Voltage @ injectors checked and is good.
Harness on top of engine checked and is good.
I decided to remove the plenum and runners to check the EGR and it's function. Here is what I have discovered. The EGR solenoid was opening and closing vacuum however it looked very rough. The casing had degraded and the coil windings were turning green. I decided to replace it with the 1994 Caddy upgrade I read about in similar threads. The EGR itself is intact. It holds vacuum and after removing and inspecting it is clear of any carbon deposits. The EGR temp switch had continuity at room temperature. If I'm not mistaken it is a normally open circuit. I have ordered a replacement. I will also be replacing ALL hard and soft vacuum lines as well as nipples. I did discover a crack in the hard line from the plenum to the FPR. After reading the shop manual in depth I discovered the EGR function was not being asked for from the ECM as my Park / Neutral switch was misaligned. I have corrected that as well. The car did not start in neutral which is why I suspected a problem. I am replacing the injector o-rings and plenum / runner gaskets upon reassembly. I am currently waiting for the EGR temp switch to arrive. A new o2 sensor is in the works also.
I also noticed a discrepancy in the vacuum diagram for 1989. The plenum does NOT have a vacuum tap in the front directly under the throttle body. I have modified the diagram to depict the routing I will take upon reassembly. I assume the EGR does not need a constant vacuum supply therefore it does not need a connection after the check valve but before it.
Please see the diagram and photos for the detail.
This is where I stand so far. I would appreciate comments from senior members with experience.
I will be updating this thread once I have it reassembled.
Mike M

 

Why are you posting TPI info in the TBI forum?

 

Sorry, I'll edit or delete when I get home today from work.

 

Please delete this thread. I will gladly repost it correctly after work this evening. I have learned that two of the images I uploaded are incorrect. I'd rather delete it than move it.
TNX MM