97 Bonneville problems

3.8 non-supercharged 103K. Plugs, wires, all coil packs replaced, fuel filter, air filter, intake leak, injectors cleaned 6 months ago. The MIL light has been coming on and off for some time. Runs rough or starts rough at a low idle. I get P0305 cyl 5 misfire and P0171 system to lean bank 1. What can I do to fix these issues? I just got a Actron CP9180 scan tool to get the codes.

Welcome to AF. Still could be a bad injector, try switching # 5, see if the misfire code moves with it. Make sure you have the proper fuel pressure also.

What do you mean by switching #5?

He wants you to swap #5 fuel injector with another. Swap #3 & #5 and see if the miss moves to #3.

How's the coolant level - has it been dropping?

All the above problems were solved by replacing the fuel pump. But of course I have a new problem. Code p1870 Transmission Component slipping. It has shifted hard since the fuel problem was solved. My freeze data shows that the problem exists at 58 mph in fourth gear. It sounds like I need to replace the valve body from what I have read. the Torque Converter Clutch (TCC) seems to be tripping the Powertrain Control Module (PCM).

How easy is this to do on this car? If not easy how much might it cost to have it done?

The valve body can be repaired for the common issue of the tcc valve bore wear, some special reamers must be bought and it is a messy on your back job, check with Sonnax.com for the info. Of course this assumes this is the source of the code. Internal pressure losses all set this code.