1988 Delta 88 Missing or Lugging?

There is about 170,000 km (100,000 miles or so) on the vehicle which has a 3.8 L engine, and within the last 20,000 km, the coils, spark plugs, spark plug wires, and oxygen sensor have been replaced as I had a cold weather starting problem. The issue was cured when the coils were replaced. Resistance was going high when it got cold. I also checked and cleaned the Mass Air Flow sensor, and a few other items at that time, before a helpful contributer here tipped me off about checking the coil resistance.

That was about 2 years ago and now I have a new problem. When you accelerate up to about 80 km/hr (50 mph), the engine has lots of power, shifts smoothly, and does not give a hint of a miss. However when you slow down some, then try to accelerate slowly again, or climb a hill, the vehicle bucks and jerks as if it is missing big time. At first I thought I had an ignition problem, but with not much left to replace, I'm wondering if I really have a transmission down shifting problem. My theory is that after the transmission locks up in overdrive, it does not shift back down when you try to accelerate or climb a hill. No tach on the vehicle, so I can't tell for sure what the RPM of the engine is when the bucking happens. You can get it out of this condition by stepping down hard on the gas, but not by the normal amount you would to slowly speed up or climb a hill.

In this model year can you give me some hints as to what causes this TX to shift down? Shifting up seems to work during acceleration. Is shifting down initiated differently than shifting up? My Haynes manual does not seem to help much and briefly talks about a throttle valve cable adjustment, and mentions a vacuum modulator.

I do have a code 41 (camshaft sensor) in, but it has been there a while. I replaced the sensor about 2 years ago, and the code went away. However, having it in then, really caused no issues, and nothing changed when I replaced the sensor other than the annoying check engine light went out. So I'm thinking that is not likely the problem, but could be convinced otherwize if anyone has experience to the contrary.

Thanks for any tips or information you can provide,

Ron

This is an easy one. Your ignition module is bad. It sits under the coils so what you need to do is remove the entire module (3 11mm nuts) and take it to a parts store (Autozone, Oreily) and have it tested for free just to be sure. More details: http://www.3800power.bravehost.com/delco_type_2_ignition_upgrade.htm

And for your code 41 read this: http://www.3800power.bravehost.com/code_41_information.htm

This can be caused by an ign misfire, failing lock up in the torque convertor or even a bad tps. By downshifting you are unloading the engine and the TCC is disengaged, as well as reducing the load on the ign system, I have seen a bad plug/coil/wire cause this as well as the TCC and even dirty injectors ( rarely though).

I called the garage that put the rebuilt TX in a few years ago and described the symptoms. He said they hear it all the time and see it in test drives. He offered to test drive it, but said he was almost certain it was an ignition problem.

So I decided to take on the ignition system and started with the coil unit. All the HV coils tested fine at about 8.5 kohms. Then tested the plug wires. All were between 12.5 and 13.5 kohms, except for two (1&6). They tested as open even on the highest scale on my meter. So much for Neihoff silicone quality -- two years and 2/6 failed. Put in new Bosch silicone ones and now it runs fine.

Thanks for the help. I will check out the code 41 link.

Ron