Won't downshift
 

My battery died a month ago and after I replaced it, you can imagine all the things I had to reset. After clearing all the instrument lights, resetting the radio and windows I have one remaining issue. One big issue.

My '99 430 has a serious power loss. It won't downshift at all and if I try to give it too much gas it gets sluggish and won't respond. I believe the power has slowly increased, but will still not downshift. Is this the car "learning" the power all over again or something more sinister?

I've read a bit about the ECU and think this may be it but I don't see my car returning to normal because progress has been slow. Will the downshift come back on it's own?

I can't stand not having that lovely V-8 respond with the roar I'm used to! Please help! :confused:

Mine downshifts fine, but has been refusing to give power over 1/2 throttle. I'm waiting on a MAF to come in. Just like yours, it doesn't want to do anything when the gas is aggressively pushed.

I had my codes pulled and came up with these:

P0170 - Fuel Trim Malfunction (Bank 1)
P0173 - Fuel Trim Malfunction (Bank 2)
P0161 - O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)

From what I've gathered here, the first two codes can cause the third one to trip and a MAF will fix it. I ordered one along with a fuel filter this afternoon. We'll see...

yep,

That's the same code I have. MAF related.

I already replaced both O2 sensors and it only "helped" a little.

Do a tranny service and reset the tranny.

Installed the MAF today and my car now runs better than I ever remember it running! :zoom: Took 5-10 minutes and after the test drive and 6-weeks of wondering what the hell was wrong with my car, I can safely say that was the best 5 minutes I ever spent.

Thanks to everyone who posts and allows others to learn!

Word.