Thread: Losing power driving down the road

Alright... This is an odd one. Driving along at 80mph today the car starts losing power. If I push the throttle further it just loses more power. It runs best under 2000rpm moving down the road and just slowly degrades until it won't hold 55mph. If I pull over & let it sit for 20-30min it restarts normally and drives fine until it starts to degrade again. I drove it 100miles home this way. Replaced the fuel filter along the way thinking it was clogged. Gas mileage plummeted as I drove from 25 down to 16mpg avg over the last 50miles. It finally threw a code of P0131. I can imagine why as badly as it was running. No idea.

well...P0131 is low voltage on your Heated O2 Sensor bank 1. So...check out the sensors connection (it'll be the front O2 sensor, on the back of the motor, in the rear manifold)

See if the connector is in good, and if all the wires are good (not burned, or split)...
Then just go ahead and replace the sensor, because it probably needs it.

(with a bad O2 sensor, it'll think the engine is running lean/rich skewing the fueling, reducing power, and killing gas mileage by dumping in too much fuel.

From driving it, the O2 sensor code seemed like more of an effect than a cause of the problem. Never had one go bad instantly where the car would accelerate under boost one second & the next not be able to maintain the speed limit because it instantly falls on its face as soon as I give it barely any gas. The cel didn't pop up until 90 miles after nursing it along.

Wonder if the cat is cloged?

Not the cat. It has full power when cold. Builds boost & accelerates fine. At this point I'm wondering about unplugging the o2 sensor to get it to my dad's house where I have 4 of them sitting.

Cold most cats are fine. They act up when heated up.

Drive it at night.. then look under after a spirited run..is yoru cat glowing red?

Update: Drove the 110miles to my dad's yesterday where I can actually work on stuff. I decided before I left that I'd unplug the O2 & see what happens. Of course, it threw the P0134 (O2 sensor inactive) within the first few miles. But it was driving fine. Not any different than normal. Reset the DIC before I left and it was even doing 27.4mpg at 70mph for the first 45miles without the O2 sensor plugged in. Then, it was all downhill from there. Within a few miles after that it was all I could do to maintain 45mph uphill. If I could keep it below 2000rpm it will pull itself as long as I didn't give it much throttle. Too much throttle & it just bogs. At full throttle it will show boost about halfway across the gauge but it's totally bogging & losing speed. I plugged the O2 back in and no change except back to the P0131 code. Sometimes I could eek it back up around 65-70. Thanks to tall gearing. Got it back to my dad's and it just sits there sputtering & shaking at idle. Made me think it was the crank sensor being freaked out. Started replacing that but a big storm came through & knocked out power so we couldn't find the puller in the garage to take off the pulley in the dark. Power never came back on so I ended up taking dad's truck home for the week. Won't be able to work on it again til the weekend since I have to go to Canada for the week for work.

Could be the cat I suppose but I'd think it would act up a lot sooner than 45miles down the road.

Fixed! Well, it wasn't the cat. Or the crank sensor. Or the ignition module. This week when my dad was driving it, it melted a fuel pump fuse. A problem I was having before & I replaced the pump & hadn't had the problem again. Long story short, the socket that the fuse plugs into was loose on the top side so as the engine compartment changed temperature it loosened its grip on the fuse causing arcing, melting one side of the fuse. And evidently causing the lack of power issue. Basically, fuel starvation with the fuel pump not getting full power. So, my original fuel pump was probably ok too... I hate electrical problems!

I was wrong. Apparently, it was the cat. I just had multiple problems going at the same time making this hard to diagnose. Drove it another 180miles before the cat re-clogged itself to the point I couldn't keep the engine running. Cooled back down, ran fine. Cut the cat, gutted it. We'll try again. I can't remember when I had such a problem child of a car. This week it's throwing a MAF code. I have 2 of those sitting around so I'll swap that out. Running out of things to replace, thankfully.

Well... It's doing it again. I think the clogged cat was an effect not a cause. When it goes to freakout mode now without the cat I can tell it's running very rich. Could have overheated the cat that way & caused it to fail. I drove it almost 2k miles since gutting the cat without problems. Hot day on Sunday, engine heatsoaked from stop & go traffic. Blah... back to bogging. Had to pull over & let it cool. Restarted & ran fine the rest of the way home. So far so good this week in my 40mile commute. Since it goes way rich I'm starting to wonder if one or more injectors go static when it gets hot and it's flooding out the engine on a few cylinders. Or the PCM is jacked & telling it to overfuel like crazy.