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Going up hill I lose power stalls stammers can't keep it running - just started - WT?

GT2001Aurora

New member
2001GT - A long run down to see if anyone has had this issue, even the auto shop is baffled so trust me when I say DO NOT jump to a conclusion after reading one or two symptoms as this just gets better and better.

To start the temperature has been low here in IL the last few weeks so nothing new there (-5 to 15 in the morning) but my car is kept in 45 degree garage then each morning down the road 1.25 miles before getting onto the highway. I have had zero issues all winter.

I filled up with gas Tuesday night, almost down to 1/4 tank, I always fill up, then drove 1.5 miles home and into garage for the night. Next morning off to work and about 3 miles into commute a sudden lost of power. Lights on dashboard/instrument panel looks okay, not a dead alt. or battery this time... dang did my trans go out... no wait it's like the engine sucked in a huge bug and is choking on it - seriously. Thank God there's an exit ahead so I bail pushing on gas pedal but no power, I can't hear the engine from the road noise/cars around me.

On the exit ramp I come to stop as the car stalls out. I smell rotten eggs? Look under hood and all seems okay, no chewed wires, etc. I was able to get the car started but really had to work the gas pedal and work it until RPM increased then quickly into gear and work it more to get it moving. At the intersection it would stall and a bugger to get moving again but once moving it was easier to keep it moving.

Pulled into auto shop and figured I'd back it into a spot while it was still running. As I'm in reverse a restore to full power out of nowhere and all seems okay now so I drive it around the lot and it's as if nothing ever happened.

Auto shop can't figure it out, codes indicate Mass Airflow Sensor or MAP sensor, they replace, we test drive and punch it a few times getting up to 70... all seems okay again.

Next morning back on the highway and BAM!!! Right as I'm going up that incline, the same spot the previous day, (it's IL folks.. no big hills here), it does the same crap again and struggle to get it back to the shop with is about 4 miles away.

Auto shop takes it for a spin later that day as it's running fine again but discover I'm right, it goes haywire when going up hill. Mechanic smells something hot, of which I recall too like rubber burning not to mention sulfur once, so he checks under the hood and notices the exhaust pipes behind the engine are glowing red. Said he's never seen that before, only when welding something. He also said he was stalling out and very hard to start... awesome they duplicated the issue but wait, he said it was hard to start so he would clear the check engine light and now the car would start up and run okay until going back up a hill, the hill where the road goes over a train track, about the height of two warehouses.

They are stumped. It could be something in the gas is what I was thinking but that does not quite explain the glowing pipes and clearing the code... does it? And what would be in the gas that only gets sucked up when going up hill? I throw this in too, back this summer I would smell gas in the garage after a fill up, drive to work and next day all was good. That continued until the cold weather came in Dec. or maybe something on tank broke... I freaking don't know anymore but perhaps that comes into play somehow.
 
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year of car? miles, engine in it?

sounds like a clogged cat. just like bananas in the tail pipe. it cant exhale. you go up this hill maybe a chuck of broken cat blocks the exhaust pipe.
 
Yup clogged cat.....you need a new auto mechanic if they can't figure it out. Red hot exhaust pipes are a dead giveaway.
 
It's a 2001 GT, 3.8 and the cateletic converter was replaced 2 years ago, when it went bad there was a total loss of power that never came back. Can't imagine the cat died in two years, but you might be right, something plugged it. HOWEVER, that doesn't explain why the car starts working perfectly normal again after they clear the "Service Engine" light, or why it starts working again after driving it a few miles as that what I assumed happened, I struggled to drive it about 3 miles to the shop but then it just cleared right up as I was backing into a parking spot. It almost seems like something in the gas tank is getting sucked up as I drive up hill and then it takes a while to flush out or for the system computer to reset/recalibrate.
 


the honeycombs in the cat break, fall apart, then block the exhaust flow and its temporally clogged till it bounces and clears. a hammer taken to the cat can clear it when this happens.

what code comes up that they cleared at the shop? does the check engine light flash when its acting up when you floor it? if so likely the cat.

what brand cat did you use 2 years ago? if it was cheap that could be why. if its a dealership factory cat and down pipe, id be looking to see if its got a warranty.
 
Not sure what brand it was, I took it to a Chevy dealership at the time because FireStone couldn't fix one of the codes coming up. Dealership said good and bad news, your cat is dead and I about dropped dead seeing $$$ but then he said there's a GM recall. I'm hoping the dealership put in a better brand over what Firestone would be never know.
 
call the dealership up, never know they may replace it again. never know.

if they dont replace it. you can buy a new 2.5 or 3 inch down pipe, for like a 100 bucks. then add a hi flow cat off e bay for like 50 bucks. have the shop weld in the cat. your under 200 with shop labor i bet.
 
I'll call the shop in a little bit and see what they have to say about the cat and if they can check it. I'll keep you posted.

So wow, looks like things in Texas are bigger there 99GT2dr
 
gut the fking thing, cut the pipe off after the cat, take a bfh and a steel pole and go nuts, start car to blow it clean, weld pipe back on and done.
 


Seems a lot of people still believe it's the catalytic converter but it's not, they ran tests and it checks out fine so glad I didn't take a jackhammer to it, torch it, etc. They found the problem, the MAP sensor. It was originally throwing a code that the Mass Airflow Sensor and MAP Sensors were bad. These two sensors go hand in hand, almost seems like they should be one sensor if you look at what they do, so the problem is that typically the MA goes bad and will throw off the MAP.

They replaced the MAP sensor and the drove it up and down a hill and then out on the highway with no issues. They put the original Mass Airflow sensor back on and ran it up and down the road again, no issues. So they didn't charge me for the MA and the MAP was half the cost. Most repair shops would have replaced both right off the bat and changed me $800 and then try to tell me the catalytic was bad so another $1500. Not these guys, in my book they were outstanding for all the work they did and only $219. This guy owns his Tuffy auto shop and his goal has always been honesty, hard to find that now days but I couldn't be happier.
 
Who pays that much money for anything???? Sheesh, 5 minutes in a junkyard and you have what you need all for 20b bucks. And 1500 for a cat??? Buy a catted dp for 175 and call it a day.
 
"Auto shop can't figure it out, codes indicate*Mass*Airflow*Sensor*or*MAP sensor, they replace"

"Next morning back on the highway and BAM!!! ...it does the same crap again"
 
I guess they could have replaced both up front, $800 and I would have been done with it. As of right now they worked it down to just the MAP senor, sort of the hard way. That's why I'll be taking it out today for a spin, on a Saturday as to a weekday. Around here you'll get killed if your car breaks down on a highway, happens all the time, someone crashes into you. Not a pleasant feeling having a hundred cars per minute going by at 70 to 80, your car rocks back and forth. Even the police will pull up and tell you to get the hell out of here if you can, if not come with me. So going to a junk yard and pulling parts might work for country driving but not when your life literally depends on something dependable.
 


Hahaha. Junkyard mafs are 100% more reliable than the ones you get at parts stores. But hey, pay 800 for nothing.
 
I have a MAF sensor for sale, verified working in perfect condition, willing to let go for $400 shipped.
 
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