1998 Buick Century Hesitation/Stumbling

1998 Buick Century, 3.1L V6, 4t60E tranny, 120K miles.......

very sluggish acceleration and stumbling/hesitation in all gears under load only after warmed up - especially bad on hills/inclines - mostly on light acceleration, if kick it down, it will go - no problems when engine is cold - engine runs fine in park or neutral, warm or cold - no vaccuum leaks have been found.....Also, terrible gas mileage now - no OBD-II codes

changed TPS as it was in bad mecahnical shape when removed - improvement for 1 day, but problem quickly returned - removed and cleaned MAF sensor - no improvement - driving with unplugged MAF sensor makes it run fine (except for CES light of course) - should I replace MAF or I am just masking the root cause by unplugging MAF ?

EGR valve problems also perhaps ?

Please help - do not want to throw money at every possible cause (MAP, EGR, MAF, O2, Coils, Ignition module, wires, plugs) as others with this problem have without success...

You should be able to find a cheap MAF sensor in the junk yard for that to throw in it.

That's your best bet if you unplugged it and it runs fine.

Highly unlikely that it is anything else, unless the problem just coincidently went away at the same time you unplugged the MAF.

Do a few more cycles to make sure that it always goes away when you unplug it and you probably have your answer.

If you had a scanner you could check the readings of it to the norm for those cars, but if not I would do the above and then find a cheap used one, clean it, throw it in and see what happens.

Hope this helps!

Let us know how it goes!

- Dale in Idaho

Thanks Dale.

FYI - Checked the input and output temperatures of the catalytic converter - much hotter leaving the cat than entering so all seems to be good on that front.

Changed the MAF and EGR sensors with parts from the boneyard - MAF made no difference but EGR that came off had a pintle that could be pushed in and out with just me blowing on it......pintle on replacement EGR was solid and could not be pushed in (btw, digital/linear EGR on this motor) without being connected to motor......much better now.....will keep you posted if the problem returns.

Could a fualty EGR cause this problem ?

Txs

Yep faulty EGR valves can create some crazy symptoms/problems and affects different cars in different ways...crazy but yeah..