Engine performance problems

Asked by Apr 18, 2017 at 05:35 PM about the 2003 Buick LeSabre Custom Sedan FWD

Question type: General

My2003 Buick lesabre custom stalls at
idle most of the time,stalls when
decellerating sometimes(both getting
worse).Ran great when I bought it a week
ago but then got codes for tpsenser and
maf senser.Replaced both.As of
yesterday it surges then
sputters,stalls,periodically idling ok but
not for long.drove in heavy rain and when
I would give it gas at 55mph it slowed
down and almost stalled.Supposed to
have a new upper intake manifold and
gasket(lower im and gasket too)but I
suspect its either Not new or is leaking
again.Sometimes doesn't kick down a
gear when trying to pass or up
hills.Another strange thing is when I take
off the oil filler cap while engine is
running the vacuum pressure is
tremendous,sucking the oil cap back on
and I've never felt/seen so much vacuum
from under the valve cover.Is it the upper
intake manifold ?Can anybody help me
here?I would really appreciate any help.

6 Answers

75,555

There is definitely a vacuum leak, and probably from the intake manifold gasket.

1 of 1 people found this helpful.

Thanks

75,555

Your welcome.

Update:My car became undriveableshortly aft3r last post.took it to shop I trust.He cleared the codes (tps,maf,there new)also cleared the computer.Mech. had no problem.Ran pretty good last night.Started it today and ran ruff,gave it a little gas so it wouldn't stall,lasted about 2min then ran pretty good.Stalled once going down hill 40 mph.Downshifted good under load.Till I drove home,on highway was not downshifting under full throttle.even when I came off exit and was 25 miles an hr,full throttle would not downshift but was downshifting good the whole time after clearing computer.no check engine light yet.acts up like that after highway driving but all day ran pretty good so so far intake manifold is ok.Does the computer need to b reprogrammed or something or will it gradually get better after the computer was cleared?It's not perfect yet but much better and driveable.

75,555

in doing a little research on this, what I am seeing is there may be a problem with the PCV valve, where it plugs into, usually with a small "O" ring. I see a kit with new seals and spring you can get, not expensive at all to do. It is a positive crankcase system so the crankcase creates pressure that is equalized threw the pcv system, it is not suppose to create vacuum. This problem is a vacuum leak, and could be causing some of your problem. Check out the pcv valve and system. Another cause is relating to the lower intake manifold gasket, or cracked intake or warped intake manifold. There is more to this issue that needs to be investigated. Here is what your looking at with the pcv valve on this sight... https://www.carid.com/acdelco/gm-original-equipment-positive-crank-ventilation-valve-kit-mpn-89017274.html?singleid=73490016&url=493683

Did you ever figure this out? Sounds like fuel injectors to me. I had that problem in my 1998 Monte Carlo. Happened after I put crappy gas in my car. My husband didn't believe me and went back to the same gas station and it happened again.

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