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Ask Tim Mohr Your Own Question
Tim Mohr
Tim Mohr, ase master
Category: Mazda
Satisfied Customers: 15723
Experience:  30 yrs experience in Foriegn and Domestic, Gas and Diesel
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2001 Mazda Protege 1.6 low power. with the car idling i feel

Customer Question

2001 Mazda Protege 1.6 low power. with the car idling i feel exhaust flow out of the tail pipe
, but it almost completely stops the flow when pressing the accelerator. like its getting blocked
I have checked the cats and the muffler in at the tail pipe and the seem ok
Submitted: 1 year ago.
Category: Mazda
Expert:  Tim Mohr replied 1 year ago.

Hi, my name is ***** ***** you check the cat converters?

Customer: replied 1 year ago.
as i said i have checked the cats can see right through them.
Expert:  Tim Mohr replied 1 year ago.

they cant be checked this way, you ned to do a exhausr back pressure tes, this is done by removing the upstream o2 sensor and installing a low pressure gauge, at idle, the back pressure must be lower than 1 psi, if its higher, then the cats are partially plugged,Tim

Customer: replied 1 year ago.
ok tim what if the cats are not plugged what is the next test i needed
Expert:  Tim Mohr replied 1 year ago.

the only thing that will restrict the flow is the cats or the mufflers, nothing else, and this test will determine if its restricted,Tim

Customer: replied 1 year ago.
ok i will preform that test, i have a off road racing head pipe with 3 02 sensors built in to it that will eliminate the cats all together. i can install it ( for testing only) as i have the cats off now already. it may change other drive ability factors but should eliminate the blocked cats questions. will this aid in my diagnosis?
Expert:  Tim Mohr replied 1 year ago.

absolutely, if it still feels restricted, then its most likely the mufflers, but the backpressure test would prove this 100%,Tim

Customer: replied 1 year ago.
i will do a low pressure test to be sure. the cats are less then one year old. but the only thing i could not visually test was the resonator i tested the car with the muffler disconnected with no change. the exhaust seem to almost stop flowing out the tail pipe when under acceleration, no load
Expert:  Tim Mohr replied 1 year ago.

yes, do the low pressure test, it will determine it 100%,Tim

Customer: replied 1 year ago.
it will tell me 100% if the exhaust is restricted or not, but were is the restriction will be the real question. as you have stated if there is reduced flow out of the tail pipe there must be restriction some were. and since i cannot visually inspect the cats does it mean i need to replace both cats?
since i do not know of a way to test each component separately, except a visual inspection does it mean i will need to replace the entire exhaust system?
Expert:  Tim Mohr replied 1 year ago.

NO, YOU CHECK EACH CAT SEPRATELY, THERE ARE 2 UPSTREAM O2 SENSORS, ONE FOR EACH SIDE, IF ONE TEST GOOD AND THE THER BAD, THEN ITS EASY, REPLACE THE BAD CAT, BUT IF THERE IS MORE THAN 1 PSI IN BOTH, THEN EITHER BOTH CATS ARE PLUGGED, OR THE MUFFLER, THE RESONATOR WILL NOT CLOG UP, ALSO, PUTTING THE STRAIGHT PIPE ON IT, WILL ALSO RULE OUT OR VERIFY THE CATS,TIM

Customer: replied 1 year ago.
Tim i by passed both cats and i still get reduced exhaust flow at the tail pipe under acceleration. the only thing i have not tried is to by pass the resonator.
Customer: replied 1 year ago.
Tim i tested back pressure test at the 02 sensor closest to the exhaust manifold. the first one in the system. it reads zero 0 psi at idle and it just barley will start to move at 3000 rpm. the gauge is a 0 to 10 psi unit
Expert:  Tim Mohr replied 1 year ago.

then there is no restriction in the exhaust, what problems are you having with this?