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Dan
Dan, Technician
Category: Pontiac
Satisfied Customers: 23683
Experience:  Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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Daughters 01 grand prix 3.8, was bogging down and wouldnt go

Customer Question

daughters 01 grand prix 3.8, was bogging down and wouldnt go past 40mph. Checked pressure b4 cat and it was very high 10-15, was told should be 1.5 or so. So changed out cat. Still bogging down. i'm lost
Submitted: 9 months ago.
Category: Pontiac
Expert:  Dan replied 9 months ago.

Hello, my name is***** your check engine light on?

Customer: replied 9 months ago.
originally just a P0107 code. Now a 0405 also
Customer: replied 9 months ago.
Did change maf already
Expert:  Dan replied 9 months ago.

Does vehicle idle good or idle rough?

Customer: replied 9 months ago.
kinda rough but not terrible
Expert:  Dan replied 9 months ago.

Vehicle still won't go past 40 mph? P0405 usually is related to the EGR. As of right now I think converter was main problem but EGR is also bad.

Customer: replied 9 months ago.
no once you hit gas at about 2000 to 2500 rpm it starts bogging down, if you ease up on gas some it will speed up a little but 40 tops
Expert:  Dan replied 9 months ago.

Have you done another exhaust pressure test? It sounds like you may have a clogged muffler or resonator.

Customer: replied 9 months ago.
no i haven't, i assume test back sensor?
Expert:  Dan replied 9 months ago.

Either sensor is fine. A quick test is to remove the front oxygen sensor completely from exhaust and open hole will relieve pressure. If this allows rpm to go above 2500 rpm you know exhaust is clogged somewhere. Let me know how it goes or if you have more questions, thanks.