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'07 pt cruiser

main pt cruiser fourm appears to have been unable to accept new user registration for probably years due to some unupdated recaptcha implementation, so will try here for some insight into this candidate for " best worst car"

'07 pt cruiser automatic (not mine, i swear).
≈168k miles
No codes being thrown. Codes previously purposefully thrown by disconnecting sensors briefly to verify pcm was working.
Compresseion : 185 170 180 170
Idle vac is good 18-20
Air filter allows light passage.
New PCV. New head cover gaskets. New case vent filter in airbox.
Does need new cv axle.

Issue: poor acceleration, Can get reach cruising 80+ about 10 seconds at about 3/4 pedal application. But, will not exceed ≈25mph on inclines no matter how much throttle. Important note is that RPM's don't increase as much either on incline.
Issue has been present for about 2000 miles, apparently and rather suddenly onset.
Selecting D, 3, 1 shift lockout positions do not alter performance.


Clogged catalytic converter initially thought to be the sole cause, and it did prove to be clogged. However efforts to attempt to address that have me wondering.

Cleaned the cat with 2 stage method of heavy degreaser in boiling water for 3 hours, then overnight bath in laquer thinner. Cat does not rattle.
Attempting to clean a cat is one of the few repair areas in which I have no experience. I would not have even tried but was requested to as hail mary type fix (family member's car).

The confusing part is that , the cleaning appears to have actually worked to remove most or enough obstruction to the point I expect should allow much better performance, if the cat clog was in fact the cause. I attached my air compressor (sealed for air tightness) line to the cat, with an inline adjustable pressure regulater to act as bench test back pressure guage. Turning the air flow on to maximum flow (compressor stores at 100psi) the line pressure only ever reached 7psi, which is what I believe is indicitaive of a healthy or at least unobstructed cat. Blocking the other end of the cat did force pressure to climb, so it was sealed properly for what I think is sound testing method.

Reinstalled there is definitely much better and steady exhaust flow , idle and/or revved. But 0 performance gain on inclines. A small performance gain on highway acceleraton after 40mph . Coolant temp sensor reading doesn't exceed 220f idling. Drops to 170 at highway speed. Good temps.

Have yet to perform a back pressure test after reinstalled, that will be first, expect it to be just slightly higher than normal.
Only thing I can think of regarding performance is that is maybe a fuel issue. Will check fuel pressure after backpressuretest. But there is no hesitation in starting even waiting minutes to start after initial fuel pump system prime, which I believe mostly rules out a back flow check ball in the pump.

idk on this. thoughts welcome.
 
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94Eddie

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Have you tried driving it without the cats installed to see if under load performance improves? It will be loud but should run. Also, it is better to check back pressure with the cats on the car and using one of the O2 sensor ports to read back pressure. At 2,000 rpm the pressure should be 3 psi or less. At idle it should be around 1.5 psi.
 
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ChildIdenticant

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Have you tried driving it without the cat
Decided against, wanting not to risk allowing the hot exhaust to collect in the engine bay as there is a plastic oil pressure sender right next to the cat and a lot of other plastic parts in there.

on vehicle bp test will be performed later this evening. And thinking about my bench test method I didn't addequately account for CFM difference between exhaust of this engine and my compressor.
 
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ChildIdenticant

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Testing delayed.
FSM indicates back pressure should be be at .5 psi MAX at 2000 rpm.
Measured at ≈6psi @ 2000 rpm. Still think that shouldn't account for the extreme power loss on incline. That's just sense of experience though. Probably all the cat. Fuel pressure not yet determined.
 
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