poor running

jerry b

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#1
02 olds alero 3.4 70000 miles. started running bad pulled codes had p0404 egr valve. replaced egr valve and replaced fuel filter didnt help. checked fuel pressure has about 50 pounds . car wont rev. over 2800 rmps it bogs down. dont pull hills good. transmission dont seam to shift right when you press the gas pedal to the floor it just bogs down. no other codes stored. any ideals?
 

Gus

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#2
Plugged cat? Have seen cases where the exhaust is plugged, it builds up pressure to unseat the EGR valve, causing a rough engine....worse case scenario I ever saw was, on a 3.8, it blew so much back pressure into the plenum, it melted the top of the plenum......this was because the owner continued to drive the vehicle with the problem....
 

billr

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#3
Do you have a vacuum gauge, or can read MAP in live-data; know how to check for a plugged cat with those?
 

kev2

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#4
If the EGR code is still present.. you need to correct that...
A Quick look I show 50psi fuel is BELOW lower limit... some else will confirm

Start with colleagues mentioned vacuum checks -record vac reading and when at idle observe if reading falls .... let us know if EGR code still active.
Do you have a scanner to read live data?
 

jerry b

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#5
egr code is gone. dont have a vac. gauge and no way to read live data. which one is the cat? it has 2 one looks close to the old cherry bomb style muffler the other is short and odd shaped.
 

kev2

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#6
The consensus is to do a vacuum check - gauges are inexpensive and sometimes available as a loaner or rental tool at parts stores... Also there is a exhaust backpressure gauge available.
The cat is FIRST in the exhaust system -exhaust flow is from engine to cat... then to the muffler (cherry bomb style) DO NOT REMOVE CAT -

Be aware Fuel pressure is LOW
 

jerry b

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#7
what should fuel pressure be? the cherry bomb style muffler is first from engine then the short odd shape one then on back to the muffler. i could unhook the exhaust system to check it that way (plugged cat) but that might not be the best way. if i had a vacuum gauge where does it need to be hooked up?
 

kev2

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#8
ok cheap NOISEY real noisey trick one of the regulars posted here - remove the first o2 sensors from exhaust this will releive any back pressure easier than removing pipes... any change?

A vacuum gauge attaches to intake manifold - often a vacuum port something such as HVAC doors, PCV, PB, emission ie Purge valves

I am suspecting there are multi issues - possiably more codes.
I show on a quick chart pressure needs to be 52 minimum - @60 psi - so 50 is out of spec - not close its out of spec.

There is nothing working against us - special parts miracle magnets, tornado air filters, K&N BS, Chips etc
 

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#9
Try a different fuel pressure gauge ( borrow from auto parts store or a friend) just to make sure your pressure is low and it is not just a bad pressure gauge.

If it is really only 50 psi, that needs to be fixed.
 
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#10
"car wont rev. over 2800 rmps it bogs down." Does it do this bogging in "Park"? If so, what happens to the fuel pressure when it is bogging? For this test, you don't gradually apply throttle; you floor it instantly (and be ready to lift foot instantly if RPM skyrockets).
 

jerry b

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#11
yes in park. fuel pressure needle sometimes bounces slightly when doing this in park.
 
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#12
If fuel pressure doesn't drop off, it's more likely you have plugged exhaust. If EGR removal is a better choice than O2 sensor for giving exhaust a way to get out, take it off to see if the bogging gets better. Don't melt anything with hot exhaust gas, also plug intake hole with something that will not get sucked into intake.
 

billr

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#13
And, you may be able to detect a plugged cat using the vacuum gauge, without disturbing either the EGR valve or O2 sensor.
 
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#15
Symptoms sound exactly the same as my kid's car after he filled the tank with also water at 4 bucks per gallon. Causes a misfire, and of course with that no power, limited RPM, and screws up the AT.

Still like to start off with a good old compression test first to get that out of the way, could be a carboned up intake valve that blows back into the intake manifold that will really screw up the EGR, or a burnt exhaust valve, causing that misfire that will lean out the entire engine with a single O2 sensor , or a misfiring or plugged injector.

Really don't care that much about codes with a rough running engine, all this stuff can be tested, could be a mess, or just a cracked insulation on one spark plug. Find the problem and fix it.