2.4 running rough

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butch1581

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So I just bought a 99 grand am that runs rough. I replaced the following with no improvement:
1. New spark Plugs
2. New coil packs (both)
3. New ignition box thing (mounts next to coil packs)
4. Removed and cleaned fuel injectors
5. New Air Filter
6. Removed EGR and confirmed that it is closed at idle
7. New spark plug boot things


I am running out of ideas! I can't find the PCV valve. Does it have one?
I can't find any vacuum leaks off hand, but didn't use anything other than my ear. It pops code P0300 (random misfires) Thanks in advance for any help.

The car is rough from 0-3500rpms above 3500 it runs great?
 
I have not done a compression test at all. It seems to be just fine over 3500 rpms though. I would guess if I had blown piston rings or something it would be different.

I have not replaces the mounting bracket. I assume you mean the plate that the coils mount to? there are just 4 springs that connect the contacts on the coil to the plate. I ohmed out each spot where the spring touches to where the plug boot attaches and each one seemed to have good continuity.

Thanks for the replies
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Nest thing I am going to check is fuel pressure. Hopefully I find it soon... getting sick of dead ends!

I will say that it defenitly runs "consistantly bad" if that makes sense. everytime from a stop it is really rough and almost no power, then at about 2500rpms it picks up a little and smooths out (not perfect) then it goes bad from 3000 to 3500.... after 3500.... perfect. Everytime. So I know its nothing like bad fuel or anything.

Also,

The one time I pulled the plugs two of them were white and 2 were brown???
 
Try replacing your fuel filter..
Plus on the IDI ignition,uses a gounding strap. I moved mine right under the ICM for the main reson you get a better ground that way. and just for the hell of it replace the strap with a new one..The strap looks similar to this one

Battery_Cables_And_Connectors
 
Thanks for the input. I have not replaced the strap or the coil mounting bracket. I tried a new MAP, TPS, and Cam position sensors with no luck.... grrrr. I tried to remove the fuel filer, but the nut is rusted pretty bad and I could not break it loose. I soaked it with pb blaster. Hopefully I can get it off... I think that is where the fuel pressure gauge has to be installed too since there is no port and the fittings dont fit on anywhere near the rail. Thanks again for all the suggestions. I may look for a coil mounting bracket at the bone yard since they are $55 new and no returns.
 
thanks for the suggestions...
Tried a new MAP, Cam position, and TPS sensors with no change.... grrr.

Tried to remove fuel filter but the nut is rusted tight. Soaking in PB blaster now...

I may look for a coil mounting bracket thing at the boneyard since they are $55 new and not returnable. Thanks again
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I tried to get the fuel filter off but the nut is all rusted. I have it soaking in pb blaster now...
 
I also checked the ground wire as you said but it is not that. I even hooked a jumper cable from the battery negative right to that plate and nothing changed. I replaced the MAP sensor, Cam position sensor, and TPS, with no change at all. Thanks for all the help!
 
here is the list of things you have not tried based upon http://www.obd-codes.com/p0300

•Faulty spark plug wires
•Faulty oxygen sensor(s)
•Faulty fuel injector(s) cleaning doesnt help if they are leaking when closed
•Burned exhaust valve do a compression test
•Faulty catalytic converter(s)
•Faulty camshaft position sensor
•Defective computer
 
Thanks man. I did try a new Cam position sensor with no luck. I also replaced the spark plug boots, and both coil packs. I also ohmed out the "wires" (which is actually that plastic housing thing) and I had good continuity for each plug.

wouldn't the 02 sensor throw a code on its own? The only code is P0300. I am going to do a compression test tomorrow so that will eliminate one more thing:)

I might try a PCM from the junk yard tomorrow as well.

Is there a good way to determine if a specific injector is bad?

Thanks again all.
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I followed this:

http://www.ehow.com/how_2387429_test-fuel-injectors.html

All injectors sound exactly the same. I even reved it up a little and they all did the same thing.

I am pretty sure its not my injectors. I also replaced all the O-rings on the injectors to make sure it was not leaking in around them. Plus the rings just looked bad.
 
I would work on getting that fuel filter fixed since it it rusted in place, that would it most likely has never been replaced.. that is a big problem... i would take it to a shop..and not a main sream shop like "firestone" but a mom and pop shop.. they will most likely cut it,attach a new fitting then re flare it to u won't have that problem again..the rule of thumb with fuel filters is "change them every 3rd oil change or every 9000 mile"..look into that first..
 
and have you replaced the fuel cap?..if not, replace that aswell since if that goes bad it could cause what the problem inwhich you are having..
 
are you serious? The car started acting up right after the previous owner filled up with fuel... you may be onto somthing. I will die if that is the problem:D Thanks for the suggestion
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I will probably have a shop replace the fuel filter like you said as well The filter looks like it may have been replaced before, but its hard to tell. The rusty nut is on the fuel line that connects to it. I am sure it is in need of a change though like you said. Thanks man.
 
Update:

180psi on all 4 cylinders and it held just fine.
Tried a new gas cap.... no luck.

It has to be the catalytic converter or the fuel filter. I may bring it to a local shop to have them replace both. Hopefully that will get me back on the road.
 
just try the fuel filter first..you dont want to keep spending money you don't need too..i just hope thats it..
 
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