Can anyone explain what i need to do?

I'm pretty sure i got bad spark plugs and now im getting terrible gas mileage, lost a little bit of power, and im not paying my mechanic $350 again for a second tuneup.

Car has 70k miles on it. I tuned it up at 57k using OEM plugs and wires (maybe that was my problem)......

apaprently my mechanic told me its a **** of a job to do, but I need some real advice. I'm not the greatest with cars but if i research enough i think i can figure out what I need to do.

Thanks, Adam

I wouldn't expect the plugs to be the problem since you used OEM plugs and they only have 13K miles. They're platinum plugs, and it's recommended to change them at 60K. But check it out, pull a plug and tell us what the number is on the plug. It should either be a PFR5N-11 NGK or a Champion RC10YPB4. What color is the plug?

I assume your not getting any obd codes pointing at something specific . Did the mechanic do a compression test for you while he had the intake manifold off allowing access to that rear cylinder bank ? . Problem may be a dirty or failing injector , plugged fuel filter , failing coil pack or a vacuum leak after having that manifold/throttle body removed . Did he reuse the old gaskets on the intake and tb . At your present mileage you are overdue for a timing belt change if it hasn't been done yet .

Well last I recall I was getting OBD codes for cylinder 5 misfire after revving out to 5k RPMs or above... Mechanic had reset the computer and after that I hadn't gotten the misfire...

Could it possibly be a bad injector on cylinder 5?

As for a timing belt/water pump change I'm pretty sure I did it at around 50k miles... Although I can't remember for sure so ill have to give my mechanic a call.

Bad coil pack - how do I determine if this is a problem? How can it be changed?

It sounds like you have a better than average maintained car , so if that misfire is not coming back then the problem was likely solved with the new plugs and wires .

If your idle is smooth and throttle response is good then it's unlikely that you have a vacuum leak .

If the misfire returns you can swap that injector with another and see if the misfire moves to that cylinder .
Likewise you could swap a module (3 modules within the 2.7 pack ) within the coil pack and see if the misfire moves .

You may have picked up some bad fuel that fouled your system , i would clean the injectors and run a few tanks of premium gas then recheck your mileage .

Yeah i try my best to maintain it. I had a high paying job awhile back so i had no problem dropping $500 to flush the fluids/etc

Idle is very smooth. Always has been. Throttle Response is definitely better than average. I do recall it stuttering on one or two takeoffs today, but It may have just been my imagination, or maybe its just a rarity.

Misfire hasn't actually come back. I'm revved out to 5 1/2 RPM's multiple times now and Haven't even gotten the stutter from the motor/trans, so i think the misfire altogether has stopped...
HOWEVER, my takeoff has been a bit slower lately...

Bad gas could definitely be the issue. I was buying shell gas at one point for every single fill up. Now that I started my new job, there is a 24 hour Exxon down the street so i'd stop by after work around Midnight once a week and fill up...


Bad Gas could actually be it... bad gas could equal Dirty injectors, which could lead to misfire...

Luckily I have a can of BG44k in the mail... We'll see if that clears it up. I'm also going to start filling up with Shell gas again.


Worst case scenario, how hard is it to change/clean the fuel injectors?
and how do i go about changing the coil packs? (an even better question for me, wtf are coil packs???)

This post has been edited by AmongthechosenX: Nov 11 2009, 01:37 AM

Misfires can also foul the o2 sensors . The delta ecu uses the two primary o2 sensors to control the a/f ratios . The quickest way to check stuff like that out would be to have a computer diagnostic check done at a dealership . They can verify that your long and short term fuel trims are within spec .

The injectors and fuel system can be cleaned by dumping a bottle of cleaner/conditioner into your fuel tank . If the injectors are really bad the dealer can remove and clean them . The front fuel-rail / injectors are easy to access however the rear is a pain and guess where cylinder 5 is ?

Here is a pic of a delta coil pack , there are 3 elements within the pack firing cylinders (1,4) , (2,5) , (3,6) .

The cylinder layout is 1 3 5 (left to right rear bank) , 2 4 6 (left to right front bank) .