You are right, there are only two fuel injectors.

 

Sorry, I missed the fact that your engine is dpfi.

Edit: Regarding the burning up of spark plugs, have you checked and adjusted the ignition timing? Also, did your timing belt recently snap or slip? If so, did you notice bad cylinder 4 afterward?

Is the engine knock sound coming from the head or block? Use a cut piece of a lawn hose as a makeshift stethoscope to locate the knock sound.

By the way, the compression on cylinder 4 is borderline. You might want to do a leakdown test:

http://www.geocities.com/dsmgrrrl/FAQs/leakdown.htm

Here's how to determine whether the ECU is throwing any CEL codes:

 

Another possibility is a problem with the ECU activating the dpfi specifically for cylinder 4. Here's how to test:

 

thanks man ima try some of the diagnos.testing the nocking went away i put 10-30 oil n on of thos old engine oil treatments the knocking when away it wasnt a all the time knock when i revd it in place nothing it was smooth n loud it was only in the morning when i went to start it n acceleration at 3 rpms n higher but the noise went away for the most part 'it wascoming from the block tho

 

the timing belt nah hasnt snappd ....iv had the car since may it wasnt running when i got it 'i got it to run its come a far way from going 5 mph to 80 its mostly going to 80 cuz the trans wont giv it anymore the car runs good but jus that last cylinder isnt giving ima try the diagn. testing tho

 

the engine light has never gone on ...n iv done a leak down test the compression is great performing lik the other cylinders jus when u disconnect the cable it doesnt die down lik the rest do so i figure it isnt poping u no so man im lost should i still do the ecu code check evn tho i dont hav the check engine light on

 

Yes, it's pretty easy to pull the carpet back and to check whether the ECU is blinking a code. If so, note the code and then clear the ECU by removing the Hazard fuse for a minute and then reinserting it. After running the car, check whether the code returns.

 

okay so i jus did the ecu check n it blinks once were starting the ignition on n blinks once turning off the ignition

on ur chart it says oxygen content thats nothing big is it so i should hav to restart the ecu

 

i shouldnt hav to restart ecu i ment

 

do you think it could be a fuel injector.
i mean i hav changed them before cuz when i first got the car there was water in the tank but i took the gas tank off n flushed it n changed the gas filter n pump n injectors i think thats were the problem came im not sure tho cuz i never really checkd the cylinders till evrything was new how does the injectors in a dpfi work

cuz im thinking maybe its an injector