2003 se manual 6speed. I got this car with these issues so I have been replacing as I go along. Previous owner knew nothing and wasn’t really helpful at all. So far I have replaced the spark plugs, ignition coils, fuel pump, anll four oxygen sensors and gutted the cats . I now have no misfires or check engine light other than the fuel level sensor. The problem I am having is the power is down dramatically mainly when warmed up. The power kind of comes and goes through the rpm band. It does not seem to have this problem on a cold start. Any reading or ideas you guys can think of to help me out here?!? Also abs light is on but I cannot communicate to the system?

 

are you still running an OEM MAF sensor? OEM air box? what brand ignition coils did you get and spark plugs?

 

Clutch still good? I would also check the rear calipers for sticking.

 

I haven’t changed the maf but it’s reading are in spec according the to fsm. Ignition coils are just Amazon with ngk plugs

 

clutch grabs fine and both rear calipers are free. This issue is only bad when the car warms up

 

my first guess would be the Amazon coils, you never know what your really getting on Amazon. I even heard of counterfeit spark plugs being sold on there years back. if your going to go the cheap route on coils at least go with Rockauto so you know what your actually getting. I've had good results with the cheap Ultra Power brand coils I got from Rockauto..

are your ignition coil connectors still in good condition? I actually had to wire in new connectors on my 02.

 

all the connectors seemed good and still click in fine. Ok I’ll try some other coils then. What’s the best brand? If it were ignition would I get more of misfires though?

 

Also if you guys could give me a idea on sensors to monitor for a red flag I can try and do that as well

 

I had a similar problem with my 5.5 gen 2003. It ended up being the alternator.

​​​​​It took some time to track down because
the usual red flags never revealed themselves. The dash board battery indicator never came on.

But. At stop lights, I could see the head lights would turn brown, then I could here
some humming sound, then the head light would turn bright again.

I had to continuously charge the battery
until I replaced the alternator.

The charging problems went away after that.n

 

I replaced the alternator but not for this issue. I’m getting a charge of 14v

 

when it comes to cheap coils you can probably get weak spark.

check all your grounds. grounds are really important cause the spark from the plugs rely on a good ground to the cylinder heads and block. the injectors and ECU also have grounds on the engine wiring harness that ground out on the front head.

I would also clean the throttle body

when it comes to alternators I actually switched to the higher power 4th gen alternator. the 15 extra amps made a noticeable difference when I crank the stereo up ..

 

Did you check the voltage under load.

I'm asking that because before I replaced
the Alternator, I would check the output
white the vehicle was standing still
just idling. The output from the Alternator
We're good values in that case.

But. While driving, I would dim headlights
and the dash also became dim.

I replaced the Alternator, a 2nd time within 6 mo. The second Alternator solved the problems.

 

I will check again.

 

Misfires will occur when the coils are completely shot. Bad or weak coils show their ugly head by robbing you of performance when in the higher rpms and accelerating more quickly.

 

Ok so I now have replaced all coils with oem spec hitachi. Oem plugs gapped at .044. Replaced all intake manifold gaskets along with replacing fuel injector orings. Replaced pcv. Still same issue. I am going to attach pictures of live data at idle and holding at 2k rpm. You can see how much fuel it is adding and o2 sensors reading crazy

 

Anyone?

 

are you feeling loss of top end power or across the entire rpm range?

maybe the VTC solenoids or the VIAS vacuum solenoid are at the point where under hood temps are causing them to malfunction. electronics can sometimes be funny like that.

 

Well I overlooked a major first play lol. Compression! All are low around 130

 

A compression check was going to be my next suggestion. I didn't suggest it at first because these engines are pretty rock solid overall.

 

Followed up with a leak down and it is leaking past the rings. Air blowing out the dipstick tube and oil cap

 

Dang, it might be time for a 2nd/3rd gen engine swap.

My son's 03 I35 was burning through a quart of oil with every gas fill up. Still ran fine and pulled hard when he sold it.

 

I’m not 100% the compression is what is causing my issue but no point in diving further with a know weak engine. Gonna get a new engine tomorrow and will keep this updated

 

dont get another 02-08 engine.