Suprjdmbro

So I just fixed an idle issue I had a few days ago, now my car has a p0308 (cylinder 8 misfire) but the thing about it is it only occurs at night. I tested resistance in all the plug wires and tested the alt with the lights etc on and I can't seem to find anything wrong. I tried searching to no avail. Anyone else ever had this happen. My car runs flawlessly during the day, I'd love to fix this issue.

Edit: also an issue that's occurred since I bought the car, it's slow to start. Not slow like a dead battery but it doesn't start in the first second or so like most cars do. After I replaced the passenger bank coil this morning it seemed like the first two starts were normal but then back to slow ish starting.

dicer

A good bidirectional scan tool makes figuring this stuff out so easy. We need Yamae to explain how and why that year ecu reports that misfire code.

Suprjdmbro

Agreed but unfortunately the only scanner I have is an older snap on unit and it only gives me a general cause and symptoms..I've been trying to use give one at work but I cant seen to find the time to snag it

Yamae

You mean when your head lights and tail lights are ON?

Suprjdmbro

Correct the misfire only occurs when lights are on...I have stock headlights and depo led tails. The misfire also isn't constant ( or I can't always feel it).. When I stop at a light the rpms will drop, pick back up...when I have constant gas pedal position at 30-40 and 40-50 mph over noticed it will buck randomly..ecu only throws p0308 still.

djamps

ECU caps maybe...

Suprjdmbro

I've thought about that, ive been waiting to see what else i can test/eliminate first. The PO had replaced the ecu about 6 months ago with a supposedly new ecu.

Update...off of work today so going to try and squash this issue. Tested all of the plug wires even though they're new. All wires are supposed to test at 25k ohms according to alldata. The passenger side coil wire only tested at 5k ohms...so I think this could be my issue. Only thing I cant `figure out is why it would only affect cylinder 8 and why only cylinder 8 at night. More testing shall ensue today

Yamae

Sounds like the ripple is causing the problem since the 12V line has more noise and ripples when lights are on.
Observe the ripple as is shown in the FAQ.

Suprjdmbro

Alright so i went and got another new set of wires and an alternator...did the alternator first, that fixed my issue. Still changed the wires out since my coil wire tested bad. I tried to simulate my driving conditions in my garage, lights on (auto) car in drive with wheels chalked and e brake on, alt put out 14.3 volts consistently. When i flipped the high beams on however it dropped to 12.9-13.3 so i figured after some low rev driving after work every night the alt wasn't charging correctly. Oddly enough the alternator still tested good on a bench tester at the auto parts house.

side question, how firm is our ebrake pedal supposed to feel? mine is super easy to push down, it does hold the car but i have not tested it on a hill yet.

Yamae

Was it an authentic tester? I make it a rule that I don't trust an alternator tester that can't observe the waveform.

The high beam lights consume only about 5A each and those should not drop that much of voltage as long as the alternator is working well. I worry that the one or two rectifying diodes in the alternator is(are) dead or the regulator is partially dead. This can be easily checked observing the waveform as is explained below.
http://www.venselenterprises.com/tec...getutorial.pdf

Another item I suggest you to do is to replace electrolytic capacitors in the ECU. Your level of ripple at the12V line should not let the ECU to cause the code P0308. The ripple rejection is not done properly in the ECU's voltage regulator circuit as I have explained in the FAQ. Without changing those, you will soon have the random misfire problem as well as the strange engine and AT problems because of the too much ripples there in the ECU's Vcc line and others.

Suprjdmbro

It showed ripple but it came up very minimal....I bought another ecu off of fleabay that I'm going to take apart and have a buddy of mine solder in New capacitors just in case mine takes a dump on me. I also agree that the alt shouldn't cause that code, so I'm going to be prepared just in case it is the caps.

SENSAY813

might just be very bad luck bent pushrod