eliii

Hey all, was looking for some direction on what to look for next with codes as stated in the title. Have had these codes for some time now. I have replaced plugs with NGK plugs, duralast coils, cleaned EGR, bought a smoker for vacuum leaks(there were none), new plenum and throttle body gaskets, and got a valve adjustment/valve cover gaskets done. The CEL went off for about a week but then went back on so the misfire is very random. Car also lugs when cold stared in first gear around 1-2k rpm. I saw some suggest it could be crank position sensor, but wouldnt it thorw some different codes if that was the case. I am by all means no expert so if i missed anything or am being dumb please let me know. Thanks

619rcr

P0303 and P0304 are cylinder specific misfires detected in cyl 3 & 4 respectively. I believe the others are not specific to a cylinder.

codes alone are not much to go on. but, you can google them pretty easy.

What's the mileage? Has there been anything significant to happen prior to the onset of codes? has it overheated? blowing any smoke or burning lot of oil?

eliii

It’s got 194,000 miles and timing belt ect was done around 160k. It burns a little oil but not a concerning amount by any means. Hasn’t overheated either. The official code was P0304 with secondary DTC codes P0304, P0303, P0300, and P1399. Not sure what secondary DTC codes mean. I thought it might be a fuel pump issue and will check fuel pressure but that seems pretty unlikely. What should be my next course of action??? Thank again for the help!

619rcr

Not knowing your specific scan tool setup, I would presume primary code is likely the one that crossed the threshold for a hard fault. Secondary is occurring intermittently or below hard fault threshold.

There are a few things you could try. But, how deep you go depends on your level of comfort with diagnostics, tools, spare parts at your disposal.

lots of things can cause a misfire, so process of elimination would help narrow it down.

easiest would be swapping the coil pack and plug from cyl 4 and an adjacent one and seeing if the code follows.

If it doesn't you could have an injector issue, or possibly wiring to coil pack/injector.

Another problem that may not be apparent is pre-ignition/ detonation. Are you using premium gas?

Also, what was the condition of the plugs that came out?

eliii

Sorry for the delay, Yes I am using premium gas (91 is highest octane here at altitude), its weird though because the CEL went off for a couple of days, does that mean the misfire is so intermittent that it didn't happen for x number of miles? I've noticed if I let the car warm up for 3-5 mins before driving it the lugging in first and sometimes second (which I'm now realizing is probably the misfire) wont happen. When the car is up to temp no issues at all. I'm also thinking injector issue or maybe fuel pump since in the secondary codes involve other cylinders. When plugs came out they were a little more worn than expected, but no oil on them or anything that was a red flag.

Thanks again

Thefireball

Do you actually feel the misfires, or is the computer just throwing the codes out without feeling it?

eliii

I don't feel the misfires unless that lurching/unstable rpm in first gear when the car is cold is the misfire. When I'm on the road and the car is up to operating temp (or even warmed up for a minuet or two), at any rpm the car feels great, no hesitation or lack of power.

Thefireball

Depending on how noticeable the misfire is can really hint at what the issue maybe be. A very noticeable misfire, like on the case of my motor before it blew, was either a rod coming loose or a bad bearing. In your case, it might be a sensor, or something electronic. I have no clue, so I'm not going to comment what it could be.
But be careful with those car lurches. I would definitely let your car idle and warm up before driving it. That bucking that feels like a mule kicking will get worse and worse, and lead to a new transmission eventually. On my old '99 CL, I had accelerated from a red light, and I counted a whole 10 seconds before she finally moved, and she was warmed up. I miss that car..

wackjum

I'm guessing secondary codes are pending ones. The engine computer monitors faults but only displays a code if it happens a certain number of times. If the computer doesn't see the same fault within 40 warm-up cycles, then the pending code is discarded.

I suspect a sticking fuel injector for cylinder 3. The solenoid is slow or stuck when things are cold. In order to access the fuel injectors, you have to remove the intake manifold so there's no easy way to just swap injectors around to troubleshoot. If you're going to pull the plenum off, I would consider replacing at least the #3 injector.

Allout

Did you do the valve adjust yourself? These motors like the valve adjustment done on the loose side. Too tight can affect the MAP sensor readings.

Thefireball

Does your exhaust sound any different at all? I remember my rear camshaft gear skipped a few teeth, and my car sounded like a Harley Davidson motorcycle. Thankfully, it didn't bend any valves or cause any damage, but it was definitely misfiring.
Maybe try some seafoam through a vacuum line? Hell, just for the peace of mind, try a compression test and see what your numbers look like.
It could be a bad injector as well, like the user above said. Getting them tested will leave you stranded with out a car for a bit, and brand new injectors are expensive. Refurbished ones are a good option, but there's no sense in throwing more money at the car if that doesn't fix it. I'd suggest going to a junkyard and just pulling some injectors out and hoping for the best.
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619rcr

If you're thinking fuel related, may want to run a bottle of techron with a full tank to clean the injectors, maybe even twice. the fuel filters on these cars are in the tank and a bit pricey, but may be worth replacing esp if it's never been done. a pressure reading on the supply line can at least verify the pump is in spec.

also suggest check the gaps on the plugs as well. if you're using a good iridium they should be preset.

on the cold start lurching thats likely old/incorrect fluid or some debris thats causing something to stick until the fluid heats up. my only experience with that was on a 99 accord and 97 prelude. the accord was a bad trans. the prelude was wrong fluid. because of those cars, I now avoid any automatics in older cars.
good luck

whitetiger5

Why Duralast coils? Many on here will tell you how finicky the 2nd gen cars are for ignition coils; and that you should go NGK or denso.

02AEMCL

Just out of curiosity there was a video on YouTube that discussed a similar issue involving the top plate of the intake manifold. The gasket there is sometimes installed wrong and doesn’t line up. It sometimes causes misfires. Hope this helps at all.

MafiaBoy