There is hope...175psi on all cylinders....

[alkemyst]

Getting p0304 misfire codes on my 4th cylinder. Don't know why.

The fuel injector does seem like it's not firing like the others, although I get good voltage at the injector lead, and the injector itself ohms out to 12 which is in spec.

Spark plug looks good and it's wire is only 350ohms.

I have a new set of injectors, plugs and wires coming. My biggest fear was broken valve/springs.

However I am getting 175psi across all four cylinders (max is 179psi in the manual)...so with 100k miles almost my engine is still healthy.

I am just hoping the valves are opening. Is there a test I can do without opening the engine cover (again)....

 

[bruceb]

First, it is not a valve or camshaft problem if you are getting good
compression and it is similar to the other cylinders. Misfires are
usually a bad spark plug, plug wire or ignition coil / ignition module.
If it is only on cyl 4 then swap the plug or the wire and see if it follows it.
I have seen a very tiny crack on the spark plug insulator cause a misfire code.

 

[alkemyst]

I was told if the valves are not opening at all your compression will still be great.

I had thought about just swapping injectors...tomorrow I am going to try and swap the wires and plugs around. I had to take some things apart to get to all the them.

Still I figured with 100k on the car, redoing the injectors (the filter was done, the pump I will be doing) and wires is a good choice.

The plugs only have about 3k on them, however they have been in and out of the engine alot so they could have a hairline crack.

 

[nismotigerwvu]

I'd try a leak down test if I were you. Tend to be a little more telling than a compression test.

 

[alkemyst]

takes specialized equipment...I do have the air compressor though...usually they are only done if the compression test shows a problem. If I had the equipment I guess it would show me if one cylinder wasn't leaking through the valves as much as the others.

 

[cardiac]

You said you were getting misfire codes on the 4th cylinder. But, you didn't say how it is running? Is it actually mis-firing on that cylinder? Usually from what I have seen, you won't get a mis-fire code from a cylinder unless it is an electrical or fuel delivery problem. If a valve is sticking (Open or closed), it may not generate a code. With the comp test showing decent results, you may have to pull the valve cover and physically observe whether that cylinders valves are functioning ok.
It sure doesn't hurt to try the injector/wire swap.

Good luck.

 

[LennyZ]

What car is it?
Usually misfire is a plug wire or coil.

 

[alkemyst]

It's running like shit. Definitely that cylinder is not firing.

The car is a 98 240sx.

I do have new plug wires coming even though the 'bad' cylinder is getting only 350ohms on the run. Still may be a short or something else.

I figure rather than try and troubleshoot further, replace some of the older parts that could use it anyway. If I still have problems, then I will have to open the cam cover again.

The cam cover isn't hard, it's just a PITA to clean up the RTV each time and then I am down for 24 hours waiting for it to fully cure.

 

[BUTCH1]

Try pulling into a darkened garage at night, have someone run it @2K RPM and look
for any arcing. I found a bad wire using that method. Might want to avoid driving if possible until
it's resolved, the "dead" cylinder is putting raw fuel into the cat which can cause problems
down the road...Good luck..

 

[Toastedlightly]

It most likely won't be this, but we had a similar issue w/ my brother's car. Turns out that the control for that injector was shot and he needed a new PCM or something like it.

 

[bruceb]

Did you try a new Spark Plug yet ? ? ? Looks can be very misleading.

Edit: Just did some research .. Your car does have a distributor with a cap
and rotor as most cars did before they went to distrubtorless ignition systems.
Please try a new distributor cap & rotor as they do wear out.

As to spark plugs see below:

USE 4 OF NGK PFR6C-11 (NORMAL HEAT RANGE; OE = PLATINUM); SEE NOTE
Make: Nissan
Years: 1994-1998 (02/1994-)
Model: 240SX 2.4 DOHC
Engine: KA24DE
Chassis: S14
Transmission: 5MT,4AT
Notes: NGK no longer offers the OE PFR6C-11 spark plug and is recommending that the PFR5C-11 (one step hotter heat range) be used instead. If the colder heat range plug is desired, NGK advises that PFR6G-11 can be used in place place of the discontinued PFR6C-11 spark plug.

 

[alkemyst]

I have new plugs coming...I use the 6953 (BKR5E-11) V-Powers though...my current plugs only have about 3k on them. The cap and rotor are less than 20k miles.

 

[alkemyst]

Well neighbor brought over one of my boxes today. They shipped it to my home instead of my work. She's had it since Friday.

The plugs and wires fixed the problem. I inspected both old parts and found nothing wrong...wires spec'd within tolerances.

I will still do the injectors. They are pretty easy and would complete all the intake and exhaust parts of my engine.

 

[BUTCH1]

Good deal, sometimes a bad wire will only show up under load, mine would only mis-fire
going up hills, it was driving me nuts!

 

[alkemyst]

yeah it's freaking bizarre. I did have my car in for service a week before this happened. I am thinking they man handled the freaking wire somehow. I hate having work done...but I didn't have time for 20+ hours of work (helicoil and some other crap).

 

[helpme]

The #4 plug wire on my SRT-4 didn't show any increased resistance, but it caused a misfire at WOT.

It, however, was a bit whiter colored thanks to the heat from the turbo and exhaust manifold, so that was my clue when I had a problem similar to yours.