Engine is misfiring why?

How do I check the fuel pressure and what should the reading b?
She says when she stops at a light it vibrates more than usual. How woul I check
The ignition components

I know all the ignition components and I know about cleanin the throttle body plate I jus dnt have a fuel pressure tester im thinkin I would have to hook it up to the shrader valve on the fuel rail

Ok, I did a fuel pressure test it was okay then I replaced eh distributor that worked perfect thanks for your help, this site rocks.

Engine Mechanical problem 4 cyl Front Wheel Drive Manual 91000 miles

Ok, my car is throwing codes p0300-p0304 and p1399, they are cylinder misfire 1-4 and random cylinder misfire. I've changed my distributor, spark plugs and wires, pcv valve, fuel filter, o2 sensor, ground wires, valves adjusted, valve cover gasket, compression test came out good, and injectors are firing. But I still keep getting these codes. The Car has no EGR because it's a SI model, and it's all the cylinders misfiring. Not sure where to go from here. Any ideas?

Alrighty, couldn't find a vacuum leak, but you hit it on the money with the MAP sensor I replaced it and the problem was fixed!

I love this site thanks guys!

The misfire has been ongoing for over a year, but throws no codes and no engine light.

After cleaning the fuel injectors, checking for vacuum leaks, and resistance checking the injectors, I decided on a lark to hook up a timing light.

When hooked up to any of the spark wires, the timing light will strobe normally for several seconds, until it "misses" a beat, which I can hear as a misfire out of the exhaust. I'm guessing this means there is some sort of ignition issue here, but I can't find it.

After finding a failed coil and replacing it, nothing changed. Before that, over the last several weeks, I have also replaced the cap, rotor, plugs, and wires as well as run just about every diagnostic I could find including compression tests and just watching the streaming data on a scan tool.

The miss is very subtle, but at idle is just sounds like a very slight pop every 3-4 seconds (it's not cyclical, it's very random). At light loads up to 2000 rpm, I can feel it losing power, but after that it seems to behave pretty normally. My gas mileage is about 20% less than it was before this started, though.

I have also checked for vacuum leaks, both with propane and by simply putting a hand over the throttle plate (it dies instantly). The IAC is brand new, as I was having an idle issue a few weeks ago, so I know that's not causing anything. There is no EGR valve on the car either.

I'd love to hear your input on what might be going on here and how to test for it in some way other than throwing parts at it (as the local mechanics are wan to do).

Oh, it does this whether the engine is hot or cold, doesn't seem to matter. I checked the FIAC valve, ECT sensor, and IAT sensor just to make sure they were OK, and they all checked out within spec.

Yes, the primary O2 is fluctuating between.15 and.85, but my software doesn't show data on crosscounts.

No data is available for the crank sensor. Is there a way to manually test it?

It's the d16y8 motor. There are no trouble codes stored. The distributor feels pretty tight, too.

I will check the resistance tomorrow (my day off) and get back to you on where that sits.

I have never checked vale clearances, but would that cause my timing light to not fire when it's on any given cylinder? Doesn't seem like it would cause the same symptoms.

The main reason I believe this to be a sensor problem is because, when I have the timing light on any wire, it fires like normal until there is a misfire, at which point the light stays off for a brief instant, then strobes normally again.

Well, the cap, rotor, plugs, wires, coil, and icm are all new. The timing light works well on every other car, just this one.

Air and fuel misfires don't cause ignition failures, do they? As long as the coil is good, I would think enough voltage would pass through the plug to make a spark regardless of the conditions inside the cylinder.

I will be checking the crank sensor resistance this weekend and will let you know what I find as soon as I do.