Engine is misfiring why?

check fuel pressure first then check ignition components. also check for a vacuum leak. This guide can help us fix it

https://www.2carpros.com/articles/engine-misfires-or-runs-rough


Please run down this guide and report back.

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

try this first, clean the throttle plate on both sides with choke or fuel injector spray cleaner. they get dirty on both sides and get all the gun k out. they get oily. check it out as you need a gauge to check the fuel pressure should be 47-52 psi.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

if lower you may need a new pump.

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 then check with an auto parts store they may have one for a rental alot of them do that andthat would be wher eyou hook it up on the schrader valve.

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.

Glad you could get it fixed, that kind of problem can be tough. Please use 2CarPros anytime we are here to help.

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?

A code P0300 follow these guides

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

and

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

and

https://www.2carpros.com/articles/repair-lean-mixture-codes-p0171-or-p0174-on-some-manufacturers

Diagram (below)

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.

Were the valve clearances checked?

Is streaming data within specs for :

1. O2 sensor.
2. Crankshaft position sensor.

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?

Usually when the sensor is bad, trouble codes would be stored.

Normal testing is the performed on the resistance.

I do not know which engine you have so I have included all the various models.

Did you check if the distributor has excessive side play, indicating a bad bearing.

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.

Did you check/adjust the valve clearances? If any cylinder has too tight valve clearances, it can misfire and compression test would not show much drop in pressure.

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.

Timing light not firing could be due to misfiring which can be due to valve clearances faults. Could it be a fault with the timing light?

Since problem is intermittent and most likely to be electrical, I believe the distributor and ignition components such as rotor, ignition coil, spark plug wires or disteributor cap is more likely to be the cause. It could be wiring fault due to loose connections that is intermittently not working correctly.

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.

Recheck the ignition coil, is it OEM or after market?

I finally had a chance to sit down with the car and here are some values I measured for sensors on the ECU through the attachment you gave me as well as the coil.

The engine is the d16y8, so I used the 3rd diagram for the pins.
8 and 9: 521 ohms
20 and 21: 204.4 ohms
29 and 30: 299.4 ohms


coil pimary: 1 ohm
coil secondary: 20680 ohms

The ignition coil readings are out of specs. For secondary readings, it is neither here nor there whereas for primary it is completely out of range.

Well, those specs are at 68 degrees, and I have to drive over to someone else's house to test, which raises resistance. The temp was prob around 200 degrees, at that point. I will try to let the engine cool down more next time I'm over there for a more accurate test.

I'm not convinced those readings are off far enough on a hot engine to be the cause.

Were the distributor sensors in spec?

Specification for those sensor resistance are 350 - 700 ohms.

The lower 2 are out of specs.

Are both of those sensors located in the distributor?

Yes they are.

Engine Performance problem
1999 Honda Civic 4 cyl 175,00 miles

My 99 Honda Civic starting chugging at stops. I took it in and they gave me an estimate of $600 for parts and $100 for labor for a new distributor. They also recommended a $100 fuel service. Is this normal pricing? How long can I wait before getting this replaced and serviced?

Hi LindaVH,

Thank you for the donation.

Pricing differs region to region so it is best to ask around for the prices. Get a second opinion if necessary.

Why does the distributor requires replacing? When the distributor goes bad, the engine would fail to start. If it is the ignition coil, it can be replaced as a componet and not necessary to treplace the complete distributor.

Depending on the problem, it could be the spark plugs, wires, distributor cap and /or rotors and how lont it can lat would depend on the condition of the fault.

Is the Check Engine Ligh t indicating and have you tried to retrieve for trouble codes?

Bought a new distributor, but before install traded coils just for fun and the misfire persisted. When I replaced the distributor, problem solved!

Thank you so much for helping me narrow that down. I have invested way too much time diagnosing this problem.

They said my cylinders are misfiring and that's why my engine acts up at stops. They told me the spark plugs and wires are ok except that one spark plug can't be removed to be looked at. My maintenance light didn't come on, but there were messages retrieved saying Misfire codes: P0300, P0303 and P0304.

I will try to get another estimate then. I'm based in Austin, TX.

Thanks!

Glad to know you have fixed the problem.

Have a nice day.

Misfiring codes are seldom due to the distributor.

P303 and P304 indicates misfirng in cylinder 3 and 4 repecively and if it is a fault with the distributor, most likely all four trouble codes should show. I would suggest getting a second opinion as well.

If there is a sprak plug that is stuck, then you should try to get it out. Any bad spark plugs could cause the problem.

You are recommended to replace the distributor and service the fuel, I have an inkling the guy is going by a do-this-and-hope-it-works way. I would be looking for a new mechanic as this shop does not seem up to the mark for the job.

while im driving i could feel the car jerking. Like is pulls back like if u are on a roller coaster. but its keeps moving and i feel it jerking all the time. what do u think is the problem .. do u think the car will just stall after a while

Sometimes engine misfires are mistaken for trans problems. Is or has the check engine light been on? if so have it scanned for codes, this will help figure it out. Start basic first though, have you ever tuned it up? if so did you use OEM parts?