P0300 code

[ericsbestshot]

so i think the code has been figured out. Checked the timing and it was off. Reset the timing and drove it around for a few minute and rode perfect. Then today was driving and the code came back along with the rough idle. I have not verified that the timing is off again. What should i look to replace? What could cause the timing to be off again?

[kcbhiw]

When you say timing is off, what do you mean? How are you fixing it? Is the t-belt slipping? Do you have adjustable cam gears? The NB's don't have a CAS like the earlier cars to adjust timing.

A P0300 code is typically indicative of a failing coil pack.

[miatastuff]

If it's cam timing, then its time for a belt and tensioners and a water pump while you are in there. If they "jump time" it is usually a belt that is about to pop anyway.

[ericsbestshot]

well tougemiata and i set the crank at tdc and the cam gears did not line up where they were supposed to. set the timing correctly and then the car ran great. drove ten miles yesterday. Today drove 2 miles then started running rough at idle then a second later the CEL came back on. can the belt expand that easily that it will jump time.

[kcbhiw]

well tougemiata and i set the crank at tdc and the cam gears did not line up where they were supposed to. set the timing correctly and then the car ran great. drove ten miles yesterday. Today drove 2 miles then started running rough at idle then a second later the CEL came back on. can the belt expand that easily that it will jump time.

In that case, either the belt is damaged or the tensioner is loose or improperly set.

[ericsbestshot]

i checked the timing this morning and it didn't seem to be off. It may have been off by a tooth, maybe. So i changed it i made sure that there were 19 teeth between the gears and started it up and no change. So its not the timing belt.

[kcbhiw]

i checked the timing this morning and it didn't seem to be off. It may have been off by a tooth, maybe. So i changed it i made sure that there were 19 teeth between the gears and started it up and no change. So its not the timing belt.


Coil pack.

[ericsbestshot]

checking that now

[miatastuff]

LMK if you need the CP back. Also, I assume that in addition to 19 teeth you are checking all three points? Crankshaft at TDC and intake and exhaust cams?

[ericsbestshot]

changed the coil pack to a new one. The CEL is still on and periodically blinking. I think the engine in still a little rough at idle. i don't know how the rough idle could have disappeared tuesday night after fixing the timing and still not being right.

[ericsbestshot]

yes i am checking all the points

[ben91]

Plugs and wires all good?

[ericsbestshot]

yeah plugs and wire all new. I just remembered that there is something missing on the bottom of the coil pack. Is that important? i guess i should add that the tab broke off the cam sensor

[miatastuff]

There is a bolt on the bottom of the CP bracket, its optional.

[kcbhiw]

i guess i should add that the tab broke off the cam sensor

Are you talking about the mounting tab? If so, that's pretty important.

[ericsbestshot]

the bottom mounting tab. does that have anything to do with the function of the coil pack or anything

[RotorNutFD3S]

He's talking about the mounting tab on the cam sensor, not the coil pack, which is why that particular part of what you wrote was quoted.

[ben91]

If the cam sensor is not properly and securely mounted to the valve cover, it would cause all your problems. Actually, if it's not mounted, you're lucky the car runs at all.

[ericsbestshot]

oh i miss the quoted part. The sensor is secured good with electrical tape

[ben91]

I'd recommend trying a new sensor that was securely bolted to the cover. This is likely to be your problem.

[Doppelgänger]

oh i miss the quoted part. The sensor is secured good with electrical tape


:facepalm::facepalm::facepalm::facepalm::facepalm: :facepalm::facepalm::facepalm::facepalm::facepalm:

[ericsbestshot]

it is bolted to the cover as it should. its the connector part that is slightly defective. the clip broke off

[ericsbestshot]

i think the sensor was not connected securely enough. Drove around for 10 min and no CEL. I'll keep everyone posted.

[ericsbestshot]

alright just drove some more. Now CEL is back same P0300 code. Now the only thing is the engine does not feel rough. It idles normal.
I have
replaced Spark plugs
replaced spark plug Wires
replaced coil pack
checked and adjusted timing

no idea where to go from here.

[ben91]

Eric... Replace the cam sensor.

[ericsbestshot]

replaced the cam sensor then drove about 14 miles with a few stops (shutting off engine) still the CEL is on. One odd thing though. I was doing some errands tonight with the CEL on and i started the car once and the CEL did not come back on. Then about 45 min to an hour later the CEL came back on. and i replaced the sensor after this happened.

What should my next step be?

[ericsbestshot]

CEL still on. bumping for help.

[ben91]

The light will stay on until cleared with a scanner OR until you have 2 consecutive drive cycles where the misfire did not occur under the exact same conditions where it occurred earlier.

[ericsbestshot]

well the CEL turned off on its own and then 30 min later it turned back on.

[ben91]

Did you read the code?

After a bunch of misfiring, I'd expect a P0420 (cat).

[ericsbestshot]

honestly haven't had a chance yet but i will.

[ericsbestshot]

replaced the Crank sensor and still have a CEL. Got the code read and it remains the same.
What should i do next?

[matredd]

you need to reset the ECU or clear the codes each time you change something. You can unplug the battery and then hold the brake pedal down for 30 secs or so to drain the capacitors. This will clear codes/reset the ecu.

[ericsbestshot]

well i have disconnected the battery and pressed the brake (not for 30 sec). The CEL turns off, but what is weird is that the idle is good except for the rpms bounce at idle when coming off the gas. The CEL also flashes.

[ericsbestshot]

bump for help. I've reset the ECU. And CEL comes back.

[RotorNutFD3S]

Only thing I can think of at this point is if your crank pulley is worn out and is sending the crank sensor/ECU incorrect readings causing your timing to be off (the rubber can deteriorate). I have a spare low-mileage 99-05 crank pulley laying around I believe, I'll have to check the garage.

[metalman]

Code 0300 = There are more then 300 reasons not to own an OBDII NB. :lol:


I have an NB crank pulley for sure.
Also have crank and cam sensors...and other engine electrical.

[ben91]

Plugs, wires, coils...

[RotorNutFD3S]

Plugs, wires, coils...

Page 1. All new components.

[ericsbestshot]

both sensors replaced. if the crank pulley is worn out shouldn't i see some wobble?

[ben91]

Page 1. All new components.Eric's description of the problem and blinking CEL both indicate misfire. Coils, plugs, and wires are the typical culprits.

[RotorNutFD3S]

Yes, I'm not debating that, but those parts have already been replaced with new components. There is something else wrong obviously.

[metalman]

Yes, I'm not debating that, but those parts have already been replaced with new components. There is something else wrong obviously.

Okay...but what kind of new components? NGK wires etc? Or Autozone crap?
I have had issues with the parts store garbage right out of the box. Just a thought.

[ben91]

Yes, I'm not debating that, but those parts have already been replaced with new components. There is something else wrong obviously.Maybe, and maybe not. For a misfire, I'd go back to basics first. Plug wires or coil packs are the likely culprits.

A P0300 without an obvious misfire would raise my eyebrows and make me want to dig into more complex or involved solutions.

[RotorNutFD3S]

Maybe, and maybe not. For a misfire, I'd go back to basics first. Plug wires or coil packs are the likely culprits.

A P0300 without an obvious misfire would raise my eyebrows and make me want to dig into more complex or involved solutions.

While Kurt makes a good point about what brand/quality of new parts used, I'm failing to see your logic, assuming he has good new parts on the car, he's already gone back to basics and there's still an issue.

*edit* Since this is a recurrent issue, I'd venture another guess to say that a connector is possibly not making a complete connection, be it a sensor or the coil packs.

[metalman]

*edit* Since this is a recurrent issue, I'd venture another guess to say that a connector is possibly not making a complete connection, be it a sensor or the coil packs.

Wasnt there an issue with a taped connector?
I would be checking that stuff too.

[ericsbestshot]

i replaced the wires with NGK iridium plugs. Never had an issue with those. With NGK blue wires. Pick up a new coil pack from O'reiley autoparts. Got used crank and cam sensor for miatastuff and he said that the were working. This also got rid of the taped connector thing.

Does the fact that once i reset the ECU the idle is bouncy (400-1100) then after a min return to normal point to any issues?

[ben91]

While Kurt makes a good point about what brand/quality of new parts used, I'm failing to see your logic, assuming he has good new parts on the car, he's already gone back to basics and there's still an issue.

*edit* Since this is a recurrent issue, I'd venture another guess to say that a connector is possibly not making a complete connection, be it a sensor or the coil packs.C'mon Eric. Car has a misfire and the most common reasons for misfire in general are bad secondary ignition parts (plugs and wires), and for a 99/00 miata in particular is the coil pack. New stuff is usually good, but it's not a guarantee. No reason to not bench test the wires and coil pack, at least it would rule something out.

99+ can also throw 0300 if there's cam sensor funkiness, but that is much less common, and typically will throw a cam sensor code.

[ben91]

Eric (other eric)--under what conditions do you experience misfire? At idle? Under load? Occurs with RPM? Etc

[ericsbestshot]

well the code always comes back at idle. And it only feels bad at idle and seems to run great at other rpms. i've made a post on miata.net and someone said it could be a problem with the MAF.

[ben91]

MAF doesn't sound likely to me, but it's easy to switch them out.

If it only occurs at idle, I may start with looking for a vac leak on a single cylinder--like say at the fuel injectors.

[RotorNutFD3S]

C'mon Eric. Car has a misfire and the most common reasons for misfire in general are bad secondary ignition parts (plugs and wires), and for a 99/00 miata in particular is the coil pack. New stuff is usually good, but it's not a guarantee. No reason to not bench test the wires and coil pack, at least it would rule something out.

99+ can also throw 0300 if there's cam sensor funkiness, but that is much less common, and typically will throw a cam sensor code.

:facepalm: Again, not debating that and you're missing my point, but whatever, I'm not going to argue with a brick wall.

[ericsbestshot]

well i went ahead i used some MAF cleaner and it did nothing.

[ericsbestshot]

how do i get to the injectors.
anything else i should try?

[FooSchnickens]

Have you had your timing belt replaced recently?

Reason I ask is that a customer had all these same symptoms right before this happened from their other "mechanic" not doing the install properly:

http://i143.photobucket.com/albums/r156/FooSchnickens/1229444872303.jpg

http://i143.photobucket.com/albums/r156/FooSchnickens/1229444929344.jpg

[ericsbestshot]

i'll take a look. Did the engine misfire? Did this throw off the timing? Did it have a code?

[tougemiata]

Thanks fooshickens. Eric this is why I have been telling you to check the crank pulley. You will have the exact symptoms you are describing if the keyway is bad. Thats what happened to mine. And I chased a p0300 for weeks just as you have. When I looked at your car you had replaced everything with the recommended NGK stuff, and shortly afterwards he replaced the coil and crank sensor and he still had the issue. From what I see theres nothing else to replace unless you have something internally wrong. But please check the crank pulley!

[ericsbestshot]

so i pulled the crank pulley and the pulley it self looks normal. But the plate on the back (trigger wheel is what i think is called) has signs of scraping against something. Part of it is not black like it is supposed to be. I notice that the timing is off. One thing i think i need to do is get the crank bolt of. What would be the the best way to get it off? I can tell the timing is off again. sorry about the lighting off the pictures i just took everything apart 30 mins ago.

[miatastuff]

Sorry if I missed this somewhere in this string, but has the timing belt been replaced since this all started? If I am reading right, the car has "jumped time" twice which is the base cause of a P0300 - synch error. The crank sensor and cam sensors are not in synch.

[FooSchnickens]

What would be the the best way to get it off?
If you don't have the special tool you can have someone pop the starter while you hold the bolt. Unfortunately, you can't use the same method to tighten it :lol: There are other methods of immobilizing the crankshaft, though. Most involve some scrap metal that is either long enough to wedge against something solid, or is bolted to something else (I've seen a lot of people use one of the PS/AC mounting bolts for this).

[ericsbestshot]

so here's some pics all of which seem normal aside from the sludge. I will be replacing the seal there. I'm wondering because the timing was off again that the timing belt is expanding.

[ericsbestshot]

bumpy

[ericsbestshot]

i changed the timing belt and tensioner and the front crank seal. installed the belt then rotated the crank a few times and everything lined up a the exact spot it should. then put everything back together, started the car up, took it for a very quick drive with out the CEL on. Then got home let the car idle for a minute and the CEL came back. I will verify the timing when i get a chance. If the timing is off again i will be out of ideas. Is there something inside the engine that could be effecting timing? Honestly i feel kinda desperate now.

[ericsbestshot]

i checked the timing and it was good. But i think my crank pulley is a little wobbly. And the car pops when i rev the engine.

[ericsbestshot]

I guess yall are thinking "damn this guy is still having trouble with this" and i'm thinking the same thing. I have the timing perfect and the car does not pop when i rev the engine. It turned out that i was off a tooth. I verified the gap between the crank sensor and crank pulley was good. Used a credit card between the two and it fit but just barely. The engine seems to run smooth but the P0300 code is still there.
Any more ideas?

[RotorNutFD3S]

How much have you driven it since resetting the timing? Or have you unplugged the battery, etc? The code will remain as long as the ECU believes there is a problem.

[ericsbestshot]

i disconnected the battery. and after i drove the car for at least an hour turning off the car multiple times. One thing i should add is that the CEL never blinks anymore.

[RotorNutFD3S]

Hmmm... have you verified that it's still the P0300 and not a different code?

The flashing CEL is to indicate that there is an emissions related problem that could possibly damage your cat. A steady CEL means there's still a problem.

[ericsbestshot]

yes i have advanced auto parts read the code right after it came back on.

[RotorNutFD3S]

The only suggestion I can think of right now is to check the plug gap. May sound funny or redundant, but so many times I've seen people think that they're pregapped when they're new (since they're ordered across the counter by a specific part number for that particular vehicle) and they have issues. The gap is not always right. Or if you find that the gap is right, you could try closing it a bit and see if that helps. Works for the boosted cars getting spark blowout.

[ericsbestshot]

well i do know the plugs are gaped correctly cause i did it before i installed them. How small do think i should make the gap. And shouldn't i feel the misfire or notice the engine feeling rough?

[ericsbestshot]

i tried decreasing the gap on the spark plugs but it seemed to make the engine run worse.

[RotorNutFD3S]

Was worth a shot...

This may be a long shot but since the usual culprits don't seem to be at fault, check your EGR operation. If it's stuck open at idle, it could be the cause. Best way to check it is start the car when it's cold, go up and put your hand on the EGR valve, if it gets hot quickly (hotter than the intake manifold), that means exhaust is flowing through it and that's bad for idle and combustion. Like I said, it's a long shot.

[ericsbestshot]

should i be looking at something fuel related?

[RotorNutFD3S]

For the EGR? No. It's the valve on the back of the intake manifold. It has a hard pipe that runs behind the cylinder head over to the exhaust manifold.

[ericsbestshot]

oh i know what the EGR is. I was suggesting maybe another cause for the issue.

[RotorNutFD3S]

Oh ok. Sorry. :lol: Possibly. Don't know if it's been asked, when's the last time the fuel filter was replaced? Could have a misbehaving injector. There is something that is still causing the ECU to think there's a problem, even if you can't feel it.

[ericsbestshot]

so i started the car today when cold. Kept it idling until up to normal operating temps and the EGR pipe did not heat up. Should i try cleaning the intake manifold out? Never have done it before.
Also the fuel filter is not really that old. I replaced it when i had a P0171 code. Which did not fix the P0171 code. Wiping off the o2 sensor did.

[ericsbestshot]

bumpy

[ericsbestshot]

i tried using some fuel system cleaner and cleaned out the top half of the intake manifold and throttle body. Cleared the code and it came back.

[ericsbestshot]

what do yall think of the MAF sensor being the culprit? One thing that did happen right before the CEL came on is that the car would shut down unexpectedly while having a hard time keeping a good idle. And it would also be hard to turn the car on after it dies.

[dingo7]

wow i had your exact same problem on my prior car but it wasnt a miata. let me just ask this, does the miata have a knock sensor?

[Doppelgänger]

Yes, the NBs have a knock sensor.

[RotorNutFD3S]

I thought the MAF was mentioned on one of these 5 pages?

[ericsbestshot]

yeah i may have been but i don't think i got an answer about it.

[dingo7]

on a miata does the stock ecu move the timing if the knock sensor picks up knock?

[ericsbestshot]

i think so but i'm not sure.
here it says the knock sensor can affect timing up to 12 degrees.
http://forum.miata.net/vb/showthread.php?t=354430&highlight=knock+sensor

if the sensor is defective i guess i can see how it can create a random misfire

[dingo7]

i had an 03 evo and some were known for having the P0300 code. in the 4 years i had my evo it would throw the 300 code just about every time i drove it. I replaced wires, coil packs, plugs every 3500 miles, timing belt etc. In the case of that car the sensor was set so sensitive it always moved timing and during that time it missfired. Granted this isnt an Evo, but im thinking your car is obd2 so its gonna be able to move timing some how. Maybe your knock sensor for whatever reason is picking it up and there is your problem.

If all else fails do what i did. I bought a obd2 scanner and would clear my own codes. there has to be a reason and maybe the scanner will help and let you clear codes and check that knock sensor or whatever it could be. hopefully you will figure it out b/c i know it is frustrating.

[ericsbestshot]

would replacing the knock sensor fix the fact that it is being to sensitive? or is that an ECU issue?

[dingo7]

In my case it was an actual ecu programing issue. It was solved in later model years. In your case its a miata, so I wana guess its the sensor might be faulty. You have to understand an number of members here might be alot more knowlegable then I am. I am just taking a stab in the dark. seeing as most of the members have already given you the steps that I took to solve the problem. The fact that you have already done all of them I suggest the knock sensor.

[RotorNutFD3S]

^^^ And you might be right on the money. Checking the MAF isn't a bad idea, neither is the knock sensor. We're running out of options...

[ericsbestshot]

well then those are the next two thing's i'll try

[ericsbestshot]

so i finally have some decent news to share. Since i was tired of not being able to drive my car in this awesome weather i disconnected the battery to turn off the CEL. Then i drove around for about 25 miles with out the CEL and was able to pass emmisions and renew my tag. Then about 15 miles later the CEL comes back on. Then driving around today the CEL turned off all on its own then about 50 miles later came back on. This is all with out me doing any work on the car.

[Doppelgänger]

Well, that's good. So keep on driving and put a piece of tape over the CEL :lol:

[RotorNutFD3S]

:lol: This is exactly why I hate OBDII.

[ericsbestshot]

Well, that's good. So keep on driving and put a piece of tape over the CEL :lol:

well i have to be honest i was thinking of that because that CEL is bright

[metalman]

:lol: This is exactly why I hate OBDII.

Ditto!! Its total sucksville.
Love my 1.6 cars, if you trigger a cel in one of those you have parts missing. :lol:

[Dr.Drew]

I got one CEL once in my 93 and it was because I didn't plug the MAF harness in before I cranked it.

Before I got my MSPNP my 97 would send a code every other month.

[dingo7]

but it does give you an idea as to what is wrong. If not your in the dark...

[ericsbestshot]

i'm still kinda in the dark. I'm not sure if my current situation really tells me anything.

[dingo7]

have you cleaned the maf, or checked the knock sensor?

[ericsbestshot]

well i have cleaned the maf but not checked the knock sensor but those were the thing i was going to replace next.

[ericsbestshot]

problem seems fixed. Have not had the CEL for a week and plenty on miles. Didn't really do anything new to fix it either.