So Iv had the p0300 for just over a week now, cleared it a few times and has come back every time. With the search function down, Iv been googling and doin as much research as I can, but any advice from experience would be great. It has a stumble at idle that isn't always consistent, but has always happened periodically since Iv owned the car(6 months). My mods are bop, spacers, gutted cats, Cattman y and SRI, installed in that order. Besides that stumble, it runs well, I have noticed good gains from all mods, although it smells like it's running very rich since the gutted cats and prob needs a tune.

The code had popped up before I did the gutted cats, y and intake, but when cleared it didn't come back until those mods were done, a clue maybe? I've done quite a bit of reading, and this really is a useless code, as it leaves a ridiculous amount of possibilities. Here is what I want to check when I get off work tonite, plugs, coils, injectors, primary 02's, cam sensors and the IM for leaks.

My laptop is currently being fixed so Im doing this all from my iPhone and can't view the fsm on this thing. I'm pretty basic with the mulimeter but know how to back probe and do basic testing with it, but without the fsm I don't know what to test for. If anyone can throw me a bone for the 02's, injectors, coils and cam sensors it would be very appreciated. I know "spoon-feeding" is frowned apon, but I'm sort of disabled without a search function or real computer

 

One of the coil is dieing. Don't you also get P1320?? Eventually you will get P030x where "x" is the cylinder number but that might take a while. You could either replace all the coils if they are old or buy a single (or two if you have different set for front vs rears) one and move it between different cylinder until the problem goes away. This assumes that your spark plugs are good. If not replace them first.

 

I just had the same problems. Several months ago (at least 6) I had the stumble at idle but then the cel would flash and my ran like it was on 5 cylinders (like crap). I chalked it up to bad gas because I did just fill up at a shady station. Well the problem worked its way out. I have had no issues until today. The idle was stumbling and I noticed that my power was not there and acceleration was jittery. It has to be a coil. My car has 128,000 miles and these things are known to go. I am in the same boat as you though because I am only getting the p0300 code. My car is not nice enough to tell which damn cylinder coil is on its way out. Search for how to test coil voltages here and you should find a very informative thread which will help you narrow down the faulty coil. Hopefully yours isn't intermittent like mine. Good luck.

 

No other codes at all, I suspected the coils but I'm not sure if they have been replaced. I'm def not buying all new ones on a whim, but I'm gonna try an find the testing procedure for them. I'm working pretty late tonite, so I might not even be able to get to do anything tonite.

 

I have a few suggestions and it's completely up to you if you want to try them out.

One way people distinguish a bad coil is by taking a volt meter and checking the resistance across the pins on each coil. If one coil deviates significantly from the others, it's most likely bad.

Another way people test it is by unplugging one coil at a time with the engine on. If the engine seems to run worse, then the coil is good. If unplugging the coil makes no difference to how the engine's running, then it's the culprit.

However, you might have one that sparks intermittently and is 'on its way out', and these tests might not help you.

My last suggestion is to try and get a hold of an obd2 scanner. Reset your codes and drive around. As soon as your CEL comes on again, check and see if a p030X is thrown so you can identify which cylinder it is. I've heard from someone that they were able to identify 2 or 3 bad coils this way.

Can't make any guarantees but these were ways I've heard of and/or seen people use to try to figure out which coil is bad.

 

Alright thanks bro, I didn't get a chance to do anything yesterday, but I should be off at a decent time today and ge to check some of these things out.

For some reason last night it turned off when I got low on fuel, but the stumble is still there and I bet the code will come back. Also it seems to run very well in the rain, clues maybe? I guess we'll see if it comes back on the way home from work

 

What a small world. I just bought 6 used coils (around 45k miles) from Knight for 80 shipped and just noticed he lives in Ontario too. Just keep an eye out for some decent used ones for sale here and ****** them up.

 

Right on, the Canadian boys are startin to come outa the woodwork. Mine have a grey zero on them, does that mean anything to anyone?

So, randomly the lights went off a couple days the light went off and stayed off for about two days. It ran pretty good while it was off, pulled hard and the stumble at idle was minimal if at all. Last night, it came back and so did the stumble, it still seems to run fine above idle but it's hard to tell power cus wet roads. I'm really suspecting an intermitant coil(s), I've been so busy this week I haven't had a chance to check anything, but I'm gonna make time tonite. I'll check back with what I find

 

When I had this particular problem, I drove with the scanner connected *all* the time. I used to check the codes every time before turning off the car and eventually I manage to get the pending code with the cylinder number. Mind you, when the actual CEL came on, the specific cylinder code had vanished. That is to say by the time CEL came on, it was too late to get that code.

If you are not in a position to do the above, do this. Buy a single brand new front ignition coil (OEM or similar) and replace one of the front. Keep the old one aside. Drive the car for a day. If the problem is not resolved, use the removed coil and replace the next coil and keep that one aside for next day. You get the idea.

If that does not fix it, then you go and buy a single rear coil and continue doing the same thing.

You could be lucky and the first front cylinder coil replacement might fix your car or you could be unlucky and the last rear cylinder coil might be bad.

- Vikas

 

Thanks Vikas, I want to test all of them tonite and see if they are all consistent with eachother. To do so I should be testing the tip of the coil while running, correct? I'm just hoping to figure this out as fast as I can as I just wanna enjoy my new mods, if I don't get anything decisive tonite I will def try what you have said.

 

Sorry Roc, but I don't follow you, I must be missing something.

 

I do not follow your question

 

Once again, I'm working nice and late so looks like it's gonna be the weekend til I get to try anything(maybe tomorrow).

Sorry Vikas, I'm kinda basic when it comes to electrical components. I plan to do some more research on how, but I mean by using a multimeter shouldn't I be able to test the output of the coilpacks, and see which one(s) isn't consistent with the others, calling it the bad one? Again I'm very basic with this stuff so be gentle

 

P0300 random misfire. Question. How much RTV did you us to seal your Spacers?

 

I just re-installed them(took IM off when I dropped the cats), and was careful not to use too much, it's pretty hard. I'll be checking it as well when I finally get a chance

 

You need to check the LIM spacers. You could have applied to much to the LIM spacers. Because I had the same problem. What happens is the build of to much RTV blocks the spray of the fuel injectors.

 

Ok thanks man, will do. You were gettin the p0300 from that?

 

I do not think you want to mess with the live coils using the electrical meter given that you want to do basic and simple (i.e. NOT leading to even more problems!) stuff. If you want to test the resistance of the coil, there is a procedure here but many times the coil resistance will NOT show the problem. Besides, you need to take the coil out to do that testing.

That is why I am suggesting that you just keep on changing one coil at a time sequentially until you find the bad one.

If the car is behaving badly all the time, then there is an easier method called drop cylinder test which involves disconnecting one coil at a time at the electrical connection WHILE the engine is running. Disconnecting a good coil makes engine run even worse whereas disconnecting a bad coil makes no difference. But I suspect that when it starts running badly ALL the time, you would most likely get the cylinder specific code.

There are other reasons why you could get a random misfire code P0300 but ignition is the most likely suspect and it needs to be ruled out before going after more esoteric causes.

- Vikas

 

Yes and P0171 system lean.

 

I'm pretty sure it's a rich misfire, but I'm gonna check regardless.

Vikas, I'm going to try disconnecting the coils today when I'm done work. If I have no luck I'll grab a new coil pack, is that something I should buy from the dealer, or are the other brands trust worthy?

 

I remember that OEM coils are made by Hitachi and Made in Japan. If I were you, I would verify the COO of the coil at the parts store otherwise go to dealer or order from DaveB

 

K thanks, last night it turned off again and has stayed off(without doing anything to it). Today it came on, flashed for a bit then turned off, twice. So I got the codes scanned and it had the 300 stored, but also an 0507 which I think is for high idle, I'm looking it up... another clue possibly? I'm gonna try unlugging the coils and if that's inconclusive, off comes the intake mani for a check, and re-install, as well as an overall check. I'll post results asap

 

When you reinstall your LIM spacers use a VERY thin layer of RTV. I used my fingers to apply the RTV.

 

Update: I have been so ridiculously busy I barely even got a chance to do anything this weekend. I tried the drop coil test, which was inconclusive because I couldn't get it to idle steady enough, to determine if it was changing from unplugging the coil or just the bad idle. It is getting progressively worse, yesterday while idling it just died but it started right back up. This morning it started fine(which it always has), but when I pulled out of the driveway it chugged and hesitated real bad til it warmed up a bit more. Hopefully, I will have time tonite to take of the IM, re-install the spacers and do some other checking because this is getting bad. I'm gonna look into coil packs today and prob buy one tomorrow if I don't find anything. I have never been this busy with work before, which I cant really complain about, but I think my car is mad at me.

 

So I finally got some time to look at this thing, and here's what I found: fist of all, I'm pretty sure I over torqued the front 3 bolts that hold the UIM on, because I found oil on the back half of the spacer and on back side of UIM/LIM ports. I also think the rtv I used was setting up to fast, so I used a different type which seemed to work better. I found a small crack in the rear valve cover, which did show a very small amount of oil leakage, I will be ordering the 04's today.

Also while inspecting/testing the coils I found out u can take the stem off, cool, I then noticed that there was rust in the tip of one coil (drivers side rear). I took it apart and found the connector spring inside quite rusted and corroded, the rubber boot iside that connection was missing some rubber, so I assume water got it there, there's also something that looks like a fuse that connects two springs into one which was also in rough shape. So I sprayed it with penetrating oil then cleaned it with maf cleaner, I'm not worried about messin it up cus I'm gonna grab another one.

So, I put some dielectric grease on the plugs, reassembled everything, making sure to properly torque all the IM bolts and let it sit for the night. It sat for a good 8hrs before I started it this morn, I don't have a very long drive to work but it didn't stumble at idle or throw any codes at all, no pending either.

I'm not saying it's fixed for sure but I believe the leak at the spacer could have caused this misfire. Even if the code doesnt return, I am going to replace that rusty coil and the valve covers anyway. Wish me luck

 

Good luck and good job addressing the issues you found.

 

Keep us update bro.

 

Will do, hopefully it stays off, there's a meet in Vaughn I wanna go to tonite. I didn't have time to take the LIM off, but I'm gonna redo all the spacers this weekend with the other rtv I used last night. Also I noticed the LIM spacers weren't port matched and I'm pretty sure it's not because of placement, they looked smaller than the size of the port, normal? I know the guy who worked on this thing before me was a total goof, so possible wrong LIM? I'll check further this weekend, just thought I'd throw it out there