Hello forum members,
Had the wee silver Miata out at the track and was having a good time. Misfire started happening at high RPM. Came off the track and then it started happening at idle pretty badly. I swapped over the wires and coils from the Exocet with no improvement. I know it can be a lot of things, but can we brainstorm why it would start happening when the car was beat on? I've got new wires coming tomorrow just to make 100% sure.
Brand New spark plugs on it
Checked the grounds at battery and to engine. The one under the brake master cylinder doesn't look great and will be cleaned shortly.
Oil doesn't have coolant in it. Water temps never elevated and oil pressure still looks good.
I have another track day on Wednesday, so I was hoping to have it back in order before then if the car gods are merciful.
**Edit: After letting it cool for a while the miss isn't as apparent at idle.
OK - so I took to beating the snot out of the Exocet for the rest of the day and let the wee silver miata rest. I had a great time, but hilariously found out that the federal 595 rs-rr seemingly had better grip (though they get greasy faster) and communication than the r888rs after driving them back to back (205 federal vs 255 r888r even). Man I can't wait to wear those tires out and swap to a7/r7s.... But alas, I digress.
SO - the problem at hand. After letting it cool the rest of the afternoon it started up and NO LONGER MISSED AT IDLE (or missed at any time I could tell). Is this indicative of anything in particular? Maybe an overheated fuel pump??? It's really hard to replicate except at the track since it takes 3-4 2+ minute laps at NCM to start missing - I obviously would have trouble replicating that on normal streets/highways.
My new wires come today - I'm considering swapping the fuel pump as preventative maintenance. It's got a brand new fuel filter in it. Brand new plugs. And swapping the ignitor/plug wires didn't help at the track. I've been running 93 in it, no pinging, etc.
I'm going to check the ECU water temp sensor, the fan and the gauge cluster ones seem fine. As noted above the water temp never elevated (I have a full coolant re-route and big aluminum radiator - more than enough cooling for a stock 1.6) and the oil pressure remained consistent through out the day.
Is it charging? I don't know what year your Miata is but NAs can have alternators fail in a way that doesn't turn on the warning light and they'll run off the battery for quite some time. When the battery gets low they'll start to miss-fire. The battery can recover enough for the issue to go away after temporarily after sitting for a bit.
I like APEowner's check for specificity and simplicity of testing.
Beyond that, I'd be looking for something that's unhappy when it's hot. I don't recall the final details of your recent cyl #4 no spark issues, but are the coils suspect at all at this point?
What year is this thing again? It sounds like ignition to me.
It's a 1990 w/ a big nose swapped in, stock everything - but a swap that was literally finished last week. Alternator might be a good suggestion - the battery is brand new.
Easy enough to check an alternator. Igniter?
I'm prone to messing things up, does swapping the exocet's wires/coils (that doesn't misfire and has newish wires on it) not narrow it a bit? It still misfired at idle/revving right after I swapped over the pieces and it was still fairly fresh off the track. Or was that test no good for some reason?
I will test the alternator for sure.
The 1.6 has a separate igniter, so if that's the problem swapping the coils and plugs wouldn't change it. I think.
In reply to Keith Tanner :
Oh, I follow now, I'll bring one of my many spares and check it if this happens again. I've never heard of that failing and was conflating the igniter with coils for some reason. Lemme see if there's an easy way to check if it's in spec while I'm at it I suppose. Really annoyed that I didn't think of that first since I have one that appears to work well on the exocet :face-palm:
Live and learn I suppose. Thanks guys!!
Igniter and coils are effectively the same unit in the 1.8 cars - that's why I asked ;)
I'm not strong in ignition function so there's probably someone else who can give better info. But to me, misfires that get worse with heat and better with no heat just screams a spark problem. Changing the coils are wires are the first thing I'd do as well.
I know you said the plugs are new, but it might be worth pulling one or two to check the gap.
In reply to Keith Tanner :
Roger! I have a decent list to go after now - Hopefully I can get it sorted - it was an absolute joy on track. The federals on those light rims really talk to you - very slidey and fun verses the very serious nature of the exocet. The back and middle straight at NCM my helmet is trying to get ripped off my head and the buffeting is intense. It's a lovely change of pace to not even touch 100 on either straight as it tries it's hardest and slides around doing it.
I can't fault it too much, it's made the 3 hour round trip twice so far - one more time for Wednesday assuming I feel like driving a/c-less in the nearly 100* heat we've been having (the compressor and friends are still there, I just haven't had the time/money to fix it yet :((( ). My CX-9/Mazdaspeed3 might be better at the long interstate legs. I am putting together a video on debugging the cruise control that made the second trip a dream compared to the first one. And the speedo may be reading 80, but my gps said between 75-78 - A LOT of variance there. That still doesn't seem to match what the gear calculators says it should be. 205/50r15's with a 4.1 rear and a 5 speed - who knows! I pretty much wear my noise cancelling head phones the entire way and it's not a terrible trip.
Miata speedos read high, always have. I read back in the day that they are as inaccurate as allowed by law to give the greatest sensation of speed :)
In reply to Keith Tanner :
Lol, sounds about right.
Well I checked the plugs, all gapped to 40, I installed the new wires, checked the battery high 12v, checked the alternator while running I'm seeing 14v after startup, and I swapped the igniter - I still have a bad miss after a lap of beating it. Does that point to fuel?
**Edit, see below comment, now it's sadly running on 3 cylinders :(
Closer inspection says cylinder 1 is not firing now. I feel and can hear spark on one and cylinder 4 is firing....
AND IT WAS AN MF'IN INJECTOR PLUG NOT SEATED. Yeesh....... As always, thanks for all the help!
In reply to accordionfolder :
Glad you found it. I just popped in to recommend checking all of your connections due to the recent swap. It's the best place to start troubleshooting when you have issues after a swap/parts replacement that isn't working right.
In reply to Recon1342 :
Being intermittent really threw me off the scent. I'm about to go and find out if I really fixed it! Fingers crossed...
Good luck and good catch!
It took it like a champ! Beat the snot out of it for about an hour on the track. A little na Miata is a wonderful thing! Slid around, and had a great time.
