Spec Miata Community   
search | help | calendar | games | forum home

  next oldest topic   next newest topic
» Hello Spec Miata Community » SpecMiata.com » Spec Miata Garage » Misfire Ignition Cut?

 - Email this page to someone! | Subscribe To Topic  
Author Topic: Misfire Ignition Cut?
Kyle Freiheit
Member

Region: NWR
Car #: #78 sorry Terrell
Year : 1992
Posts: 270
Status: Offline
Icon 1 posted  Profile for Kyle Freiheit     Edit/Delete Post  Report this post to a Moderator

This weekend I developed a high rpm misfire or what seems is an ignition cut under load. It would rev to about 5k and then my RPM would quickly cut/jump lower and then back again, extremely fast. Couldn't figure it out at the track basically ruining my Double National weekend. The problem will now happen even at lower RPMs and I can replicate it by just free reving it.

What I have checked/changed so far.

1)swapped AFMs
2)checked AFM wiring, checked plug, pulled back boot and checked wires
3)swapped CAS
4)Checked CAS wiring
5)swapped Coil pack
6)checked Coil pack wiring
7)replaced the temp sensor on the back of the head
8)checked temp sensor wiring
9)pulled the ECU plugs and put them on and off a few times
10)Spark Plugs
11)Sprak plug wires
12)bought a battery/charging system tester, Battery is good but battery charge is a little low, battery is currently on the charger but I did check by starting the car, pulled the positive battery cable and ran just on the alternator and the problem is still there.
13)Alternator is new and checks out very well

My RPM data on my DL1 shows that the RPMS jump very fast and sometimes my shift lights would light up during the RPM drop(wierd). Right now, my next step is to swap ecus and ignitor.

Any other ideas? I didn't think it could be fuel related but could it?

Kyle

Keith in WA Verified Driver Made Donation to Website
Pack Fodder

Region: NWR / Oregon
Car #: 88
Year : 95
Posts: 2000
Status: Offline
Icon 1 posted  Profile for Keith in WA     Edit/Delete Post  Report this post to a Moderator

Kyle,
That was painful to watch and hear trackside. Especially as slick as it was, I was worried about an artificial mid-corner lift sending you off.

Have you checked the ground straps both from the back of the head to the engine bay and the one from the main wiring harness to the PPF? Some of the intermittant electrical issues, like the one Terrell had, only appear at the sort of RPMs yours did. I'm guessing it's the vibration when the engine comes on the pipe, but it's enough to cut the circuit. His BTW, was due to a bent pin in the ECU connection so you might look at that too.

Good luck!

--------------------
Keith Novak
(Will work for tires)

Dawson
Member

Posts: 11
Status: Offline
Icon 1 posted  Profile for Dawson     Edit/Delete Post  Report this post to a Moderator

I had the same symptom in my '96. Checked all the stuff you did and more, ad nauseum. Turned out to be the cam angle sensor. Got a replacement from a parts vendor who sells miata stuff on this planet. Fixed it.

Good luck.

Kyle Freiheit
Member

Region: NWR
Car #: #78 sorry Terrell
Year : 1992
Posts: 270
Status: Offline
Icon 1 posted  Profile for Kyle Freiheit     Edit/Delete Post  Report this post to a Moderator

I swapped out the cam angle sensor with a known good unit and still had the problem.

Swapped ecus and ignitor. No change.


kyle

Terry Whitlock Verified Driver
Member

Region: BUCCANEER
Car #: 23 SSM, 36 SM
Year : 1992, 1990
Posts: 136
Status: Offline
Icon 1 posted  Profile for Terry Whitlock     Edit/Delete Post  Report this post to a Moderator

Try checking your injector wiring harness at the connectors. We had a similar problem and found that the latching mechanisum on a connector (at the injector) had broken and the contact was being lost at certin RPM harmonics.

--------------------
Terry Whitlock

Kyle Freiheit
Member

Region: NWR
Car #: #78 sorry Terrell
Year : 1992
Posts: 270
Status: Offline
Icon 1 posted  Profile for Kyle Freiheit     Edit/Delete Post  Report this post to a Moderator

Update. I swapped to a known good ecu in my dads ITA car and ignitor about an hour ago and nothing changed. It feels like the rev limiter and now happens any point along the range. Going back to the drawing board I went back and thought about the last thing I changed and it dawned on me that I moved around the 02 sensor on Sunday morning. So, thinking that I had it figured out, I went and bought a new 02 sensor and put it in, well that didn't work either.

I will pick up a fuel pressure guage tomorrow and start down the fuel route. I will also go back and start swaping the other parts to other spares just to make sure I am covering ALL bases.

I will also check the master switch and wiring.


Kyle

TillerTech
Member

Region: SoPac
Car #: na
Year : 89
Posts: 441
Status: Offline
Icon 1 posted  Profile for TillerTech     Edit/Delete Post  Report this post to a Moderator

I had a friend's car do this during an entire weekend. We had the whole thing apart, including dropping the fuel tank. Nothing.

I started chasing the kill switch wiring, not the batery side, the low v ignition kill. It was wired into the CAS power wire. I eliminated the kill switch and wired it direct. Problem solved.

John

--------------------
Miata Race glass and CF from Legacy Molds. 4 1/2# CF Hood
http://www.jnent.net

Kyle Freiheit
Member

Region: NWR
Car #: #78 sorry Terrell
Year : 1992
Posts: 270
Status: Offline
Icon 1 posted  Profile for Kyle Freiheit     Edit/Delete Post  Report this post to a Moderator

Thanks John, My kill switch is wired like Dave W. says to.

So, was it the kill switch or the wiring? I will bypass the kill switch and if that is bad I have another kill switch that I can wire in.

Kyle

B Wilson Verified Driver Series Champ
Gold Member

Region: Oregon
Car #: 68
Year : 91
Posts: 2359
Status: Offline
Icon 1 posted  Profile for B Wilson   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

Ignition switch is an easy swap, should definitely try that. unplug and remove the screw and it slides right out -- swap with known good unit.

-b

--------------------
Bruce Wilson
2010 Oregon Region Champ
2010 Monte Shelton Driver of the Year
2010 25 Hours of Thunderhill E3 and Under 2 liter Overall Champion
Oregon Region SM Class Advisor

davew Verified Driver Made Donation to Website
Veteran Member

Region: chicago
Car #: 72 and ?
Year : 90 and 90
Posts: 1051
Status: Offline
Icon 1 posted  Profile for davew   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

After you check the fuel pressure check the fuel filter. I had one a few weeks ago that was plugged and caused similar symptoms. Pump put out plenty of ressure but not enough volume for high rpms

Dave

--------------------
Advanced Autosports, The Midwests leader in Spec Miata Service, Parts and Rentals
608-313-1230
Authorised Spec Miata service center
www.advanced-autosports.com

Jamie Tucker Series Champ

ARRC 2010 Champ

Region: CFR
Car #: 97
Year : 1990/99
Posts: 788
Status: Offline
Icon 1 posted  Profile for Jamie Tucker     Edit/Delete Post  Report this post to a Moderator

Also try disconnecting your shift light or anything else that is using the rpm pulse.

--------------------
2010 ARRC Champion
2010 CFR Champion
2010 instigator of the year
2010/2011 Andrew Von C Wingman

DionJ Verified Driver
Member

Region: SF
Car #: 68
Year : 91
Posts: 186
Status: Offline
Icon 1 posted  Profile for DionJ     Edit/Delete Post  Report this post to a Moderator

Check your engine ground wire, only takes a second and has some of your symptoms...

Randy Thieme
Member

Region: Oregon
Car #: 51
Year : 1993
Posts: 322
Status: Offline
Icon 1 posted  Profile for Randy Thieme     Edit/Delete Post  Report this post to a Moderator

Last I looked at the wiring harness on the 1.6L cars there's a common wire which goes from the ECU to the ignitor and the tach. Could be a problem along those lines. Last two cars I've seen with tough electrical problems (including mine) were harness related. Some of those symptoms were similar to yours.

Was the ECU swapped with someone else's before the problem started to occur? If so that's a likely suspect. Some like to put a slight twist on the ends of the prongs in the ECU that insert into the harness connector. Problem is if you swap in an ECU that was modified like that it permanently distorts the connectors on the harness end. Then when a normal ECU is put back in it never makes good connection. Sometimes you can find it by wiggling the connector but not always (ask me how I know). I know of two cars, including my own, which lost three race weekends between them due to that very issue. Fortunately Mazda designed the ECU connector on the harness so it can be disassmbled and repaired. A good automotive electrician can do that.

If you're going to be in the Portland area PM me and I can get you the name of a top-notch automotive electrician. If he can reproduce the problem in the shop then he can fix it whether it's the harness or something else.

Jamie Tucker Series Champ

ARRC 2010 Champ

Region: CFR
Car #: 97
Year : 1990/99
Posts: 788
Status: Offline
Icon 1 posted  Profile for Jamie Tucker     Edit/Delete Post  Report this post to a Moderator

Also try disconnecting your shift light or anything else that is using the rpm pulse.

--------------------
2010 ARRC Champion
2010 CFR Champion
2010 instigator of the year
2010/2011 Andrew Von C Wingman

suck fumes Verified Driver
Veteran Member

Region: Lonestar
Car #: 75
Year : 3rd in the nation
Posts: 522
Status: Offline
Icon 1 posted  Profile for suck fumes     Edit/Delete Post  Report this post to a Moderator

Simple solution that I have seen happen many times. Unplug all the connectors under hood and spray contact cleaner inside all plugs and let dry for about 30 min. Then start it up and try again. I would have done that before buying a bunch of sensors u don't need. It worked for me.

--------------------
THAT JUST HAPPENED!!! -RickyBobby-

Kyle Freiheit
Member

Region: NWR
Car #: #78 sorry Terrell
Year : 1992
Posts: 270
Status: Offline
Icon 1 posted  Profile for Kyle Freiheit     Edit/Delete Post  Report this post to a Moderator

Update and Background.

I put this motor in before this weekend and it ran just fine when I broke it in on the dyno and tuned it and all of saturday and one session sunday morning without any indications. I purposely left all sensors and accessories the same as they came off my previous motor so that if there was an issue I could easily narrow it down. oops.

I removed my data RPM wire from the mix in the beginning in an attempt to make sure nothing else could be causing this. The problem still occured with my ecu and a known good ecu from another car. I have swapped the ignitor to another unit no change.

I have also changed out engine ground straps(I had a better looking one) and cleaned and scrubed the area around the ground strap.
How is the coil pack grounded? I cleaned up the area under the ground

Right now the car stumbles even at partial throttle and when you step on it, it will cut out on the way up. The cut out sounds like if you hit the rev limiter once.

I pulled the positive cable off the battery and checked continuity across the kill switch and it seemed fine both ways.

kyle

Greg Bush Verified Driver
Thread Killer

Region: NW/OR
Car #: 04
Year : 90
Posts: 1765
Status: Offline
Icon 1 posted  Profile for Greg Bush     Edit/Delete Post  Report this post to a Moderator

Plug wires?

tony senese Verified Driver
Phew, that was close!

Car #: 99
Year : 1994
Posts: 836
Status: Offline
Icon 1 posted  Profile for tony senese   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

check the connector to the cam sensor

--------------------
Tony Senese
SM#99
2008 NASA-NE SM Champion
NASA-NE SM Director
2008 PRO-IT SM 3rd place
http://www.nosenseyet.com/coppermine

Kyle Freiheit
Member

Region: NWR
Car #: #78 sorry Terrell
Year : 1992
Posts: 270
Status: Offline
Icon 1 posted  Profile for Kyle Freiheit     Edit/Delete Post  Report this post to a Moderator

plug wires have been checked.

I checked the cam angle sensor connector but I will look even closer.

Just pulled all the electrical connections in the engine bay and sprayed them down with electrical connection cleaner.

Kyle

Kyle Freiheit
Member

Region: NWR
Car #: #78 sorry Terrell
Year : 1992
Posts: 270
Status: Offline
Icon 1 posted  Profile for Kyle Freiheit     Edit/Delete Post  Report this post to a Moderator

Alright, looks like its fixed, although I used a little bit of a shotgun approach I think it was the ground that is on the fuel rail that goes to the CAS and Coilpack I think. From the top it looked tight and clean but I pulled it off and cleaned it and when I did it could have been a little tighter, I then used connection cleaner on all the engine connections as well as added dielectric grease to them all. Right now it revs smoothly without any hesitation or cutout.

I knew going into this it was going to be something simple and embarrassing but whatever, its fixed.

Thanks for everyones help.

Kyle

PS: It was the ground off of the engine hoist eye. I loosened it just a little and the engine went back to having a miss. Feck.

George Munson Verified Driver
Member

Region: 83
Car #: 127
Year : 90
Posts: 284
Status: Offline
Icon 1 posted  Profile for George Munson     Edit/Delete Post  Report this post to a Moderator

Thanks for posting the fix. It is posts like this that help me the most. [Wink]

Kyle Freiheit
Member

Region: NWR
Car #: #78 sorry Terrell
Year : 1992
Posts: 270
Status: Offline
Icon 1 posted  Profile for Kyle Freiheit     Edit/Delete Post  Report this post to a Moderator

No prob, turns out the 2 grounds that are on that post were clocked a little wierd where it looked tight but there was some wiggle room. Took a few hours of running to probably work themselves loose. I didn't take much either.

Kyle

Qik Nip Verified Driver Made Donation to Website Series Champ
Loose Member '09 & '10 Great Lakes Regional Points Champion

Region: Cincinnati Great Lakes
Car #: 60
Year : 1990
Posts: 1487
Status: Offline
Icon 1 posted  Profile for Qik Nip     Edit/Delete Post  Report this post to a Moderator

quote:
Originally posted by George Munson:
Thanks for posting the fix. It is posts like this that help me the most. [Wink]

+1 ... If it helps someone else enjoy thier race weekend, it's worth it!
Rick`

--------------------
Fortune Cookie Racing SM 60
Directions for use: Race, Rumple, Repair ... Repeat!

Mark Verified Driver Made Donation to Website
Member

Year : 1990
Posts: 367
Status: Offline
Icon 1 posted  Profile for Mark   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

WTG Kyle. Those intermittent bugs are the hardest to find and fix.

--------------------
Mark
http://www.ironcanyonmotorsports.com

   

   Close Topic   Feature Topic   Move Topic   Delete Topic next oldest topic   next newest topic
 - Printer-friendly view of this topic | Subscribe To Topic
Hop To: