17 replies to this topic

[Sean Allen]

Gents, 

 

Car is a 1.6 tub-up build from 2009, hasn't really ran much since 2010 except for a track day.  I'm pretty sure I replaced the transmission a few years ago, and when I brought it out for a track day recently I was getting a strange cut out issue.  The best way I can describe it, would be similar to the sensation you may get when a ground wire is loose (like the PPF brace ground) and the wire separates during turns.  

 

While at Laguna Seca during the first session the car would cut out on Right hand turns momentarily before the apex, through the turn and then it would come back to life and continue on with no problems.  I pushed it on through another session, and by that time the issue seemed to get worse and would happen during most turns, while at the same time remaining "cut out" for slightly longer.  Sometimes even going in and out, before settling back down and running fine.  

 

From what I remember, it was just the motor losing power.  I'm fairly certain the dash remained on.  

 

I've gone over the car, checked wires and grounds and nothing is out of the ordinary.  

 

Thoughts?  

[LarryKing]

Have you ever replaced the fuel pump?

[Sean Allen]

I thought that may be the issue at first, so a new filter and FP went in.  No dice.  

[Tyler Dahl]

I think Joey Jordan had the same problem at Miller in 2013. I think it was a bad Afm.

[Ron Alan]

Does this mean we will see you out at the track soon Sean? Does this only happen under G loads? Can you repeat it in the pits or in a straight line? Seen a rash of bad cam sensor plugs...harness side.

[Tom Hampton]

A similar thing happened to me twice at msr houston in january.  On saturday, the cas plug was separating under g load.  On sunday, the plug on the lower left of the steering column switch was doing the same thing.  Both were a bear to find, because the plugs were not completely pulling apart, but were just enough to imterrupt the connection.  so, a visual inspection didn't reveal a dangling connection.

 

We found both by starting the car and then wiggling and pulling on all harnesses until we repeated the problem.

[Bench Racer]

Welcome return Sean.

 

Posted by Keith Novak under thread 97 Miata Electrical Issue.

Posted 08-25-2015 12:24 PM

 

 

Although it sounds like it's not the issue in this case, one thing it reminded me of is a kill-switch issue.  Not everyone wires them the same and when the switch goes bad, many strange electrical issues can occur.  Symptoms when mine just went out included:
â—¾Car died on track while I was sorting out a fuel pump issue. (Thought it was pump related).  Would not restart.  Restarted fine after being towed back in and allowed to cool.
â—¾Car would run fine on the track for about 20 minutes and then start to die like it was running out of gas
â—¾Transponder died.  Light on but no signal.
â—¾Battery wouldn't charge.  Alternator measured it was putting out 35-40 volts while voltage was steadily dropping at the battery.
â—¾Electrical components started getting abnormally hot.

I bypassed the kill-switch and the voltage went back to normal then replaced it and no more problems.

Just a diagnosing tip for next time to take one wild-card out of the equation.

[Sean Allen]

Ron, I'm not sure, it may also go on Craigslist.. ha.   But yes, only on G's.  I will start it up today and start pulling around on cables.  Interesting about the kill switch, I may have an extra one to try out.  The only problem is I can't exactly drive the car around to see if it fixed it haha.  

[Keith Novak]

How did you check the grounds?  They don't have to be loose.  Corrosion builds up in there over time and yours has been sitting for a while.  I've known several people with problems just like yours that solved it by removing the grounds, cleaning them up with sand paper, and reattaching them even though they were already tight.  I attach all mine with star washers.

[Diller]

Sounds similar to the issue I had on my 94. The harness going to the cam sensor had a broken wire but the insulation was still good. Check to make sure you are getting a good 12V, 5V, 5V, and 0V signal (cant remember what wire has what voltage off the top of my head)  at the cam sensor with the ignition on. Mine would do this but once I wiggled the wires one of the 5V signals would drop out.

 

Just something else to try thats pretty easy to check.

[Steve Scheifler]

Oh, the joys of vintage racing!

[Sean Allen]

Thanks for the tips, I will check these out.  

 

As far as the grounds, which ones would have enough of an impact to cause the engine to cut out? PPF brace, and the motor ground near the header.  Any others? 

[Bench Racer]

Rear of engine pass side engine lifting loop has a welded on bracket. Two wires to one attaching loop from wire harness attaches to said bracket.

[Sean Allen]

I don't actually have the loops on the motor anymore, I would always just use a bolt to the hoist when pulling the engine.  In the image below, are you talking about the grounds under the gold nut? Looks like part of the wires go to the cas etc.  

 

 

Attached Files

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[Tom Hampton]

I don't actually have the loops on the motor anymore, I would always just use a bolt to the hoist when pulling the engine.  In the image below, are you talking about the grounds under the gold nut? Looks like part of the wires go to the cas etc.  

yes.

[Bench Racer]

[Sean Allen]

I will try everything mentioned in here in the next few days and see how it goes.  Updates to follow I'm sure.  

[Sean Allen]

Kill switch.   

 

 

I hope.