Overheating | Bad Idle | Backfiring = the suck - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 07-12-2007, 04:24 PM   #21
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duty cycle 125%?

maybe your map is F'd up. reload?

same map the previous day only hit 54% at 11,8:1 AFR at 5000RPM and 195kPa

it's really getting hot...and that cant really be to blame of the tune.
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Old 07-12-2007, 04:54 PM   #22
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f it. im just going to check & machine the spare head I have and give er a go.
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Old 07-12-2007, 05:02 PM   #23
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Just a thought, when you removed knocksense did you maybe stir up some wiring to your MS? Doesn't one of the knocksense wires go to the coolant input? Doesn't explain everything, but with no signs of leaking and really weird readings (rpm, coolant, DC), I'm thinking that maybe when you removed the knocksense, you either dislodged some wiring or left a stray wire loose? It seems to be the only other major change beside the engine swap, etc...

Also haven't looked at the setting for awhile, but isn't there a setting for pulling timing at certain coolant temps as well...
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Old 07-12-2007, 05:30 PM   #24
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The only wires that go into the MS are clt and the signal...I'm pretty sure I desoldered the wire and taped it back up to cover....

If you're talking about the lat/clt ignition settings, mine's off.

It also wouldn't explain the IAC valve acting so strange, as MS does not control it. Wiring harness hasnt been touched besides cutting two wires.

I also was able to drive the thing almost 2 hours, with everything perfectly normal, before I noticed the funky idle. the next day it overheated....
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Old 07-12-2007, 05:56 PM   #25
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Overheating without any coolant loss under "normal" driving must be some kind flow issue. Even a car with a blown headgasket won't overheat if it has an endless supply of coolant. You're sure there's no coolant loss? What about bubbles in the rad with the car running? and if you raise the revs- more bubbles? Just another head gasket check.

Just throwing it out- the dowel pins were in the block or head? If they're missing, the head gasket will actually slide between the two and cause oil/coolant flow restrictions.

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Old 07-12-2007, 06:04 PM   #26
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hey scott, you can always pull the rad cap with the car COLD and start it up to see if you're having coolant issues.
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Old 07-12-2007, 06:57 PM   #27
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Jay-
Can't say with confidence that the ignitor failue does or does not have anything to do with the overheat event. However, I can say with confidence that the ignitor is bad, and that is what caused Scott's stumbling and backfiring when he tried to boost. It is also very likely the cause of the missing cylinder(s) events.

It's possible that he also has a misalignment between the head and block, a bad headgasket, or other trauma that may or may have either been caused by, or is a product of the over heat event. But this is on top of a bad ignitor. Failed 1.6 ignitors and MS seem to go hand in hand.

I would wager that once the ignitor is replaced, the car will run fine... But the motor needs to be monitored for HG issues.
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Old 07-12-2007, 08:13 PM   #28
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But Ben, wouldn't my car not start at all?

If I drove over 30-45 minutes with no trouble, and then had lumpy idle loss of power and no signs of anything wrong in the datalog other than the low vacuum, why should i suspect it?

even the next day when i drove it home hot, I had 0 issues with stumbling backfiring, etc.

it was only today when i gave it some boost where it happened. it was seriously like i was hitting a fuel cut rev limiter and everything went crazy.

car starts up without issue. idles fine (without the IAC). and acutally drives like normal out of boost.

I've had the same spark output settings on my MS since installed months ago.


It would be easy to think an aluminum head warped as I pulled it off, wouldn't it? Even with a new head gasket and proper torque, if its warped its warped.

Seriously I wish it was something electrical and not mechincal, but in the case I dunno if it is.

I'll be doing a leakdown test and pressuizing cooling system this weekend to test all possiblities before I tear things apart again, but I dont have my fingers crossed.

Anyway I can test the ignitor in the meantime? resitance? And also if you look at my log the: A/F, DC, AIT & CLT all freak out at the same time. But it's something to look into....I really want everything fixed, freaking cocktease...
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Old 07-12-2007, 08:24 PM   #29
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I don't know how to test the ignitor. Perhaps ask for the procedure in the NA section at miata.net. Folks there like to paraphrase the shop manual. Bill Strohm I think is his name, he does it all the time.

However, your problem is the same problem I had when my ignitor was failing. The ignitor sends a false RPM signal to the ECU, the ecu immediately retards timing and cuts fuel. Then the RPM signal corrects and the ecu fuels again. It does it over and over. That's where your popping and stumbling comes from. Mine was exactly the same... It was fine for a while, then I would get some missing, then it would clear up and be fine for a while again. It got worse with time. It's possible that your ignitor started failing when your last block took a crap, so you didn't notice escalation of the problem until now when you have a (hopefully) good block.

You may also need to look into a COP set up. I'm waiting to hear about the newb Sean's pending install w/ Toytota COPS w/ built in ignitors--since he's pulling his stock ignitor and not using an ignition box like MSD DIS or AEM TwinFire. I hope it works out. That's kick *** for $50--about what a used ignitor will cost.

BTW, what is your DWELL? Jerry adivised me to drastically lower mine after the first ignitor crapped out.
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Old 07-12-2007, 09:42 PM   #30
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dwell is 5 | 4 | .5

I have the factory service manual, so I'll get looking at it.

I have a feeling you may be right, but I have a feeling there is more than one problem afloat....lucky me :gay:
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Old 07-12-2007, 11:51 PM   #31
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i would change the ignitor out with a known good one and see what it does. cheap.
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Old 07-13-2007, 01:14 AM   #32
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when my valve cover gasket started to leak,i was able to drive the car for a hour or 2 before it started to feel like it was running on 3cyl.

at first i thought i blew the rings in cylinder number 4.it happened at night,so the next day i went to start my car and the problem was gone.

hopefully its something stupid.
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Old 07-13-2007, 09:43 AM   #33
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i would change the ignitor out with a known good one and see what it does. cheap.

I'll see if I cant find an unsuspecting victim. Brad does get his car back next week.
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Old 07-13-2007, 09:48 AM   #34
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I better not come out of my house to see you digging in my engine bay.
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Old 07-13-2007, 09:53 AM   #35
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when my valve cover gasket started to leak,i was able to drive the car for a hour or 2 before it started to feel like it was running on 3cyl.

at first i thought i blew the rings in cylinder number 4.it happened at night,so the next day i went to start my car and the problem was gone.

hopefully its something stupid.
That's a good point. Try pulling your plug wires and checking for oil on the boots... might be grounding out.

I agree that the over heating is probably unrelated though. Concentrate on one problem at a time.
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Old 07-13-2007, 10:34 AM   #36
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plugs were dry when i pulled them to do the compression. The bad thing on the ignitor is it requires a special tool + the mutlimeter to test. But once i dot eh leakdown and whatnot, hopefully I can point my issue. Just a PITA.

I'm at least dropping my spare head off to a machinist today to check the surface for warpage. That way I can drop the hat on having them true it really fast for me and I can pick it up the next day. So I can spend the rest of my timing pulling the current head, which wont take very long. Just tired of repairing it, i wanna UPGRADE it.
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Old 07-13-2007, 10:43 AM   #37
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Blue line = stock 1.6 w/ FMII @ 12 psi
Red line = stock 1.6 + worked over head w/ FMII @ 12 psi

Head work FTMFW
Attached Thumbnails
Overheating | Bad Idle | Backfiring = the suck-headwork.jpg  
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Old 07-13-2007, 12:45 PM   #38
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26ftlbs gain?!
What exactly encompasses "worked over"?
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Old 07-13-2007, 12:52 PM   #39
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The stock 1.6 head has a wicked lip in the chamber that could use a major deshrouding, I'm sure thats a major part of that power increase. Also the bowls have a pretty poor transition into the valve seat (read lip thick as 2 thumbnails), and the short side radius has a very minor sharp edge to shave off. The ports themselves though are pretty smooth, some casting lines but overall ok. That would incase a decent p&p for the 1.6 and probably make alot of that power gain in that dyno. That dyno proves though that the 1.6 could make huge gain from some more duration even when turboed.
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Old 07-13-2007, 01:00 PM   #40
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Quote:
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26ftlbs gain?!
What exactly encompasses "worked over"?
Don't know. It's FM's work, so assume they did the whole enchilada. I would speculate that a standard P&P, port match the intake to head, and unshrouding the valves is where the money's at. Could probably be done for a grand or less... That's BIG improvement for a grand, IMO.
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