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Old 03-05-2014, 10:27 AM   #1
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Default SAAB Miata won't idle

Going with the assumption that everyone doesn't read worklogs so re-posted here. After starting the SAAB a time or two last night it won't idle. Runs fine, revs fine, will idle around 1000rpm if I keep my foot on the gas but dies as soon as I let that off. No old gas in the car. Tank was removed and emptied and lines were empty as well.

I may just say "good enough" for now and deal with it after MS and injectors but it used to run and idle fine two years ago. My only concern was to start with a Perfectly Running car before going to the MS. A couple of things that are different from the original car that may be affecting it are

Idle air port on the TB is just wide open now. Didn't think this would be it as it would be wide open to the intake but who knows.

Extended wires on MAF so I didn't have to cut a hole in the inner fender for something that was temporary. Used old three wire trailer wire which was kind of suspect.

Factory O2 was cut, lengthened and installed in WB O2 port 36" back.

Exhaust is passing through turbo with wastegate wired open

The "two o-ring under injector to replace missing insulator" shouldn't affect anything but it's different. It seemed to run fine for the trip home when I bought it with no insulator. Injector must have been just pushed into the rail.

Possibly missing or improper grounding somewhere. I only have one engine ground now to the subframe. Need another for sure for head to unibody.
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Old 03-05-2014, 11:29 AM   #2
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Do you mean to say the little hose for the iac isnt connected to the intake tube post maf?
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Old 03-05-2014, 11:47 AM   #3
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Quote:
Originally Posted by Leafy View Post
Do you mean to say the little hose for the iac isnt connected to the intake tube post maf?
I was talking about this one. It's running open right now.

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Old 03-05-2014, 11:50 AM   #4
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Well there's your problem. The car is getting enough air to idle but the maf is reading practically nothing so its not injecting like any fuel.
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Old 03-05-2014, 11:53 AM   #5
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it must be plumed into intake when a AFM/MAF is used for metering that amount of air in the system.
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Old 03-05-2014, 12:01 PM   #6
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Old 03-05-2014, 12:17 PM   #7
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Quote:
Originally Posted by Leafy View Post
Well there's your problem. The car is getting enough air to idle but the maf is reading practically nothing so its not injecting like any fuel.
OK. I have an AEM cold air intake that came with the original car hooked up now with the MAF. It has an elbow/port specifically for that port that I just taped over. I'll throw the little stock hose back on this port to the CAI. I just threw it together to see if it would start.

So when using MAP and no MAF and using MS I can just run this port with a filter?
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Old 03-05-2014, 12:18 PM   #8
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Sure, but it'll leak if you boost.
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Old 03-05-2014, 12:45 PM   #9
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Sure, but it'll leak if you boost.
has this ever been proven?
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Old 03-05-2014, 01:00 PM   #10
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has this ever been proven?
I thought you were the one that proved it.
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Old 03-05-2014, 01:13 PM   #11
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Quote:
Originally Posted by Leafy View Post
I thought you were the one that proved it.
I've only had a turbo NB so never had this port. How do the eleventy billion other people with turbo NA's do it? I don't need to understand, just copy them.
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Old 03-05-2014, 01:20 PM   #12
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We either block it off (I don't think a lot of people do this) with a plate and deal with the crappy cold idle, and otherwise tune with the idle screw; OR, plumb it into the intake. You can see the ~1" pipe on most intercooler routings.


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Old 03-05-2014, 03:38 PM   #13
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At first I didn't see plumbing into the intake as working due to positive pressure but after I thought about it, it's only needed when at idle which would put the IM in vacuum, no different than if it was in the intake tube. When pressurized it wouldn't be needed as it isn't at idle unless you are running a GT15 turbo, lol.
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Old 03-05-2014, 05:38 PM   #14
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Quote:
Originally Posted by Leafy View Post
I thought you were the one that proved it.
no. It should close, fully, once out of idle. If that's a good enough seal to hold pressure, I dunno. That I never tested and I dont think I have a spare laying around.
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Old 03-05-2014, 09:18 PM   #15
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Quote:
Originally Posted by Braineack View Post
no. It should close, fully, once out of idle. If that's a good enough seal to hold pressure, I dunno. That I never tested and I dont think I have a spare laying around.
Weird, i always thought you had to run it to the IC pipes on the 1.6. My old setup was like that too:

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Old 03-05-2014, 11:47 PM   #16
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^^This keeps it filtered, but otherwise, without the AFM/MAF there's no point. Unless it leaks. Cause boost from the other side would theoretically negate any leakage.
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