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Old 07-22-2013, 08:54 AM   #1
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Default Urgent! Engine idling oddly

Regarding a 1990 na6 Miata.

Hey guys, im in urgent need of your knowledge and experience. I decided i would install my new radiator along with a coolant re-route kit. Doing this i removed the CAS, Rocker cover (fitted new gasket), and installed the re route and new thermostat.

Oh and i also removed the throttle body to give it a clean, and installed new seals for my injectors.

Another note is this car is stock standard, no nothing!

So far the car idles, its set to 10* degrees btdc, oh and new spark plugs. I checked the coils were working but having spark plugs in them and cranking briefly. The problem im having is there is alot of white smoke coming from the exhaust, and when i rev the engine up to 3k it will automatically drop quickly to 2k then go back up and down repetitively if i hold the throttle in that position. Any other position of the throttle is fine, who the hell knows why.

Checked for all wiring to be plugged in properly and grounded. But honestly knowing me i must of f*cked something up while unplugging and installing stuff..... fml.

Anyone been through the same thing?
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Old 07-22-2013, 12:14 PM   #2
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I'm betting it has to do with the throttle body clean. Why do people do this, it always finds a way to screw something up.

You probably have some type of leak in the throttle body area. Vacuum, coolant, who knows.
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Old 07-22-2013, 12:16 PM   #3
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Take a clear pic of the butterfly. If the black coating is gone, there's your problem.
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Old 07-22-2013, 12:17 PM   #4
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fix your vacuum leaks. report back.
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Old 07-22-2013, 01:19 PM   #5
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i wouldnt have touched the tb if it didnt stick, which causes idling to get caught and drop slowly. Oh and definately left the black ring on, because i know this stops air getting throw when closed.

Yeah ill actually be checking the ISC because im sitting here thinking if i remember double checking it or not. I shall let you know

But does this sort of thing, ive heard its called idle hunt? when it just goes up and down 1krpm +/- between 2 values. Yeah does this sort of thing happen from vac leaks? anyone had the same issues before and found the solution.
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Old 07-22-2013, 01:22 PM   #6
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yes.
the problem is a leak
the solution is fixing the leak
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Old 07-22-2013, 02:21 PM   #7
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Has anyone had a vac leak? no never.
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Old 07-22-2013, 03:56 PM   #8
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Quote:
Originally Posted by FRT_Fun View Post
Has anyone had a vac leak? no never.
What's a vacuum leak? Is that like ---- leak?
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Old 07-23-2013, 12:11 AM   #9
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lol does that make you guys feel better about yourselves? going to be blunt but take the stick out of your a$$, have you never asked a stupid, clueless question. Im asking because i want to learn more ya ******.

if you looked closer what i meant was a vac leaked that resulted in idle surging ... i asked that to see if i could narrow it down.

Anyways, it looks like its not a vac leak but the iac unit is dead, anyone else having similar problems should read this it might help you, did for me.

Motor: IAC Valve: High Idle, Surging and a bad IAC valve - MX-5 Miata Forum
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Old 07-23-2013, 01:17 AM   #10
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OK. get you some brake cleaner or starter fluid. When you spray it on a vacuum leak the car will idle up.

Check injectors for a leak. and also spray fluid on them to see if they are leaking as in sucking air.

Blue smoke= oil
Black = gas
White is usually water like a blown head gasket......check oil to see if it looks like coffee and creamer....

Now lets say it is blue white. may be oil. Did you disengage the timing advance when you set timing.

I would have to see smoke. try finding leak with spray

also check hoses on tb.
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Old 07-23-2013, 01:23 AM   #11
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Quote:
Originally Posted by peterwho View Post
lol does that make you guys feel better about yourselves? going to be blunt but take the stick out of your a$$, have you never asked a stupid, clueless question. Im asking because i want to learn more ya ******.

if you looked closer what i meant was a vac leaked that resulted in idle surging ... i asked that to see if i could narrow it down.

Anyways, it looks like its not a vac leak but the iac unit is dead, anyone else having similar problems should read this it might help you, did for me.

Motor: IAC Valve: High Idle, Surging and a bad IAC valve - MX-5 Miata Forum
I was about to say that.....BUT I have Never had a IAC make one smoke. Mine just made them not idle.

I have had miatas that acted like a IAC and wound up being a head gasket with a slow leak.
Not all head gaskets leak into engine. some leak into exhaust.

Are you ever having to add water? or have problems overheating?

I had a car that through us for a loop for a year. Then the gasket started finally blew and stranded the car.
Hope it is a simple fix.

Good luck!
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Old 07-23-2013, 01:25 AM   #12
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Oh its fixed. good deal
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Old 07-23-2013, 01:39 AM   #13
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White smoke coming from the exhaust and IAC is the fix? Now that is one I haven't heard. Coolant runs through it.. was some leaking into the TB?
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Old 07-23-2013, 07:06 AM   #14
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Started the car up this morning, white smoke is gone, who knows lol!

But for now, im not having to top up the coolant, no overheating. I will be replacing the head gasket shortly but thanks for all the info.

I don't know why i didn't try the spraying fluid and seeing to see for leaks. Injectors aren't leaking i had just put new rings and seals on them

Oh and new PCV valve also a few weeks ago, and checked the hose was sealed properly.

For now it just idles high around 1.2k, and surges at a particular point on the throttle, up and down for example 3k-2.5/2k, that is if i hold that throttle in that position.

I havent yet fixed it, i just picked up a used working IAC, tomorrow ill pop it on and fingers crossed!

Thanks again fellas
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Old 07-23-2013, 07:47 AM   #15
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Did you ground out "TEN" in your diagnostic port when you set your timing ??
You did check your timing after re-installing the CAS, right ?!

"White smoke coming out of the exhaust" could be the leftover cleaner and gunk you sprayed into the manifold when you were cleaning it



or




we have a new Pope.
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Old 07-23-2013, 08:06 AM   #16
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Quote:
Originally Posted by peterwho View Post
For now it just idles high around 1.2k, and surges at a particular point on the throttle, up and down for example 3k-2.5/2k, that is if i hold that throttle in that position.

so you still haven't fixed your vacuum leak...
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Old 07-23-2013, 09:23 AM   #17
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Quote:
Originally Posted by Boris View Post
Did you ground out "TEN" in your diagnostic port when you set your timing ??
You did check your timing after re-installing the CAS, right ?!

"White smoke coming out of the exhaust" could be the leftover cleaner and gunk you sprayed into the manifold when you were cleaning it



or




we have a new Pope.
haha!! i put some sealant on my current iac and tightened it up but that still didnt fix it, yeah timing is set after touching the cas of course.

Ill be fitting the newly purchased iac on tomorrow... i have fixed the vac leak but not the problem ....
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Old 07-23-2013, 09:40 AM   #18
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Quote:
Originally Posted by peterwho View Post
...i have fixed the vac leak but not the problem ....
Oh yeah I forgot, your IAC stopped working the same instant you pulled a bunch of stuff apart and introduced a vacuum leak[s]. You didn't even bother to even check to see if you're leak free, so how can you say you fixed the issue you created?
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Old 07-23-2013, 10:06 AM   #19
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before i had posted i thought i had checked everything i could think of for leaks, but then i had an epiphany and remembered i hadnt double checked the IAC if it was tightened properly etc. So dont even know if i had an initial vac leak or not lol, but i know its always good to check. My method was tightening stuff and listening for noises haha going to go with the fluid method, seems more reliable :P
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Old 07-23-2013, 10:12 AM   #20
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did you replace the TB gasket? did you remove the IAC? if yes, did you replace that gasket?

you need flammable brake cleaner, and you need to spray it in all your 4 new injector seals while the car is running. If the engine gets upset, fix the leak, if not continue to spray the entire mating surface between the TB and IM and the IAC and TB to be absolutely certain there's no vacuum leak.


also, are you saying your iding issue is only that if you hold the RPMS are 3K then the engine speeds starts to oscillate? I wouldn't consider that "idling oddly;" what is the behavior at idle?
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