Urgent! Engine idling oddly

peterwho · Postby **peterwho** » Mon Jul 22, 2013 10:55 pm

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?

koop21 · Postby **koop21** » Mon Jul 22, 2013 11:04 pm

peterwho wrote: 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.

The problem you are describing is a tuning issue. It sounds like the tune for that range is not right which is causing your car to hunt.

plohl · Postby **plohl** » Mon Jul 22, 2013 11:08 pm

did you bleed the cooling system correctly?

peterwho · Postby **peterwho** » Mon Jul 22, 2013 11:09 pm

really? because before me doing all this it was running fine with a air leak from the injector seals

peterwho · Postby **peterwho** » Mon Jul 22, 2013 11:12 pm

I just unplugged the lower radiator hose from the radiator end and let it drain then once that was done the other end of the lower radiator hose. And of course the rear thermostat housing. Is that right? i actually wasnt aware there was a particular technique woops :S

Hmm just had a quick search, read briefly people let the engine run a bit without the cap and ensuring levels of coolant in the overflow bottle. I just had it on a hill, filled it from the radiator and apparently this burps it? didnt have it running though.. :S could this affect it ?

peterwho · Postby **peterwho** » Mon Jul 22, 2013 11:51 pm

Just remembered my isc could have a vacuum leak could this be a problem?

maxgus · Postby **maxgus** » Tue Jul 23, 2013 9:45 am

I had a similar issue after replacing cam cover gasket. My engine was hunting between 1500 & 2000 repeatedly. I however did not have any smoke issues. That must be a different issue. I like you double checked everything and still the same. I disconnected the battery allowing the ecu to reset itself and the problem was no longer. This was on NB model. Hope you sort it out.

manga_blue · Postby **manga_blue** » Tue Jul 23, 2013 1:00 pm

How did you clean the throttle body? There's a fine bead of rubbery stuff around the edge of the throttle plate. Some solvents or cleaning actions can remove or damage that bead leaving an increased gap between the body and the plate. If that's the case then you can remove all of the bead with a solvent and reset the throttle stop screw to bring the plate closer to the body when shut and finally readjust idle with the idle bleed adjuster screw. It might take a few iterations to get the relationship between stop screw and bleed screw right.

Given the work you've done the white smoke is a bit of a mystery though. Coolant entry via the throttle body or idle control??? Does the white smoke have that sweet smell or burning glycol?

manga_blue · Postby **manga_blue** » Tue Jul 23, 2013 5:58 pm

manga_blue wrote:Given the work you've done the white smoke is a bit of a mystery though.

Please don't be offended but you have checked that your PCV and other engine ventilation and small coolant hoses are all connected up the right way, have you?

ralt · Postby **ralt** » Tue Jul 23, 2013 6:16 pm

Hi.
If you have removed the sealant from the butterfly you can reseal using nail polish. With the the throttle closed put a bead around the edge to cover both surfaces and wait until it starts to go off and open the butterfly until dry completely. No it doesn't matter what colour polish you use.
Why nail polish? it is self levelling so you get a nice smooth finish.