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 Post subject: Miata Engine Bad Idle
PostPosted: August 22, 2019, 2:41 pm 
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Joined: December 6, 2017, 2:20 pm
Posts: 125
Location: San Jose, California
Hi All,

I sourced a 1.8L 1999 Miata engine for my project. The engine runs well, but I have a funky idle issue where I dont know whats going on. I'm using the stock ecu

1) Blocked off the EGR Valve
2) Kept the EGR, but disconnected it
3) Removed Charcoal Canister
4) Remove the Boost sensor next to the charcoal Canister
5) Removed Powersteering
6) Removed AC
7) Rebuilt the Air intake

I have a video of the car idling ,you can hear the popping/rocking at the end of it. The rocking in the video is quiet tame, sometimes it can get super rough.

https://www.youtube.com/watch?v=IDpTFgpfsP4

Any suggestions would be greatly appreciated. The coil pack does humm a little. I plan to replace the sparks and the cables.


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PostPosted: August 23, 2019, 3:43 am 
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Joined: December 6, 2017, 2:20 pm
Posts: 125
Location: San Jose, California
I took a closer up video of the issue. I reattached most of the egr stuff. I will try to add the exhaust next.

https://www.youtube.com/watch?v=5cpzZWA ... pAvnM3jT1o


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PostPosted: August 24, 2019, 3:01 am 
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Joined: December 6, 2017, 2:20 pm
Posts: 125
Location: San Jose, California
I did a compression test. Engine seems okay then. Must be the computer or some sensor going off.


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PostPosted: August 24, 2019, 6:37 am 
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Joined: December 22, 2006, 2:05 pm
Posts: 8037
When you say "boost sensor", I think you are describing a MAP sensor. It's is important.

EGR function is also important because of what the stock ecu does to timing and fuel when it commands the egr to be open.

I suggest you put off any unnecessary changes at least until you get running well as-is.

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