Miata down
 

01 Miata. Son took to autocross this morning. Car will not idle now, will run with foot on gas. Any thoughts on obvious things to check. I’m an hour and a half away. I can always AAA.

First is search with "won't idle" in the title , second is with it in the post Good luck, sensor or vacuum deal is my guess without looking

https://forum.miata.net/vb/search.php?searchid=20215263

https://forum.miata.net/vb/search.php?searchid=20215253

Fuel filter? Possible that debris in the fuel tank has been put into circulation.

Large vacuum leak....look at all hoses carefully. Or...clogged fuel filter.

Thanks all. I will relay the message. This is the 1st time his new throttle bodies are being tested.

That's your answer

Glad he paid a fortune to have them tuned. 😀 Thanks.

Want to finish a race season with $1M in your pocket?

Start with $2M.

Curious as to how a clogged fuel filter would only allow it to run at higher rpms and not at idle? That’s a strange one.

I'll also throw in a $0.02 and say, if you can't find an obvious loose hose, make sure to go back and retighten the throttle bodies and everything intake related.

Got car home. Plugs were black so something not right. Runs fine but won’t idle. No abnormal smoke out of muffler. No change in sound. I told him to call the guys that tuned it and go from there.
Thanks everyone.

Timing belt jumped a tooth?

Timing belts do not jump one tooth. They either break or completely jump timing if the tensioner fails. The car would not run fine at higher rpms.

How many teeth do they jump? How does one determine this? There is no reason they couldn’t jump just one tooth if blipping the throttle aggressively or engine braking.

How many Miata engines have you built?

Here is the first one I did for the endurance car I race in… it has had many podium wins since and we are racing it again this coming weekend in an 8 hour race.

http://forums.pelicanparts.com/uploa...1716832052.jpg

Miata engines? Zero. Other engines? More than you. With chain/belt and gear driven cams. Air and liquid cooled, gas/diesel, motorcycle/car/truck, etc. If you want to use the argument of competence, I’m almost certainly a better skier as well. :)

Maybe there is something unique about Miata engines that allows them to jump one tooth of timing and exhibit symptoms of a bad airflow sensor, you might have me on that one.

We have had the not idle issue after a race before. Mass airflow sensors have been an issue.

A cam jumping is also possible. I think that car also has VVT and this could be the issue. Didn’t throw a code?

My race car is a 99 but that engine in the photo was a 1.6 for an 89 Miata. It is also SM legal (except for my endurance hubs).

I’m not going to disagree with the skiing thing… but I did get 11 days in this spring after breaking a leg and blowing up my ankle in January… next season we can reevaluate my position on this matter.

I’ve got a similar engine building resume to you.

I'm just internet jostling with you, buddy. You might be better at everything than me. :)

me too. SmileWavy

A friend of mine is the local Miata Guru (hes had probably 40 and built MANY Spec Miatas). He has atleast 3 'in stock' right now.

He says check for vacuum leaks first.

More from Chris, the Miata Whisperer...

Scan it for codes and check for vacuum leaks.

Could be the idle bypass screw and the idle is drooping too fast for the idle air control valve to catch it. Has the throttle screw moved any? Does the idle need to be barely cracked for it to run or is it a case of needing 1500 rpm to keep running?

No actual idea other than agreeing with Zeke.

My experience: look at the last thing you messed with. This is so often the issue.

vacuum leaks and check whatever you did last to it.

Right, that's backwards. Normally a clogged filter will allow enough fuel to idle, but then restrict the fuel required to perform under load and/or higher RPMs.

We checked for leaks, nothing showed up. I mentioned the throttles needing adjustment but what do I know, I just watch Vice Grip Garage a lot. It’’s also a Bit more challenging for a non stock car imo. I have another question for later on, I’m burning out my asks.

Did you get your son to clean the plugs to see if it would idle okay with clean plugs? (of course they'd foul again, but you'd know it was probably a tuning problem then.)

No expert on Miatas, but if it were me, I would try disconnecting the Idle Speed Control Valve ISCV. When disconnected, it should produce a somewhat normal idle. If so, Google Miata ISCV troubleshooting and you should be able to figure out what needs done.

if its running ITBs it no longer has an idle control valve.

and 99% chance its a leak or other issue in the ITBs. ITB converted miatas tend to be a little fickle.

We cleaned the plugs, same issue. On hold until he gets back next weekend. Also, would a light come on if throwing code? I unfortunately left reader in far away car. He was going to call the ITB manufacturer.

depends on the programing for the ECU. if its aftermarket, all bets are off, you are probably on your own.

Did you get it sorted?

We just finished up an 8 hour endurance race with the 89 NA miata… my engine now has 80 race hours on it. We got bumped out of E3 into E2 because of 4 laps that were a second too fast for E3… still got 2nd in E2 and 6th overall. Not bad for the car with the least displacement and lowest horsepower in the race.

Making Miata guys proud. He’s tinkering with a motor he has on a stand so he hasn’t messed with it.