Intake backfire?
 

After the car has been sitting outside in the heat all day, I get in and turn the key to "on" I get an intake backfire. Doesn't really harm anything, just pops the boost gauge line off of it's vacuum tee and I have to put it back on. It was mentioned to me by someone here that a leaky injector could cause it to do that? I just want to make sure it's not something with the MS.

It has to do with how the megasquirt handles the coils. Look for joe's "a better spark output" thread, he explains it well.

basically, your coils let out a spark when you went to key on and you ignited some unburnt gas that was still in the cylinders.

Thanks for the info. Weird that it does it only when it's warm outside.

Not really, fuel stays vaporized better in hot air.

This happens to me 83.49% of the time I turn my key to start my car. I'm going to do Joe's new spark out mod, but i'm concerned that I need to fix whichever injector is doing this. Sometimes it's bad enough to foul a plug and make it difficult to start the car/keep it running.

do you have a tps wired up? you can always try flood clear after you shut the car down, see if it really is a leaky injector....

Yea I do, good idea. I'll give this a shot. I've tried revving the engine to 2k before shutting down but cant tell if its helped or not. I'll set up flood clear tonight, need to do some other MS stuff anyway.

Weird, I never had this problem with the MS1.

Jim

Lots of people never have. Seems most commonly its happening to those of us running RX7 550s. I want to figure out what the problem is before changing my spark out mod. The new mod will get rid of the pop, but if i'm still leaking fuel into the cyls. I wanna know as its still going to be fouling plugs now and then.

I'm running 450s, and only backfire after a failed start. I had my injectors cleaned at RC before the build also.

It sounds like you're leaking fuel, there shouldn't be enough fuel in the intact tract to backfire unless they are. I would have them cleaned (well, let RC do it.)

The new owner of the car knows about it, and he is going to try and find a solution. I have officially parked the car until the transport comes to pick it up. Thanks for the info guys.

The solution is Joe's spark output.

True dat. I have RX7 500's and whilst I wasn't exactly plagued by the issue, it certainly reared it's head at least once a week. made the car a bitch to start and idle until the superheated air had been run through the system.

Joe's output mod solved it. (I'm sure if my tune was 100% rather than it#s ever present 90% it'd have been an even rarer occourance).

I'll let him know.