Hi,

I'm having a weird problem that I'm not sure how to diagnose. When I drive my car, 93 rx7, 13b some piggyback tune, rebuild ~8k miles ago, 7psi boost because pills are missing, it pulls what I would classify as fine every gear to redline except 4th (and I would assume 5th but haven't checked). When I get to about 120ish MPH (somewhere around 5.5k-6.5k rpm) the engine seemingly cuts out (ie car starts slowing down, boost drops to vacuum, aux systems stay on no engine light) until I lift my foot off the gas and continue to push it where it comes back "alive" and continues pulling. I didn't take it up as high in speed after it cut out because I was worried about it. Any ideas on what this could be?

Thanks

 

Is it a JDM car? Speed limiter at 112mph or 108mph cant remember exactly.
Early cars have a wire you can cut 96+ models do not.

 

No its a U.S. 93 Touring. I am worried it could be a fuel cut/fuel pump issue but I have never experienced one before so don't know what I am looking for.

 

Is it a JDM car? I know some Japanese cars had speed cuts where they would cut out past a certain speed. Or maybe a Japanese ECU in the car.

Dale

 

It sounds like a speed cut or boost cut. You say you have a "piggyback tune" is it a modified factory ecu, or something else?

 

I believe it is a modified factory ecu.

 

Is it cutting out pretty hard like the ignition can't fire spark plug or it is just that the boost drops off and you don't have enough power to push past 120?

 

Could it be a JDM ECU?

 

^That's my guess. Many of the chipped ECU's are from Japan. The part number on the front of the ECU should give a clue.

May also be worth finding a US ECU that you can borrow to test the theory out. Most other problems (fuel, ignition, etc.) would manifest itself in any gear or speed.

It could also be fuel cut from too much boost, are you certain the boost isn't creeping up and is staying low?

Dale

 

I don't think its a JDM ECU, I believe it could go past 120 I just needed to pull my foot off the gas and put it back on. I have newer cars where I have hit the speed limiter and it keeps the speed but just doesn't go any faster. This is like removing my foot completely from the gas pedal and slowing down via engine vacuum. I don't remember much else, but I confidently remember the boost falling to vacuum on my boost gauge when this happened.

 

I just got new spark plugs like 700 miles ago and SP wires(the old ones were arcing), it felt like a pretty hard cut out, I don't have experience with ignition cutouts, but this could have been that? It doesn't happen in any other gear though which is curious.

 

You're going to need to look and rule out the JDM ECU thing. Remember, this is an ECU that was designed in the late '80s, the speed cut (and the fuel cut) is not smooth and easy, it's harsh.

If it was plugs, fuel pump, etc. you would notice this in any gear.

Also, please be safe!

Dale

 

Yep! Don't assume, verify instead.

Cloveh,

It takes five minutes to check. Open the kick panel and look at what you have.

 

Ok so I pulled the kick panel, what is the difference between the JDM and USDM ecus?

 

Take a picture of the ECU and post it up.

Dale

 

Look at the big number, N3A1, N3A7 etc