If this is already a thread...sorry. I have tried to search but it seems everyone has or had the opposite of what I am experience.

Start car in the morning. Idles fine, all seems normal. I drive it work,accelerate is normal, boost is normal, driving experience as expected. However. It sit in my office parking for my work day. I get in and car has a little extra crank to start. Idle is noticed to be in the upper 600 instead of about 820 give or take. Car will accelerate slowly to 6k but if i wot or even press accelerator same way I did that morning car bucks, backfires, wont rev. It is clearly only when boost comes into play. Doesn't matter if engine is hot, cold, warming up. No smoke, pops, grinds, etc. No coolant leaks. No oil leaks. TPS on multimneter seem correct. MAP is clean.

I just seem to be having the opposite issue of everyone. Its not a cold start, hot thing. It is after the car sits for my daily drive but it drives perfectly in the morning...just not in the late afternoon on my way back home. This has been for about 4 days now. Prior to this everything was fine. Please help/advise.

98 Rx7 FD
Greddy elbow, intercooler and piping. HKS power intake. Apexi AVCR for .8 boost. Stock twins.

 

Fuel pressure..... bet anything this is a fuel pressure issue. At work...... check fuel pressure before you start it up. However you want to go about doing that lol

I know it sounds crazy but the stock connection at the pump in the tank has a connection to temperature. Overnight sitting it will be fine on the first start until you shut it off and then all hell brakes loose.

Either check fuel pressure or just pull the pump and fix the hanger by bypassing the o ring seat. Even if it doesn't fix it, it's good to do regardless

 

Would it still be fuel pressure related if i can "creep" it up to 6.5k without any hesitation? It will not boost. as long as I stay in vac or .01 of boost its okay.

 

Yes.... thats further makes me believe it's a fuel pressure issue or the secondaries not coming on but I'm leaning fuel pressure

 

You're not asking the FP to do much "creeping" up at 0 boost. So fuel pressure could fall off under boost if the pump, etc., is having an issue.

 

DaveW...fair enough hah.
and FDAuto...I'll look at the hanger bypass this Sunday.

 

We have a video on our YouTube page about it. You can ignore 95% of it. Just the section about cutting the pipe is relevant

 

Consider that a jealous co-worker is sticking a potato in your tailpipe.

 

Your symptoms sound somewhat like your ecu is going into limp mode.

And then the ecu is resetting once the car is turned off at night

Then going into limp mode again the next day.

I see you have a "98 RHD.

You might want to learn to run codes. There is no CEL.

Also make sure your coil and plugs are hooked up in the correct order.

 

https://buyee.jp/item/yahoo/auction/q1135244486


Click on the seller's name and search him for "Mazda Rx7 RX-7 FD3S"

I believe he continually reposts the device for sale (Hint: Buy two)

It only works for a stock ecu, mind you.

 

This seems to be the only notice Mazda gave for the change of position of the coils. It is buried in an FSM update your version (Version 4) of FD. The lower illustration is the "new" set-up.

Notice of this change was not likely made to US garages, as Version 4 cars have only just recently been allowed into the US (as you know).

 

Your coil harness should be hooked up like this. Note, it is very easy for someone to flip the order.

 

An OMP that is starting to fail might trigger "limp mode" intermittently.

So you might not get a "code" for a failing OMP, at any particular time you check codes.

It is usually recommended that one "pre-mixes" even if they think they have a working OMP.

 

Sunday hasn't gone as planned hah. But will grt around to the YT video for the fuel hanger. I did pick up some new spark plugs I need tog rt in tonight.
for the OMP, I do always run premix but...i haven't checked that tbh.

Regarding limp mode. I had thought of this and the absence of CEL is...fun. for the coil and plugs order...i have not changed that myself at any point and the car has been fine for the past years and years...till recently. So I'm safe to assume the order is correct?

 

As fresh update though. If I do creep the throttle up to about 5.5k rpm and let it down down to idle. The car will then rev like normal. So once the back pressure builds...it doesn't do all this nonsense. But then shortly after, allowing to just idle again, same issues occur. But will update soon as i can check through all the above mentioned.

Appreciate it 🤘

 

Has anyone else changed your plugs recently?

Was there anyone doing anything to the car that might have involved removing the plug leads, to get them out of the way, for instance?

BTW, Mazda recommends replacing the plug wires annually, and the coil harness every five years.

Last time my car was on the dyno, power was breaking up at about 210 hp. Tuner thought my starter /ignition harness might be degraded.

As a start, i replaced the coil harness with a new one. This eliminated some stalling I was having at low speed and some backfiring I was having when the engine was hot.

New coil harnesses for Version 4 and later are available new ($100). Ignition/Starter harnesses are not, although new ones are still available for earlier versions ($550).

I am thinking of getting our local harness builder to modify an earlier one for my Version 5 car.

 

Still suspect limp mode. You can check codes with a led lamp (with resistor).

 

Sounds like possible Temp sensor or broken plug/wire for the temp sensor making intermittent good connection. Make sure it is plugged in all the way

 

for limp mode. I discon (-) and hold brake for 30-45 sec. Doesn't seem to change my situation.
Check wires and replaced plugs. They do spark. Wires haven't been changed annually, been a few years, but till recently I maybe drove this car 2k miles annually.
Now it is all the time...regardless of sitting overnight or sitting at the office.
picking up LED lamp w .resistor today to try and read codes.

 

ohhh...sorry. bypassing the FP O-rings > issue remains
I have not changed the fuel filter though. (waiting for it to arrive)

 

 

Ignore the long red wire heading into the engine bay.

Somewhere in the USDM FSM it describes how to do this. I don't know if USDM and JDM are the same arrangement of plugs in the diagnostic module.

The codes in the USDM and JDM FSM are pretty much the same, perhaps one or two are different (i..e JDM has fewer pieces of smog equipment).

 

Be mindful that you may have a bad tank of gas. Some refiners are still learning how to handle ethanol blend gas. Ethanol attracts water, so if the blended gas sits for a while, it will self dilute.

 

I dump some fuel injector cleaner stuff into the tank. Not sure what really does tbh if anything

 

So i may be doing this incorrect but it seems I don't have any codes thrown or from all my attempts to grt out of limp mode it is cleared/ nothing stored. Leaves woth not much to go from.

The only beeps I can hear when I drove are five beeps...but i beleive that is because I no longer have a driver airbag.