Hey everyone,

Looking for some advice on order of things to check after coming up against an issue with my 99 fd.
When on a WOT I get backfires untill I lift off the pedal, and also on pulls where i dont get this it feels like power isnt as good as it should be.

I'm on twins still, stock ecu, plugs are 9s, Intercooler and a greddy elbow is pretymuch all thats been done to the car.

I'm going to check for boost leaks, and then look in to the coils. Any other info on this would be greatly appriciated and may save me a lot of time and hastle! !!

Cheers Paul

 

fuel pressure. Check fuel pressure. Could also be your secondaries aren't coming on. If you do partial throttle, can you get it to do a pull?

 

Also make sure your plug wires are hooked up correctly. If you get that mixed up the car will run VERY weird and do weird stuff.

Leading - Lower
Trailing - Top
#1 rotor is at front of car, #2 closest to firewall

Anything in particular done between when it ran right and now?

Dale

 

Yeh, so if i feed the power on sometimes I gan get it to pull prety well, other times adding throttle dosent seem to gain me any power.

 

Cheers Dale I'll doubble check that as a priority.

 

Also, No Dale, nothing has been changed since I purchased the vehicle a while back, other than a cooland and oil flush with some new plugs. (It did the same thing before the plug swap) Done about 2000kms.

 

Check the coil harness connections as well. The plugs on the coil harness can get attached in reversed order.

Also if you have let anyone else touch your car, they may have hooked up the plug wires wrong(ly).

Have you tried to run codes? There is no check engine light.

The way a JDM tells you something is wrong is to make your car run bad so you take it back the dealer for diagnosis.

(This is what the owners manual - in Japanese - says.)

Until you check codes and the coil harness, very bad idea to drive the car, let alone do pulls.

You could blow the engine.

After codes run a smoke test to discover any vacuum/boost leaks you can't see.

 

We need to make Dale's thread on the coil positions a sticky. This problem is coming up everywhere.

And costing people motors.

Any FD from Version 4 onwards had the coil position change.

There was no big announcement. Just a short entry in an JDM FSM addendum

Easy to miss.

It is becoming ,more prevalent a problem in the US as Version 4 (or newer) cars have just become legal in the US, so herd mentallty regarding this issue has not been established.

 

Running codes, of course, only works with a stock ecu. Most cars have already been modified away from the stock ecu.

However, people buying Spirit R want to maintain the stock set-up.

Accordingly we have had three Spirit R pass through our area in the last year, and each of them threw codes for defunct solenoids in the solenoid box. (*)

As your car is a '99, there is a high likelihood one or more solenoids (there are seven of them) in your solenoid box will have let go.

If you stay stock, good idea to swap in a new solenoid box, while they are still available (budget $550).

Mazda also recommends changing the coil harness every five years. I recently changed mine and it made a noticeable difference - I had backfires on decel and some stalling when coasting to a stop. New coil harness for '99 spec cost about $80. Don't use an earlier model version.

(* two of the cars had symptoms similar to yours)

 

Thanks for the Info! Theres no engine light on at the moment, I'll report back with my findings over the next few days. I also second making dales post sticky, thats going to be a great help to many people myself included!

 

How much boost is the engine making when those backfires occur?

 

Would have to drive it and check on my gauge. At a bit of a guess just over 0.6mmhg, it's not all the time.

Checked my leads, everything is on in the correct place.
For reference: Front of engine - T1 - T2 (Blue caps) and then both black caps to the leading plugs.

Don't have any means of checking for codes as it's a JDM car and they don't have a Light. Looks like it was replaced with an Oil light 🥹

 

Search around, there is a technique with wiring in some LED's to the diagnostic box to see blink codes on JDM cars.

Vacuum line to MAP sensor is hooked up and hasn't come off?

Dale

 

Easy to run codes off the diagnostic box. You need a LED light with a resistor and a jumper wire. I think the uSDM FSM actually explains how to do it in the case the check engine light is not working.

Meanwhile, a guy in Japan is now selling a little 3D printed black box that plugs in the diagnostic module. It costs about US$35.

 

This is th ecorrect connections for the V4+ coil set up.

 

Here is an article in a Japanese tuner magazine, freaking out about the problem.

 

This is the newer coil harness;

https://buyee.jp/item/jdirectitems/a...n_DirectSearch

 

Here is the little black box. Click on "seller" to see if he has a new listing. He also does some 3D printing of certain trim pieces.


\https://buyee.jp/item/jdirectitems/auction/v1152024479

 

Here is the current listing "one day left"!


https://buyee.jp/item/jdirectitems/auction/c1181272385

 

Cheers guys! I've ordered some stuff, got myself some kit to test solenoids too, been reading the other threads you guys have done, brilliant info👍
I'll check vacuum line to map today luckily all the lines look really recent.

I also found a guy on YouTube who had exactly the same issue. Hia turned out to be an ignition problem causing the break up at 5k and changing the plug leads sorted it. So I got a set of ngks in the post haha!

 

Get the coil harness as well. Just sayin'.

(That article in Japanese says change tte leads every year and the coil harness every five years.)

 

Got a harness on the way along with a diagnosis led box thingy, some new gaskets, HT leads, and some equipment to test solenoids 💪

 

I had a flooding issue we could not resolve. Went through the engine bay subbing in sensors, replacing wires and vacuum hoses. Several sets of plugs.

Turned out it was a bad tank of gas made worse by weak coils/coil wires.

But the car responded very well to the overall refurbishment.

This might be something to keep in mind for your now 26 year old car.

Although replacing all the sensor (etc.) with new can seem very expensive, good deals on parts can still be found on Yahoo Japan/Buyee

Pick up new, or at least spare, crank sensors, ISC valves, TPS, even coils, etc. when cheap ones pop up.

 

Sometimes it can just be the simplest thing overlooked, Gals you found a resolve, it's great that we can all share our experiences for the benefit of others.

 

Coming back to finalise things here, Turns out it was the HT leads causing the issue. Took some time to swap in some NGK ones and it's great now.

Will be doing a look replacement when it arrives though.

Thanks for all the help your all really appreciated 👍