So The JDM FC is still fighting with me.

I brought the car to Dave at Mazdees and had the engine rebuilt (again, 2 rebuilds in 3500km). It had a chipped apex seal and a burr on the housing.
It runs much better, but I still have a hot start issue with flooding and I still constantly need to use the fuel cut switch to get it to fire up. Fires right up if cold. If you try and start it hot, and crank for more than 2 or 3 seconds, the plugs (brand new again) are soaked to the point of fuel dripping off of them in both rotors.

At idle, it smells rich, and I can hear popping or chuffing in the exhaust, which I believe is extra fuel getting dumped through the system and popping in the exhaust. Under light load (~40% throttle >4000rpm) i sometimes get huge backfires from either too much fuel or ignition breakup Other times it feels fine, it's about 50/50. I am leaning towards too much fuel, as the damn thing always smells like gas and I am only getting about 250-300km (

 

For some reason the second halp of my post keeps not appreaing....

...

 

less than 170 miles per tank is rediculous...
can't get any more temp tags this year and can't pass e-test.

IDLE
HC limit 200 reading 1796
CO limit 200 reading 876

2500RPM
HC limit 200 reading 743
CO limit 200 reading 416

Dave and Johnny at Mazdees have a reputation for putting things together properly, so I'm not sure what could be amiss here....please help!

 

One thing you can test is the TPS, and pressure regulator control valve (valve is used for hot starts). Might also want to check the water thermosensor (helps regulate amount of fuel injected dependent on temp). And also test the AFM according to spec as stated in the FSM.

And does the backfiring occur on acceleration or decelerating?

 

with HC's that high you need to look at the ACV and the rest of the air injection.

you want to make sure the ACV is good.

it is also easy to get the vacuum lines on the ACV and in the back of the intake mixed up, as the pictures in the FSM aren't specific enough. i always end up pulling the hose off the valve and the solenoid, and make sure they go to the right place.

set the TPS, the two test lights are literally on the ACV solenoids, so you're literally setting those.

Mazda sets the car up to be in "port air" where the air pump air goes to the exhaust ports, during an emissions test.

if you have working air injection, and a good 02 sensor, basically the car should be under 100ppm HC's and nearly zero CO

 

Acceleration.

 

TPS verified ok.

I do not have an air pump and am not sure if the JDM cars even came with one.

I will look up how to test the ACV, but the car is outside for the time being because it won't pass e-test and can't be driven; I need to get my girlfriend's Civic fixed so she has something to drive while I'm using the Accord for work...Canadian 15-year-old brake lines sure are fun, lol. Hopefeully I can get to it in the next few days, but if I can't figure it out it's going to have to go back to Mazdees; I simply don't have the time to be messing around with it like I wish I did.

 

When testing the TPS you also want to check the range of voltage as it should be from 1 volt at idle (completely warmed up) to about 4.5 volts w/the TPS fully extended and there should not be any jumps in voltage as it should be smooth throughout the range (an analog meter should be used).

Also, is your car an S4?

 

that is the exact procedure I used, and exactly the readings I got. I feel like it's pretty safe to say that the TPS is not my problem.

Yes, the car is a JDM S4 (Zenki, VIN starts with a 1) built October 1988. One of the last S4s.

 

The readings though could be different when taken at the TPS versus the ECU so it's not completely ruled out.

 

Did you check the AFM like Satch said?

 

Typically:

Backfiring bucking hesitation on acceleration is AFM or ignition.

Backfiring on decel, poor idle, etc is TPS. (car will actually usually run pretty good WOT)

 

As soon as I have a moment, I will. I'm stuck at work right now and have to get my girlfriend's Civic (15 year old Canadian rust belt brake lines, ugh) back together first. She was using my regular daily Accord while I was trying to get the FC on the road, because I was trying to avoid having to fix her car until the fall when the snow comes back...

Guess that's what I get for putting faith in the FC hahaha.

 

Hmm....the only time my FCs have failed me is when i've done something stupid to them.

 

they did, it'll never pass an E test without one.

 

Well, sounds like I'm fairly screwed.
I've already spent way too much money on trying to get this thing legal this year. Two engine rebuilds, a turbo rebuild, a differential replacement, and countless other little things.

I'll probably give up for now and try again next year when I can afford to put a standalone in it and get it through e-test with a tune, or just sell this thing. I've got 5 figures into her in the last few months, and I can't justify any more. I just want something fun to drive to work and back in, and I love the feeling of the boosted rotary.

But at this point, I might be better off getting out of this nightmare and just buying a used Corvette or something....

 

There you go. Do us all a favor...

 

What'd I ever do to you?

 

You may be right, sometimes knowing when to cut bait is the best skill of all.

Of course, having already spent more than the car is worth and still not running properly, you take a terrible bath in the process.

 

Was the first rebuild not warrantied? What happen to cause it to need two in a row? It sounds like a trip to someone willing to do proper diagnostics is in order or spend the time doing tests yourself if you are capable.

I also second that you will not pass emissions at least tests equivalent to ours here in AZ without an air pump. An air pump isn't going to be enough though if the engine isn't running properly anyways which your acceleration issues indicate it isn't.

 

Definitely true, as soon as time allows I will get back at it and troubleshoot keeping the suggestions of helpful members in mind. It'll probably be a few days until I can do that, but that's life. I am starting to realize that this summer is not going to be the summer where I get back into the FC, but at least that gives me time to figure out where to go from here.

I really want this car to work; I love these cars. But wasting any more money on it this year would be irresponsible at this point.

 

I bought this car from a self-proclaimed rotary master with no engine. I have no time on my hands as I travel a lot for work and spend most of my time driving to different integration companies and factories with industrial robotics.

He assured me that he could build me an engine with brand new rotors and housings better than anyone else around, but it wouldn't be cheap.

Understanding that you get what you pay for, and foolishly tricked by someone who is very good at telling people what they want to hear, I paid him for the car and to build me a motor. (this person is most likely a member here)

When I took delivery of it I immediately knew I had been ripped off.

The differential was destroyed, the clutch hydraulics were ruined, the turbo was whining, it leaked fuel and oil, the bolts holding the front suspension together were all finger tight, and many many other very frustrating things.

I ended up with something carelessly slapped together for $8500; and having bought it privately, I have very few possible methods of recourse.

I spent several months trying to figure out wtf all of my issues were, with quite a few all-nighters mixed in between work. I found an s4 n/a pressure sensor, rtv between the turbo and manifold, kinked turbo oil lines, missing gaskets, ghetto-fabbed block off plates, incorrect bolts, no oil in the transmission, the wrong cluster in the car, missing fuel injector seals, wiring crushed between the upper and lower intake manifolds, misrouted coolant hoses,and the list goes on and on.

Eventually I checked compression and it was all over the map; my worst fears were confirmed. I had paid the price of a good reliable fc, and received a worthless pile of parts.

Dave at Mazdees did the second rebuild; inside he found a chipped apex seal and a burr on one of the housings that most likely caused the chipped apex seal. He also voiced his concers over the mental capacity of the dude that built my first motor. Which makes me wonder about mine seeing as I bought a car from said idiot.

I intend to go back to Mazdees if I can't figure this out on my own, but if for a few more dollars, maybe it can be sorted......I mean, I've come this far......

 

Sounds like a pretty huge mess.

Just remember the best course to less wasted money is proper diag first then repair. Don't just throw parts at it.

 

Thanks.

As soon as I can get to it I will continue troubleshooting, I'm not throwing another dime at it until I'm sure it's necessary/worth it.