H8stock

Hey all,

I have an '04 rx8. Bought the car with rebuilt engine. The car only starts when it is cold, and it takes quite a bit to get it started. It will run for 20 minutes then stall. Whenever I give it gas, it stalls, and won't fire back up. My scanner only comes up with front o2 sensor code. I have changed starter, coils, plugs, wires. Cel blinks while starting. The cat doesn't appear to be plugged, doesn't glow red, exhaust comes out tail pipe. I have reset nvram. I have not done compression test. Any ideas? The engine had 0 miles on it when I bought the car just had a fresh rebuild with Atkins rotary kit.

Legot

iTrader: (1)

Rebuilt by who?

H8stock

Rebuilt by a mechanic friend. He works for a Mazda garage.

tgaffner

Doesnt sound good

Legot

iTrader: (1)

Is he good at it?

wannawankel

The key will be the evidence - a mazda rotary compression tool test from Mazda. Cannot wait to hear the results

Loki

iTrader: (1)

Mazda mechanics aren't allowed to open the engines, much less rebuild them. There is a separate facility just for that. Not saying he botched it, but this would not have been his daily job.

Misfire on start up is weird. A common mistake people make when putting the engine in the car is mixing up the injector wiring, which usually leads to very poor running/not starting.

It's normal for a fresh rebuild to be a little difficult until the seals bed in and it builds better compression, but you shouldn't get misfires.

You have a scanner, can you look up the fuel trim values when it's idling?

H8stock

I had the scanner plugged in while the car was running, it's a basic scanner that you can get at any parts store. The fuel trim or percentage while idling was right around 35%, give or take 2-3%. I kind of thought that the seals might have not seated yet, but I have had it running 3 times for more than 20 minutes each. I thought it might have seated by now. I have the car up to temp all 3 times and even burped and added coolant to the radiator. It starts hard when cold, and cel flashes which tells me misfires, but no codes saying that and I've replaced the whole ignition including battery.

H8stock

When I have revved it or given it gas while running it sputters and misfires, and makes popping noises, then when I let off rpm's nose dive and it dies.

Loki

iTrader: (1)

Did you check the injector wiring?
When you say you ran it, did you drive it around or just idle? Because idling isn't going to do much for breaking that engine in It will take more than an hour in any case.

35% short term or long term? That's insanely high, you have extra air coming in somewhere. Look for a leak in the intake tract or a loose hose.

H8stock

That is idling, I can't drive it without it dying. I have not checked injectors, but that will be my next move. I can't see any obvious vac leaks, everything seems to be hooked up except my ac which the lines are cut on, but I don't think that is it. I put a brand new maf in, but have a bad front o2 sensor so that may explain a little bit of the richness. Or the scanner I used doesn't show fuel trim, it was just a percentage while it was running.

H8stock

Would a vac leak make it die after 20 minutes of running or make it die when revved?

Loki

iTrader: (1)

Combined with a fresh rebuild, yes. Confirm if the 35 is fuel trim or not, we're chasing the wrong thing if it isn't

While you're at the injectors, check also the ignition routing is correct: right coils on the right spark plugs.

By the way, don't let it idle for a long time like that, it's not good for a rebuilt engine's future longevity. Break-in requires load.

9krpmrx8

iTrader: (46)

It could be sooooo many things. And I didn't even think a -35 fuel trim was possible with the RX-8 ECU.

A compression test would at least rule out a shoddy rebuild or shitty Atkins parts (my buddy received Atkins cryo apex seals that were scalloped out of the box). Did you use cryo treated apex seals from Atkins?

But like I said, it could be anything, you just need to verify and troubleshoot.

H8stock

I have quadruple checked the coill pack harness order. I went by the diagram that is on here with the colored wires and order, I'm confident the coil packs are hooked up right. I will verify whether the fuel reading on my scanner is trim, or just a percentage. I'm hoping that I've got a vacuum leak somewhere I can't see, or an injector wrong. I am not avoiding the compression test, just delaying it. There are certain characteristics that lead me to believe vacuum leak, or possibly upstream o2 sensor. Either way, thank you for everybody's input so far, and please don't stop with the ideas lol. I live in Maine, there are 0 reputable rotary mechanics here (that I know of) .

9krpmrx8

iTrader: (46)

Well, sometimes, home built rotaries need mileage before they will run and idle normally. I have seen it a billion times, even with engines from reputable builders (although my builder says a proper rebuild should fire first crank and mine did) and personally that is why I paid a pro to rebuild mine.

I have helped with quite a few Renesis rebuilds locally and most of them took a while before they would idle and run correctly. And that's not a big deal because a couple of them are still running fine after 50k+ miles it's just something that happens with more inexperienced builders since the engines are not balanced, questionable parst are reused, they not clearanced to exact specs. etc.

As for the fuel trims, a negative STFT would indicate a vacuum leak but if it is -20+ then it would be a huge leak that shoudl be obvious.

Loki

iTrader: (1)

I might be heading to Maine/Kittery area for Thanksgiving. If that's close and you're not running by then, could stop by.

Bit of a long shot, but it's also possible the connectors from the car's wiring harness to the coils are mixed up. I don't know how, but people have managed to make that happen.

H8stock

I'm 2 hours north of kittery, in auburn. Not exactly close. If I'm not running by then, and your feeling charitable, I would compensate you for the time. I'll do my best to try and get things sorted before than, hopefully there is an obvious boo boo underneath the uim. As for the backyard rotary resurrection, I did do my research before buying, I knew there would be a degree of difficulty. I'm thinking I have a smaller issue that is preventing my car from starting, idling, and revving well. Once I find the culprit, I'll hopefully be able to actually drive it and break it in.

H8stock

9k, since my car didn't fire up first try, and it has had 4-5 starts/stalls but no drive time, do you think I have done damage to my seals? I read about fuel wash and how flooding the car can kill your seals. Since mine are new, and unseated, I'm worried about that. Though I have yet had a situation where I felt like the car was flooded. I have pulled the plugs a couple times and turned the engine over to empty gas, and nothing came out. Only the top plugs (trailing) where a tiny bit wet. The leading plugs where dry.

9krpmrx8

iTrader: (46)

I mean if it will run for 20 minutes before stalling then there is no carnage happening.

H8stock

It has ran for 20 minutes at least 3 times, it ran for 15 another time. It sounds pretty smooth during it. Just choked out after 20 minutes, or whenever I give it gas. I have a couple videos of it running during those time periods, but not sure how to upload from my phone without a link

H8stock

UPDATE: I started the car, and hooked up the scanner to see what my stft's where. At idle, my stft was 0.0. When I rev, it is still 0.0. Doesn't that mean I'm in open loop? Engine was cold, just started it. Any ideas?