right so I bought this S7 rx7 for cheap a few months ago and know nothing about it, it has 88,000kms on it, stock turbos and stock porting

The car starts hot and cold and for the first few weeks behaved perfectly. I'm sure this next bit came totally out of the blue, I parked it up one day, and the next day it started easily, but suddenly had a large engine vibration and sounded like a bridgeport! brap brap brap brap.... after it idled for around half a minute it shuddered and died. and it's done that every start ever since. it can generally restart easily enough once it dies, and the smoke increases rapidly with RPM. I can hear the turbo spooling quite audibly

The intercooler piping is full of oil, so for a start the turbos need attention and I am in the process of pulling them off. But would oil in the intake cause the pulsing idle and poor running? I thought it'd just be smokey. what can I do next to try and diagnose the issue?

 

Start with basic maintenance.... the spark plugs must ignite whatever mixture is in the combustion chamber and subsequently take on whatever that mixture is. If your mixture is oil based then the spark plugs will be the first thing to go causing combustion related anomalies to include what you have described.

The rotary is not unique. It is still an internal combustion engine.... troubleshoot it like one

 

If you're saying leaking turbo seals can cause the misfiring then that's fantastic - I should have added I flooded the engine at some point too, and I think my premixing has been on the generous side so there's probably a considerable amount of oil (and residual ATF) being burned

I suppose I haven't given the engine a good chance to warm up and clear itself up (I live in a very public area so I get self conscious with my loud, bright coloured car blowing smoke everywhere!)

I suppose I was worried that I was grasping at straws and was giving someone the opportunity to come in and say "don't waste your time on the turbos, that's a clear sign of a busted engine" or something similar

 

It could be anything up to a blown motor or it could be as simple as spark plugs. You need to troubleshoot to find out what it is exactly.

 

If you're concerned that the engine might be damaged, try the poor man's compression test while you have the spark plugs out.


Either way, I like to always have a set of fresh spark plugs ready to swap out. If you're buying online, I like sparkplugs.com they have been around for a long time. Amazon and ebay vendors have been known to sell fake spark plugs, and the potential cost savings isn't worth the risk.

 

Check that you, or no one else, has attached your spark plugs lead or coil harness in the wrong order.

For s7 and s8 Mazda changed the order of hooking these up, and many people are still unaware of that, so a simple spark plug change can lead to some of the issues you are describing.

You should also do several simple tests:

- run codes if you still have a stock ecu. There are about 50 codes that can give you an idea of malfunctioning electrical components (such as turbo control solenoids)
- run a smoke test. this will tell you if you have any boost/or air pressure leaks
- run a proper compression test

Oil in the cross-over pipe is a concern and could point to failed oil seals or cracks in the turbo.

But there is another less serious thing that can happen.

Although it has often been long ago removed, in the stock set-up, there is a breather tube that runs from the top of the oil filler neck to the intake elbow in front of the front turbo. It is there to recirculate fumes from the oil pan. However, if you overfill the oil (above the halfway point of the hash marks) oil can overflow down that breather tube into your front turbo and blow into your cross over pipe. People have had scary smokey events from that issue.

 

A major leak in you UIM area can cause the sort of noise you are describing. Perhaps the vacuum line to your brake servo has popped of. Here is what my car sounded like with the ISC removed.

 

well done, you correctly identified that I'm an idiot (I'm pretty sure). I noticed that some diagrams online had the layout of the coils in different locations, and realised that there was a difference. I made very, very, very sure to hook up the ignition leads correctly. I also thought that I hooked up the harnesses correctly, but it would appear that this is not the case:


here's the google translate version of the coil wiring for the 97-2002 model



here's the plug that's currently hooked up to T1, the forward-most coil. Unless I'm missing something, that aint right

I guess I could just swap the T1 and T2 leads between plugs. The weird thing is that I was SURE that I hadn't done any work to the car between the time it was parked up happily, and the next time I went to run it! who knows.

Anyway now I'm wondering if I should persist with pulling off the turbos which is turning out to be a pretty humbling experience. But here's the oil in my intercooler pipes;


probably warrants some surgery? I am having some real trouble getting the turbo off, I've got the plumbing and downpipe off but man it's hard to get at the heat shields, I'm guessing they need to come off before the unit itself unbolts? I think I've been spoiled working on simple old cars, this thing is a headache to get out.

 

That might not be the right wiring chart. Be careful.

 

Hre is the download for the Japanese manuals. You need to look at the wiring manual for your year of car. Password is embedded in the file name.

https://www.rx7club.com/3rd-gen-gene...002-a-1127911/

 

Here is the wiring diagram for Version 4 (S7) FD. The diagram you show above is likely for Version 1~3 (S6). It shows the unusual grounding wires.

 

This is what the s7~S8 coil harness hook up should look like.

 

 

This is the only warning (I can find) that Mazda gave showing the change of coil position. The lower diagram is the "new" arrangement for version 4 cars.

[The leading coil has been moved from the middle to the right side in the diagram].]

 

Here is the Version 5 (Early S8) wiring diagram. It has the wire colours in alphabet.

 

Here is a comparison of the the two diagrams. The "shield wire" in the lower pic a clue that your are dealing with an earlier wiring diagram.

 

is the venting piipe still running from your oil filler neck down to the intake elbow ahead of your front turbo? Did you overfill your oil? If you remove that intake elbow, is oil pooling so that it is visible at the lower edge of the impeller fan?

 

We were able to get the turbo in and out without removing the engine. Separately removing the rear intake pipe was tricky. Also you have to get the steering column out of the way.

Mazda recommends you replace all the gaskets if you have the turbo out. That can be very expensive.

But the oil line gaskets are not.

 

you're too sharp mate.. I could have sworn the manual I had was labelled as "2002"... pretty sure looking in the wrong manual is an instant fail in any trade test. BUT, still a bit rude of Mazda to pull a switcheroo like that, where it looks visually the same but just the labeling of the coils changes... and it doesn't even match the physical arrangement of the coils! all in all though it looks like the coils ARE wired correctly, which is disappointing as it's not a smoking gun. in fact from your photo of the harness I don't think it's actually possible to switch T1 and T2, the plugs simply wouldn't reach

Yes I have the oil neck venting to the inlet ahead of the forward turbo, and yes there is oil pooling at the compressor (I assumed it was from a failed turbo oil seal). The vent pipe itself into the inlet pipe looks dry but I suppose the oil might have dribbled down away from it. The oil is overfilled, about 1/2 an inch above the hash marks. It smells a bit fuelly, I suspect it might be diluted from flooding. would an overfilled sump immediately cause significant smoking? I would have thought it'd need a minute to build up pressure

 

That really sounds like that is what you oil problem is. Congratulations. yes the effect can be surprisingly quick. Plug off that vent pipe and see how quickly your engine stalls.

Many people route the drain pipe to a catch can and seal-off the nipple to the turbos.

A tech at our local shop recently switch the ends round when re-installing the coil harness. Happened in just seconds.

My car bogged badly upon leaving the shop. Could not believe that that problem happened to ME!

The oil your compressor will cause smoke pretty quick. But you have little choice but to let if burn off now.

I suppose you could soak some of it up with a rag,

I suspect you have badly flooded your car.

That may account for the gassy smell in your oil.

How old is the gas in your tank?

 

Oil should only be filled to half way up the hatch marks.

 

there'll be a mixture of various age gas in the tank for sure, but the vast majority of it probably under 6 months (some very fresh). I definitely flooded it in the past, had to pull the plugs (actually replaced a couple) and did the ATF trick to get it running again. Started quite easily so that's probably a good sign. Do FD's have problems with sticking injectors? It sounds like there's about a litre more fluid in my sump than there should be, I'd like to think that I didn't just arbitrarily pour a whole bunch in there without checking the dipstick

more to the point I've got the turbos half off, not too sure if I should carry on pulling them or start putting it back together. Anyway I'll pull and clean the plugs again, and do something about the oil level. That'll cross a few other things off the list

 

Injectors can stick and that would ad to flooding risk. It was part of my flooding problem

I'd put the turbo back on for now. See if the oil overflow remediation helps.

Get the compression test done. Always good to know where you stand.

Check your coolant for any oil residue. May indicate any oil seal leak.

I'd change out all that old gas for new and pump clear your system of the old gas.

Is your gas there blended with ethanol. If yes, you likely don't want it to sit more than three months due to water attraction.

 

in your video earlier it looks like the car is running with the intercooler piping off... can I just reconnect the exhaust down pipe and oil feeds to the turbos, and run the car like that to see if the smoke clears up? the turbos are still bolted onto the block and oil feeds etc are still on. it would save me having to refit the Y pipe and rear turbo inlet etc

we don't have ethanol in our fuel, and my coolant is nice and clean

what's a good way of finding out if an injector is stuck? I guess I could put a pressure gauge in the fuel system and prime it?

 

I had not noticed the pipe was off in the video. Maybe that was to allow us to spray in starter fluid. I do not recall.

When you have pipes off like that you have to be careful not to suck in debris, so i would be cautious about what you are suggesting above.

Having said that you may try buttoning everything up and leave the intercooler end of the cross-over pipe open (as per your picture) and let the oil blow (smoke) out there.

Again you have to be mindul of sucking unfiltered air into your motor/turbo fans.

In that video we removed the ISC valve from the back of the UIM.

That allowed us to bypass (a lot of air) around the throttle body while letting the ECU run the motor within its hunting ranges.

The purpose of that is that if we used the throttle to rev the motor, the TPS would trigger the ecu to add gas and re-flood the motor.

The large of amount of air being sucked in the ISC would help clear the flooding

The tech used his hand over the ISC port to act as a throttle plate.

You have to be mindful not to over-lean the mixture.