Doofry

Hi guys,
I'm looking for some advice. I have a 55k jap FD3S, which as far as I know hasn't had a rebuild (I know its about that time that they go). It's seemed fine, always started fine, power felt fine, etc.

The other night it all went worng. Luckily I was only about 1 mile from my home when I'd gave it a wee blast down to a roundabout (only to about 5-6k rpm), slowed down and when round the roundabout then went to accelerate and suddenly my sweat rotary engine bogged down big time. I didn't feel or hear any mechanical or metallic noises and didn't see anything unusual coming from the exhaust in the mirror (it was night though). The best way I can describe it was of a really boggy response (i could only get to about 30mph) as if a plug lead was disconnected (though I doubt this to be the case ). I checked the temp guage and it was normal. So I thought if it's a rotor then I'm screwed anyway so I soldiered on and limped home. As I came round my street I did notice a red warning light come on for a second, which said 'HEAT', which after searching the forum is see is the exhaust temp sensor lamp (Pleeeease.....tell me its just a collapsed CAT..lol). As I said the temp guage was still normal. I let the engine cut out after this and free wheeled down the road and into my drive.

I was looking for some advise as to how I go about diagnosing the problem. Honestly, I expect that knowing my luck its a rotor and I'm going to need a rebuild and being in Glasgow, Scotland I'm not looking forward to trying to organise this as there seems to be very limited support for Rotaries in the UK and most of what there is is in England (I'll probably be cheapper importing another from Japan just for the engine lol). I'd love to hear that it's maybe something less expensive like a cracked hose, etc. but I won't hold my breath, so....

Should I start with trying to arrange a compression test? Would this be a good first step to see if its the rotors? Would the tips normally fail like this? If this doesn't look as if it's the problem what else should I check?

S....O....S....

rotaryinspired

iTrader: (3)

If the car will idle smoothly you are probably ok. I have yet to see a blown engine want to idle very well. If not get a compression check. It sounds like it could have went into limp mode from the cat getting too hot.

Doofry

I guess i really need to get out there and check some things out. Compression test i suppose should be ther first one.

The car does start though not easily and then smokes quite a bit.....not brown more an unburnt fuel type cloud. Runs pretty sluggish and lumpy. Symptoms sound similar to disconnected vacuum sensor pipe but i've checked this and it does seem well secured.

When the power went it happened between braking from full boost and accelerating. As soon as i accelerated there was virtually nothing. Would an apex seal go like that? As I said i did not hear or feel any mechanical sounds, etc when it happened. If an apex seal failed this quickly would you expect to hear something as it scored the housing, etc?

All input is appreciated

impactwrench

Clogged cat, bad fuel pump, bad leading coil? You'll just have to start checking, one by one

Doofry

Impact wrench, which of these are more likely to fail so quickly and which are easiest to start with on an FD3S?

- I'll get a compression tester, modify it and try doing that (though will try pulling plugs out and listening to compression beet first maybe)

- Fuel filter i should be okay with

How hard is it to get to the CAT using a trolley jack in my drive? Is it a garage job?

Thanks

ehos

How much fuel did you have in the car? I don't know, but you said you went on a 'roundabout', just thinking the fuel might have cut out.

Doofry

Yeah i had a pretty full tank of petrol(sorry gas) when i went round the roundabout (sorry circle or what ever they're called in the US). Things didn't get better when i hit the flat again anyway and i'd pretty much took the 2 o'clock exit off the roundabout anyway.

Car say in the drive over night and is still the same.

kerry chandler

If you want to check if an apex seal had gone and don't have a comp tester,try this:

Pull the EGI main Fuse so you wont get spark
Remove one of the plugs from the front or rear rotor
Crank engine and listen for HISS HISS HISS sound.if you hear even HISSES
from that rotor then that one is OK.Do the same to the other rotor.
If you had blown an apex seal you won't haer the HISS.

GOOD LUCK

impactwrench

I've had bad cat and coil. Fuel pump is still fine. Which is most likely? You just have to go thru them one by 1. Do you have a fuel pressure guage? Should read about 38-42 I believe. Coil is a bitch to check but if you can get at it, the specs are in the field service manual. Clogged cat can be checked by disconnecting at the flange where it meets the down pipe and running the car.

Doofry

Thanks for the input guys. I'll update once I get a chance to check some of this out.....looks like I'm gonna be a busy boy :-D

DaveW

Did you check to see if the MAP sensor hose is connected? The map sensor is the small rectangular unit attached to the firewall (says boost sensor). Car will run very poorly if this is not connected.

Doofry

Ahh....sorry I knew this as the Vacuum sensor. Yes, I've checked the connection on thias as well as the vacuum pipe going into it. Do these sensors themself ever fail? Can themy be tested with a multimeter?

Harold93

Doofry,
i would start buy taking the flange off at the main cat if it is a block in the precat on the downpipe you will have more problems, in fact if it was on the precat it would explain why you had the light only flicker, also why you had such a sudden loss and a boggy feeling. because your steering colom is in the way you will have to get at the bolts from the top and bottom at the same time make sure you are carefull when i was changing my down pipe i snapped the head off of one luckily we got the threads out too. once you have it disconected start her up if she runs smooth you found the problem if not go to the comp test, if you dont have the set up Kerry had it right but also put your thumb over the port for the plug and feel the pulses you will hear them pretty much no matter what but you want to feel how strong they are, test both rotors both should feel about the same. if you have three strong pulses on each rotor i would do to the lead coil nxt the fuel pumps are pretty reliable, there is a good write up in the manual for checking the fuel system. what you said about the exhaust being ritch sounds like a coil it seems you are geting fuel in but not igniting good liuck letus know what it was

Doofry

Harold93 thanks a lot for the practical tips (especially the one about feeling the compression pulses rather than just listening) and the sensible order to trouble shoot them in. I think I may be in luck with the CAT bolts as this is a JDM model in the UK so the steering column shouldn't be in the way.

Its going to be a couple of days at least until I can get over to have a look at the car so I've been doing a bit of searching of the archived threads and came across one of interest as it ties in with the fact that the symptoms sound like the MAP/Vacuum sensor pipe coming loose. Here it is:

https://www.rx7club.com//showthread....83#post3240283

It may just be wishful thinking but from what i've read on the UK forums (www.mazdarotaryclub.com) the symptoms sound like a MAP sensor related problem. The thread above discusses a problem with the left front wheel rubbing on a piece of the wiring loom under the wheel arch. The guys who've had this problem find that the wheel rubs through the insulation and eventualy in a right hand turn it shorts out two of the wires related to the MAP/Vacuum sensor. This seems to 'blow' the sensor which would explain why the problem still exists. Also if you remember I said I was breaking into and turning around a roundabout (which since I'm in the UK where we drive on the left means I was turning right as I'd be going around it in a clockwise direction) so that would tie in with it being this problem.

Again maybe this is wishful thinking but what do you guys think? Sound likely? If this sensor fails does the engine run rich, explaining the smoke and undurnt fuel smell?

Cheers

Doofry

Sorry screwed up the URL above, here it is again:

https://www.rx7club.com//showthread....83#post3240283

kerry chandler

Non of the engine related wiring loom runs under the wheel arch.The map sensor wiring goes with the main engine loom that goes into the firewall on the passenger (JDM) side under the ABS motor.

Doofry

Oh well, that blows that idea out the water :-(

Narfle

iTrader: (16)

Sounds like you blew out your cat. It is a garage job(your garage). 2 bolts on either end and the 2 airpump bolts. Make sure shes secure when youre under there. Youll need a good socket set and breaker bar to get the job done. Should take a couple stouts.

Doofry

Had a quick look under the left front wheel arch and alas no wiring harness as you guys said....shame lol