rx7roller02

ok-car is a stock 86 GXL. Last time I drove it there was a random stumbling when I hit the gas. Then it would not start again. I have new fuel injectors, which will be going in this week, but I am also planning to upgrade to the MSD 6A or 6AL with blaster coils. I have a suspicion that the problem was caused by the ignition system, and I want it done in either case because of future planned mods. I have searched and found a lot of posts that suggest leaving the stock trailing coil, so I plan on just replacing the leading setup. Anyone running this setup, what issues did you experience with installation? Was it worth doing? I am just looking to see what I can expect to run into on this project. Between the new injectors and this, it should be running just fine again. Incidentally, my truck had the same exact symptoms the other day and the fix was with the ignition system.

Any info would be appreciated.

vaughnc

Just to clarify, you did put a timing light on the leading sparkplug wires to confirm you're getting ignition to both rotors. Also assuming you have new plugwires & sparkplugs.

rx7roller02

I did not use a timing light, as I intended to replace the stock system anyways. I do know that I am not getting consistent spark. Plugs, wires, fuel filter, air filter have all been replaced. I pulled plugs on it and they were not flooded at all, but they did have excessive black scoring--which is from what I have been told an indication of excessive unburned fuel through the engine. What I know right now is that it is not flooded but it gets fuel. The only other place I can think to look is the afm, but that was replaced with a (lower mileage) used one this past year.

I am not sure if the ignition system is the culprit here, but most of the usual suspects have been ruled out, and since I planned on doing it anyways, I figured on doing it now.

RETed

I think you're chasing the wrong culprit.
If the ignition system fails, it totally dies.
If you're chasing an inconsistent spark, check the spark plug wires for arcing or dead spark plugs.


-Ted

rx7roller02

Thanks Ted--where else should I look then? As stated above, fuel filter is brand new and injectors are going to be replaced this week. Will check those plugs and wires, but it doesn't even act like it will start....it turns over properly but it does not act like it will fire at all.

Anyways, the msd is still on the plans, so that will be included in this week's work. Any other suggestions?

YearsOfDecay

Honestly, the MSD 6a is not a bad idea, but, in reality un-necessary. You'll get a bit better gas mileage and it may help the idle a bit... but don't expect a kick in the *** when you put it on.

the 6-al is totally worthless (well the L part) Don't pay the extra cash for the rev limiter.. not a good idea to run a rev limiter on the primary coils and not on the trailings... get it????

The blaster coils...... I think thats a waste of money... but you go on with your bad self, some guys swear buy running them on the leadings..

before you start tearing everything apart, buy new plug wires and plugs and all that jazz.. check your compression... just to be sure... bad compression on a rotary may seem like a faulty ignition system on a piston car... (if 1 Apex seal is bad.. you just lost 33% of your motor) and will definately cause starting problems and stumbling once it gets running.

rx7roller02

that's the thing--it ran just fine, and then one day it started the stumbling. it would still start just fine, but the stumbling happened under accelleration. Honestly, the first thing i thought of was a clogged fuel filter--that's how it was acting. I cannot get good comp readings now because the engine wont start at all, so i cannot warm it up. but it was stumbling one day and the very next it would not start at all. I will get new plugs and wires just in case, but the ones on the car are not that old at all. When I swapped the fuel filter, it took away a little of the stumbling, but only for a short while. then it was right back again. and the next day it would not fire at all.

if I lost an apex seal, wouldnt the car accelerate poorly every time you hit the gas? This one did not....it was really random. some times it was fine.

Ted Webster

You may also want to check the fuel pressure from the pump. Also, possible is a bad fuel pressure regulator, and it is easy to check---both are outlined in the fsm and hayes manual

BuffDaddy915

Check your distributor cap. Maybe ya have something burnt/just needs to be replaced in there.

rx7roller02

thanks for the tip ted--gonna go look that up right now.

rx7roller02

You are of course aware that the 1986 RX7 does not have a distributor cap, right?

Jrodwnc

i've had a mysterious "cutting out" in my 87 na, and it showed up more recently at an autocross. a fellow Rx7 guy said that the main fuses on the left strut tower are bad to corrode, but look ok. they will work most of the time, but can "bounce" apart intermittently when you hit a bump. I also pulled the fuel pump out of the tank, and the in-tank filter is 50% covered in silt. It was $10 from mazda. Just some other things to check.

spot_skater

About the stumble then no start...you might want to check your TPS, AFM, CTS, timing, fuel pressure, and make sure the intake isn't plugged up.

That might help figure that out.

I've read, and a lot of people seem to agree, that the stock ignition system on FC's is pretty good and isn't really necessary to replace...Might want to think about investing in something else.

Good Luck,
James

rx7roller02

The intake is fine, and as far as the AFM, i thought there was no way to check it. is there one that you know of? for some reason I thought that there was no way to check it out. timing is not an issue, because IIRc the timing being off would make the stumbling a constant thing, right? I was able to drive it for fifteen minutes with no issue, and then randomly it would stumble. then it would stumble almost constantly for a minute or two, then back to running more normally. TPS is ok too. I am going to check out that filter at the fuel pump, thanks for the suggestion--i forgot all about that one. when you said CTS, did you mean CAS? The fuel pump filter is my next shot, followed by replacing my old injectors with the new ones.