akageals

Guys,

Car runs good but occasionally has just a small burble in the idle....it also seems to have more power sometimes than others. When I went to check the timing I noticed that I get a steady stream of flashes from the trailing coils and almost the same steady stream from leading 1 BUT on leading 2 the light flashes sometimes and cuts in and out. I'm wondering if it could be something about the RX ingnition system (i'm using an inductive timing light) or if there is actually something wrong with the coils or possibly wires.

Todd

akageals

anybody else experience this?

Henrik

I have the 'more power sometimes' issue as well. When it's in the less power mode, idle quality is good with a little bit of burble and boost has some lag to it. When its in more power mode, idle quality is perfect and boost is instant. I'm suspecting ignition but haven't figured it out yet. My ignition drops out now and then on all four plugs when timing it. Plugs and plug cables are good.

An inductive timing light should work fine on RX7's.

Anybody else have any help??

Henrik
87TII

Scott 89t2

if your plugs are badly fouled you won't even get a timming light to show up. get some new plugs if they are not too new.

RETed

That is actually "normal".&nbsp I believe that Gary Mounsey (is he here too?) from the TeamFC3S.org list mic'd the output of the stock ignition system.&nbsp He found out the stock ignition system was dropping every 3rd spark on the leadings!&nbsp So this is "normal"...



-Ted

akageals

Ted....it's not just every third pulse that gets dropped. It will actually stop flashing for a second or two then start back up. It does this sporadically. This condition does not seem to affect the trailing plugs though.

Todd

akageals

Henrik,

What you described sounds exactly like my car! I sure would like to figure this out. When your car is in "less power mode" does it limit the amount of boost you have? My car sometimes boosts to 3/4 on the factory gauge and sometimes to 1/4. It even sounds "meaner" when it's running in "high power mode" as you put it. Car seems fast all the time but it's Holy ____ fast when running right. I have a downpipe and no cats so i'm sure it's not the exhaust.

Todd

NZConvertible

Mine does exactly the same thing, but it seems to be only when cold. i suspect plugs, leads or coils.

RETed

This was the input to the leading coil, I believe.&nbsp If you drop the input signal, it takes a while for the coil to charge back up, so therefore it misses for more than one pulse.



-Ted

akageals

Ted,

What would cause it to "drop the input signal" ?

TOdd

Henrik

And I thought I was the only one... In either 'mode' I get full boost, it just takes longer to build in 'slower mode'. It also only seems to affect response below 3000-3500rpm, above that response and power seems to be the same either way. I also sometimes get a noticable bump in the butt dyno when passing 3000-3500rpm at WOT, boost doesn't change though.

I did have one thought, last time I was timing the ignition I noticed that if I went above idle by opening the throttle, say to 2-3k and hold it steady, the timing advances (as normal) but once in a while the timing is retarded (no pun intended!), almost to the idle mark. Are you seeing the same? And what can cause the timing to retard (light throttle about 2-3k rpm)? I know in my case its not fouled plugs as it happens with brand new plugs as well as comes and goes with old plugs.

A case a good CDN beer to the person who comes up with the solution!

Henrik
87TII

von

When im cruising I get this slight hesitation or jerk . one ever second. Feels like ignition cut but can someone tell me if this is related. Its an 89N/A

RETed

Poor design, basically.

Fortunately, there's a relatively "easy" way to fix this - run a CDI ignition box!


-Ted

akageals

Ted and Others,

Appreciate what you are saying. There MUST be some explanation other than poor design. I think we are all saying that there is a noticeable difference between the two "modes" and that this is not normal. Anybody know if a coil or ignitor can fail this way??? What about the CAS could it be causing this???? The only other thing I could think of would be the TPS (could cause the same symptoms but I don't see how it would affect the spark).

Todd

HAILERS

Why don't you see if the spark is REALLY not there? Disable the trailing coil assy and start the car so you will only run on the lead coil. If you really not getting spark to the lead 2, then the car would stumble all over the place.

akageals

Hailers,

I'll try that this week and see what happens. Car is in the bodyshop now thanks to this bimbo that backed into the front bumper with her SUV.

Todd

RETed

I don't know if you know some basic ignition system theory, but let me try and run it down for you...

Majority of (stock) ignition systems out there are a inductive design.&nbsp This is due to a primary coil voltage that is stepped up to a (higher) secondary coil voltage.&nbsp Basically, the stock ECU fires the primary side signal which, in turn, triggers the secondary side of the coil.&nbsp This is how you get a "low" voltage signal (i.e. 12V) to trigger a "high" voltage signal (+20,000V).&nbsp Now, for the high/secondary coil side to trigger, there is a voltage trigger threshold; if this minimum voltage level isn't attained, the secondary coil does not fire - there lies our problem.&nbsp The ECU/low primary side signal is NOT strong enough to trigger the secondary coil - this is what I call the "poor design".&nbsp This is what was uncovered by Gary Mounsey when monitoring the input signals to the primary coil with an o-scope - there are signal drops that prevent the secondary coil from firing.

Now, I dunno how you would "fix" this, but a CDI box is easily able to take the low-firing primary coil signal and spit out a consistent output signal to always fire the secondary coil.&nbsp This is the beauty of a capacity design - consistency.

NZConvertible

Sounds like another good reason to ditch the stock ECU!

Henrik

I have an MSD6a and still have the problem. My car will start with both trailing or both leading coils disconnected so I know the coils are firing although they may be weak (this was before my MSD6a install). Doesn't make ****-all power on the trailings only, even though boost still builds to normal. This is why I'm suspecting the timing is being retarded somehow or maybe there's a problem with the leading coil/ignitor (the MSD6a still gets its signal from the ignitor)

Henrik
87TII

Keith

Akageals,

I am not sure what your problem is, but I strongly suggest your timing light. You stated in your first post that if you put the light on lead #1, your light triggers without missing. If you put the light on lead #2, it "cuts in and out". Well, this might make sense if you had 2 leading coils, like you have 2 trailing coils, but, YOU DO NOT! You have a single coil, firing across both leading plugs. If you are getting a good signal to lead #1, you are getting the same good signal, albeit reverse polarity, to lead #2, because it is the same circuit! Try turning your pickup around for lead #2, maybe it'll work better! Or, get a timing light certified for DIS ignition, since the output of a DIS system "floats", that is, it is not ground referenced. Or, better yet, if you have decent plug wires (that is, not leaking), and you get a good reading on leading #1, the leading plugs are firing ok, don't even bother with leading #2.

Henrik,

No simple answer here, imho. Advance is controlled by the ECU, completely and totally. Also, there is only 1 pair of timing signals, from which the ECU derives both leading and trailing advance. So, if the ECU has a problem, both leading and trailing will experience it. Possibilities? Uneven amplitude out of the CAS, usually due to some mechanical problem. You probably need a 'scope to determine this. Unstable output out of one of the temp. sensors, or even the knock sensor (timing retard could be a result). Pressure sensor fluctuation (sudden "vacuum" signal, retard!). Weak output on the tach signal from the trailing ignition to the ECU. TPS fluctuations. ECU grounding problem. ECU voltage problem (spiking). In short, anything that can confuse the ECU (and with this ECU, it doesn't take much, believe me!!) I'm sorry I can't be more specific, but I have not been able to find a flow diagram of the ECU's program, so I can only guess. Good luck in finding the problem!

Irv, Keith's dad

RETed

I don't know what you're trying to say.&nbsp the engine will merrily run with just the leadings OR trailing firing.&nbsp Hell, my car ran a 13.9 @ 101 JUST ON THE TRAILINGS!&nbsp An experienced owner would feel the midrange revs a bit slow, but once boost kicks in, it feels rather normal.



-Ted

von

Well I have done better. I ran on just my trailing and beat a civic in a drag race.. These rx7s are tough as ****. My timing was advanced as well so that was probly why I can barly notice a diff. Loss of power everywere basically but no jerks or hesitations. I had the coil completly off just in case someone asks...

akageals

I think i'm going to try new spark plug wires and maybe a new coil and just see what happens.

Anybody know if the coil from a 90 NA will fit an '87 TII???

TOdd

Henrik

What I was trying to say is that I'm getting spark at all four plugs and with the MSD, I shouldn't be seeing the dropout that you were talking about. What did your car run with leading's going as well cause there sure is a difference between having the leadings present or not (unless you advanced your timing). I do see dropouts on the timing light but I'm suspecting that's either weak ignition or the light itself. The wear patterns are the same across the plugs so I know they're all firing more or less the same amount.

I have seen the timing change when holding the RPM's steady above idle which I think is more likely the cause, so I'm going to try to track this down - ugg, auto electronics suck. Thanks for the suggestions Irv, time to break out the 'scope. Its intertesing that of three cars affected, they're all turbo's - maybe the knock sensor is the problem. My airpump (soon to be replaced) sounds likes its got rocks in it, maybe its falsely tripping up the knock sensor.

The coils are the same across the years but Irv is correct, if you've got spark on one of the leadings, you've by design also got spark on the other as they are part of the same circuit (and fire at the same time).

Henrik
87TII

Henrik

Irv, re the DIS ignition, are you saying then that in an RX7, the secondary coil is not ground referenced? I tried measuring the secondary coil resistance (on the trailing coils) but it doesn't appear to be referenced to any other terminals on the assembly. Simlarly for the leadings, there's resistance between the two plug towers but not between either of them to anything else (like ground). What does the secondary 'push' against then when it sparks?

Henrik
87TII