I have a 85 rx7 that will not adjust in the timing on the trailing ignition. The leading timing is perfect on the 1st notch and the car runs great until I let off the gas and then a big backfire. The trailing timing is in line with the first notch (needs to be on the second) and will not move regardless of how much I adjust the trailing vacuum unit. I'm connecting to the trailing spark plug wire on the front bottom of rotor and when I adjust the vacuum unit it is connected and moving the points inside the distributor. This all started when I was doing a test run and was running approximately 115mph. Thanks

 

The trailing plugs are on top, not the bottom. If you are connectd to the bottom wire, you are actually seeing your leading marks - and it sounds like it's dead on.

 

You are correct, trailing is on top I screwed up in my original post. Connected to the trailing "on top and front rotor" if I adjust the vacuum unit it will not adjust away from the 1st notch. I would not even be concerned about this if the car did not backfire when I let off the gas, but it is very loud.

 

That's weird. If it's moving the magnetic pickup then it has to be changing the timing.

Unless the wiring's messed up and both coils are running through the leading ingitor. How long you had the car for? Maybe the trailing ignitor's broken and someone wired it up like that.

 

I've had this car two years. This problem started after I drove it for around a mile at 110 to 115 mph. As soon as I let off the gas it started backfiring and it hasn't stopped since. I first thought maybe the carburetor had a problem, but the carb is fine. Then, I replaced the distributor, cap, and ignitors. I'll check the wiring to see if I'm loosing power to either coil.

 

Ok, I replaced the trailing coil and found that it has no ground. If I measure the voltage on the trailing coil it reads zero. If I measure from the positive or negitive on the coil and ground to the frame I get 12volts. If I remove the trailing coil wire I have fire, but the car continues to run without the trailing coil connected at all. With or without the trailing coil wire the car starts and runs OK. It does at times and runs very rich.

I attempted to run a new ground wire to the trailing coil, but that only creates a short and the car shutdown.
Any good input would be appriciated. Thanks

 

The ground actually goes through the ignitor. The ignitor acts kind of like a switch that opens and closes the ground circuit for the coil, thus creating the magnetic field wich creates the spark. You can actually re-wire the wires going to the trailing ignitor.

Go to www.mazspeed.com go to the facts link and download the wiring diagram. it will help you out significantly. Then you can just re-wire it yourself.

 

It sounds like the trailing ignitor died and the trailing ignition is running by induced current crossing from the leading coil wire to the trailing coil wire - running long distances parallel to each other will do that.

Try disabling the trailing ignition and see if it runs at all.
Then swap ignitors (I *assume* you have a '81-85, not an '80 or better yet a '79 with points) and see if you can adjust trailing timing.

 

I replaced both ignitors and if I unplug the wire from the trailing ignitor the car will still start and run. Adjusting the trailing timing does not work. I'm sure I have a serious wiring problem because if I remove all three fuse links located near the battery the car continues to run. To date I have replaced the plugs, plug wires, fuse links, wiring harness, distributor, and all the relays that are located under the hood.

I have a truck load of parts, so hopefully I'll find what is causing this problem.

 

Thats why I'm saying get the wiring diagram and re-wire it.

 

I'll give it a shot. Thanks

 

Looking at your original problem of not being able to time the trailing reminds me of a common problem with these cars. With 2 ign systems, they are a rare breed. Timing light mfg's dont take this into account. Ive had timing lights that keep picking up the wrong signal even when Im on the correct plug wire. Which gives the symptoms you described exactly! My expensive light does this, but my cheapie wal-mart one works great, go figure.

 

coudlnt the backfire be from a burnt cat, 10 mins at 110 could do that, then ur gonna be gettign a rich mix into your exhaust and itl combust, ive seen it a few times

 

BigJim,

Nice car.

B

 

The timing light is new, but once you take in consideration that I have no negative on the trailing coil
the timing light is not a factor. I'll replace the wiring to both coils and see if that is the problem. Thanks for your replies.

 

I have the same problem with my car.
I have a 89 that some one put an 86-88 engine in, I got the car cheep because it wouldn't run. I put a carburator on it and MSD ignition. I have a 6AL to the leading and a 6A to the trailing, with a 83 distributer. I can get the leading timing on the mark but the trailing will not adjust. the timing being off is causing the rotor not be aligned correctly so the spark jumps from the coil tower to the coil wires. I have already burned up one coil. no matter how much I move the vaccum advance the timing stays the same. any ideas?

 

I started this thread. The solution was when checking the trailing with your timing light clamp, make sure the clamp is as close as you can get it to the top of the distributor trailing plug wire.

 

Sounds like it was picking up stray siginals from the leading eh?