Sorry, I think I posted this message in the wrong place the first time.
Hi, I’m a first-timer to the Forum and I’m hoping someone here can help me with a problem I’m having.
I have transplanted a 2nd generation 13B engine and transmission from a wrecked1986 RX7 into a 1978 Fiat Spyder.
The engine starts and runs fairly smoothly but not as smooth as it ran in the Mazda. It will only take about ¼ throttle before it coughs and sputters.
I have tested every sensor and connection, and traced virtually every wire and they all seem fine however, I have run into an odd thing.
The manual I’m using talks about the timing and says that when using a timing light, the “leading plugs” should fire on the first timing mark (yellow) and the “trailing plugs” should fire on the second timing mark (red).
Right now, both the “leading” and “trailing” plugs are firing on the first timing mark (yellow).
At first I thought there was a problem with the shielded wire from the crank angle sensor to the computer, being too close to the other wires that I had to route into the new car. That, I thought, could induce a voltage into the wire from the crank angle sensor that goes to the computer and that was firing the “trailing” coil at the wrong time. I separated that shielded wire from all the other wires and ensured that the “shield” was grounded to the car via a condenser.
I have two engine computers, the 326 that it came with and a 327 that I bought off Ebay when I thought it was the computer at fault. I was told the 327 was from an automatic car.
Both computers run the engine with the same timing issue.
I believe the problem is a wiring issue but I’m stumped where to look.
Can anyone there help with their thoughts?
Also, there may be a wiring issue with the trailing coils. Does anyone have a photo of the 4 wires going to the actual coils? I did some cleaning of the coils some time ago and although I think I got it back together right, I can't find a picture any where that I can check it with and so I'm thinking I may have gotten it wrong.
Don

 

Is this what you're looking for? If not, let me know.

BTW, this coil pack is an N326. T1 is on the right and T2 on the left.

 

Great photos !
I can see at least 1 of my problems already. All I need to know now is;
Does the pink wire that goes from the 2 connector plug to the top of the coils, go to the T1 or T2 coil?
Thanks a lot.
Don

 

That's not a question that can be answered easily since there is a sheath around the wires so without cutting off the sheath, you can't visually see which coil it connects to. But maybe this will help.

When checking the continuity from the 2-connector plug this is what you get.
Hold the connector so that the little protrusion on the outside of the connector is on the top and the contacts are to the left and right. The left contact has steady continuity (0.2 ohms in my case) with the T2 lug and the right contact has steady continuity with the T1 lug. You may get erratic continuity with the opposite connection.

 

The two wire plug on the Trail coil assy carrys constant batt voltage to the assy. Matters not which coil it goes to . One and the same thing the two wires in the two wire plug.

 

Wow, thanks for the quick reply.
I have a question about "continuity" as you are describing it.
My understanding is that when you check continuity you are checking that there is NO resistance between the 2 points you are touching with your probes. In other words the wire you are checking is intact and not cut at some point. If you are checking resistance to get an ohm reading then you need to specify the 2 points that you are checking between.
So if you are checking which pink wire goes from the 2 wire connector to the top of the coil, only 1 wire will give you "continuity" with 0 resistance.
Am I right on that?
The left contact where you are getting 0.2 ohms with the T2 lug, are you on the + or - side of the coil. They are marked.
The right contact where you are getting steady continuity, does that mean you are getting 0 resistance ( 0.0 ohms).
I know we are talking symantics, but up here in the Great White North we may use different teminology.
Thanks again for all your help.
Don

 

I just went out and checked my 2 wire connector and you are absolutely right. The 2 black/yellow stripe wires that are there are connected together somewhere because they have continuity so it shouldn't matter which pink goes to the T1 positive lug.

Okay, 2 more questions.
How is timing advance handled?
My crank angle sensor doesn't seem to have any advance mechanism so I'm assuming it's done by the computer and there must be a tach input to the computer somewhere. Since I'm not getting any advance, (no movement of the timing as the engine revs higher) my problem might be with whatever input the computer needs to change advance. Sound right?

Second, as mentioned in my original post, my leading plugs are firing at the right time (yellow mark on the crank pulley), and that is set by loosening the adjusting nut on the crank angle sensor and setting it. How do you adjust the timing of the trailing plugs if they are also firing on the yellow mark and not the red mark where they are supposed to.
There are some kind of electronics contained in the base mount of the trailing coils. Do you know if that is where the timing is handled or is it again a computer function?
Any input would be much appreciated.
Don

 

When looking at the timing the rpms must be below 1100 rpm. Over 1100rpm or so, the ECU will advance the timeing all by itself. So make sure you set the timing under eleven hunderd and should be close to the stock 750rpm......but really does not matter as long as the rpm are under 1100rpm. Also don't set the initial set coupler right now.

Pin 1X is where most people pick off the rpm signal for a SAFC or other device.

IF the ECU sees a start signal on pin 3B it will fix the timing to 5*BTDC instead of the normal 5L and 20L ATDC as seen during idle.

The only time both lead and trail coils fire at the same time is when your STARTING the engine. The ECU has to see a START signal from the start circuit for this to happen. That would be pin 3B seeing the trigger signal to the starter solenoid. See various wiring diagrams and follow the trail from the ignition switch to the starter solenoid........to the circuit opening relay.......to the ECU pin 3B on a series four. Series five is a different pin.

The second jpg attached shows more or less what I just wrote directly above.

Other times the lead and trail might be seen to fire on the yellow mark is if there is some cross firing b/t ingition sparkplug wires. You'd have seen that by now if that were so.

I've no real idea why your seeing the trail and lead sparkplug wires fire on the first mark that comes around. Got me. Some of the above is a clue I suppose.

If both your trail sparkplugs are firing I'd suspect the wiring to them is okeydoke, I suppose.

What is it? Four wires on one of the trail plugs? One goes to the tach in the stock car and also splices off to a diagnostic connector that is bullet shaped near the trail coil. ....another wire goes from 0 to five volts and determines which of the trail sparkplugs fires at a given time. One plug fires when the signal goes to zero and the other fires when the voltage on that wire goes to five volts........like I said one goes to pin 1X and is the rpm wire........I guess that's all four in that one plug to the trail coil. The other plug at the coil assy is for power for the two coils. Comes from the Main Relay when the key is put to ON or better.

 

You might download the FSM for the right series car. Then look in the FUEL AND EMISSIONS section of the FSM. Then go to the sub section called CONTROL UNIT that lists each wire in the ECU's plugs and the value for each of those plugs. Then idle the engine and probe each of the trail coil assy wires and compare YOUR reading with what is called for in the CONTROL UNIT pages.

FSM links are in the FAQ thread or google ROTORWIKI and the links are there also.

On a normal car if your looking at the timing with a light with the rpms around 750-800, and then slowly rev the engine to just over 1200rpm, you'll see the sudden jump in timing plus hear the revs jump up a couple of hundred rpm.

While at the ECU also check the value of pin 2G, the TPS input to the ECU. Should be approx 1vdc at idle with a HOT engine. Then go look at the 2B for the boost/pressure sensor input to the ECU and compare that to the CONTROL UNIT expectations. Then look at the pin 2I the water thermo sensor input signal and it should read approx a half volt with a HOT engine. Cold engine does not count here.

According to what I slightly remember Henrik saying about timing, it's the afm signal that is a large input plus various other sensors like TPS/boost sensor and also to some extent the air intake temp sensor on the intake manifold. Lots of stufff. Just do a search on this site using HENRIK and TIMING as the inputs and search around for different posts he's made.

Some of the above is a little disjointed because I hear on the tube that somebody or other wants ANOTHER stimulus package. Buch of damn jar heads that know not what is up and what is down. Send 'em all to Levenworth for life with Bernie Madeoff. Ah heck, throw in the coffin with the pedophile to boot.

 

You're well beyond this what with the help that HAILERS has provided, but I wanted to follow up on your question.

Think of continuity as the same as connectivity. Specifically in this case, the meter is set for resistance (ohms) and when you touch one end of a "wire" with one probe (+ or -) and the other end of the wire with the other probe, a very small current is applied to the wire by the meter. If there is no connectivity you will not get any reading on the meter. If there is connectivity, you will get a small number--usually the same number you would get just touching the two probes to each other. In this case, 0.2 ohms resistance for the short wire.

No, see the above comment. You should get the same resistance as you would get just touching the two meter probes together.

On the lug where the "pink" wire is connected.

TUTORIAL: Lets say you have a bunch of wires that are enclosed in a sheath, as in a wiring harness, for example. You cannot visually trace any one of the wires since you cannot see the entire length of the wire. So, in order to identify or verify both ends of the same wire you set your meter to measure resistance. You then probe one end of the wire of interest and go to the other end of the wire bundle and touch the end of each wire until you get a resistance reading on the meter. By running a very small current through the wire and reading the resistance when you connect both ends of the wire to the meter, you are confirming connectivity/continuity. For the other wires in the bundle you would get no resistance since you are not passing any current through those wires.

However, this is an over simplification to some extent. In a situation where wires are or may be connected through other electrical components, you may get connectivity, but the meter in those cases will likely register higher resistance readings. In a situation that you have, you are looking for a basic resistance value that equates to the value you get when just touching the meter probes together.

 

I seem to have forgotten to add the jpgs that I meant to add in my posts above. These might help in some fashion.

I'd first idle the engine. Then pull one of the trail coil sparkplug wires out of the coil bore to see if its sparking and then do the other sparkplug wire to see if it's sparking. IF both are sparking, then I don't see a problem with the trail coil assy myself.

I'd go to the ECU and make sure there is a signal from the trail coil assy to the pin called 1X on the large plug on the ECU. That is the rpm signal.

In one of the jpgs attached (the second jpg below), they mention that both lead and trail are at 5*BTDC when trying to start then engine. So it's possible that you could see both lead and trail hitting the same mark on the pulley. Should not happen unless your in the start mode though. Once idling that should not happen. So I ask myself how does the ECU know it's not in the start mode no 'mo? Seeing the rpms over 500rpm on pin 1X is the way I suppose. Mabe you have no input on 1X from the trail coil assy? And that is why you see both lead and trail hit the same mark? Got me. Others have seen this in the past and I've no idea what their problem was/is.