Check your engine bay wiring harness grounding points, make sure you got good ground.

They all looked fine the other day when I hooked my map sensor up. It' done this before and gone away but now it' back. I replaced the coil pack a few months ago because it did this and wouldn't go away. I have brand new coil pack and ptu installed with no change.

I should also mention that the caps were replaced two years ago when they did their thing at Ecmtuning. According to the emails I received at the time, everything else checked out fine.

Any suggestions?

Are these new coils and ptu or used and new to you? Also check your plugs and wires. Does the car run? Is it normal or rough?

They are "New" new. Plugs and wires are fine as well. Just changed them about 4 months ago. The car will start and run but it has the classic low idle and obvious stumble from running on two cylinders. Pulling plug wires off 2&3 has absolutely no effect. 1&4 make it nearly die out.

Well to run only on two cylinders i would go after the coil for cyl 2&3 or the ptu. I would disconnect both and check the pins. See if any of the pins on the ptu or coil are bent. See if the female pins in the connectors are all the same or if one is damaged/opened up. Also check the wiring. These cars are old and the wires are brittle. If you can get your hands on a multimeter then you can start checking voltages at each pin to ensure the wires are good. A multimeter which may seem like a waste of money is prob the number one tool to have. You can diagnose any electrical problem before throwing parts at it and guessing.

I own a multimeter but I lent it to my brother several months ago and haven' gotten it back. He has the memory of a goldfish so I guess I'll just have to go get it myself.

Just tested the ptu and it checks out fine. Bulb lights up nice and bright. We tried checking voltage at the plug and even in the wire. Both spots on pin 5 only showed .36v when cranking. Is there a better way of testing this? Were our results and effort pointless? I really don' know much about electrical and such so please... point me in the right direction.

With the key on and the ptu unplugged you should have battery voltage at pin 6 8 1. Pin 3 should have no more then a few ohms of resistance (horseshoe shape) to battery ground. Pin 2 and 7 is what the ecu uses to provide ground and fire the coils.

If everything tests ok( good voltage at pins and ground) the. Id suspect the ecu is bad

I have a 6 pin plug with only 5 wires. There is nothing in pin 4 on my plug.

This is the only thing i could find talking about wire swaps to a 90 style ptu. Im not really familiar with a 90 wiring because... well i never had one haha. Ive had 91 92 and 94.

So if I'm interpreting this correctly... I should have battery voltage at 1 and 6, a few ohms on 3, and 2 & 5 would be my signal wires?

Yes that is what it seems.

Should the signal pins fluctuate when the engine is turned over?

It should drop to ground(you’d have to backprobe the connector while its plugged in).

You can also check the Cas

I'l check the connector and cas when I get home from work tomorrow and report back with my findings. I appreciate the help.

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We both own one . His batteries died and he was doing a road call so I left him use mine and he forgot it at his garage. I got his from him last night so I'll just hold it hostage until I get mine back. Being a mechanic his is obviously better than mine.

Just got done testing the plug. With the key on I get 0 voltage at 1 & 6. Resistance on pin 3 was 0.4 ohms. I checked for voltage at 2 & 5 just out of curiosity and it showed 0.6v with the key on.

Should I have somebody bump the key to get the voltage at 1 & 6 or should it be there just having the key on?

This is what I had handy.

On a 90 PTM:

Pin 1 Y/G From Coil A (Power Transistor Collector)
Pin 2 Y From ECU pin 54 (Power Transistor Base)
Pin 3 B Ground (Power Transistor Emitters)
Pin 4 NA
Pin 5 Y/R From ECU pin 55 (Power Transistor Base)
Pin 6 Y/B From Coil B (Power Transistor Collector)

There are pullups on the 2 ECU pins to 12v. 0.6v on 2 and 5 would be normal for when the ECU is trying to charge the coil. (It's the normal base to emitter voltage for an active transistor) The ECU can pull that low to switch off the PTM and fire the coil.

With the PTM disconnected you should have 12v at pins 1 and 6 when the key is on. What the voltage is when the PTM is connected will depend on if the ECU is trying to charge the coil. Spinning the CAS should cause them to pulse.

If I remember right the 44 fault is caused by the ECU not seeing a signal on Pin 109 from the Tach Gate on the 1990 coil after it fires one of the coils. That runs to the noise filter on a 90 and also goes to the Tach.

steve said:

With the PTM disconnected you should have 12v at pins 1 and 6 when the key is on. What the voltage is when the PTM is connected will depend on if the ECU is trying to charge the coil. Spinning the CAS should cause them to pulse.

Click to expand...

Excuse my lack of experience in ignition system issues but does this mean I have to spin the CAS in order to get the voltage to show up? If so, I had my wife turn the engine over a few times while I checked for voltage at 1 & 6 and still got nothing. What doesn' make sense to me is that I have spark on cylinders 1 & 4 so I shoukd have at least had something happen on pin 1. This all has my brain fried.

Just checked the CAS and everything is well within spec. Just for the sake of trying things I checked every fuse I could find and they'e all in proper working order as well. The thing that is really throwing me for a loop is not having battery voltage at pins 1 & 6 of the ptu plug. I would fully understand not having voltage at 6 because it' my 2 & 3 cylinders not firing. But the fact that I got nothing at pin 1 either has my head going in circles trying to figure it out.

Let's take a step back.

This is your 1990 Talon, what version of the various parts like the PTU, coil pack, Gauge cluster and ECU?
It's throwing a 44 Fault code and not firing on 2 & 3? What's the factory Tach reading.

You've changed PTU and Coils lately and no change.
Did you change or test the wiring to the Noise Filter?

Everything is stock oem as far as wiring and versions of the parts... all 1990 spec. The coil has been changed 3 times with no effect of the problem and the ptu has been swapped between 2 different (tested good) units. I have done nothing to the noise filter or tach adapter... they are the same pieces that came on the current coil pack. The tach seems to be functioning properly. It reads around 500rpm due to only firing on cylinders 1 and 4. Cam sensor testing also came back with good results. I plan on pulling the ecu and at least looking it over today after work. But again... the lack of voltage on pin 1 of the ptu plug is throwing me off. Cylinders 1 and 4 are most definitely firing with a very strong spark.

So I just started the car and checked for voltage at 1 & 6. While running pin 1 was fluctuating up and down real fast like it should because of it firing that coil. Pin 6 just stayed at 14.5v. So does this mean it's an issue with pin 55 of the ecu? How do I test to see if pin 5 on the ptu is doing it's job? The connections all seem to be tight so I don' forese it being a bad connection.