EJ25 running rough

[aussie_paul]

I put the injectors back. They seem to spray ok. I"ve tested the TPS with an ohm meter, and seems ok. It all happened so suddenly. Very rough running. Prob. wouldn"t leave the ground. Very rich mixture, soot out exhaust. Still reading manuals and thinking.Max, I would be looking next at some sort of sensor or wiring problem that is telling the ECU to run richer. The value of an aftermarket ECU is you can trouble shoot with a laptop.Aussie Paul.

[mad max]

I"ve tested the temp., cam and crankshaft, and throttle sensors right back to the ECU. Only thing I"m not too sure about now is how to accurately test the mass air sensor. In some ways I"m enjoying the challenge. (but also frustrating at this point) Even tried another ECU. Lucky I"ve got a spare gyro. Russ tells me to fit an oxygen sensor, and Iv"e got one so will try one but after I"ve sorted this problem.

[mad max]

I"ve got 1.4 volts at injector 1-2 and 3 at 2000 rpm but 2.7 volts at injector no. 4 -

[aussie_paul]

I"ve got 1.4 volts at injector 1-2 and 3 at 2000 rpm but 2.7 volts at injector no. 4 -

[asra]

Here is a page on injectors might help;

[chook]

Maxi, that voltage reading is a bit tricky. If you had a cathode ray oscilloscope you would actually see a series of pulses. I assume you are using a multimeter set on the DC range. Whats happening is at 2000 rpm there are say 600 pulses being fed to injectors 1,2 & 3 but say 1300 pulses being fed to injector #4. So the meter is adding the pulses together (which are obviously VERY fast) and giving you an averaged reading. Each pulse opens the valve to allow a small spray of fuel past and this would most definitely be giving you your rich mixture on that cylinder.So something is causing this high pulse rate. Because you don"t have any "techy kit" you have to find the faulty bit through elimination.Try swapping the injectors between cylinders and take another voltage reading on your injectors again. Same with the spark plugs - swap them around and take another voltage reading on your injectors and so on.Initially try measuring directly across the injector itself (without the wiring loom plug connected) and compare that with the reading from say injector #1. Set your meter to ohms and take note of the resistance between the pins. Also swap the meter leads across the pins to see if there is a diode within the injector which may have failed.(this would explain the double pulse count depending on how they "fire" the injector). If you don"t understand this suggestion get back to me and I will explain further - you will have 2 readings per injector.It may be something stupid like 1 wire in the loom has shorted to earth. Ok there are some tests you can try.Good luck.........Chook.At least now you have discovered the voltage anomaly and that is the clue.

[mad max]

I"ve Had a spark plug on the lead and all"s ok Paul. I"ve renewed plug leads, plugs and tried another coil. I"ve done every test you"ve suggested chook. I even have an ocilloscope and have compared the four patterns. The injectors all have 15.7 ohms both ways. I"ve swapped injectors. However I"ll do some more ocilloscope tests as the tests were only brief due to a shaking engine. Thanks for the advise. As the injectors are neg. controlled I suspected an intermittent short to earth on no. 4 inj. control lead. But can"t fault. I"ll keep posting. I"m a retired auto sparky but avoided similar problems on cars as you would just send them to the guy with the test equipment. Still enjoying the challenge but I want to take her on a maiden long distance flight! Prob. hug a highway for the first few hrs.

[Brian]

Frustrating to say the least !The EA 81 factory turboed

[Russell]

You have probably covered it first off but are you sure a valve isnt sticking cause 2.5"s are renown for valve problems?Since when.........

[chook]

Ahh Max - a CRO. (you bewdy) If it is a dual beam unit then just use one of the "workers" as your source and compare it with your #4.Remember that damped oscillations will indicate a short and it may well be a coil within the injector breaking down. You will spot that in an instant. Also compare the incoming pulse stream, I would expect them to both be the same frequency (and shape without curves on the top of the waveshape) although not aligned. There will be a delay between each pulse stream to align with each cylinders intake stroke. Adjust your CRO timebase to get the minimum number of waveshapes on your screen which will allow you to really see what"s happening. (a single pulse would be good). You probably already know all of this stuff anyway.Regards........Chook.

[mad max]

Actually Chook I"m a bit of a dumb ******* when it comes to crows. My brother gave me this one, and I"d never used one in my trade. It didn"t work, it had some lightning up it"s butt. An E.T. (electronics technician not extra terrestrial) mate fixed it. Just a safety diode was U.S. So I"m learning how to use it. I think the great consciousness is punishing me for avoiding fixing peoples tricky auto. elect. problems over the years. Now I"m faced with my greatest challenge. I still appreciate all the advise and stories. I"m determined to master this crow as the guy who fixed it keeps hinting that he would like to have it. This way I can justify carrying it around in the gyro. (It"s a little light digital beauty)

[gbw]

Mad Max,http://www.ozstock.com.au/6007/Diagn...terTrackerJust came across this gadget which I have not seen before. Checks cable continuity audibly, so you know where the break is. Probably no use for your present troubles, but neat.Graham

[mad max]

Good one Graham. 35 yrs ago I was working in port Hedland and devised a way to send an electromagnetic signal down a wire using a "buzzer" made from a modified DC relay and you could trace the wire all the way even with panel steel in between. It was great for tracking shorts on road train trailers. I told other auto sparkys about it but they showed little interest. You simply hooked the buzzer across the fuse box, with a resistor to match the load, and used a telephone listener (EMR) detector

[mad max]

I"ve done a more thorough test on all injector feeds and no 4 has a definite different pattern. Lots of fine vertical lines while 1-2 and 3 have just 2 lines. It seems the ECU is feeding much higher frequency pulses to no. 4 injector. Another ECU makes no difference.

[gbw]

Max,Could you be picking up interference from somewhere else? Is it worth isolating so only ECU fuel pump and starter motor are connected?My TR6 had mechanical injection. Much easier to understand. But it did allow you to reassemble it 180 degrees out. That had it running a little rough...I hope you soon have a Xmas present. Very frustrating.Graham