Need help crazy loss of spark and injector pulse on cyl 1&4

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03-10-2015, 09:10 PM
chrisorbics

Need help crazy loss of spark and injector pulse on cyl 1&4

OK this car has been driving me nuts. I have a misfire on my 1993 dohc 5 speed stealth. I have the check engine light on most of the time. It is on for cylinder 1 and 4 misfire and another for the injectors. It sometimes runs good for a few minutes and then runs bad. It looses spark on cylinder 1 and 4 which are on the same coil. I have swapped the coils (no change), changed the ignition module that everyone has issues with, and change the ecm capacitors. The car still runs the same. The other day it was intermittently running good.

When it does not start it cranks like the ignition and/or injector timing is off.

Today is was running on 4 cylinders on startup and then after running for awhile it start firing on all 6. I checked to confirm both spark and injector pulse. As it was running good it would have an occasional misfire at times then loose spark on 1&4 and then go back to running perfect. I have power at the coil and the injector even when it starts misfiring.

A friend of mine that has a shop and 40 years experience said that the trigger for the injector pulse and ignition is through a ground and that if I have power even when the car is misfiring that the issue must be on the other side of the circuit.

I am not sure where to go from here. I am leaning toward wiring or the ecm but I do not want to just throw parts at this car. I want to figure out what that issue is.

Has anyone had a similar problem?
03-11-2015, 01:49 PM
RealMcCoy

93 does not have misfire codes.... the exact codes it's throwing would be a start.
03-11-2015, 08:58 PM
chrisorbics

Codes 14 injector circuit and code 16 ignition coil cyl 1-4, power transistor unit. I changed the PTU and the coil is good.
03-12-2015, 12:18 AM
RealMcCoy

Pretty easy to test the resistance of the injectors right from the ECU connector with an ohm meter.

The ignition code means the ECU commanded the ignition transistor on, and feedback indicated the event did not happen. This can also be tested with a volt meter or low current draw (led) test lamp, backprobed at the ECU and/or PTU.

I've found terminals pulled out of the connectors causing intermittent connections, and failed injectors are not uncommon, but the vast majority of the time, your symptoms are the result of an ECU issue.
03-14-2015, 06:32 PM
chrisorbics

Ok I just swapped in a junk yard ecu that looks like new. I have spark all of the time now and the snap on code scanner that I am using says code 41 injector. How do I check the resistance?
03-14-2015, 06:48 PM
chrisorbics

cylinder number 5 has no injector pulse. The rear ones I can not check
03-14-2015, 07:07 PM
RealMcCoy

Quote:

Originally Posted by chrisorbics

cylinder number 5 has no injector pulse. The rear ones I can not check

Did you determine that with the scan tool function? Or just pulling connectors? On a front one I'd just check the injector directly with an ohm meter. Should be around 2.5 ohms.
03-15-2015, 09:21 PM
chrisorbics

Quote:

Originally Posted by RealMcCoy

Did you determine that with the scan tool function? Or just pulling connectors? On a front one I'd just check the injector directly with an ohm meter. Should be around 2.5 ohms.

I got the code from the old brick snapon scanner.

I used a noid light to check for pulse.

I did a quick check on the front three injectors and they were all the same but after that I noticed that unplugging the cylinder 5 injector had no effect on the engine running so I checked in with a noid light several times and nothing. So with no pulse the injector resistance means nothing anyway.

What should l do to trace down the lack of injector pulse?