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Discussion Starter #1
I have an issue with my 91 SE that has me scratching my head a little. So last wednesday I drove my car to work no problems ran great, I came back out a half hr later and it was misfiring, I let it sit for a few hours and tried again and it still was missing. I started doing some basic diagnostics with spark, and it seemed that my spark was weak on cyl 2 and 3 as compared to 1 and 4. I could pull off the boot for either cyl 1 and 4 and the car would just about stall, with cyl 2 it did nothing when I pulled off the boot and when 3 was pulled it actually ran better. I tried swapping out the coil pack for cyl 2 and 3 and it made no difference, I also put in a ignition module and had no change. the car sat from Thu-Tue, I started it up to do some more poking around and when I started it it ran fine for 2 minutes then started misfiring again. I hooked up a noid light the injector plugs and found that cyl 2 was not pulsing at all......unless you disconnected the number 3 injector plug and then 2 would start pulsing. I tried to see if cyl 3 did the same thing but it always pulsed no matter if 2 was connected or not. I ohm'd out the injectors themselves and they had from 2-2.8 ohms each (with engine warm). Im thinking that this is an ecm issue due to the sporadic nature of the problem and wiggling wires didn't change anything. Anyone run it to this or have some thoughts on some more checks?? I plan on hooking up freescan in the next couple days to see what I can see on there and also following the flow chart for the injector issues in the manual, but I figured id ask first before just in the slight chance that someone may have run in to this.
 

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The ECM has a single driver for each pair of injectors, so if one works and the other doesn't you have either a bad injector or a wiring issue.
 

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Discussion Starter #4
So even though the resistance of the injectors is ok one of them still could be bad? What would be the best way to test that, just swap the suspected failed injector to one of the cylinders that is known good? THanks
 

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yep that is what you do.

I once had 2 bad injectors, by coincidence they were #2 & #3. Electrically they were fine, however they weren't spraying (clogged). So I moved them around to all the different combinations to see if the problem followed the injector or the paired coil pack/driver circuit. In my case I had 2 bad, and the car ran fine after replacing those 2.

I just placed a paper towel under the injectors to see which ones were spraying.

BTW, while removing a spark plug wire to see if a certain cylinder is running, you should first disconnect the IAC electrical connector (after the car is idling) so the ECU can't adjust the idle to compensate for the dropped cylinder.
 

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There is a huge difference between 2 and 2.8 ohms -- what were the individual readings? I have a nearly new set of four (for sale, BTW) that all read 2.2 ohms.

Swap the 2-3 pair over to the 1-4 position and retest, I'll bet the problem follows.
 

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Discussion Starter #7
Just to let everyone know it was the number 3 injector, thanks to sanj for getting a set to me quickly and at a good price, runs like a champ again
 
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