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Here's one for you to noodle on. Its got me baffled.

I have a 1998 Caravan 3.3L and its been running rough. Most noticeable with accelerating, can't notice it much at idle. Check engine light didn't come on but I checked the codes anyway and got a P0202 ( Injector circuit open - cylinder 2) with a yellow light on the tester.

Now for the weird stuff.

1. Swapped out the connector from Cylinder 2 Inj with cylinder 4 right next to it. I reset the codes, expected the code to now read . . . P0204 Injector circuit open - cylinder 2. However it still read P0202. THAT TELLS ME ITS NOT THE INJECTOR, BUT INSTEAD THE COMPUTER OR WIRING BETWEEN THE INJ AND COMPUTER
2. I don't have a scope so next best thing was to connect a test light across the cyl 2 injector wires (while it was plugged into the cyl 2 injector) light flashes as engine is run. TELLS ME THE COMPUTER IS SENDING A SIGNAL AND THAT THE WIRING IS GOOD BETWEEN THE COMPUTER AND THE INJECTOR

Extra tests for background - in case you're wondering:
* Checked Cyl 2 injector with a ohmmeter - reads 13 ohms (same as cyl 4 inj)
* Checked Cyl 2 injector with DC12v with connector removed. Could hear it clicking when 12v was applied.
* With engine running, unplugged inj 2 - noticeable drop in engine pwr. TELLS ME ITS WORKING
* With engine running, unplugged inj 4 - same amount of drop in engine pwr.

So my question: What could be causing the rough running/lack of power? If its really Inj 2 that is bad, why didn't the fault move to Inj 4 when swapped.

If Inj 2 is stuck open, wouldn't I see smoke at tailpipe due to rich?

Since this is a pretty involved procedure to replace an injector, any other ideas on what could be causing this?


   
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contributions: 2275
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Location: Oregon
you could trying to switch the #2 and #4 injectors and see what the computer sees. it's not too hard to do that. If it still says #2 and there is no wire harness malfunction you may have a bad computer.


   
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Do an engine revision of the pistons.


   
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Thanks for your responses.

To Reply 1: Yes I reversed connections between #2 & #4 cylinders. Even after resetting, the computer still says #2 bad so I suspect the computer too. If computer, will car function if I put a used computer in or do I have to take it to a dealer to reprogram? btw, I even hardwired from computer to the injector. Same result so it tells me harness is good.

To Reply 2: I don't understand. What does "Do an engine revision of the pistons" mean?


   
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contributions: 2275
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Location: Oregon
you tested the injector harness with a test light but you said you didn't notice the roughness at idle but more on acceleration. So, it may be working at idle but not on acceleration. You should check it while driving.

Using an inductive amp clamp on your injector harness for injector #2 you can get a graph (with a graphing multimeter or lab scope) of the current ramp on the injector. This way you can see what the current is doing while you are driving and the missing occurs.

using a used computer may need a reflash to match your vehicle. but you could try it first it might run. But I would check the current draw on the injector first. You should have power from the asd relay on the dark green/orange wire and the computer should be grounding the circuit on the tan/white wire for cylinder #2. If you rewired the wires is it possible you have a bad connector? While it is idling and it seems to run normal at idle try wiggling the wires. you might have a break inside the insulation right at the connector. Most of the time if there is a wiring problem it is close to the wire harness connector by the valve cover where the harness is mounted.

I don't know what it means either???
("To Reply 2: I don't understand. What does "Do an engine revision of the pistons" mean?")


   
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Thanks for your help . . . wish I had a scope!


   
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