Damn. I really should have caught this sooner. I thought everything was good by the end of Sunday. I had the last remaining wires connected in the FX and it started running ok. Prior to that it was running really off and I attributed it to those last wires, even though I could have sworn they were just for instrumentation and wouldn’t effect the engine. Anyway, it seemed to be running alright for the 30 minutes I left it idling to run the radiator flush. Meanwhile I put the dash back together and I was getting a pretty positive feeling about things. Turns out that was premature.
After I finished the flush and put in the new hoses I found, I drop the car down and started up for the test drive. WTF? The check engine light was back on and it was running wonky. The drive around the block was sad. It felt like it was running on two cylinders and burning really rich. Crap. It was too late to do any more.
So tonight I got home, quick dinner, then went to look at the FX again. I hit all the sensor connectors with that Bullfrog pancake syrup scented contact cleaner and blew them clean, plugged everything back together. Start car, no joy. The check engine stays on even with the diagnostic jumper, no blink codes. I start unpluging sensors. Unplugging the O2 sensor caused no change in how badly it ran. That might make sense as that connector was suspect with corrosion and when the car was running correctly it was throwing a O2 heater error. As a temporary measure I cut off the connector and joined the wires directly. I was hopefull, but no change. As a desperate measure, I unplugged the stereo as that was the only thing I could think of that changed from when the car ran to not. No change.
I hadn’t measured sensors, but I was really suspecting the ECU itself. That’s not easy to test, but the check engine light is controlled by the ECU and is supposed to turn off once its running. If there are bad sensors, the ECU should be able to go into diagnostic and tell you.
I had opened up the ECU earlier to look inside. It is actually a known problem of bad capacitors. I however didn’t see the classic bulged top so I put it back together. So the final thing I did tonight was crawl under the dash and pull the ECU out. Opened it up, took a close look, and lo and behold the capacitors are leaked and corroded the board. There even still liquid stuff still there. maybe it just happened, but the board is corroded. Hopefully it can be rescued. Repairing the traces are going to be a pain for these eyes if it comes down to that. Oh my. AT least I know whats wrong.
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