Hi all.
I have a 1991 Mazda MPV V6 (automatic) with 202k mi on it. I am the original owner, always changed oil every 6k mi, and I do all the other suggested maintence at the scheduled intervals(spark plugs, timing belt, etc).
Recently I was washing the car and wanted to clean out the engine compartment. I wrapped all the electricals with plastic bags, blocked the air intake with a plastic bag, disconnected the battery terminals and cleaned the engine bay with some water. I've done this before without issue and was told by my Mazda mechanic it's safe.
I also found some debris near a fuel injector (left side, middle cylinder if I am looking at engine) and while removing it, the plastic clip that holds the injector cable harnass to the engine broke loose.
Anyway, when I started the engine, it ran, but I noticed after warming up, the engine idle was low, around 500 RPM or lower. Once or twice it went too low, the engine nearly stalled, the Check Engine light came on and the RPMs got boosted and the Check Engine light went off. But the van still has a low idle. I didn't smell any gas in the engine compartment and the injector with the broken plastic harnass was not leaking any gas (I checked with a flash light and engine running).
I also noticed the RPMs do up slightly when the AC is on.
With the engine off, I verified the distributor/ignition wiring set is mounted correctly without any water in the connections. I checked around and made sure that the rest of the cables and connections in the engine were solid and didn't have water or anything else in them.
I also have an oscilliscope and the shop manual, so I put the ECU in diagnostic mode (by grounding the single green pin) and probed the Yellow/Black pin on the diagnostic connector. I didn't find the pin was pulsating (I tried with engine off/key in ON position, and engine on), it just stayed high, so it doesn't seem like the ECU was giving me any errors. I checked the other pin which is supposed to be a Diagnositc Bulb pin and it also did not pulsate.
When the ECU was in diagnostic mode with the engine running, the RPMs dropped even lower, when I lifted the single diagnostic pin mode connection to ground, the RPMs went up slightly. When the key in the ON position(but engine off), and diagnostic pin lifted, the Check Engine light is ON, when I connected the diagnostic mode pin, the Check Engine light went off.
Does anyone have any suggestions? I'm going to use some high temp tape to hold the injector harnass in place. I did make a short trip and the car didn't stall and the car didn't sound like it was misfiring.
The only thing I can think of is to make sure the idle screw is clean and set correctly.
Thanks in advance.
-- Jay.