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.
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