M42 puzzle

[Boris3]

So my 1991 318is, has gone from intermittent cel flash to flashing any time I'm on the throttle. Standing or moving. No cel on idle. Bavarian Auto code reader shows no codes.

Ideas?

[roguetoaster]

How is the idle, stable, bouncy? How about using the stomp test for codes?

My car did something that sounds similar, but only intermittently on throttle, when the TPS wires were stress cracked and separating from their pins.

[Boris3]

Idle dips/stumbles every once and a while. But that predates the cel flashing. Does look like I've got an oil leak from the filter housing that started a few months ago.

I remember seeing a thread somewhere saying that a cps on the way out would result in a cel flash but no code. Something about the m42 dme?

I'll check the tps and try the stomp test. Maybe code reader is off?

[Boris3]

Stomp test 1444 no codes.

[roguetoaster]

I would probably try something as simple as unplugging and then plugging every connector you can lay your hands on back in. May just be a loose connection.

Just to be clear, the CEL is flashing, not staying on steadily? When it flashes how long between each one?

Oil filter housing leak at front or the rear? Surely not related, but something worth fixing.

[Boris3]

Flashing, and rapidly but only when I press the throttle.

[kwill22]

Notice any misses or problems when this happens?

[Boris3]

Not on throttle. Some slight stumbling at idle but no cel at idle.

Pulls fine. I did a 30 minute interstate run this morning with no issues. But on the return trip a few hours later the cel started to flash intermittently and after a bit was flashing like crazy. Again though car ran fine. I pulled off the road to see if there was any indication of something wrong and that's when I noticed it would only happen if I have the car gas. No flash at idle.

[TobyB]

I wonder if the AFM can do this... and then yeah, the throttle positon switches...

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[Boris3]

Today idle rougher, runs, stumbles and almost dies with cel, catches and runs etc. Still have flashing cel on throttle. Unplugged and replugged connectors, swapped out main and fuel pump relays with new ones, replaced fuel filter (needed it), no difference. Also still no stored codes.

[roguetoaster]

Perhaps it's time to unplug things one at a time to replicate the fault at or near idle.

[Boris3]

True, suggestions on what to pull while its running?

Rechecked the vacuum hoses which I had all replaced last fall. Replaced the intake boot with a new one. No difference.

ICV is humming on ignition, though need a mechanics stethoscope to hear it. Couldn't tell by touch or sound otherwise. Quiet compared to the one on the 325i

Checked the resistance on the crank sensor pigtail: read 540 for pins 1-2; meter didn't register anything for pins 1-3 or 2-3.

Also checked the resistance on the cam sensor; read 1330 for pins 1-2; again meter didn't register anything for pins 1-3 or 2-3.

TPS wires look fine.

[roguetoaster]

Does it do the CEL flicker prior to the engine being warmed up?

I would start with the TPS, then ICV (in case it is triggering incorrectly), then O2 sensor (only if above is false).

There is always the possibility that you have a vacuum leak that is being caused by collapse or expansion when you go between off/on throttle.

[Boris3]

Yes, if I hit the throttle I get the cel flicker both before and after it warms up. Added issue today is that the idle stumbles almost dies and also triggers a cel. Didn't have this issue before. Two issues related and something getting worse?

[Boris3]

Posted this on m42 club as well.

Removed and cleaned the CPS which was pretty badly gunked up though ohmed correctly. Also cleaned the Cam sensor. Fired it up. Starts out smooth idle, after a minute or so gets rougher. CEL when I hit the throttle. Stumble at Idle and flash CEL. Basically same as before.

Turn it off and unplug the following one at a time, and restart to see if any difference at idle. Unplugged the O2 sensor no change still rough idle no better no worse. Unplug the ICV idle a bit rougher, unplug TPS no change at idle (expected), unplug coolant temp sensor CTS big change barely run.

Noticed a puddle underneath my muffler/tail pipe. Water/condensation with a sweet smell. Head gasket? Profile gasket? No milkshake on the dipstick or milkshake under the oil cap.

Still no stored codes.