CEL after driving for 1/2 hr.

[mazzo]

Check engine light flashes (but not constantly on) after driving for 1/2 hours, and flashing stops when I release the throttle and let the car rolls for a bit.

Stomp code is lamba1, but I replaced my O2 sensor just 3000miles ago. I cleaned my afm, icv and replaced my CPS, but issue persists. I check the intake boot and there is no crack too. I also opened up my AFM (M30 from e28) and check the contact as I move the door, no issue)

Seems to me like somewhere the heat causes a bad connection somewhere. Any idea?

[earthwormjim]

Check the wiring that goes to the O2 sensor. It runs in very close proximity to the exhaust manifolds, so it is prone to cracking and melting.

The wiring for the O2 sensor heater on my car melted, and had to be replaced. Also check your fuses.

[mazzo]

I checked and the wires looks ok.
I just did a round of cleaning with throttle body / intake cleaner to AFM, ICV and throttle body. Let's see if that helps. If not, I will see if changing O2 sensor helps.....

[mazzo]

So the latest update:
Updating O2 sensor is not helping.
I cleaned my ICV, AFM, boot, Throttle body, and the issue presist.
I now believe that I have some loose connection somewhere that when the temperature of my engine compartment reached certain degree, the connection gets lose. Or when I go uphill / downhill / over bumps.
I tried to check all the obvious one like ICV, AFM, TPS (and obviously the O2 connector). They all look good.
Any other place that I may have missed?

[ForcedFirebird]

Could be the o2 heater relay, but doubtful as a stock m20 runs just fine without an o2 plugged in at all. Easy to swap with the horn relay to test. Motronic is rather dumb when it comes to OBD. It just basically only CEL's after something completely fails or is unplugged.

Since it happens on bumps, check all 3 relays on the driver side under the black cover. It's common fro the race cars to lose a relay when mowing the lawn during an off track excursion, so it's habit to zip tie them down. All kinds of weird things happen when the main relay connection is loose. I have also had them come in with just a little corrosion on the relay blades, just took a little cleaning.

Your car is a mid-facelift year and a vert, so it may not have the c109, but if you do have the round connector under the TB, unplug it and check the pins for corrosion, and even peel back the rubber boots and check for gunk/buildup/green. It's a common thing, can't tell you how many I've repaired over the years. That connector is for the injectors and the blue temp sensor (for the ECU), and the ECU relies heavily on it for fueling. The CEL for the o2 could be because it's way out of range due to the failing injector connector either spilling fuel, or not spraying any for a brief moment.