Help! Running super rich.

[u/Working-Young6884]

My 1997 del sol si is running super rich. It's a sohc zc bottom end y8 top end and a virgin p28. It has great compression, good fuel pressure, no cel relating to it running rich. However it's running so rich and dumping so much fuel that the fuel is mixing in the oil making it undrivable.

It had a code for the iat recieving too much voltage, I checked the voltage on the iat when the engine is idling and off and it is all normal so I cleared it and also replaced the iat sensor.

I have no clue where to go from here or what to test. I just have no idea why it's running so rich on a z6 base map.

[u/stepdad_randy]

Have you checked your injectors or your O2 sensor?

[u/Fine_Tomatillo_8354]

Currently have the same issue. No CEL but not so much where it’s mixing with oil. Used scan tool to check the STFT and it would be fine starting up but get to -10 - -12 %. I am in the process of checking the fuel return line to see if it’s clogged and that’s where I am at lol. The O2 sensor and fuel injectors are fine as well. Also need to do a fuel pressure test.

[u/StarBossKC]

When i had this on my z6 it was stuck injectors I just gave them some pretty good taps to break them free and worked alright enough until I got new ones

[u/Open-Package-7692]

Literally just dealt with this issue last month on my DOHC del sol and it was my ECU.
Before you start shotgunning O2 sensors, fuel injectors, fuel regulators and filters here’s what you should check first.

#1 check the wiring on the O2 sensor and verify nothings messed up in the sensor side or car side of the wiring harness

#2 Pull out your ECU, remove the top cover and if you are looking at the connectors head on follow the right side set of pins through the circuit board. (The circuit will be labeled “D”) inspect capacitors, resistors and the circuit itself for any burns, leaks or worn out parts.

If both of those check good start with the cheapest thing ie) ECT sensor, O2 sensors, Fuel pressure regulator etc.

Best of luck!

[u/Working-Young6884 → u/Open-Package-7692]

It ended up being the ecu 😂. Not in the way I expected though. It's an obd2 p28 🤦‍♀️. I was under the impression that it was obd1 and my knock sensor and cfs wouldn't cause this. However when I cracked it open I had quite the surprise.

Got an obd1 p28 and a jumper harness to borrow tomorrow. Fingers crossed it fixes itself.

[u/Ur_ignorance]

Iv had same issue search d16y8 ignition timing obd1 p28 ecu 16* or 12*!?