98 non turbo running rich when cold

grottu · Post by **grottu** » 27 Mar 2025, 22:57

Hello.
Have this car as a spare since a month....i can smell (and see) thats running rich when cold, everything goes away when gets up to temp.
Zero starting issues in -30 or +20, idles great, nothing out of ordinary, no check engine or codes.
MAF sensor is clean and fine.....what to check next? oxygen sensors?

dikidera · Post by **dikidera** » 28 Mar 2025, 01:37

You do realize they ARE programmed to run rich while starting up. Cold engines need more fuel. Granted it should stabilize way before operating temp.

Post by **Clemens** » 28 Mar 2025, 03:43

coolant temp sensor might be off. don't replace with Chinesium, OE only.
Unless you drive alot of short trips I wouldn't worry about it too much

grottu · Post by **grottu** » 28 Mar 2025, 08:19

Yeah I know that it should run rich at startup, choke thing, just smell a bit too much for my liking.
Have to crawl underneath, maybe someone gutted out cat and spaced second sensor, it would look exactly like that....reality of no inspections

Post by **foggydogg** » 28 Mar 2025, 09:00

grottu wrote: ↑28 Mar 2025, 08:19 Yeah I know that it should run rich at startup, choke thing, just smell a bit too much for my liking.
Have to crawl underneath, maybe someone gutted out cat and spaced second sensor, it would look exactly like that....reality of no inspections

Even a basic scan tool should be able to read the signal from the coolant temperature sensor; if the connector has some age related issues sometimes the unplug/plug back trick can get it to feel better.
Agree with the above, if you replace that sensor use an OEM brand, and as always, avoid anything URO anywhere, any time.

grottu · Post by **grottu** » 28 Mar 2025, 09:19

foggydogg wrote: ↑28 Mar 2025, 09:00
grottu wrote: ↑28 Mar 2025, 08:19 Yeah I know that it should run rich at startup, choke thing, just smell a bit too much for my liking.
Have to crawl underneath, maybe someone gutted out cat and spaced second sensor, it would look exactly like that....reality of no inspections
Even a basic scan tool should be able to read the signal from the coolant temperature sensor; if the connector has some age related issues sometimes the unplug/plug back trick can get it to feel better.
Agree with the above, if you replace that sensor use an OEM brand, and as always, avoid anything URO anywhere, any time.

Good hint, will clean connector and test it with multimeter at cold and after 5 minutes of running. Found resistance chart.