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Old 12-13-2021, 04:17 PM   #11
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Posts: 18

2001 SL
Default Re: P0131 code with hesitation when accelerating and poor gas mileage

Originally Posted by alordofchaos View Post
Yep, that's my '98. You can see the white shrink-wrap showing the ECTS connector had been changed at that point.

The spark plug brand doesn't matter much, spark plug type does. Fine-wire/single platinum plugs have a reputation for fouling in these engines, causing the P0300 series of misfire codes. Double-platinum or copper-core plugs will be fine. If you are not sure of the type, the auto parts store you got them at will have a record if you have an account there.

If not, they can do the parts lookup and see what their recommended plug is (probably a copper-core plug), and what t they recommend as the next step "up" is (probably a single-platinum plug). IF you got the single-plat, then at least inspect them, and if fouled, definitely replace with copper core.

Does the car run rough at idle?
How many miles on engine?
Has fuel filter ever been replaced?
good spark at all 4 plugs?
There are some good (free) troubleshooting steps here (pulling O2 sensor to check for blocked cat - or precat, since you have a 3rd gen and put a metal heat block to cover plastic parts in front, ICM switching, EGR blocking), worth a read:
Does the car run rough at idle? no it runs fine at idle
How many miles on engine? about 75,000
Has fuel filter ever been replaced? i dont think so
good spark at all 4 plugs? and yes good spark on all 4 plugs
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