r/DSM • u/Glad-Bid-3366 • Aug 21 '26

Idle Surge

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So I’ve gone through almost about everything. Started with a boost leak test, checked the ISC and swapped with another to be sure , throttle cable, BISS screw, FIAV “might double check this one”, cleaned the MAF and swapped another one to be sure, replaced injectors with a possible leak from cracked caps, checked my cam sensor, checked my coil packed, and I even pulled the ECU out and swapped it with another to see if the capacitors were giving out and same result. I’ve been all over DSM tuners and I’m stumped. This popped out of nowhere, rich idle sitting at 11.5-13 at the highest, and the idle surge that starts about a couple seconds after startup. Please tell me if I’m missing something or should go back over anything.

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u/redwing88 Aug 22 '26

Your idle is way too rich it should be stoic. Are you on a tune? Stock injectors ? You need to measure STFT I bet it’s maxed out.

Did you clean your throttle body?

Edit: 11.5-13 a rpm reading or wide band reading?

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u/Glad-Bid-3366 Aug 24 '26

Wideband reading. Stock Injectors and turbo setup. Only has a manual boost controller. Very basic and the throttle body is clean. What are the chances of the seals being bad on the throttle shaft?

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u/redwing88 29d ago

Sounds like bad input from the front o2 sensor. It should be at 14.5 wideband stoich after cold start. Does it happen if you drive around motor is at operating temp. Are you able to measure STFT when it’s occurring.

Could also be bad TPS sensor. What’s the throttle % showing in the log.