Engine Oscillates RPM from 400 to 800 RPM

scn101 · #1 (**permalink**) 05-12-2008, 02:10 PM

'98 Jetta 2.0L ABA engine. Normally runs fine and steady at 800 RPM. However when it it hot outside (>90F) and you're idling with a high demand on the alternator (AC blower motor on high, also tried with read defroster and no AC, same effect) the engine will start to oscillate in RPM eventually going as low as 400 RPM. Turn down the electrical loads (AC blower motor on low) and it evens out to 800 RPM.

No DTC trouble codes present.

Any ideas on where to start looking? Thanks.

Handeye · #2 (**permalink**) 05-12-2008, 04:50 PM

Most common correction for this would be to clean the throttle body. Is the TPS making any noise at any time? Like a high pitched chirping?

scn101 · #3 (**permalink**) 05-12-2008, 08:42 PM

No noise from the TPS.

To clean the throttle body would you use a spray cleaner, gas tank additive, or ?

Thanks.

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