cough/stumble 99 GT

[MDW25gt]

I have an intermittend cough/stumble off idle. Any ideas? Plugs have 30k and are the bosch 4power. Wires a year old.

 

Where to start??

 

Thanks

[Legacy777]

Replace the bosch plugs with ngk copper plugs.

 

Subarus don't like bosch plugs as much.

[Commuter]

Second the comment on the Bosch 4's.

 

Consider a MotorVac treatment or some sort of good combustion chamber cleaning. The Phase I 2.5L engine runs rich and has some carbon issues.

 

Also, have you ever changed the O2 sensor? Mine was weak (no codes) and was aggrevating the carbon issue by throwing off the fuel maps even further.

 

Been there twice with the "off idle stumble" on my 97 OB over the years.

 

Commuter

[MDW25gt]

Update: I removed the MAF and cleaned with a spray cleaner. Put it back on and have not problem since. I will probably swap out the 4 power Bosch's for NGK's eventually. For now its happy.

 

Thanks

[OB99W]

Update: I removed the MAF and cleaned with a spray cleaner. Put it back on and have not problem since.

I seem to remember reading about a fairly recent "campaign" by Subaru for MAF problems on the 99s. This may not have been a "recall", so letters might not have gone out to owners. I realize that you've resolved the problem for now, but perhaps you could call a dealer or Subaru of America and ask them about this. If you do get confirmation of a campaign, please let us know here. Thanks.