Carwash underbody spray causes surging, 02 Sport - also front dif pinion seal questio

[93nav]

I have a 02 Sport w/ 164k, all original and no current CEL/codes. Last time I went through the car wash, the underbody spray at the beginning caused serious surging, rpms did not get that high, but it was quite noticeable. As soon as the underspray was done, the surging went away. This has not happened in the past, but I have had minor surging (100 or 200 rpm variation) right after cold start up for a long time. This may be getting worse, and now I get it after the car is completely warmed up when I stop at traffic lights etc. Not always, not serious, but I don't want to have problems. Rain has not been a factor.

I did recently replace the DPFE because of P0400?? and P0401?? codes.


Also, at the last oil change, I was told the pinion seal on the front dif had a small leak. I asked them to look because I had small spots on garage floor. This will get fixed shortly. My question is, (just before I had a 200 mile trip, I saw a larger spot) does the front dif turn if NOT in 4wd? Could I have damaged the front dif by driving (2wd) without enough fluid? It has been about 1000 miles since the leak was discovered. Also, recently, I would catch a wif of something that smelled almost like burning when I get home. Just a wif, and then nothing. Kind of smelled like hot/burning rubber. Could this be related to the dif fluid? I use 4wd in winter, and try and run it on sand/gravel for about 1/4 mile monthly during non-snow season.

Is synthetic dif fluid recommended? (I am in MN). Other than confusion, running syn in front and non-syn in back, ok not ok? Cause to much confusion??

Thanks

 

[93nav]

Update on the surging/running rough caused by the underbody spray. Turns out there was a vacuum hose that had come lose/been disconected, probably when the air cleaner was check. Re-attach and ran great.