Emissions Test Question
 

Hi Everyone,

I recently had the TB/WP, fuel pump, and fuel lines replaced on my 1988 928 S4.

Prior to the repair the car ran perfectly without issue and had passed its emission test back in 2012.

The car has been tucked-in all winter long since Nov 1 2014 to March 20 2015.
I will go on the assumption that the battery was disconnected during the 2-week repair period.

My question is how many kilometres (or miles) should I drive before going in for my emissions test?

I was thinking 100-200km tops. The repair tech suggested 2,000 km…I’m lucky if I drive that in a season :)

Kindly provide your thoughts or advise if the 2,000km estimate is accurate.

Thanks

RJ

I would think you are correct, fresh fuel and drive it ~ 100km should be fine, I would do at least one or two WOT shifts to clean her out.

Dave K

Edit: what did the mechanic say about belt re-tension?
As this should be done w/ new belt at about 1500km or if the "!" light comes on :)

Did the mechanic say why you should go 2000km?

That really doesn't make much sense.

TB/WP shouldn't affect emissions.
I wouldn't think that a fuel pump or fuel lines would either. Maybe you need to flush the "new stuff" out of the lines, but I wouldn't think that would take even a full tank of gas to do.

But I could be completely wrong on that.

Thanks for the replies.

Dave, I forgot to mention my 928 is an automatic- therefore I'm wondering if the WOT procedure would be applicable. Great point about the belt tension matter, I will follow-up on that.

Joe, he suggested the 2000km run would allow "something" to reset. I forget what that "something" was...the computer perhaps. In any event, that lengthy run seems to be a bit overdoing it though.

I'll go for the 200km drive and advise you both of the emission's results.

Thx

RJ

I assume that it's the adjustments that the ECU makes to its maps that are lost when power is removed for ~30+ minutes. 2km does seem like a lot though. The idea is to get the full range of throttle and load, so that the ECU can fine-tune the maps.

2000km sounds more like the timing belt run-in period after which the belt tension must be checked and adjusted.

That is what I believe your mechanic was try to tell you.

Also, the LH ECU will re-learn parameters lost during a battery disconnect in less than a hour of mixed-mode driving. (Note: mixed-mode. Not idling. Not all-highway. And WOT is not required as the parameters lost are those that govern the adaptation for the oxygen sensor loop which is not used during WOT.)

**Update**

My 928 successfully passed it's emissions test today. :)

I only logged 150km since April 1st.

The drive clean tech advised vehicles made in 1997 to 1988 are tested via their tailpipe (a two speed idle test is performed), therefore the disconnection of the battery during the repairs would not have impacted test procedures.

Testing of 1998 and newer model cars are done via the On Board Diagnostic System test.

As suggested above, I will revisit the repair shop after 2000km of driving to re-check the belt tension.

Thx for all the replies to my post.

RJ

Glad you passed. With the TB, WP and fuel hoses done, you just need to enjoy some worry-free miles. Have fun!