1996 Q45 Check engine light (knock sensors)

[hansQ45]

My friends, I need your opinions once again!

I have a 1996 Q45 with 133,000 miles on it. Recently purchased it and have been doing suggested maintainence per NICO forum experts.

I recently had a seeping oil leak on the valve cover gaskets. I took it to my local mechanic for repairs after getting the parts from Joe in AZ. My mechanic is an old muscle car fan and isn't really too familiar with the Q, but is liking it more all the time.

My mechanic had to remove the plenum to replace the valve cover gaskets. Once he told me the plenum had to come off I quickly called Joe to order the plenum gaskets (8, I think), 8 new NGK spark plugs from Wes, a few hoses that needed replaced under the plenum and also two knock sensors. Good advice from NICO forum advisors!

My mechanic only replaced one knock sensor (left bank side), said the other one was an extra hour so he didn't do it.

My oil leak is fixed! No problem. The car runs great!

When I was driving home I noticed the "Check Engine" light was on. When I took it back today my mechanic he said it was a knock sensor code (left back side-same one he replaced). He cleared it and it came on again quickly.

He said just drive with the Check engine light on and wait to see it it starts running bad then address it. Otherwise forget it. More $$ to pull the plenum off to deal with it.

What are your thoughts?

As usual, your thoughts are valuable to me!

[STECH]

First of all you dont have to remove the plenum to do the valve covers,Sounds like to me that the connection is bad with the connector(not on all the way or corrosion in connector.I i do beleive that when it pops a code for knock sensors it dosent tell you left or right.it just says knock sensors.

[Q45tech]

The plastic KS housing hardens then cracks due to prolonged [6-7-8 years] exposure to under plenum heat [and the usual spike overheating in summer] when you turn engine off........the under plenum goes from say 250F to 350-400F momentarily.

The plastic keeps the 2 metal end discs and the microphone element in place [think sandwich], when the plastic cracks the elements shift and resistance changes along with sensitivity.

Just a routine wear and tear item.

Nissan used the same design on lots of engines just the Q has 2 and the plenum is tough.

You must think of all plenum hoses, ks, valve cover resealing [$1700-$2000] every 7 years as just routine maintenance on a 90-96Q.

2000/7=$285 per year just a tiny fraction of the $2,500-$3,000 per year prorated the Q cost to keep to standard.

People don't put the EXTRA 15 cents per mile driven in the piggy bank just think the 12-14 cents per mile for gasoline is the cost to drive.