Knock Sensors and the Crow's foot

[Aus94Q45]

Finally after months of avoidance I tackled the knock sensors this weekend. This was in part caused by the leaks in my rear fuel hoses that I could not longer tolerate, as the Q was smelling like a gas can on the inside. It was time to pull the plenum.

It took about 2 hours to slowly remove the plenum, disconnecting all of the hoses and accessories that mount to it. No big deal getting it off.

The knock sensors were first up. The passenger's side knock sensor is offset enough to remove WITHOUT removing the dreaded Y-pipe. Nor did I have to remove the lower intakes or fuel rails. I easily fit a 12mm socket on a 1/4" racthet and broke it loose. However, you could not back it all the way out with the socket as it unscrewed and raised high enough to cause the socket to pin against the underside of the Y-pipe. Yet, I was able to turn it out with my fingers. Reinstalled a new one, tourqued to spec.

The drivers side sensor proved a bit more diffcult. The water intake on that bank sits a tad more to the rear and blocks direct access to the sensor. However, a 12mm crows foot did the trick. Backed it out with my fingers and installed the new one. You just have to be careful that the wrench has a solid seat on the bolt head when breaking it loose.

The knck sensor housing on the driver's side sensor was cracked. I imagine that the heat way down in there was grueling over the years. Installed the new harness. In all about an hour to do the knock snesors and harness.

Next were the rear fuel lines -- the ones under the plenum in the back that run from the feed/return lines to the fuel regulators. These had been replaced three years ago. They began to leak at the fittings, and I had previously tightened the clamps with brain surgeon-like skill weaving tiny make-shift tools through limited access provided under the intakes. But by now they were leaking worse and stinking up the car -- not to mention the fire harazard.

This proved to be more difficult as I replaced the three hoses without removing the fuel rails or lower intakes. Removing those components would have provided more access to the area, but I did not have the gaskets handy and I needed the car today. Also -- my simplistic theory is that the more you dig-in, the more your chances something going wrong -- broken or stripped bolt, etc.

I was able to remove the driver's side fuel regulator and cut the hoses off to replace the lines. Although I had drained the pressure (pulled fuse and gas cap) the fuel return line had pressure and caused at least a pint of gas to spit out of the line when I cut it. I ended up clamping the return line where it runs from the hard lines back over the valve covers -- stopped the leaking. Two tiny screws hold the regulator to the rail -- be careful not to drop them into the abyss.

Next on to the passengers side regulator -- two 10mm bolts on the back side hold it on. I removed the bolts and again cut the old lines. Replaced the lines and reinstalled. I double clamped each hose connection as I do not want to do this again after only a year or two.

The hose ordeal took about 2 hours. Tedious work.

Checked and replaced various other hoses and vacuum lines under the plenum. Checked the fuel injectors -- all were fine.

Cleaned the plemum, IAC and Throttle Body -- lots of carbon. Removed tons of carbon from the intake for the ERG on the plenum -- almost clogged.

Put it all back together -- lots of hose connections -- about 1.5 hours working carefully. When you put the plenum back on the alignment is critical. First, the rubber o-rings and sleeves that seal it to the lower intakes are easy to knock out of place. The rubber o-rings make the plenum "float" over the assembly, so it is hard to tell when you have it lined up. Next, CAREFULLY HAND THREAD the plenum bolts into place. The intakes are very soft aluminum. They strip out in a heartbeat -- one of mine was stripped apparently by the guys who last worked on it for me. I was able to retap hole and rethread the bolt for a usable connection. That said, I can see how easy it would be to cross thread these based on the centering sleeved bolts and "floating" plenum. I sprayed the bolt holes with a bit of oil, and carefully worked the bolts into place, before very carefulling torquing the assembly back together. Take your time here.

After all of this, the moment of truth -- fired-up on a single crank! Runs great, no smell and I detect a bit more umpf with the new knock sensors. I am glad that I did not have to remove the Y-pipe, that would have added time and a bit of frustration. My back is a little sore and my hands have the usual nicks and cuts, but my wallet is probably about $1.5K happier!!!!!
Modified by Aus94Q45 at 7:20 PM 10/31/2005

[Aus94Q45]

(PS Brian I would ahve called you, but I had a raging cold though this and figured I would remain in quarantine!)

[Rex]

Wow, nice write up.

If anyone has any pics of the different parts/steps he mentions, they could easily be added and make this into a tech article??

Thanks for the info.

[CrimsonQ]

excellent write up again dude.Perfect as Im about to tackle the same thing

[elwesso]

I still think its easier to remove the Y pipe, as torque is CRITICAL to the function of the KS.. as the ground circuit for the KS is on the block...

Either way good job..... id still recommend removing that pipe.. Next time ill put some grease on the inside so i can move it around easy.

[Jeff Williams]

Great write-up, this almost gives me the encouragement I need to do this project.

[Aus94Q45]

Thanks guys -- it can be done! Wes, I understand about the torque issue, but with the torque range given in the manual and the minimal offset of the wrench I feel comfortable that I am in the specified range. I just had nightmares about pulling that Y and having a leak that you find only after you have reassembled the whole deal. My Y hoses were replaced 15K mi. ago, so they are in good shape. If they were old or originals, I would have surely pulled it. If you were just going in to do the knock sensors, you could get it done in about 3.5 hours (agressive) to 5 hours (methodical) -- regardless of the what the "book time" is at the dealer.

[Q451990]

My Y hoses were replaced 15K mi. ago, so they are in good shape. If they were old or originals, I would have surely pulled it.

Glad you clarified that... great write up!

Heath

[elwesso]

OK well then I concede to your judgement... Jolly good......!

[Meaux]

Good writeup...It took me no less than a month because everytime I would get aggravated, it would be "Beer Thirty". :-) I put away cases of Corona during this job, also the heat and rain this summer, and doing it outside seemed to take forever.

I replaced KS's, Harness, Coolant Hoses and Lower Intake Gaskets. I didn't drop an ounce of blood till I removed the oil filter after the job was done. I made sure it would run before I changed the oil and filter. :-)

[maxnix]

(PS Brian I would ahve called you, but I had a raging cold though this and figured I would remain in quarantine!)

Cool, but thanks for the write-up! I just got my flu shot, but I guess I could have worn my decontamination suit and taken pictures.

This willl help me soon, but the Y hose and all others are coming out because I don't want to go back for a very long time.

[elwesso]

You mean.... BRIAN, is going to DIY SOMETHING???

[maxnix]

You mean.... BRIAN, is going to DIY SOMETHING???

Always do if it doesn't require a lift.

Never have any parts left over, either.

[elwesso]

I dont have parts left over, its called weight reduction...

Take one bolt out at a time and as soon as it falls apart put one more back in...