checked codes today on 94 Q

[ahardb0dy]

Hello, I checked the codes on the comp today, first time I got a 32 (EGR), and a 34 (knock sensors), I checked for vacumn at the EGR valve as it said in the FSM and the hose had vacumn.

Cleared the codes, and checked again, this time I only got code 34, I followed the procedure to test the knock sensors and checked for continuity between the harness plug under the hood ( engine sub harness I think it was), and the ECU and had continuity at both terminals, couldn't do the next step, as I thought I read you can't get to the knock sensors without removing the intake plenum??

What effect do the knock sensors have exactly on how the engine runs??

Is it common for the sensors to go bad or could it be something else related to them? car has 163K on it and have no idea what was replaced or when.

Thanks

[elwesso]

I would suggest readling some of the previous posts on the knock sensors. They have a significant impact on power, however they dont have much effect on engine longevity or fuel economy.

[Q45tech]

The KS failure reduces the ignition advance and thus changes the point of BMEP which increases Nox. The engine efficiency drops noticeably [push accelerator more to try to get acceleration].

MPG drops noticeably at cruise.

Guess you could postulate that engine's ultimate life won't change much just that it becomes harder and more difficult to drive.

http://www.visteon.com/utils/w...6.pdf

Not totally applicable to question but a good read:http://sitemaker.umich.edu/mhr...s.pdf

[ahardb0dy]

I read somewhere on this forum that someone was able to replace the knock sensors without removing the plenum, is this really possible or is it a pain in the as-? I know I should replace all the hoses and all under the plenum but don't have the funds to do everything all at once. Any idea what it will cost to do all the plenum hoses?

[Q45tech]

90-96 Q all require plenum removal to replace KS.

We usually add 1 hour to a plenum hose replacement job if KS are done at same time as all hoses. So that would be 8 hours labor [$600] plus all parts [$375 for KS and harness] and variable for hoses and plenum runner gaskets depending on what ends up getting changed [left up to tech when he see and feels condition of each one which one break ot right and which crack in the removal process...........usually $1300 to not to exceed $1450.

We usually try to tie in the valve cover reseal/replacement and spark plugs and a throttle body/intake clean to give the customer a break on labor....getting everything done for just under $2000.

[daegrigg]

what, how did you check the codes?

[elwesso]

pull the ECU out and count blinks. its in the previous posts.