94Q Knock Sensor testing

[hherbson]

Hi, my 94 Q (130,000 miles) has had a noticeable loss of power. 0-60 time used to be 7.7 seconds, now it's 11.2

The midrange also feels flat, and from mucho searching it seems the knock sensors are suspect.

Tonight I gave it 2 full rail flushes (home made job using my old fuel pump). Idle is slightly smoother, although it was excellent before.

I have had the factory service manual on backorder for some time (they have to have an order of 100 before they will re-print, and they only have around 70.) IF YOU HAVE A 94 Q, please order one.

I had to "wing" the fuel pump, water pump, struts, upper links, trans flush, rail flush etc. I really hope I get the manual before something big happens.

My questions:

Where is the connector for the knock sensor harness and how do I test it? Are the two sensors fed through the same connector?

I believe Q45tech said the resistance for each sensor should be 500k +- 50. Does this still hold true at the harness connector?

Also, how do I activate the onboard diagnostic, and what is the code for "knock sensor" ?

Any help would be GREATLY appreciated.

Thanks.

[DAEDALUS]

http://www.nissaninfiniticlub....10938

http://home.socal.rr.com/robverna/injks.htm

The harness should be next to zero resistance; you would want to know if either it and/or the knock sensors were bad. There is no on-board diagnostic available without an error code to investigate, unless you have had a check-engine light go off recently.

[Q45tech]

The KS harness is a shielded wire to each sensor and each sensor ground is thru the mounting bolt to the block.......550,000 ohms +- but that doesn't prove it works only that the plastic case hasn't cracked from heat.

You still have to use a Consult to check as it will not light the MIL nor set a code you can read.

I wouldn't think the acceleration would be this bad usually 10-20% slower from KS.........what is WOT fuel pressure? 43 psi just after filter?

[hherbson]

I just finished checking my KS and injectors via harness. Looks Like I'll be ordering new knock sensors/harness.

Right KS: 540k ohmsLeft KS: Infinity (I'm having trouble now remembering that it DOESN'T end with an "i")

Injectors:

#1 12.3#2 11.5#3 11.5#4 11.6#5 11.5#6 11.6#7 11.6#8 12.9

Injector #1 was replaced by dealer (PO) at 90k miles. The plactic top is purple while the others (original) are tan. Palmerwmd said the purple is OK for the 90-93, is it OK for the 94's (4 port)?

Daedalus, thanks for the links. The testing page with diagrams was excellent.

Q45tech, thanks for the info. I haven't checked WOT fuel pressure. Until I can buy/make a gauge assembly, I'll test the flow rate through the filter.

The filter had been changed at 120kmiles, 5 months ago.

I replaced the fuel pump last month, and noticed improved power at WOT. The old humming pump made the power fluctuate at WOT. The pick-up sock on the old pump looked clean, but was slightly darker than the new "white" sock.

I've noticed the cars power seems exponentially reduced as coolant temp increases. When "just warm" the car has good power. After driving for 30 minutes in warm weather, it feels like my 4 cylinder Camry.

I remember reading posts about the ECU reducing timing as coolant temp increases (with faulty KS), so I assume this is the case. I'm going to replace the thermostat too, just to make sure it's within spec.

Looks like I found my reason to remove and clean the plenum...... Back don't fail me now!

[Q45tech]

The oem radiator loses efficiency year by year by year and the stablized coolant temp goes up and up and up.

Besides the normal 1% loss in air density per 11F say 7-10% winter to summer heat.......any coolant temp beyond 194.9F will reduce power by extra amounts and KS failure [reverting to reg fuel timing...failsafe] is good for another 5-15% power loss.

You can only do something about the last two items and the 5-20% power loss they can cause.