bckncook

When I tested the knock sensor at the harness, I got an "open lead" reading... what could that mean?

The car runs weak some times, hesitates sometimes, and absolutely perfectly sometimes.

The coils test perfectly on an ohmeter for what that's worth.

Checking the ECU yields no codes whatsoever.

What gives?

Akumachan

iTrader: (12)

i got the same problem here, tried all kinds to get a decent read on the ohmeter on that knocksensor, but it still reads open. far as i can tell that means its broken, but just like you, my ecu doesnt seem to think so. im thinking of just replacing the bloody thing when i have money again, i dont like the power loss

Stephen Max

iTrader: (59)

If you are testing across the two pins of the harness leading to the knock sensor, you will get infinite resistance. That is because only one pin goes to the knock sensor, the other goes to the harness shielding.

Try testing one pin at a time, with the ground probe against the engine block. Now if you get infinite resistance at both pins, you do indeed have a bad KS. A good KS will give you around 550 Kohms. (Be sure you have your multimeter set to the proper range. A resistance that high will register as infinite if your multimeter is set to measure a low resistance.)

bckncook

But I'm not getting infinte/0/zero. I'm getting OL. When I get infinite, it changes from OL to 0.

And if my KS is indeed bad, why does it drive perfectly sometimes and why don't I even get a ghost code?

Would a bad KS cause very rough acceleration... I don't mean weak... I mean major hesitations in the middle of the acceleration range, sometimes so bad that they make the CEL blink briefly, then go off and, yes, still yield NO codes. Sometimes I feel like my torque curve must look like a stock price history graph... and the stock being tracked is different every time I drive it.

99se5spd

hey bckncook, i was thinking, and a couple of questions. what did you gap your new plugs at? you do run 93 octane right? or at least 91? when you replaced the fuel filter were you sure you put it in with the flow arrow in the right direction? the blinking cel is misfire and its strange your not getting a code for misfire either (at least then you would know which cylinder) it has to be fuel or spark, a ks wouldnt make the engine miss that badly. i forgot to tell you too, ive got my old coils too, i know they are not all bad, you can borrow them if youd like.
-dustin-

z32drifter

try changing the setting on your meter..... "OL" is normally "over limit" not "open lead" if you were in the ohm setting and testing K ohm it would show "OL" ... and blinking MIL is missfire indication.... later

bckncook

Q. What did you gap your new plugs at?
A. Don't remember the number, but I checked each one and I think all were within Haynes' specs out of the box.

Q. You do run 93 octane right? or at least 91?
A. Always 93.

Q. When you replaced the fuel filter were you sure you put it in with the flow arrow in the right direction?
A. Had it installed professionally, too much of a pain to get to. I assume they did it right as it drove the same before and after.

Q. The blinking cel is misfire and its strange your not getting a code for misfire either (at least then you would know which cylinder).
A. Strange puts it a bit mildly.

Q. It has to be fuel or spark, a ks wouldnt make the engine miss that badly.
A. Yes, but it seems like the misses aren't the only problem since the engine's overall lust varies drastically as well. I'm thinking faulty/dirty injectors, bad coils, AND/or knock sensor.

Q. I forgot to tell you too, ive got my old coils too, i know they are not all bad, you can borrow them if youd like.
A. I could do that, but I don't know how much faith I'd have in the results of any testing since they're the faulty (by default) 99's as well. I guess we could try it though. I just think there's more to it than the coils, although I would like to swap those out as well for thoroughess.

Dustin, per z32's point on the ohmeter range, is there any chance we didn't have the range set high enough? I seriously doubt you did it wrong, but thought I'd clarify to be sure.

DAVE Sz

iTrader: (2)

It has to be set to the 10M range.

bckncook

I'm sure we had it set to that. We even had to find another ohmeter with a range that high.

Anyway... assuming the range was set right and we did indeed get an Open reading... next suggestions anyone?

DAVE Sz

iTrader: (2)

What kind of ohm meter are you using? Did you do stephen told you? Put the red lead to one of the holes on the connector and the other touching the engine? Are you sure you're even checking the right harness? Are you checking the female connector, with 2 holes or the male with 2 pins?

bckncook

99se5spd did it for me. I'm confident he did it correctly, but will wait to hear his confirmation.

Aside from the KS test, any suggestions as to the big picture issues?

njmodi

iTrader: (4)

Any stalling? The symptoms really point to bad coils - but my buddies 97 Max did similar things and it ended up being his MAF... a MAF can cause similar driveability problems... my buddy's car never posted a ECU code for the MAF.

bckncook

It got close to stalling one time while idling at a light, but a little extra gas solved the problem in that instance. Other than that one time, there has been no all-out stalling.

99se5spd

we checked it with the meter correct, it was on auto range and the meter reads resistance up to 40 meg ohms(i double checked that later that evening). i was under the impression that the second (ground) terminal on the ks connector terminates in the plug at the ks and uses the ks body as a ground to the engine block. but yeah i did check the pins together as well as with the neg. battery terminal. a bad maf sensor would give you problems with the car reaching higher rpms, along with other things, im almost certain that is not the problem. see if you can see the arrow on the fuel filter just to be certain its in there correctly, ive put them in backwards before, its easy to do. also try tapping on the coils(with the back end of a screwdriver or something) while the engine is running, also maybe wiggling the coil connectors. (maybe unplugging them while the car is off and check the pins for bends or corrosion), you never know. one more thing you can try is drive the living he!! out of the car for 10-15 mins and than quickly check the coils with an ohmmeter. im sorry, i wish there was an easy explanation here. just let me know if you want my old coils for a bit, ill drop them off one day after work.

Stephen Max

iTrader: (59)

OL usually indicates more resistance than what the meter can measure for the scale it is set at. If you have infinite resistance your meter will show OL.

If your knock sensor is bad you should be getting a ghost code.

A bad knock sensor results in loss of power, especially midrange. I can't remember if my car accelerated roughly when it had a bad KS, though. Like someone said, it sounds like it might be a misfiring problem.

bckncook

So if the a 40 M-ohm meter was used, and it was set to auto-range, and you only need a 10 M-ohm meter for testing the KS, then I am sure he was testing it correctly. The meter usually shows a 0 for infinte resistance.

bckncook

Summarizing my thoughts so far: Based on the view of several org-ers and a friend at the Nissan place, the 99 ECU's are notorious for not providing codes for misfiring, hesitating, etc.

Given my car's multiple personalities, I'm guessing that an INTERMITTENTLY working KS as described in the FAQ's is causing my varying power characteristics. And I'm thinking that the crappy 99 coils are exacerbating the problem by causing the misfiring, hesitation, etc., and may have even caused the KS to start fritzing.

The only other thing I can think of are injector issues. What is a fair price to pay to have them serviced/blueprinted? This is the cheapest car I've had so far and the first I've not been scared to mess with myself, but because of that, I'm not completely skilled in these areas yet. Are they reasonably simple to service myself or should I take it somewhere?

Finally, should I pay to have the injectors serviced first or replace the coils and KS first? What is everyone's thoughts here about my conclusion? Accurate? Way off? Overlooking many things? Etc.?

Thanks for all your input guys. Keep it coming.

Stephen Max

iTrader: (59)

How bizarre. Why would it use 0 for infinity? Kind of a big difference between the two, ya know? What does it show for no resistance, i.e. when you touch the probes together?

By the way, open lead is the same as infinite resistance.

njmodi

iTrader: (4)

Not always - and my friends car showed us that. He had no trouble getting over the 2k RPM mark (or whatever the cut-off is when the MAF is actually detected as being faulty by the ECU).... if the MAF is not detected as faulty, the problems can be very intermittent and can include hesitatation, stalling at idle, stalling/bucking during acceleration from a stop.... these are the exact symptoms my friends 97 GXE with 80k had... and he never had a CEL posted.... the part that fixed the problems was a replacement MAF.

Pearl99GXE

I had the same blinking cel when it was hesitating. No code. Replacing the coils solved the problem for me. I started with the back three, that fixed it for about a year. The same simptons came back, so I replaced the front three. Runs great now.

99se5spd

thanks for the info njmodi. if you want to try bckncook, we can swap maf s for a couple of days and we will see. anyone think it will be aproblem swapping a fed and cali maf? (mines the cali spec). you can take it to a shop and have them do their fuel injection cleaning, it think it runs about 30-50$, if theres gunk in there making one of the pintles stick that should free it up. you can pull the injectors but you have to remove the upper intake manifold to get to the rear ones.

njmodi

iTrader: (4)

MAFs should be no different between cali and fed spec.