PDA

View Full Version : timing and knock sensor



skbradshaw
11-25-2010, 04:21 PM
98 GT
I have picked up a rattle upon medium to hard acceleration in 1st and 2nd. I could be spark knock, although I don't get it in the higher gears and how hot the engine is doesn't seem to matter.

Does anyone know if a completely failed knock sensor on the 5SFE will allow the spark advance to go unchecked?

Thanks.
Steve

alltracman78
11-26-2010, 04:19 AM
Completely failed as in not sending a signal back to the ECU?
It would do the opposite.
First, no signal from the knock sensor would cause a knock sensor code [the knock sensor is ALWAYS sending a signal to the ECU, it just varies all the time].
Second, once you had no signal and the code, the ECU would retard spark timing. Try unplugging your knock sensor and see how sluggish the car feels.

I'm going to guess your engine is seeing more load in 1/2 than in the higher gears. You can completely dog the engine in 1/2 and not be going all that fast. Once you reach 3 and higher you tend to be going a lot faster so you might not run it to quite as high an RPM or quite as much force on the pedal.
Both of these will lower the load your engine is seeing, which will lessen the chance of knock.

How do your plugs look? Right heat range?
Is your engine carboned up inside? Fuel injection service?

Are you sure it's not rod knock?

skbradshaw
11-27-2010, 05:12 AM
Thanks for the response.

Plugs have only about 9000 miles on them, wires were replaced when the plugs were done, new cap and rotor last weekend. Engine seems to run good but it is a little less responsive on the top end - it doesn't seem to want to pull all the way up as hard as it used to. On the other hand, it does have 160,000 miles on it but doesn't smoke or use any oil.

After more careful consideration, I am wondering if I may have a right front cv joint going bad. It does not make any noise going around corners but that may just be a matter of time. I think I will just to let it ride a little longer until I can get a more definite set of symptoms.

Smaay
11-30-2010, 05:36 AM
check your distributor, maybe it has rotated advanced

skbradshaw
12-03-2010, 11:29 PM
Well, a mouse got on top of the engine and ate the insulation on plug wire #1 all the way to the core and about 6" long. It sure runs better with a new set of wires...

I think the rattle is just something loose in the body of the car somewhere - finding it is this weekend's project.