<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font size=-1>Quote:</font><HR></TD></TR><TR><TD><FONT SIZE=-1><BLOCKQUOTE>
On 2002-02-18 11:31, anippy wrote:
I hope ya'll don't mind me posting, as I have just a plain ole '01 GT.
I've been having a spark knock/detonation problem practically since the day I brought the car home in September. It is most pronounced when using 87 octane fuel (which the owner's manual recommends). Ford dealer said "Try 89 octane." The problem hasn't cleared up.
So this past weekend we put it on a dyno. Knocked like hell through the entire range with 87 and 89 and at the top with 93.
As I am posting this, the dealer has the repair foreman and Ford's engineering department involved. They are asking for more dyno printouts showing "normal" graphs versus my EKG-like dyno graph. They all seem to be completely stumped.
The garage also measured the timing during the runs. That fluxuated really bad too, from 21 degrees all the way down to 7.
Gas mileage has been atrocious, about 13-14 in the city, barely 20 on the highway (with 89 octane).
We'll see what Ford has to say about it.
As you've found, octane is not the answer. My current guess is that there is something hosed between the sensors and the computer, or a defective computer. The system as a whole is not stable: the engine does not pull smoothly (dyno plots would be interesting).
So, the question is, what sensor(s) could be bad:
1. Mass Airflow Sensor (MAF)
2. Throttle position sensor
3. Engine (crank? cam?) position
4. Exhaust (O2, etc., if the readings are used for engine control)
5. Temperature sensor(s)
6. A short somewhere causing the computer to get constant, spurious interrupts which effectively introduces lag in control response.
7. Any other sensor / computer control path that introduces invalid sensor readings or causes invalid output responses.
8. Any pure mechanical component that could possibly affect the system.
What's the fast and dumb way to debug this? Find a similar vehicle that does not exhibit these problems and start swapping parts: computer, MAF, throttle position sensor, any other possible sensor.
Why not use new parts? Because we need to test with parts we know work correctly. New parts could also be defective.
My car exhibits behavior very similar to yours. Thank you very much for your post. The more information we can compile, the sooner we can figure this thing out.
One more thing: it's possible that the detonation issue and rattle sound are unrelated (two different problems). My primary concern at the moment is the preignition+detonation issue.
<font size=-1>[ This Message was edited by: DrivingSimulators on 2002-02-18 12:29 ]</font>