Welcome to Ultimate Subaru Message Board, my lurker friend!
|Welcome to Ultimate Subaru Message Board, an unparalleled Subaru community full of the greatest Subaru gurus and modders on the planet! We offer technical information and discussion about all things Subaru, the best and most popular all wheel drive vehicles ever created.
We offer all this information for free to everyone, even lurkers like you! All we ask in return is that you sign up and give back some of what you get out - without our awesome registered users none of this would be possible! Plus, you get way more great stuff as a member! Lurk to lose, participate to WIN*!
* The joy of participation and being generally awesome constitutes winning
** Not an actual guarantee, but seriously, you probably won't regret it!
Serving the Subaru Community since May 18th, 1998!
Hesitation an Acceleration
Posted 26 February 2004 - 04:33 PM
Posted 26 February 2004 - 04:59 PM
Originally posted by crazyjam
My 1998 Subaru Legacy has hesitation on acceleration between 1500 and 2500 rpms. This starts to occur after oil changes, and usually lasts for 3-4 weeks. Searches of websites have indicated that an air pocket in a new oil filter creates an initial vibration in the engine when it is first started up after an oil change. The knock sensor incorrectly reads this as an engine knock, transfers the info to the ECM, and subsequently retards the ignition timing to -10. This has happened three times in the past year, always after an oil change. The first time it went away on its own after 3-4 weeks, the second time I followed a procedure for resetting the ECM and the knock went away. The procedure for resetting the ECM is to disconnect the negative battery cable for 3 hours, then let the car idle for 15 mins without touching the gas, then turn the car off, and restarting and driving around for a while under normal commuting conditions. This time that procedure didn't seem to work. Anyone have this problem???
Why not fill the filter with oil before installing it?
Posted 26 February 2004 - 05:01 PM
Posted 26 February 2004 - 05:03 PM
Posted 26 February 2004 - 11:51 PM
Originally posted by blitz
My '02 OBS had a knock sensor that was being triggered more or less constantly by mechanical engine noise, but I fixed it.
Posted 27 February 2004 - 12:38 AM
You might want to replace the knock sensor. Sometimes they break down interally and create a "lose connection" which amplifies engine noise, and gives you timing retarded to the back-stop.
Posted 27 February 2004 - 02:36 AM
Posted 27 February 2004 - 10:56 AM
Originally posted by DaveWV
Well... since it wasn't smart enough to be able to distinguish spark knock from normal operating noise, I removed it from the circuit and substituted a resistor in its place to keep the ECU happy.
Now I'm the arbiter of timing adjustment via a 6-position switch on the console. If you'd like details, speak up and I'll ramble-on.
Posted 27 February 2004 - 04:16 PM
Posted 27 February 2004 - 04:26 PM
Originally posted by 99obw
Yes, please ramble-on.
Sorry, didn't want to hijack the thread with my technobabble unless someone was actually interested.
Anyway I installed a 6-position rotary switch that allows me to add resistance in series with the IAT sensor in 5 steps 2.2k, 4.7k, 10k, 22k, & 56k. Each step gives about 1 degree of advance on the butt dyno (and on the spark-knock-o-meter), so I load up the tank with premium and just crank the knob all the way to the right. It also adds fuel to the WOT (open-loop) map, but doesn't affect the part-throttle fuel since closed-loop mixture is based on the O2 sensor target.
Most modern emissions engines seem to have timing retarded a fair amount in an effort to reduce peak combustion pressure/temperature, so adding advance really wakes up the throttle response and the low & mid-range torque. It doesn't seem to add anything to the top-end (above 5k). The timing advance work really well together with cold-air induction, like peanut butter & chocolate.
As mentioned, I have the knock sensor removed from the equation. If I hear any trace of knock, I just back the switch down a notch. If my exhaust system were louder, I'd probably use the knock sensor to trigger a dash-mounted LED that would indicate knock.
Posted 27 February 2004 - 05:52 PM
Posted 27 February 2004 - 08:17 PM
Posted 10 March 2004 - 03:43 AM
Of course, it would make much more sense if blitz can upload the pic of the knock sensor & IAT fixes.
Thanks in advance!
Posted 10 March 2004 - 03:47 AM
Posted 10 March 2004 - 05:17 AM
Posted 10 March 2004 - 11:49 AM
Some Sube models have a stand-alone IAT sensor mounted on the front of the air filter housing. On my '02 2.5, the intake air temperature sensor is combined together with the MAP sensor (it's a two- in- one combo), and it's located on the top surface of the intake manifold plenum just to the right of the coil pack (looking into the engine bay). It says Bosch on it.
A four-lead connector (labeled #1 - 4) mates to it of which leads #1 and #2 are associated with the IAT sensor circuit and the added resistance can be inserted into either lead.
In order to get a feel for the range of resistance that the sensor normally shows the ECU, I heated it with a heat gun and put it in the freezer. Here's what I got:
100*F - 800 ohms
28*F - 9k ohms
A general rule seems to be that a value higher than 100k is out of range and will throw an error (CEL). By messing with various values, I found no noticable change in the map beyond 47k. I reasoned that a log curve is probably used at the input to make a linear change at the output so I settled on five fixed values:
Position 1. OFF
Position 2. 2.2k
Position 3. 4.7k
Position 4. 10k
Position 5. 22k
Position 6. 56k
The switch is available at Radio Shark.
Posted 10 March 2004 - 07:03 PM
Now I even know where the oil pressure sensor is!!!
By the way, I am wondering what you guys do for a living. Perhaps automotive design engineers?
Posted 11 March 2004 - 10:02 AM
Posted 11 March 2004 - 10:23 AM
Originally posted by 99obw
Based on your data my guess is that the IAT sensor is an NTC thermistor.
Yeah, I think that most all light dependant resistors and temperature dependant resistors that are based on the natural characteristics of organic materials have a curved transfer characteristic that starts out fairly straight at one end, and compresses at the limit.
The resistance measurement can be converted to temperature in the ECU using one of several techniques.
Thanks, good info ...that.
Posted 11 March 2004 - 10:52 AM
I went to an auto repair vocational school after I graduated high-school, and became ASE certified in all areas but didn't relish the thought of breathing hydrocarbon fumes 40 hours a week. I own a little shop where I service guitar amps & vintage studio gear, etc. My famous client list:
Originally posted by hb_kim
By the way, I am wondering what you guys do for a living.
I love dropping names, it's such a cheap way to latch onto stardom. Also if there's any guitar players reading this and you're hip to the Naylor amp, I designed that in '93.
I'm a hopeless tweeker, so there's no way I'd be able to tolerate a daily driver suffering from a poor fuel or timing map for more than half a year with out devising a solution. The amazing thing (to me anyway) is that electronic controls almost seem to make tinkering easier.
Posted 11 March 2004 - 11:39 AM
I am an electrical engineer, but I work on telecom stuff. I did work on the automotive stuff for a couple of years in college for Motorola. I did mostly comms stuff like CAN, UART, and J1850 VPW. I would really like to tinker with the electronics aspect of the cars more, but my responsibilities keep me pretty busy most of the year.
Blitz, it might be fun to colaborate on a music or automotive electronics project. My forte is mostly digital so if you wanted to put a microprocessor or DSP on something I'm your man. My brother and I have been kicking some ideas around for a while. Fun stuff.
0 user(s) are reading this topic
0 members, 0 guests, 0 anonymous users