Air Flow Sensor Pot Help
04-30-2005, 07:11 PM
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Air Flow Sensor Pot Help
Greetings folks.
This is a continuation of the "Huge Flat Spot" ("90 300E) thread, but I just got a chance to do a few more diagnostics, and the weak link seems to be the Air Flow Sensor Pot (TPS?), but this is only a seat-of-pants assessment, without access to the correct diagnostic routine.
Measuring resistance the values are as follows:
Between Top and Center Pin
closed 20K
1-2mm 3-4K
.25" 5K
.5" 7K
1" 9K
1.5" 10K
2" 9K
WOT 8K
BetweenCenter and Bottom Pins
Closed 20K
1-2mm 10K
.25" 10K
.5" 6K
1.0" 7K
1.5" 7K
2.0" 6K
WOT 6K
I would expect the response to be linear, and the values from about 1.5" to WOT would point to the flat spot I'm experiencing. I'm assuming that hitting the WOT switch enrichens the mixture, and accounts for the outstanding response at WOT.
Dan Landis' excellent write up on mixture adjustment mentions that the test for the Air Flow Sensor Potentiometer as Job 07.3-121.
If anyone could copy me on that test (and tell me where I could purchase the CD or book with this test for future reference) I would be much obliged.
The Potentiometer seems to be pretty firmly attached to the body of the air flow housing. Any BTDTs from anyone that has either replaced the unit, or cracked it open and successfully repaired one?
If anyone has any links, attachments or tech CDs to offer, my address over the weekend is markwoodland@hotmail.com
Many thanks in advance,
Mark
This is a continuation of the "Huge Flat Spot" ("90 300E) thread, but I just got a chance to do a few more diagnostics, and the weak link seems to be the Air Flow Sensor Pot (TPS?), but this is only a seat-of-pants assessment, without access to the correct diagnostic routine.
Measuring resistance the values are as follows:
Between Top and Center Pin
closed 20K
1-2mm 3-4K
.25" 5K
.5" 7K
1" 9K
1.5" 10K
2" 9K
WOT 8K
BetweenCenter and Bottom Pins
Closed 20K
1-2mm 10K
.25" 10K
.5" 6K
1.0" 7K
1.5" 7K
2.0" 6K
WOT 6K
I would expect the response to be linear, and the values from about 1.5" to WOT would point to the flat spot I'm experiencing. I'm assuming that hitting the WOT switch enrichens the mixture, and accounts for the outstanding response at WOT.
Dan Landis' excellent write up on mixture adjustment mentions that the test for the Air Flow Sensor Potentiometer as Job 07.3-121.
If anyone could copy me on that test (and tell me where I could purchase the CD or book with this test for future reference) I would be much obliged.
The Potentiometer seems to be pretty firmly attached to the body of the air flow housing. Any BTDTs from anyone that has either replaced the unit, or cracked it open and successfully repaired one?
If anyone has any links, attachments or tech CDs to offer, my address over the weekend is markwoodland@hotmail.com
Many thanks in advance,
Mark
Last edited by mwoodland; 04-30-2005 at 07:24 PM. Reason: Additional info
