bad MAF?

[Iron]

Hey guys, I've got another problem with my car. It sometimes loses power when on the accelerator, causing it to feel like its shifting into the same gear (lugging, rough surges). My mechanic says its the Mass airflow sensor, but I am not sure that this is the case because it was replaced just over a year ago, it isnt giving any codes, my check engine light isnt coming on, my milage is the same, and it only happens randomly. A friend suggested that the Throttle position sensor may be the culprit, so we checked the voltage of the sensor while opening the throttle (we think so at least), to check if it was working, and if we did it right (attached to bottom and top prongs, nothing was touching the middle one), the throttle position sensor isnt working. So basically I've taken 2 pictures of the area, and I'm wondering if anyone can confirm which of these sensors is which (so we know we were actually testing the throttle position sensor)? It would also be great if anyone could shed some light on my problem, do you think it's the mass airflow sensor?
http://s281.photobucket.com/albums/k...nd_TPS_010.jpg
http://s281.photobucket.com/albums/k...nd_TPS_009.jpg

[BNaylor]

The TPS is number 2 in your pics. Did you measure the TPS output with a multimeter (DMM)? Let me know if you need the voltage specs.

[Iron]

Cool thanks, that's the one we thought it was . So inside that sensor there are 3 connectors, are we doing it right by testing the top/bottom connectors and ignoring the middle one? I would love your voltage specs, we weren't getting much of any change though.

[BNaylor]

Of the three pins on the connector the middle, pin B is the TPS output. Wire may be color coded DK BLU. It will vary from .4 volts dc at idle to around 4.5 vdc at wide open throttle (WOT) as you move the accelerator. Pin A is TPS chassis ground. Pin C is the PCM 5 volt reference signal which will stay fairly constant. To check WOT and linearity of the signal you can check it with car off, not running but with ignition to ON. In most cases if the TPS is bad a DTC should set like P0121, P0122, etc and trigger the SES/CEL light.

[Iron]

I'm not sure I get it, how do I check pin B only with a multimeter (I need to attach it to two things)? That's the one I should be checking right? And if it doesn't go up as the throttle goes to WOT then it's time for a replacement?

[BNaylor]

Unless you partially disassemble the electrical connector obviously it is easier said than done. I use a pin or needle inserted into the output wire which corresponds to pin B on the connector and then attach the meter positive lead to it with a clip like an alligator clip. Black lead to any good ground.