First off (99 Ranger, 2.5L)...Whenever I start the truck and let it warm up, I put it into gear and the RPMs drop a lot and you can kind of feel the engine surge (I really dont know how to explain it)..Could the IAC be causing something like this or would it be something else?

1/9/2009 10:28:06 AM

could be a sluggish iac, do you have any other driveablity problems, like stalling coming to a stop, or hesistation?

1/9/2009 10:29:50 AM

nope, none what so ever, however, sometimes when i slow down hard, the transmission likes to jerk when it goes down into a lower gear...but thats entirely another problem i assume

1/9/2009 10:44:08 AM

Could definitely be the IAC valve...pulse width modulated solenoid type. If it's sticking in its bore then you could indeed have such a problem. I'd pull it off and clean well with carb cleaner. Enough fuel standoff vapor will indeed cause these things to foul up. Just like a throttle body. You might also want to clean your throttle body. Do you have any error codes or illumination of the MIL?

Other things that could cause said issues: excessive deadband in the throttle position sensor, faulty EGR position sensor, fouled EGR valve. Error codes should pop up for any of the above faults though. I know that EGR pos. sensor and valve will result in MIL illumination. The IAC, maybe not as much, as it has no means of actual feedback other than RPM, and under highly transient situations may not actually result in an illuminated MIL.

1/9/2009 12:58:18 PM

No, the CEL is not lit up, so I should first check into cleaning the IAC and TB? What about the MAFS?

1/9/2009 1:15:09 PM

i'd be willing to bet the iac ports are full of carbonized crap, take that shit off and clean it

1/9/2009 3:32:34 PM

ok thanks guys, I'll try that next time I'm home and see if it helps

1/9/2009 3:52:30 PM