Sinking Creek 4WD Association

Ive been having this problem with my truck for a while now and havn't been able to figure it out. The motor idles differently depending on the outside temp. When its cold out (below 55) it idles obnoxiously high around 1500 to 2000 rpms. This causes the idle to bounce when I step on the breaks. When its warm out (above 70) it tends to idle low, below 400 rpms. When its really hot out and the motor is warmed up, it will stumble and die if I don't give it gas. I researched the problem on yotatech and tried a few things. I replaced the MAFS after it tested bad, checked for vacuum leaks, and checked to see if the EGR valve was clogged. None of this helped
The motor works fine under load and I havn't noticed any major drops in mileage or power, but its kind of embarrassing when my truck dies at a stoplight for no reason so it you got any ideas please spit em out.

Per Will:

Check to see if you have/good IAT (Idle Air Temperature Sensor) or an IAC (Idle Air Control Sensor/Vavle). The former being on the intake manifold probably and the latter on the throttle body.

Have you pulled any codes?

Check to see if you have/good IAT (Idle Air Temperature Sensor) or an IAC (Idle Air Control Sensor/Vavle). The former being on the intake manifold probably and the latter on the throttle body.

-Thanks Ill look into it when Im done with finals. Ive never had access to a code reader before, but I would give it a try if somebody has one. Does it have to be specific to your engine?

1
Turn off the vehicle's ignition and open the hood. Locate the connector box, a small box just behind the main fuse that is marked "Diagnostics."

2
Open the connector box and connect terminals E1 and T with a jumper wire. Do not connect other terminals.

3
Turn on the ignition, but do not start the engine or press the accelerator pedal.

4
Observe the check-engine light. A regular on-off-on-off pattern (both "on" and "off" lasting about one-quarter second) indicates no trouble code is stored. Other patterns are irregular, for instance, one-half second on, one-half second off, one-half second on, one and one-half second off, one-half second on is diagnostic code 21 (fault in the O2 sensor). Code 13 (RPM signal) is indicated by one-half second on, one and one-half second off, and three one-half-second "on" intervals separated by one-half-second "off" periods.

5
Record the blink code, and check it against the cross-reference chart in the owner's manual. The chart will show which electronic system or sensor has detected a fault.

Also, Advance Auto has code readers they let you use for free in their parking lots.

ridemx wrote:Also, Advance Auto has code readers they let you use for free in their parking lots.

Pretty sure advance and all other auto parts stores only have code readers for OBD-II equipped vehicles which I think is 96 and newer or something like that. His is a 93 which is OBD I which is not a standardized hook up like OBD II vehicles

Matt612 wrote:

ridemx wrote:Also, Advance Auto has code readers they let you use for free in their parking lots.

Pretty sure advance and all other auto parts stores only have code readers for OBD-II equipped vehicles which I think is 96 and newer or something like that. His is a 93 which is OBD I which is not a standardized hook up like OBD II vehicles

Correct

Right, my bad, I didn't even look at the year. OBDII is 96 an newer.

You can download the FSM here
http://www.ncttora.com/fsm/

It'll have the blink code chart Stinsons talking about and instructions on adjusting your TPS.

The temp sender Will was talking about is right infront/below the thermostat housing.

Try plugging the line to the brake booster to check that it isn't leaking vacuum.

Good stuff guys. Ill try to mess around with it on Thursday. I had two today and got two more on wednesday

Well its not throwing any codes and the brake booster doesn't seem to be leaking vacuum. Im flying home tomorrow so Ill have to wait till next semester to test the temperature sensor and the TPS.

One thing I forgot to mention: I think there are some bubbles in my coolant system. I can hear them occasionally while driving. It seems like that could mess with some sensors/ affect idle? Ive tried running the motor with the rad cap off on a slope, but I guess I can try again with a steeper slope when I get back.

Ok. I tested the TPS and everything is in spec according to this website:

http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

I was wondering if anyone knows where I might find the specs for the temp sensor so I can test that.

Well the temp sensor tested bad so I replaced it and it didnt fix the problem. If anything it idles higher now . Yota tech suggested taking off the throttle body to see if the auxillary air valve is stuck open so i guess ill try that next. As always Im open to suggestions.

Also: does anybody have thoughts about the bubbles in my coolant? I can hear them in the heater hoses ocasionally. Ive tried burping the system on a hill but they wont come out.