Cold Idle/Warm Idle

[RustedRanger]

Just one CTS Coolant temp sender. The other single wire sensor is for the temp gauge and has nothing to do with the computer or the way it runs.

 

[nooberiffic]

Thanks, im headed to the parts store now. If this doesnt do anything, I guess Ill have to start looking for a computer.

 

[nooberiffic]

k. havent put in the coolant temp, or air charge. But adjusted the TPS to .86 volts. Now the engine dies almost immidiately. I set it to .95 volts and it chugs for half a second and then dies.

Will the ECM need to be for a 1990 MT 4x4 2.9, or can I get for a 89 or 91 4x4 MT 2.9

So. To get my truck to run, I have to set it at around 1.5-7.

Do you still think it is the ECM? I replaced the Air chage and coolant temp sensor today

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[RustedRanger]

I don't know how much difference it would make but have you unhooked the battery to "clear" the computer? I do this every time I change something that could make it run better. The computer can't adjust for running better only worse. In other words as it gets miles and time running it will not run as well and the computer can adjust for that but not the other way around. Does that make sense? Have you tried to pull the codes?

 

[nooberiffic]

K. Update. I have not tried to pull codes. Previously everyonce and a while I would get a check engine light and then after a few minutes it would go away. After I changed the CTS and Air charge sensor I started having a lot more movement on my temp gauge. Before it would slowly get warmer to about the "O," then dive down to right before the "N." While changed the CTS I lost about two quarts of coolant. I replaced it after I was done. Well, to make a long story longer, now the temp gauge goes up to the "R" and then dives down (after, I assume, the thermostat opens) to almost out of the the "normal" bracket. It will move up and down slowly and randomly between there and "N." Now I notice that the check engine light will sometimes come on when it almost moves out of the normal bracket. Is this just because my sensors are actually working now, or something else? Ill go unplug my battery again, and look into ordering a ECM.

BTW, all this happened on a 165 mile trip on the highway, with pulling a few canyons and hills.

 

[Area 52]

First off, clean the throttle body.

Then pull the idle control valve...remove two screws holding the electric solenoid and pull off the solenoid. Use carb or throttle body cleaner liberally...cover holes with hand/fingers and shake it vigorously. Do this three or four times and then follow up with soap and water rinse. Dry and reassemble and bolt it back on the intake manifold.

For the temp gauge issue, loosen the sending unit and tighten it...do this a couple of times as there may just be too much resistance to ground.

Report back.

 

[nooberiffic]

The throttle body was just installed and was already very clean (thanks Maverick) but I went over it again prior to putting it on.

I will do as you say with the IAC and report back. But... The unit is new with less than 2500 miles on it. The one it replaced was still in working condition and I did take it apart and clean it (with carb cleaner, no soap though) about 500 miles before replacing it.
I will also do as you say with the sending unit (thats the one on the drivers side correct?).

Thanks for all the help, I really appreciate it.
When I get this sorted out then we can move on to the 4X4 and Low Range lights not lighting up on the dash, the sensor on the tranny that has no plug just wire (not sure what it goes too) and a lift.

 

[Cyberbeer]

Is this a manual or automatic tranny?

 

[nooberiffic]

5 speed

 

[Cyberbeer]

That plug on your tranny is most likely the nuetral sense switch. Having it unplugged will likely cause idling problems while not in gear. The vehicle wont know wether it is in nuetral or in gear so will idle funny...

 

[nooberiffic]

hmmm. Well, Its missing the male portion plug I think. It still has the wires with metal ends, which I just pushed into the female end.

Update. I loosened and tighened the sending unit. Cleaned the IAC. Still about the same. Still thinking ECU?

 

[RustedRanger]

You could take it somewhere and have it put on a machine to see if it shows something wrong with the computer or sensors. The first place I went charged $65 and they spent four hours and could'nt find the problem but did tell me the computer was working right,plus they couldn't find the problem cause it didn't "fail" while they had it. I saw a friend from high school at the exhaust place while getting an exhaust leak fixed and found out he does mobil diagnostics. He checked it today and found a broken ground and that the purge solenoid that controls fuel vapor into the throttle body is gone. Also he checked the sensors and they are fine as is the computer. I replaced a lot of parts too trying to find the problem,some helped,but it still had problems and wouldn't idle right. I have heard that the ECM's are very expensive so if you get it checked then you might save yourself some money and find out what is really wrong at the same time.

 

[Cyberbeer]

My truck has been doing something similar lately. When the engine is still cold the truck acts erratically. If I let off the gas or hit the brakes during this period it kind of bucks and sasses. The idle might surge for a few seconds and then other times it may not. I've checked for vaccum leaks and havent found any.

As soon as the motor gets to operating temperature it smooths right out without a problem. I've cleaned the IAC, and did a sea foam induction cleaning on it. I dont know how old the TFI or MAP sensor is.

 

[HndMeDnBroncoII]

in the libriairy system on line i found an article tsb actually about how the newer iac valves have a resistor in them.and apparently even though new would still cause a rough idle.the correction was to reverse the wires on the plug .but follow the link from this site to the online librairy and read for yourself itll make more sense when u do

 

[nooberiffic]

Well, an update.
For some reason the check engine light has only come on once for about 2 minutes in the past few weeks, but im still having the problem with the idle (still idleing low around 550 RPM cold and 850 RPM warm. I tried to adjust my TPS with my voltometer but it wont run unless up about 1.06, not the recommended .86)

Im going to get a picture of what someone thought was the neutral sense switch, so I can get it confirmed and a replacement socket ordered. MIght it bve the nuetral safety switch?