93 transport eratic idle

Hello, my 93 transport has devoloped an eratic idle problem last month after i disconnected a bunch of wires to change the thermostate. This did not happen before unhooking anything. service engine light goes on when idle goes up. any advice would help thanks.

What engine type do you have?
If a 3.8, this describes exactly a EGR valve problem. Then you should have one of these codes 53/54/55/56
HOwever, unless wires going to the EGR valve were tampered with , I see no direct relation with the work you have done.
In fact, why did you change the thermostat?...If a 3.1, my guess would be a steaming radiator/poor heating problem, then the erratic idle would be indirect relation with the problem that was mot at all corected by changing the thermostat.
Come back with more details.......
Do you know how to retreive the codes?

Hello, i changed the thermostat becuse of no heat. the motor is a 3.8 and the wireing connections go over the houseing. I took it to auto zone for the free scan and he came up with nothing, he did the paper clip thing! Just find it strange it started to happen after things were unplugged. the egr was not one of the ones disconected though i did take the plastic cover off for more room to work

If service light comes on and off, then at times there should be some code to be read. The EGR valve problem does in fact cause on and off CEL because wit the 3 egr valve sections, the combinaison of valves is not always the same depending on conditions. If one section is faulty, and the actual valve response matches the computer command, CEL goes out. If computer happens to ask for the faulty one, CEL goes ON. So this is evasive.
There is always the possibility for a coincidence.....but I would check again . Fact is a disconnected EGR secton will not hurt idle, but will light up CEL. Check also for disconnected temperature sensor....
Also, if battery was disconnected, it is possible adaptive constants in the computer have been erased, so for a while, before the computer "learns" again, it might have some erratic behaviour.
So.....it is kind of puzzling anyway......If you want to run the code test from time to time, easy:
connect A to B with a paperclip
www.avigex.ca/xport/plug.jpg
turn key on
will flash 12 (one then 2 flashes) 3 times, then codes: 54 is 5 flashes then 4.
read codes here:
www.avigex.ca/xport/3800codes.jpg

..BTW, did the change of thermostat effectively correct your heat problem? very important to know that detail! What mileage do you have?

the new thermostat did correct the heat problem but what a pain in the neck,no room to work,stripped bolt holes and it took 30min. just to get the houseing surface clean for every thing to seat properly! mileage is 106K . I may just take it to the dealer for a correct scan so i dont buy any parts i cant return. I will post the results soon. I JUST TRIED THE PAPERCLIP AND IT SHOWED CODE 21 TPS HIGH VOLTS THE IDLE WAS GOING UP AND DOWN AT THE TIME. DO YOU KNOW WERE THIS SENSOR IS LOCATED? THANKS MIKE S.

OK Throttle Position Sensor is just there:
www.avigex.ca/xport/maf.jpg
..although you say "idle was going up and down at the time", you mean that was before stopping the engine and doing the test..eh?
Yes...TPS is a variable resistor. in fact a potentiometer. the "wiper" can have a dirty contact with the resistor track, and send "varying signals" that are seen by the compuiter as rapid throttle position change..and it sends varying amount of fuel accordingly.
Once in my hands, and although it is not really possible to "open" it, I have been able to force WD40 into it - I do not remember exactlky how, may be through shaft bushing - and it cured the problem....something like 8 years ago.........so before buying parts......Caution: easy to loose little nuts in that area, and you do not know where they go.
some more reading here: www.avigex.ca/xport/dtc21.jpg
BTW, scanning it at the dealer will not reveal more about the engine than what you see...except maybe other codes about ABS and transmission that at this time you do not want to hear about .