Hi there, new member, new ride.
I have a 89 sidekick 1.6 8v automatic. it will not restart when warm until its totally cooled down. At least a couplea hours. Truck has been a long project. First the history I guess. Bought it 6 months ago, PO had put the battery in b wards but cable correct. Shorted out wiring. Repaired all of that including fuel pump and ECM and it started, ran like crap. A compression test showed a dead hole. A supposedly mechanic pulled the head, found a broken valve. I had the valves all redone and or replaced. He put the head gasket on and somehow plugged off the oil hole in the head. Saved up and bought a used motor, I put it in and it ran. I let it run for over 2 hours outside (utah 25 degrees) shut it off and immediately restarted it, did this twice and ate dinner I went back outside and it wouldnt start. Next morning started fine, shut it off after 30 mins of steady temp, waited 10 mins and no restart. Checked spark, great. Used starting fluid and she ran, stopped and so did the engine. Let it cool for the day. I returned that evening and exactly the same issues after it warmed up. Pump kicks on as PO had it wired to a toggle switch. I put it back in the harness to the ECU after it cooled, she restarted, when I shut it off warm, waited 5-10 mins, no restart. There is no wet plugs (new NGK) i dont smell it rich outta the pipe. I replaced the o2 sensor also with a Bosch. The idle is as it should be. Fast idle when cold, drops right down when warm. I did use the original intake and distributor. The one that came with the motor was different. I did use plugs for the 89 NGK gapped at .28. vacumn hoses all hooked up. New timing belt, tensioner and water pump, alternator, starter, hoses,radiator, fan. Doing this for my girlfriend, she loves the looks at it has the (4) fender flares, side panel , vbra etc. Gotta whole lotta money and it wont stay running. One other thing, are these things supposed to be at 4000 at 65 mph? sounds like it needs one more gear. Sorry for the long post, just want all the info so someone can help me. I am thinking about changing out the injector and TPS from the intake that came w the junkyard motor. Could it be shorting out when warm and shutting off fuel to the injector? It always start w starting fluid when warm, just wont stay running. THANKS for ANY help. David

is it tbi or carbed? is the fuel getting back up to the injectors.u could take fuel line off at tbi and check but could be weak fuel pump. yes 65 mph |removethispart|@4000 rpm is correct

sorry, injected, new pump and filter,  over 20 psi fuel to the tbi. I cannot get a reading ohms on the tps. range is 0-500. I cannot get it above 0 between c and d. Does that help?

One last update for the nite. I checked as per my Haynes manual the Ohms on the TPS and the Injector. All reading within specs. I am concerned that I cannot get a range on the c and d above 0 on the TPS. If I do try to adjust it, I can get an infinity reading or zero, all the rest of the readings are in the middle range. A to D and B to D as well as the injector. I took off the fuel filter, turned the key on, appeared to have great fuel pressure as it flooded the floor really quick. As I said earlier, this only happens after i shut the motor off warm, then let it sit for a couplea minutes, no restart. If i immediately try to start it, it will start two or three times, then nothing. I still have spark and can fire it with ether when its warm, just wont run on fuel. Its been in a 60 degree shop for 3 hours, wont start till it sits in the 20 degree weather outside. Then it starts in less than an hour. HELP?

Sounds like a fuel problem to me.  Could be the ECM.  Could be something in the wiring.  I doubt a bad TPS would cause the issue, but it might.  Have you tried holding the gas pedal at various positions while cranking the warm engine?
It sounds like the fuel pump is working like it is supposed to and providing fuel.  My guess would be the injector isn't getting pulsed for whatever reason.  ECM could be causing that.  You are gonna have to get your test meter out and start checking wires for the proper voltage.  You can also rent/borrow a noid light test set from the auto parts store to see if the injector is getting pulsed, when cranking a warm engine.  The noid light test would probably be my first test.  If the injector isn't getting pulsed, then you need to start backtracing to see where the issue lies.
If you can get a copy of an FSM (factory service manual), it will tell you what kind of voltage (or ground) you should see on each wire in the ECM connectors, depending on whether the key is off, on, or in the start position.

This was happening on my bosses porsche. It ended up being the fuel lines themself. They were swelling when warm from the ethonal gasoline I beleave is what they determined. Put new ones on and starts everytime.

I think I would drive it around till it got hot. Turn it off. Wait a few min as if you were going into the store. Then put the pressure gauge on and turn the key to run. See if you have fuel pressure. I think the theory was the lines got hot and swelld but there is pressure when running so it keeps it open enough to still allow fuel. Then when you turn it off you lose your pressure and it swells shut.

FIXED!!!!!!! I replaced the ECM, TPS as neither was operating correctly. Truck started and finally idled down and restarted twice when hot. Ohmed the injector, right in range. waited 5 mins, no start. Ohmed injector coil again 16 ohms instead of 1-2. Spent way too much money for a new injector and she runs better than she ever has. Starts when hot, everything.
 Now to sell it, Need something that can at least do the speed limit (80) I will post pics later. It has new everything as well as a body kit? fender flares, body moulding etc. Thanks for all the help and suggestions. Y'all rock!