2ToyGuy

That ground at the back of the head to the firewall is critical. It's the main ground path for the spark plugs, and the alternator both. The head is isolated from using the ground on the block by the head gasket, so it's very important to have a good quality ground path for the head. Since it's grounded to the battery through the body metal, it's also important to ensure the ground wire from the battery to the body is in good shape as well.

Sorry. It's just that so many consider ground wires to be an semi-necessary item. Drives me nuts. They're as important as any other part of the path for current flow.

Anywho, good fortune!
Pat☺

Troy68

Well, whatever it was, it didn't last through the engine change so that points to something I would have disconnected or replaced (basically the entire engine harness, ECU, battery harness, and alternator). It also wasn't mechanical (engine related) as that engine worked fine in the other vehicle. Since it was intermittent it likely wasn't a broken wire - probably more like a loose connection that was affected by the elements. I have another vehicle currently where the gauges don't power up unless I cycle the driver's side power windows. I'm sure that's a ground - but there are about 10 on that side of the vehicle!

Troy

coopster

LMbO. That's gotta be aggravating at times.

AlfaMessi

where exactly would this wire be?

AlfaMessi

Yo this crap is pissin me off. I drove it today to the store and it drives like a champ but once I turn it off and come back 10 min later it turns over shakes then shuts off and back to not wanting to turn on smh. I have to wait at least 1 hr for it to come back on. Any idea what could be the problem?

coopster

You were asking where the ground on block is? One of them is on the passenger side; it connects from the rear of the head to the firewall (actually the wiper mechanism box thingy under the cowl vent).

You might get better mileage by just creating a new post. I think Scope published a link (or check the stickys) to a FSM That should have a trouble shooting guide.
Symptoms and possible causes and resolutions.

2ToyGuy

The back of the head ground usually runs from the rear bolt that holds the pick-up hook on to the firewall behind the head.

It sounds like your trouble could well be the "pressure-up" the ECU calls for when the engine gets very hot, as it does when you shut the engine off after running it to make it as warm as it will get. Watch the temp gauge after shutting the engine off for a few minutes. Say 10 or so. As soon as you turn the key to ON, you'll see the temp gauge run on up to a very high reading. This is called "heat soak". The ECU senses this high heat, which can cause "bubbles" in the fuel rail(s). It's supposed to, anyway. When it senses that very high temp, it will apply vacuum to the hose that goes into the top of the pressure regulator. This will allow the pressure of the fuel in the fuel rail to be higher. The highest your pump will provide. It thus reduces, or eliminates, the bubbles the high heat can cause in the fuel rail(s). Bubbles will not allow the injectors to function properly. This may explain your trouble starting/running when the engine has been run for a while. until it cools down somewhat.
I may be wrong on the vacuum, though. IOW: There may be vacuum applied to the regulator during normal operation, and the ECU opens a VSV to remove the vacuum during heat-soak conditions, raising the pressure.
You should check the FSM for your engine to see which way it works, but you get the basic idea.

IF the ECU isn't sensing the engine coolant temp, or the VSV (Vacuum Switching Valve) that controls the vacuum to the fuel pressure regulator, the ECU, the wiring feeding them, or the vacuum lines are damaged, any of them could well cause the trouble. The BEST way to tell is get a fuel pressure gauge you can connect to the CSI. That way, you can check the fuel pressure the regulator is holding the fuel in the rail to under normal conditions, and during heat-soak conditions. The FSM has the readings you should be getting. Point is, higher during heat-soak, lower during normal engine operation. That way, you can check to see if the vacuum is applied properly to the regulator, if/when it is, does the regulator change the pressure, does the VSV change the vacuum applied, does the Coolant Temp Sensor feed the correct info to the ECU, and so forth.

Most Auto parts type stores have "loaner gauge" sets, including the adaptors to hook it up. YOU will have get the crush washers you need, and you'll probably need a number of them. Bear in mind, they can NOT be reused, under any circumstances. As soon as they are installed, even if you don't tighten down onto them hardly at all, they must be discarded and replaced, not re-used. They are readily available from you local Toyota dealer, and they're not very expensive at all. They are a very intelligent investment to have plenty of spares of, you know? You'll find yourself needing, and using, more of them than you might expect.

Hope my rambling helps you in some way...
Pat☺

AlfaMessi

thanks Pat,

this truck belong to my dad till he gave it to me about a month ago and it was sitting for about 2 years. I changed out the engine and did all the tune up u can think of except major sensors and fuel pump. I noticed that when i got it to drive the very first time it would always run cold. It was missing the thermostat and I asked my dad about it and he said he always ran without it smh. I put a new one on there and it was running hot after a while so I purged the coolant system and that fixed the problem of over heating. Now I did notice that when I am sitting still and turn it off I do see the temp gauge go up more than normal but just a bit. Is this what you are talking about? Please if possible give me very strategic things to stop this. The truck runs very good until I run it for a while and turn off it does this and it is very annoying! Thanks in advance bud.

2ToyGuy

The cooling system will actually function better with the thermostat's restriction in it. The way it as explained to me, the restriction caused by the thermostat, even wide open, slows the water down slightly, allowing it to give up more heat to the air via the radiator.
Ensuring that the cooling system is properly "burped" is also vital. These cooling systems are known for holding air bubbles in nooks and crannies.
The truck will actually run better at the proper operating temp, and the ECU is designed to control the mixture best at that temp. Since you say you didn't replace the major sensors, check the Engine Coolant Temperature sensor, which is different than the one that feeds the gauge. Make sure it's producing the right value at "cold" (not run overnight), and "warm" (run to the store and back, for example). To actually see a good example of "heat soak", you need to run the engine under load for a while, and warm up the oil, and all it's other fluids. They will all contribute heat back into the engine once you stop it, making it get hotter than you might think. Leave the hood closed. Let it sit for around 10 min or so. You should see the temp, when you turn the key back on, actually go up to almost the very top of the gauge. At least up to 3/4 or so. If not, you may have a problem with the sensor feeding the gauge, or the gauge itself. Bear in mind, these gauges are notoriously inaccurate. Just sitting and idling until the thermostat opens won't give you a good example of heat soak. It takes making the engine work under a load for a while to see that.
Vital to ensure the sensor that feeds the ECU's connection, through it's threads, to the head, is clean. If it's got corrosion built up, it will give the wrong reading to the ECU. Same for the O2 sensor, and so forth. Make sure the wires coming out of it are connected properly. These sensors are known for having the plastic part with the wires break off. It may not look broken at first, but a small wiggle on the plastic will tell the tale. Make sure you don't break it when testing to see if it's broken the plastic gets very brittle over the years.
Same with the vacuum line connections. If the vacuum line goes to a plastic connection at either end, make sure none are cracked or broken off.
Make certain the IACV (Aux Air Valve) opens and closes at the right temps, and when it opens or closes, it does so completely. If it, for example, is feeding too much air into the throttle body, it will be hard to start/run. The ECU will be expecting a certain amount of air going into the throttle body for a given temp, and if the Aux air valve is staying open too long, for example, the engine will be getting too much air for the fuel the ECU provides.

OK, I'll shut up now...
Good luck, and keep us up to date on how things go
Pat☺