If you pull the EGR circuit connector and stick a wire between the pins, it will help determine if there's an issue with EGR system, the vacuum port of the switch clogged up or broken / bad connector wiring.
Shorting the 2 wire connector with a wire or paper clip, tells the computer you have a working EGR switch = proper vacuum = non-clogged vacuum switch. (+5v)
If your truck runs:
Clean the EGR first because it is likely stuck open. It probably needs to be done, either way. Rule it out and go from there. When you pull it, try not to ruin the gasket or buy a new metal style lead coated gasket before you pull it. It takes a lot of heat and it can also cause a vacuum leak if it's burned up.
The EGR has 2 holes under the vacuum disk/actuator. If the gasket is burned up between the 2 ports, you have a cross leak from a burned gasket and a clogged EGR.
An EGR, will likely require annual cleaning to clear the soot and carbon build up inside the Valve. It is easy to clean and a lot cheaper than buying a new one. PB Blaster, let it soak for a few hours. Dig out the crap with a small flat blade. Wire brush it up as best you can. New gasket.
If cleaning the EGR and reconnecting the circuit cases the issue to come back, then the vacuum switch is shot or plugged with debris or the connector has a short. The EGR connector circuit is famous for working when you mess with it and then not working when you plug it back in and drive.
Pigtails have worked well for me.
You can probably do the same thing, by shorting the H20 sensor Connector with a small gauge wire or clip and see if either or both are screwed up, at the same time.
(I'm fairly certain the H20 circuit is normally opened and the water temp heats the mercury and closes the circuit, somebody correct me if I'm wrong).
I would suspect you are getting a dash ECM warning Code? If not, why not? ECM ground?
The aftermarket MAP sensors are known to be bad out of the box. Use GM or Delphi or Standard Motor Products only. (Same with ignition modules). You may have installed a faulty brand new MAP or H20.
Your TPS could have a bad connection? The connector is known to crack and not seat correctly. The tubes have grooves in them and break. Any water leaks and they short out.
The TPS connectors get bent way over and break inside. Make certain the harness and connectors are not damaged from the head job.
Check all the blue and green seals and verify the H20 sensor does not have water filled up under the seal. (It holds water in there very easy and gets wet during the install. You may have to dry out the pins with a paper towel to make it function again). Check the seals to your ignition module too.
If water gets into your ignition module pins, it will allow water into your distributor and corrode the coil under the cap and rotor. It may run awful because the module has become damp and the 5000K resistor is now only 4500K. When I lost my blue 4 pin connector seal, there was rust under the rotor, on my screws, weights and springs from moisture leaking through the pins. Wet distributor will cause a lot of problems.
Verify your new H20 sensor connector is properly grounded, without teflon tape blocking the ground. The ground wire at the water temp is the ground wire to reset your ECM, at the harness firewall disconnect. If you are not grounded, it will be impossible to go into closed loop, with either a bad H20 Ground or broken brown wire at the sensor ground. Teflon Taping or using gasket sealer on the sensor can block your ground.
I have also accidentally cracked a new H20 sensor housing, while working on the engine, crushed the blue weather pack gasket so it was not sealed or connected properly and had a bad unit out of the box with off brands, of those as well. (Half of my issues were sub-standard parts, but missing weather pack seals is a cause of many issues).
Make sure the ground strap to the rear of the driver's cylinder head was put back and has excellent ground to the firewall. This is how your O2 and your coil get grounded to your ECM and every other circuit. Make sure your ground wire from the battery to the alternator bracket is good, not corroded.
Check the vacuum lines to your purge circuit, to the fumes canister. If there's a broken port on the canister, it causes the vacuum lines to the MAP and EGR to leak, as well. They break when they get old and leak.
Usually try to put my MAP vacuum line to the front left TBI port, as you are facing the engine, so it is no longer associated with either the PCV or the EGR circuit.
After you go though this list, unplug the battery ground wire and then unplug both ECM connectors for 10-20 minutes and reset the ECM. Plug the ECM back together, BEFORE connecting the battery ground wire. (It's easy to get distracted during the 20 minutes and screw the process up.)
Verify the 2 fuses to the ECM are not blown.
Verify Rocker Arm adjustment.
Pull your covers and triple check your rocker arms are set to your cam manufacturer's adjustment specs. Comp only recommends 1/8 turn. GM requests 1/2 turn...
You may have a collapsed lifter or the pushrods may have not been properly seated when they were set. A sloppy rocker arm will cause a lot of problems. I have seen brand new rocker arms with brand new OEM style lock nuts, loosen up, because the threads on the studs have worn out and no longer hold the crush style OEM lock nuts from spinning during idle. I had to buy Poly Locks and use an Allen wrench to hold my new Comp Roller Rockers because the new nuts were worthless.
The quality locks, forced me to buy taller valve covers. The shorter locks, which fit the OEM covers, only allowed me three threads to lock my rockers. Re-studding the brand new $900 Vortec heads was not an option. Wish I had bought better heads with removable studs. Remanufactured heads are known to have lose threads on reworked rocker studs too.
2nd to Last item to check, Clogged Cat?
A lot of cylinder head failures cause the extremely hot CAT to clog up, with all the coolant hitting a molten converter core. The back pressure could cause reversion, forcing exhaust back into the cylinders, instead of exhausting. If your back O2 sensor got wet with coolant, then it is contaminated too. (If you have a down stream O2 at the Cat).
FWIW, my truck does not get above 180 in the summer and 160 in the winter either and I'm running a 195 degree thermostat in the winter and swapped to a 185 for the summer and it stayed the same. No idea why. Single core stock radiator, no A/C core blocking the air flow anymore, is all that's changed.
I have no experience with the air pump system. If there's anything that could go wrong there, you'll have to ask somebody else.
Hope this helps out.
