Hello to all. I'm new here and hoping for some info that will help me get my son's 2001 Blazer running right again. It's a LT 4wd 4.3 with 150,000 miles on it that he bought new. It was running well when the water pump went and engine overheated pretty bad. Since then it will barely start, and dies shortly after. I checked codes and got P0101 & P0102. I dismantled air intake, cleaned sensors with spray, and replaced MAP sensor because it looked melted on tip that inserts into manifold. Also replaced air cleaner and inline fuel filter, as well as water pump.

I reset codes and they didn't come back on (even though engine hardly runs long enough to be sure) but a P0300 code came on now, which is misfires, and I'm sure that's correct. I bought new plugs and will do compression check tomorrow. After that I guess I'll have to get a fuel pressure tester and check that, but fuel pump was replaced by a mechanic within the last year.

Anyway, my question is this, due to the severe overheating, is it possible that the spider assembly may now be compromised? I ask because when I removed MAP sensor it was wet in the hole. Is there any other areas I should look into, or teasts I need to do to find problem?

I know It's an older car with high mileage, but my son currently cannot afford to replace it, and neither can I. Appreciate any advice or info anyone can provide. meanwhile I'm going through all previous posts that may pertain to this problem.

 

It is worth a look. With that kind of distortion on the map sensor, I would take the upper intake off for a visual. It doesn't take that long to remove and will give you peace of mind. Just make sure you have the plug wires in the correct position again before you move on in the diagnosis. Double check the simple stuff. Also that is not an old car! It is a Blazer. That mileage is not high either.

 

150K is not considered "high mileage" for a 300K capable engine. It's doubtful that the spider was damaged during the overheat, unless you really cooked it. 4.3L head gaskets are not usually an issue; again, unless you really cook it! After an overheat, it's always a good idea to check compression: Remove all spark plugs. Disconnect the electrical connector from the ignition coil. Remove the fuel pump relay. Prop the throttle wide open. Install the tester and crank the starter. Allow the tester needle to "pulse" 4 times while cranking on each cylinder. Write down the results for each cylinder and mark it "dry test". Next, squirt ~1 tablespoon of clean motor oil into each spark plug hole and do the compression test again. Write down the results and mark them "wet test". Performing the dry & wet tests will check the condition of the piston rings as well. Post the results and we can analyze them.

Several things can cause P0300 however, it is almost always caused by a fault in secondary ignition: spark plugs, wires, distributor cap & rotor, ignition coil, and incorrect camshaft retard. Other common causes include low fuel pressure and a worn distributor gear. These engines are very fussy when it comes to tune up parts, (they don't perform well with aftermarket stuff). Plugs, cap & rotor need to be AC Delco. Wires and ignition coil need to be name brand, good quality, (not a store brand).

 

Thanks guys! Great info. I'll do the compression test tomorrow and replace the plugs and go from there. I'll get back with compression results.

 

Well, today was disappointing. Pulled plugs and did compression check and all six holes were in the 165lb range. Replaced plus, wires, cap, and rotor with new. Engine still barely started and died shortly thereafter, like before. Triple checked plug wires, etc. Two things I noticed though, 1. when I first did compression check on number six cylinder, compression gauge went to high 200s because cylinder was full of unburnt fuel. Fuel pump relay was already removed, so it was residual from running. I spun it over a bit and blew out the cylinder. (I'll have to change oil because I'm sure it's compromised with fuel? 2. When I turn key on, fuel pump runs and builds pressure. After shutting key off and waiting a few minutes no pressure shows when depressing valve on fuel line.

I think either injector(s) are stuck open, or pump or something in the system is not right. I just bought a fuel pressure tester and will see what I come up with tomorrow. Anyone have any other good ideas of what to check?

 

If the fuel pressure does not hold, sounds like fuel pressure regulator is not working...so the fuel injector is not firing, which of course means the engine is not going to run very well.
Search for the fuel pressure leak-down test on the forum here....this will tell you what numbers you should be seeing.

 

Thanks Lanny, I' ll check that out tomorrow.

 

fuel pressure regulator is leaking, you need a new fuel spider. There are just replacement regulators but i've never had long term success with them

 

If leakdown is excessive, something is leaking. If #6 is full of fuel, chances are pretty good that #6 injector or poppet valve is stuck open

 

I just hooked up fuel pressure tester. Turn key on and pressure goes up to low sixties and then drops down to 0 in around 5-10 seconds. I'm currently in the middle of removing the plenum/intake and that is presenting me with a problem. All connectors are removed as well as fuel lines, wires, etc. Plenum is loose and moves around, but does not come off. I assume it is connected to spider assembly or something, how would I go about getting it off. I'm going to search old threads for info on this before I break something.