Well....I am getting closer to having an expensive large paperweight. Changed ignition module and slightly better, not that that means anything as the Blazer sat for two days. I did have my OBD2 cable arrive so can hook my laptop up to it and see what codes I am getting. This has been the most maddening frustrating couple weeks of my life. Oh to go back to points and a carb.

Well....just pulled three codes. P0107, P0122 & P1351. My scan software shows MAP/Borometric Pressure circuit low input.

 

Keep in mind that these code sheets were originally for the 98+ and as such, the wiring colors may not match those found on the late 95 and 96-97 trucks. They should give you some idea of diagnostic steps though:
P0107 - Manifold Absolute Pressure [MAP] Sensor Circuit Low Voltage
P0122 - Throttle Position Sensor Circuit Low Voltage
P1351 - Ignition Control [IC] Circuit High Voltage

It would appear that the +5V reference feed from the PCM to the TPS & MAP is dropping out... I would start by testing the +5V leads at both the TPS & MAP while moving the harness around.

 

I think I am about to lose it and shoot the damned Blazer. I have replaced cap, rotor, plugs, plug wires, crank sensor, cam sensor, cleaned the EGR, disconnected the antitheft device, replaced the MAP sensor, fuel pressure is good...I am running out of options and have run out of money. Two shops, one of which is a local GM dealer could not find out more than no injector pulse...that cost me $140 at one shop who sent me to the dealer, and another $270 at the dealer. It ran roughly leaving the dealer and died the next day again. If I still lived out in the country I would have introduced it to Mr. .44 already. Oh...I also swapped out the PCM....that wasn't it either. Every now and then it would fire up and run beautifully and then die....lately I don't even get that. I did squirt a bit of starter fluid into the air intake and it fired right up....so must be the injector pulse. Rats.

 

Have you replaced the injector wiring harness inside the plenum?

 

How's your IAC wolfsnack?
Airleak(s) somewhere?
Are the right plug and wires for blazers installed? (Alco Delco-i think i'm spelling it right)

 

Yes and yes....if not running in the New Year after my buddy removes the various antitheft devices (factory plus 2 aftermarket....no idea why that was done) then it is going to the shop again...but not the rip off dealer.

 

Off to the wrecker yesterday and picked up another VAT module...interestingly enough their books don't list such an animal, but I found one on a wreck. Got home and pulled the old one out and put the new old one in...turned the key and vroom...ran crappy a few minutes and you could hear the thing adjust itself and smooth out. It ran perfectly...instant throttle response, and purred at idle. For maybe five minutes until it warmed up and then just stopped and would not restart. I went out this morning and it fired up cold....warmed up and died. The thing is it runs like new until it is warmed up and then dead as a doornail. I guess it will go to the shop again, I think I have found a reputable one...and see what they can figure out. The one bright note is a couple thousand bucks I was waiting on finally showed up in my account, so I can at least afford a few hours shop time. Oh....and why oh why did GM decide to go with effing piece of crap plastic distributors? I have an aluminum one ordered.

 

I've read through all your posts and I wanted to ask you if when checking your fuel pressure with the key on but engine not running, does your fuel pressure hold at 55psi (or higher) for at least 3 minutes? I had a very similiar problem with mine and I replaced the spider injection because it was leaking. I had great pressure when the key was turned to the on position, but the pressure would drop a few seconds after. Then when I would crank the engine the pressure would come back up to 59psi. For me it was a bad nut kit, or fuel line assembly because of the fast bleed down time. I know you have mentioned that the pressure was good when the key was on, and when you cranked the engine, as well as when it was actually running, but I just thought to let you know the pressure should hold at 55 or higher when not running as well (for a few minutes anyway).

I just saw your photo from I think post 6 and you are correct about the gold color showing signs of leaks. I say those popets on the left side are leaking when vehicle is running and you are going to have to replace spider. Again as I said in last post if pressure drops quickly I would also replace nut kit assembly. The inside of the plenum should not be gold like that is spots, shows fuel leaking. When vehicle is running you can look inside plenum through the hole in the top with a flashlight and see fuel spraying. In your post 8 you say it's all back together, but you don't mention if you replaced the spider or if you just put everything back together because you did not see ant spraying when you cranked the motor (at least that's what I read, unless I missed something you said). I have a spider for this vehicle that should be good if you want to try it. Just email me if you want it.

 

Gee, going on two months of hardly to not running to hardly. In addition to all of the other stuff I just put in a new crank sensor. the old one failed at testing. It fired right up but then gradually ran worse and also won't start without starter fluid. So...next is a new flashed PCM and a brand new aluminum instead of plastic distributor. We ripped out a couple miles of aftermarket alarm crap and all is back to stock. Still thinking about the .44

 

Did you replace the engine coolant temp sensor? Sorry if I missed it but it sounds like from your description, it could be flooding the engine if it's reading at -40d (that's what mine read at years ago when pooched and sitting in my heated garage) when warmed up. They don't always throw codes and that sensor has very high priority over fuel delivery/control/ I believe that in open loop mode (prior to warm up), it has full authority over pulse width. A failing ECT can cause huge pulse swings right down to no pulse/fuel cut out. Obviously if you have a baro code though you should chase that down. I am very interested in your progress/fix.

I also agree very strongly with checking that damn injector harness 5x if you have to. If you search my posts I had a similar problem that was an intermittent open on the ground side. You mentioned that one of the diagnostics had trouble verifying pulse so that's why I was wondering. Sometimes 'warmed up' may mean bounced around enough to short or open a wire harness.

Did you get the fix? Good luck and please let us know as we're all making mental notes no doubt.

A.