Is the backfire on accel from the throttle body or the tail pipe? Does the SES light come on for the bulb check? Is the SES light on while driving? Does it blink when the engine acts up on accel? Are there any DTC's in memory?

 

Yesterday we got a light up while test driving it, it came up with:

p0151
p0131
p0143
and I think
p0137

we did some diagnostics after that, unhooking o2 sensors and driving it, the symptoms were the same.

I did some tests just now at lunch, key on engine off fuel psi was about 60, started it up and it ran about 50 steady. Turned key off and pressure slowly dropped over about 5 minutes to 30, not sure if that is proper test or if just on key on engine off. still think that could be my gauge and will probably go rent a better one to confirm either way.

Engine vacuum was registering at only 15. Hmmm. open the throttle and it acted as it should. Then my wife says, hey look at this, and as I was opening the throttle the top of the meterbody spider where the electrical and fuel lines hook in was sucking into the intake manifold by about 1/4 inch. I suppose that could be my whole problem. I thought I had a good seal there. I bought a new gasket set for the last time I took it apart and put it back together. Is there a trick to getting that thing up? I was using vicegrips towards the fuel regulator end while prying up with a door panel tool where the fuel lines hook in. very brutal, but I could devise nor discover on the internet a better way.

That has to be my next task to fix that, unless I should replace / warantee out the FPR and put whole new gasket set (third) into the thing.

Before the engine had too much fuel and too much air and said me likey, but me too stinky! Now engine has right amount of fuel and too much air and says me chokey me chokey.

 

All of those DTC's are caused by a lean condition, the leaky O ring is probably the cause. It can also cause backfire on accel through the throttle body. When you install the plenum, make sure the O ring is not cut or twisted, and that fits in the groove on the fuel meter body. Coat the O ring with clean motor oil and make sure the inside of the plenum is clean where the O ring seals. Shouldn't need any tools to make the O ring seal, just constant, even, downward, pressure. Should just pop in.

Fuel pressure: GM does not publish any "engine running" fuel pressure specs. There are far too many variables involved. See post #3 for fuel pressure specs & procedure. Leakdown to 30psi is too much, better make sure the fuel pressure tester is not leaking before jumping to conclusions.

 

Thanks for the continued comments. I will go get another tester and try it, then will retry that seal. It seems to me though that the bracket the spider sits in doesn't push it up enough, and it has to be pulled up. will try oil on the oring, maybe that is my only problem. Wasn't sure if I was supposed to replace the bracket.

 

Bracket? Did you install the upgrade injector that relocates the injectors to the intake ports? If so, yes, you need the upgrade bracket.

 

no I simply rebuilt the spider I already had. I just saw they sold new brackets for like 15 bucks at autozone, thought maybe it was one of those things that needs to be replaced.

 

I thought I read this from many posts ago and was correct, could the the junkyard spider be the updated spider without the braket update. I am not qualified to identify the update as I have never seen one. I know to make them fit properly they need the bracket update.

 

The meterbody I used was exactly the same as came out of my truck. In retrospect I should have just rebuilt that one and saved $30 bucks, but now I have an extra one to play with. interesting thought though, I will compare them thoroughly if I pull the cover back off today or tomorrow. one other possible vacuum leak I found. there are 4 twisty screws to lift up the air intake and change the airfilter. one of the corners where the screw is is cracked, so I might not be getting be best seal right there where the airfilter is. Would this cause vacuum issue? More than the spider being sucked in and out of the plenum by a quarter inch?

 

IMO you have a mis-match somewhere. One out of four "twisty screws" anywhere in most cases will not cause SH*T. For the spider to move 1/4 inch you would have to have all kinds of mis-alignments period. It's just not supposed to due that!

 

I was talking about one of the screws cracking the air intake housing directly above the airfilter. I do agree with you. something's just not quite right. Time to tear it back apart. It's about time to get out the saddle and get me a horse.