My 88 IROC 5.7 has the following mods: free flow cat, flowmaster muffler, Hypertech chip, tpis airfoil, k/n airfilters, pocket ported heads, zz-3 cam, accel 8.8 wires, and flow improved maf.
The problem is the car runs fine at idle and for the first 100yds or so then it just falls flat until you let of the gas at which time it will roughly idle. The computer set a code 33 and 36. I replaced the maf and it changed nothing code 33 was back immediately. The car hasn't been driven far enough to be able to tell if the code 36 comes back. Fuel pressure at idle is 39 psi when the throttle is applied it raised to 45. When I unhook the regulator and block of the vacuum tube pressure raises to 45 and the car will now run better than it has in a long while but for only about two miles then I have the exact same problem even while the car is acting up I have a steady 45 psi of fuel. When you turn the key on with the engine off fuel pressure shoots up to 45 and then falls quickly to 0. When opening the gas cap air can be heard entering the tank because of a strong vacuum. After along drive if you park the car you can hear the tank actually pop back out. The car also will not keep from popping the 3 amp crank fuse. I haven't checked what effect removing the gas cap and releasing the vacuum has on fuel pressure if any but will do so tomorrow. checked the fuel pressure with the cap on and off there was no change.

Any help on this will be greatly appreciated.
Thanks in advance,
Jason

 

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you said you modded the maf, did you take the screens out and the heat fins?? that might be your code 33..
replace your maf burnoff relay for code 36.. change the maf power relay too...

"When you turn the key on with the engine off fuel pressure shoots up to 45 and then falls quickly to 0. "

soething aint right there, your fuel pump may be going..

 

Thanks Ron, I thought the same thing about the fuel pressure.
I have two MAFs one with both screens and fins removed and one with the rear screen removed only. There is no change between the two.
I will try changing the relays and see what that does for the codes.

 

oh yea,, also make sure your tps voltage is within specs .54vDC, that can throw a code 33.
also make sure there are no vacuum leaks in the air tubing between the tb and maf..
make sure the connections are clean too, no oxidation or dirt on them..
i'd find a STOCK maf and put it on, one with nothing removed from it.. or put the screen back on the maf and see what happens..
and make sure you plug the maf back in, it sounds silly but a lot of peole forget to and wonder why they are getting codes..
good luck

 

Not meaning to rub anything in but because both MAF's are modded can mean both MAF's are bad. These are extremely fragile pieces. Replacing both relays may solve the 36 and the 33.

Leaky connections usually show up as a 44.

 

sounds like the same thing my car is doing. As long as I take off slow and dont bring it up over 2500 rpms it runs ok if I hit the gas or try to go higher with the rpms it will cut out but it wont stall it just looses power It spits out a 33 I tried everything maf, power and burnoff realy nothing. Hope you figure it out so I can try the same thing. GOOD LUCK

 

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Well, I ended up putting a new ecm in shortly after my last post and the car runs great I still have a problem with the 3amp crank fuse blowing. Any ideas on this?

 

That fuse provides power to the cold start system. The power runs through the C207 connector and out through the harness to the cold start control on the front of the intake base. From the cold start control power is switched to the cold start valve (injector).

You might start by splitting the system in half. Unplug and isolate the connector for the cold start control and install a new fuse. If the fuse remains intact, check the cold start control and injector wiring, and the cold start injector coil resistance. If the fuse blows with the cold start control disconnected, check the wiring in the C207 connector and harness.