My 86 tpi has a bug i cant get figured out. When i first start it up for the day, it idles bad, like its missing alot, when i give it some gas, it will stumble some, but after about 30 sec, its completely cleard up and runs fine with no missing at all the rest of the time. ONLY on a cold startup. If I come back an hr later and it's still got some heat in it, it starts up and idles fine still.

Here's all that has been done to it since I bought it,

new fuel pump, rebuilt injectors by cruzsin performance, new fuel pressure regulator, new upper, lower intake gaskets, new egr, egr temp switch, new vacuum hoses, new pcv valve and pcv molded hose to intake, new radiator, new harmonic balancer, new ac delco rapid fires, new ac declo plug wires, hooker 2055 headers and 3 in y pipe combo, !cat, !air, swapped in a different complete distributor with icm and all, and still runs the same, new iac, and completely reconditioned wiring harness. New MAF, MAF burnoff, and Fuel pump relays. Maf sensor is newer, only about 8 months old, and the o2 sesnor is new. ALL new parts are AC Delco factory replacement parts.

One thing I do know, is that I have the base timing set at 0 degrees, I am going to set it to 8 degrees BTDC like everyone here likes, and I am starting to wonder if this is the cause. Otherwise, any ideas are welcome.

 

i had this problem on my 89 305 tpi. my teacher suggested the cts located in the intak manifold by the thermostat housing. to see if this is reading properly get a scan tool and plug it in on cold startup.
i didnt do that.
instead on cold startup i tried unplugging my maf and the idle imediately cleared up. i have been running with the maf unpluged for over 2 week. i plan tor get a new on if cleaning the maf with maf cleaner doesnt work. next time you start up cold unplug the maf and see if that clears it up.

some may say that it will clear up because the car is than running in ipen loop due to the maf being unplugged, and thus running wicher. i disagree with this because on cold start up the car is already in open loop.
hope this helps.

 

What about this vent valve for the gas tank? I just realized I haven't had any pressure in my tank for a good while. It never relieves pressure when I remove the gas cap. Does this possibly have anything to do with it?? And thanks for the suggestion, I will certainly try this out.

 

IMO you shouldnt get a hiss when you remove the gas cap. if the cap is working properly it should vent automatically and not just when you remove the cap. i believe that that is one of the tests they do for emissions here in illinois. some people will say that removing the gas cap releives fuel pressure but as far as i know that is not the case. ill ask at school just to make sure though.

 

Well, come to think of it, ever since I got a new GM gas cap for a replacement it hasn't hissed at me. Maybe it is a good thing and says it's working like it should?