Quarterhorse636

If you bore out a 302 to a 306 and now there is more volume to fill would it be best to upgrade maf and injectors? When my car is cold it sounds like it's starving for air and stumbles till it gets warm.

88 orangepeel notch

I don't know your set up or mod list, but just boring to a 306 is going to have a minimal affect. The stock efi is more than capable of compensating. Look at my Sig, I'm still on the stock 19lbs injectors, albeit at their limit. And stock computer controls everything just fine.

Pull your codes to see if any are stored. Might lead you in the right direction to cure your problem.

cema93

Boring that much probably will not be worth the time or money. Like the other person said. Gains would be minimal and probably not noticeable.

Quarterhorse636

its already been bored and I didn't pay for it. I bought it like that . I have codes 41 and 91. im pretty sure I have a vacuum leak but I cant find it. I've done the carb cleaner trick. the vacuum will stay at 14hg or so with no surging then all the sudden It drops out of nowhere to 9-10hg and stays there. if I turn the car off and back on it will go back up to 14 and then drop again. something is causing the vacuum leak is my thought. thanks for your responses.

88 orangepeel notch

I should say boring to a 306 is normal when rebuilding a 302, it's just taking .030 off the cylinder walls.

Also, does your vacuum drop with the idle? That's normal for the idle to be alittle higher at start up, then settle down to 750/850 rpm.

Quarterhorse636

ill be a little more descriptive. my vacuum will stay at 14hg and run decent till I hit a red light and after about 2 minutes of sitting my vacuum will drop to10 hg then run like crap. ill turn it off and back on then it will go back up to 14 till I hit the next red light.
im about to run out of ideas of what it could be.

do you know how the evr (egr? vacuum regulator) works? another forum said to hook up a mighty vac to the port where the vacuum sucks and it should hold pressure. mine did not so I do not think that my egr is working properly because the regulator is not opening the diaphragm on the egr. would that cause this kind of problem?

88 orangepeel notch

Yes, the diaphragm in the EGR is not sealing, its either ripped, tore at the edges, or a pin hole somewhere. This will cause the problems you described. Replace or delete EGR.

Quarterhorse636

I just replaced the egr and egr postion sensor and its still doin the same thing. I got a code 96. would that cause the symptoms?

88 orangepeel notch

Did you clear the old codes after you can installed the new parts? And what does code 96 represent?

Quarterhorse636

96 is somethin about the secondary fuel pump circut but that one went away. It has come up before but it went away before also. I think I'm on to somethin though. I put a 70mm maf housing and kept the stock maf sensor. Now the only code I have is 91 and my car doesn't miss and the idle doesn't drop anymore. Maybe because before the engine was sucking in even just a little bit more air the air current wasn't hitting the maf sensor correctly? I'd but it hasn't acted up since yesterday. Still starts and dies in the morning though.