jxxc41985

Hello, I'm new here so not sure if i'm doing this right...
Here it goes.. I have a 85 C4, stock everything, 85K,
I went to change out the injectors, it didn't run right, cheap injectors i think, anyway I put the original injectors back in and now the car won't run right
when you start it, it won't stay running unless you tap the accelerator, but when you tap it the rpms surge up to 2000-3000 then right back down, then you have to tap it again(accelerator)
after it warms a bit you can feather the throttle and keep it around 1300 rpms but back fires and sputters, I can get it to drive but when you go it surges and takes off for about 3-4 secs
then drives kinda normal for 15-20 secs then surges again... any help would be awesome
thank you

icsamerica

I would suggest you may have a large vacuum leak, Consider rechecking everything for proper fit and propper connections. A good place to get TPI injectors is South Bay Injectors in Long Island NY

jxxc41985

Thank you, I will look into that...
would low fuel pressure cause the same symptoms?
my fuel pressure is around 25-30psi

icsamerica

YES. Should be 40 to 43 PSI

ssro

So first thing i would do is change both fuel filters, this is mostly your problem, 1 is in the tank and 1 under pasenger side, second could be a vacumm leak but i dont thinck it be the problem. Fuel filter is the compliss, ive repaired cars before that had the same simptoms.

Joe C

actually, the normal running fuel pressure for an 85 is 34-39 psi. there are too many loose ends here. i suggest the OP get a factory service manual, start with the basics, and run a proper fuel system diagnosis. if he doesn't have a factory service manual, he should get one. we could second guess all day on this one.