86 c4 running rough

[nram007]

When i start my 1986 C4 vette it runs perfect then when the idle kicks down from the startup, it starts to run rough, knocking and pops when you give it gas. The motor is a L98 that was rebuilt two years ago.

Fuel pressure is 34PSI at rough idle
New plugs, rotor, dist cap, wires, and fuel pressure regulator.
Maf sensor is a new digtal one, also has SLp headers with no emmsions on it, no air pump.
Maf relays are also new.

Not sure it the Vaccum lines are route or connected properly they do not look right to me.
where could i get a vaccumm line diagram?

but you could please give me help fixing this C4.

thanks nick

[stevebz06]

I believe the Haynes service manuals which were designed for idiots like me would have a picture of the correct routing. On my 86, I found that a number of the tubes had rubbed holes in them and were contributing to vacuum leaks that didn't help it run any smoother.

Did this rough running begin about the time of all these mods were made?

[nram007]

this car has been a head ache since i purchased it. which i dont understand because ever hotrod i see with a TPI motor in runs perfect.

[stevebz06]

I forget the exact specs, but the fuel pressure sounds a little low. I would also check for vacuum leaks, dirty injectors, ignition problems, etc. Also, check the throttle body and see if it needs cleaning. A saturated charcoal cannister could be causing problems.

There a bunch of things to look at, but I'm a little suspicious of the add-ons since an air leak could cause problems like what you are describing.

[nram007]

can anyone else help??

[nram007]

can anyone else help??

[c4c5specialist]

HI there,
The fuel pressure is ok.
HOwever, you may want to test the injector resistance.
16.5 ohms is what you should have for each injector.
Post your results.
Allthebest, c4c5

[nram007]

This car had the injectors replaced once with accel fuel injectors will the residence be the same??

[c4c5specialist]

HI there,
The resistance should be the same.
Allthebest, c4c5

[nram007]

ok i tested my injectors

starting at front drivers side injector and going towards the rear of the motor.
17.5
17.5
17.5
18.0

then passenger side of the motor from front to rear
16.5
16.5
16.5
16.5

i tested each one 3 times and got the same numbers all 3 times

so should i change out all 8 injectors?
can you recommend good injectors that i wont have this problem with?? acdelco?