still rough idle

[1bad89]

since ive owned the car its always had a rough idle. Thru the rpm range its fine and pulls hard.
when i first start it no matter cold or hot after the initial start and once the engine drops down to normal idle then it starts missing. Ive tried pulling each wire while running and all cyl's seem to be the same as far as rpm drop.
Its got new plugs, ( rn12yc gapped at .035 ) wires, cap, & rotor ( a-zone brand ). MP performance computer, MBC, new timing belt ( set correctly ) timing set at 12 deg. the motor has 128k on it. My boost gauge shows about 16in. vac at idle. fuel press. is 56psi with vac line disconnected.
I just cant pinpoint the problem and dont wanna start part swapping.. any ideas ??

** update ** its a TII motor, on the throttle body there is two metal nipples sticking upward, one is larger in diameter than the other. The larger one is where the hose that comes off my pcv goes and the smaller one was capped. I use it now for my boost gauge. Just screwing around i swapped the hoses around and the motor smoothed right out. Any ideas whats going on ???

[shelbymonster]

try gap to 0.025 mine always missed a bit

[cordes]

The two nipples on the top of the throttle body are not both vac. One of them is in front of the blade the other is behind. I don't use either of them so I can't be of much assistance other than that.

ETA: That is much to small of a source to use for your PCV.

[1bad89]

ill try droppping the gap on the plugs...
thats where the pcv is hooked up per the factory ...

[cordes]

ill try droppping the gap on the plugs...
thats where the pcv is hooked up per the factory ...

I believe you may have your terms mixed up. Unless I'm way off base, the charcoal canister should be hooked up to the TB, but not the PCV. That goes to the intake and also the air box.

Further more, you should not need to close the gap in your plugs to get a good idle.

[1bad89]

The hose that "t"s off my pcv goes to the larger nipple on the TB and the other nipple was capped off. I use it now for my boost gauge.
That's the two lines I swapped around. Basically I applied strong vacuum to the pcv and the car smoothed out. So.. What is that telling me?

[cordes]

The hose that "t"s off my pcv goes to the larger nipple on the TB and the other nipple was capped off. I use it now for my boost gauge.
That's the two lines I swapped around. Basically I applied strong vacuum to the pcv and the car smoothed out. So.. What is that telling me?

Perhaps that the PCV wasn't correctly hooked up? There should be a large fitting on the intake feeding the PCV and others, while the other side of the PCV goes to the air box. You may want look into how to get that set up properly. There are a couple schools of thought, but if your only source for vac on the PCV system is coming from the nipple on the TB, that is bad news.

[1bad89]

no, its not my only source, i truly think its hooked up properly from other pics of engine compartments ive seen.

one thing i forgot to mention, when i was checking my timing the mark on the flywheel was kinda moving around, kinda blurry looking. Ive read a bad HEP can cause that, which in turn can cause the poor idle ???

[cordes]

no, its not my only source, i truly think its hooked up properly from other pics of engine compartments ive seen.

one thing i forgot to mention, when i was checking my timing the mark on the flywheel was kinda moving around, kinda blurry looking. Ive read a bad HEP can cause that, which in turn can cause the poor idle ???

It can jump a little bit when setting the timing an that won't be a huge deal. Pull of the dist cap, and hep to make sure the shutter wheel is in there tight.

[1bad89]

I pulled the dist cap and checked under the hep and everything is tight

[cordes]

I pulled the dist cap and checked under the hep and everything is tight

I'm sure you have, but you are unplugging the coolant temp sensor when setting the timing correct?

[1bad89]

yep i unplugged it... this one has me stumped..

[cordes]

yep i unplugged it... this one has me stumped..

So long as it is just a little blurry that is normal then.