intake manifold removal

[johntom]

Hi
when removing the intake manifold on a 1990 GT, will the manifold come off with the injectors/fuel rail still in place or will i have to remove them first?

[Mrmerlin]

it is easier to remove the injectors and the rail above them, this gives access to the intake nuts.

BUT first,
use compressed air to blow out the injector seats and the V .
Cover the intake where the MAF sits so dirt wont go in,
WARNING if you dont do this first there is a good chance you have the sand fall into your cylinders,
after this spray some WD40 onto the injector lower seals ,
this will assist in them sliding out of the intake manifold. Use a bit of anti seize on the collars of the pipes and the threaded portions of the dampers and FPR when you refit so they wont seize

[tisilrad]

be careful with all the plugs for the sensore..one at the MAF, one at the throttle position sensor, and the one under the intake at the idle air control. there are several vacuum hoses too...tough job.i am just putting mine back on my 87 s4. I would suggest replacing the o-rings on the injectors when you reinstall and replace ALL rubber lines/hoses...

[riber.bentsen]

This is a great write-up on the rr-procedure of the manifold, including referb..

Executive Summary:

[johntom]

WOW, what a write up!
basically my car won't tickover properly when cold, it stubbles around 400-600 rpm and cuts out etc unless you keep your foot on the gas (it tickes over smoothly around 1500rpm). When warm the tickover is around 900-1000 rpm and still lumpy. I have tested the vacuum (warm at 900 rpm) from the front f p damper and get 12"HG ?

[steve davies]

The vacuum is way low, should be nearer 21in HG. Sounds like an air leak.

[johntom]

Hi
are there any suspect areas or pipes that are most prone to leaking, or could it be anywhere?
Whats the best approach to finding the leak and would a leak make the warm tickover high (at 900-1000 rom)?

[steve davies]

Yes leak would make idle high at warm, 900 to 1000rpm would seem typical. Check under the air box, there should be a 5 way vac splitter there, check connections. Main vac feed comes from under throttle body to the 5 way connector. Also check the 4 way(?) connector naer brake booster/firewall. One of these connections dissappears through firewall to vac actuators in dashboard. Try plugging this at the 4 way ( use golf tee) in case you have leak under dash

[johntom]

Hi
I have already replaced the vac hose from the throttle body to the 5 way splitter below the airbox with new silicone vac hose and 't' pieces (from throttle body to the pressure regulator and dampers). I used 4mm ID piping, the original rigid plastic has a smaller ID (3mm?), would this increase in pipe diameter effect the vacuum pressure? Obviously I am aware there's still a leak elsewhere which needs finding, just curious about the pipe diameter?

[steve davies]

I think the original vac pipes were 3.5 ID

[steve davies]

My concern would be about the fit of the larger pipe on the vac nipples etc. They need to be tight