Wrong Setup?

885.0conv · Sep 14, 2012

Recently I was getting the sign on valve seals leaking so I changed them and decided I should change the spark plugs as well. When I pulled the 3, 4, and 7 plugs they were coated with oil. I put the engine back together and it sounds a lot better. The TFS heads on the car are the old style and when I bought them they were ported to the max (stage 3) and have 1.6 roller rockers in them. I am running the stock cam. The problem I am having is from a dead stop at WOT there is a hesitation to get up to 2.5K-3K and then the car rockets. On the highway the car is a beast and pulls from 3.5K to 5.5K when it shifts. At idle the vacuum is 10-11 and stays between the 10-11 with a slight lope. My question is with this setup is that normal to have the hesitation and is the idle vacuum too low with this setup.

Rick 91GT · Sep 14, 2012

Sounds like you have a vacuum leak, the stock cam will pull over 16" easy, most in the 19" range with idel around 750-800rpm. That could cause the issue you are seeing...

885.0conv · Sep 14, 2012

Rick 91GT said:
Sounds like you have a vacuum leak, the stock cam will pull over 16" easy, most in the 19" range with idel around 750-800rpm. That could cause the issue you are seeing...

I was hoping you would not say that. One thing I have done is block all the tubes coming out of the intake and measured the vacuum which is still at the 10-11. So to me it looks like vacuum is being lost inside the engine. I was reading about the leak down test which I guess could be where I am losing my vacuum. I will try to preform one this weekend. Thanks for the reply.

gearheadboy · Sep 14, 2012

Um...a leak down test measures how the rings/valves are sealing. Does not detect a vacuum leak. You may need the can of carb cleaner at idle method of leak detection. But be careful and keep it away from the plug wires. With it at idle spray a little around all the intake gaskets and injectors and listen for an idle change. Use a pair of pliers to squeeze off one vacuum line at a time to see if it changes as well. Remember the brake booster hose too if you have one. I feel that you probably have a spark miss. Wire arcing somewhere or a cracked plug.

gearheadboy · Sep 14, 2012

And if the vacuum gauge is bouncing you could have a broken spring. Ignition timing will also effect vacuum.

885.0conv · Sep 16, 2012

gearheadboy said:
And if the vacuum gauge is bouncing you could have a broken spring. Ignition timing will also effect vacuum.

I will check for leaks also as for as the timing I believe its is set at 12* should I go more if I don't find a leak.

gearheadboy · Sep 16, 2012

12-14 with the spout connector unplugged.

Rick 91GT · Sep 18, 2012

un plug the brake booster and see what the reading is then, I wonder if the diaphragm is leaking a little.

jrichker · Sep 19, 2012

Finding vacuum leaks

Revised 04-Aug-2011 to add pintle cap, PCV grommet & power brake check valve grommet to checklist.

There is no easy way to find vacuum leaks. It is a time consuming job that requires close inspection of each and every hose and connection.

Small vacuum leaks may not show much change using a vacuum gauge. The range of "good readings" varies so much from engine to engine that it may be difficult to detect small leaks. The engine in my first Mustang pulled about 16.5" of vacuum at 650-725 RPM, which I consider rather low. It was a mass market remanufactured rebuild, so no telling what kind of camshaft it had. Average readings seem to run 16"-18" inches at idle and 18"-21" at 1000 RPM. The only sure comparison is a reading taken when your car was performing at its best through all the RPM ranges and what it is doing now. Use one of the spare ports on the vacuum tree that is mounted on the firewall near the windshield wiper motor.

Use a squirt can of motor oil to squirt around the mating surfaces of the manifold & TB. The oil will be sucked into the leaking area and the engine will change speed. Avoid using flammable substitutes for the oil such as propane or throttle body cleaner. Fire is an excellent hair removal agent, and no eyebrows is not cool...

The vacuum line plumbing is old and brittle on many of these cars, so replacing the lines with new hose is a good plan. The common 1/8” and ¼” vacuum hose works well and isn’t expensive.

The PCV grommet and the power brake booster check valve grommet are two places that often get overlooked when checking for vacuum leaks. The rubber grommets get hard and lose their ability to seal properly. The PVC grommet is difficult to see if it is correctly seated and fitting snugly.

Fuel injector O rings can get old and hard. When they do, they are prone to leaking once the engine warms up. This can be difficult to troubleshoot, since it is almost impossible to get to the injectors to squirt oil into the fuel injector mounting bosses. If the plastic caps on the fuel injectors (pintle caps) are missing, the O rings will slide off the injectors and fall into the intake manifold.

Fuel injector seal kits with 2 O rings and a pintle cap (Borg-Warner P/N 274081) are available at Pep Boys auto parts. Cost is about $3-$4 per kit. The following are listed at the Borg-Warner site ( http://www.borg-warner.com ) as being resellers of Borg-Warner parts:
http://www.partsplus.com/ or http://www.autovalue.com/ or http://www.pepboys.com/ or http://www.federatedautoparts.com/

Most of the links above have store locators for find a store in your area.

Use motor oil on the O rings when you re-assemble them & everything will slide into place. The gasoline will wash away any excess oil that gets in the wrong places and it will burn up in the combustion chamber. Heat the pintle caps in boiling water to soften them to make them easier to install.

Diagram courtesy of Tmoss & Stang&2birds

Vacuum leak due to slipped lower intake manifold gasket...

Ask Nicoleb3x3 about the intake gasket that slipped out of place and caused idle and vacuum leak problems that could not be seen or found by external examination. I don't care what you spray with, you won't find the leak when it is sucking air from the lifter valley. It simply isn't possible to spray anything in there with the lower manifold bolted in place.

Wrong Setup?

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