I need tech help for my 968
 

I have a 1992 968, when driving the car at about 3-4000 RPM's then I try to accelerate the car has a hesitation. Once the car is revved up its fine (lots of power). But the hesitation drives me crazy. Also when I remove the gas cap it builds up a lot of pressure. I never seen a car build up this much pressure before. I am not sure if the problems are related or not. The timing belt was replaced 5K ago with the wires and plugs. Also I replaced the fuel filter. CAN SOMEONE PLEASE HELP?????
http://forums.pelicanparts.com/uploa...1393639099.jpg

Have you tried posting this on the 968 board on Rennlist?

It is very active and you might get some good info!

Pressure or vacuum in the gas tank? Have you tried leaving the cap loose?

On some cars the gas tank can balloon or be sucked into a wad of metal by venting issues so be careful.

The hesitation can be a lot of things if it is unrelated to your fuel tank issue. Knock sensors, fuel pump, ignition, tps... I would test all the basics and replace any questionable ignition components.

Maybe vacuum leaks as well...

Regarding the tank pressure: The first thing to do is to check that your evap system up at the engine is all working. There is a "rabbit ears" temp switch on the vacuum lines that helps to control the flow of gas vapors from the tank/charcoal canister into the engine, along with 2 diaphragms.

Next are the lines and check valve in the rear of the car above the gas tank. Since you're building pressure and not complaining of gas smells it sounds like the lines are not leaking. However, I would make sure that the check valve is working. This is located in the filler neck region.

If all of that checks out, then it is likely that the charcoal canister needs to be replaced. This is where I am now on my car...

Oh, and welcome to the forum :)

A common cause of hesitation like you describe is the fuel check valve. When you changed the fuel filter did you change the check valve between the filter and pump? If not that is your next move.

See here for details: Changed the fuel pump check valve - Rennlist Discussion Forums

have you done a blink test yet?

Thank you so much. I just replaced the fuel check valve and it took care of the hesitation problem. Now to work on the gas tank vent issue.

What on Earth is a blink test?

it is a test that can be done to check the fault codes stored in the ECU which gets a lot of inputs, any number of which being wonky could cause some of your issues

you have a PM