Help Please!!!!

[Tankster]

I have posted before about my '95 Yukon. I just did a full tune-up to it(Plugs,wires,cap.rotor,pcv,fuel filter).I still have NO power when I put my foot to the floor.I kick it down from 20mph and it will stumble for a second,then will go.I have had it where I kick it down at 60 mph and it will just sit in 3rd at 4000rpm and will not go into Overdrive till I lift the gas pedal.
I am lost with this one.
Will a ignition module cause this?Coil?
Thanks,
Trev

[2000CAYukon]

What is the fuel pressure? Are both injectors spraying fuel?

You need to check the exhaust backpressure looking for a restricted exhaust. You can remove the 02 sensor and drive it to see if the problem improves. This will be loud but can be done if you don't have an exhaust back pressure gauge.

//2000CAYukon

[Tankster]

I have not checked the fuel pressure,will do that this weekend.we changed the coil last night,no difference.What does the fuel pressure have to be(idle,under load).What about pick-up coil in the dist.? It is funny sometimes it works fine when acc. and sometimes it falls flat on it's face.The injectors are flowing fine.
Thanks for your help

[2000CAYukon]

Originally Posted by Tankster

I have not checked the fuel pressure,will do that this weekend.we changed the coil last night,no difference.What does the fuel pressure have to be(idle,under load).What about pick-up coil in the dist.? It is funny sometimes it works fine when acc. and sometimes it falls flat on it's face.The injectors are flowing fine.
Thanks for your help

Fuel pressure specs are 9 - 13 PSI for TBI engines. Not much difference between idle and under load. Just make sure it is good under load. Unfortunately, you need a special tool to test the fuel pressure (there is no test port).

Typically, the pickup coil will affect lower rpm but I guess that is possible. How is the idle quality?

If you have a vacuum pump, you should make sure the MAP sensor holds a vacuum. Also make sure the vacuum hose is in good shape and that it also holds a vacuum. A blocked port on the TBI for the MAP can also cause acceleration problems.

//2000CAYukon

[Tankster]

The idle quality is ok at first then it warms up and is alittle rough.A friend of mine said the TPS(throttle position sensor) will not always throw a code,If it has the right volts.He said this could be the problem.Thing is it doesn't always do this.What do you think?

[2000CAYukon]

Originally Posted by Tankster

The idle quality is ok at first then it warms up and is alittle rough.A friend of mine said the TPS(throttle position sensor) will not always throw a code,If it has the right volts.He said this could be the problem.Thing is it doesn't always do this.What do you think?

Yes a bad TPS can cause your acceleration issues. If you suspect the TPS, hooking up a scan tool to watch the TPS would be a good idea.

The TPS value is also used by the ECM to control the shifting of the trans, so if it is bad, the tranny will not shift correctly (i.e. delayed shifts or shifts too soon).

//2000CAYukon

[Tankster]

We are going to hook the scanner on Sunday.Thanks for all your help 2000CAYukon,hopefully we will figure this out soon.

[2000CAYukon]

Originally Posted by Tankster

We are going to hook the scanner on Sunday.Thanks for all your help 2000CAYukon,hopefully we will figure this out soon.

Also look at (or post) the BLM values. This will tell you if the engine is running rich or lean. Values below 128 mean the engine is running rich and the ECM is removing fuel. Values above 128 means it is running lean and it is adding fuel.

Good luck and keep us posted on any progress.

//2000CAYukon

[Tankster]

Well after going over a bunch of stuff we found out the cat. converter in the exhast had come loose.Only 2 beds in the converter were loose,and turned sideways enough to restrict it I guess.We cut a hole in the converter pulled the stuff out and welded it back up.Run awesome now.Does anyone know where I can get an cat. converter cheap and cat. back exhast.
Thanks