Irritating problem - NEED HELP!!!PLEASE!!!!!

Well it would help to know what kind of vacuum you are pulling at idle. If it is a fuel related issue with #8 cyl I would suggest swapping injectors to see if its a bad injector. Good place to start. What is your engine combo also (not in your sig) this may have something to do with it also. Good Luck i will try to check back soon

jbj454 said:

actually its a friends car that I'm working on. Its pulling about 15 in. whatever vacuum at idle. It has a 306 with a Vortech S-Trim. Car was running fine until an Edelbrock RPM 2, long tube headers, and 3" x pipe was installed. Changed o2 sensors also. I was thinking of changing the injector to another cylinder on Wednesday. It has 36 lb. injectors at the moment. thanks!!!!!

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That would be useful info to put in the original post.

Do a cylinder balance test to isolate any faulty injectors.

Cylinder balance test:
Warm the car's engine up to normal operating temperature. Use a jumper wire or paper clip to put the computer into test mode. Start the engine and let it go through the normal diagnostic tests, then quickly press the throttle to the floor. The engine RPM should exceed 2500 RPM's for a brief second. The engine RPM's will increase to about 1450-1600 RPM and hold steady. The engine will shut off power to each injector, one at a time. When it has sequenced through all 8 injectors, it will flash 99 for everything OK, or the number of the failing cylinder such as 22 for cylinder #2. Quickly pressing the throttle again up to 2500 RPM’s will cause the test to re-run with smaller qualifying figures. Do it a third time, and if the same cylinder shows up, the cylinder is weak and isn’t putting out power like it should. See the Chilton’s Shop manual for the complete test procedure

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.

See http://www.troublecodes.net/Ford/
OR
See http://www.dalidesign.com/hbook/eectest.html for more descriptive help
OR
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at Walmart.

Fuel pressure OK, the injectors are not firing, OR one or more injectors stuck open

The red wire on each injector is powered up whenever the ignition switch is in the Run position. The computer provides a ground to complete the circuit and fire the injector. The injector must have a ground to squirt fuel on command. A short to ground in the injector return wiring can cause one or more injectors to be continually open or triggered


A.) A Noid light available from Autozone, is one way to test the injector wiring. If the light stays on constantly, either the wiring has a short to ground or the computer has failed
B.) I like to use an old injector with compressed air applied to the injector where the fuel rail would normally connect. I hook the whole thing up, apply compressed air to the injector and stick it in a paper cup of soapy water. When the engine cranks with the ignition switch on, if the injector fires, it makes bubbles An injector stuck open will release a continual stream of bubbles. Cheap if you have the stuff laying around, and works good too.


The wiring for the injectors may have some bare spots in it causing the injector to computer control wire to ground out. This would cause the injector to remain on anytime the key was in the Run position. Remove the injector wiring connectors from the injector. Note that each injector has one red wire for power and a non red wire (wire some color other than red) for computer controlled ground. With the key off, use an Ohmmeter between the non red wire and ground. You should see more than 100 ohms resistance.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif

i bet you its a real simple problem set your timing correctly mine was off just a little bit and it lagged big time