My 91 mustang is gettin real bad gas milage, and i also noticed that if im going say at 3k rpm and i let off, it seems to kinda jump a little bit as the rpms are falling. Anyone have any ideas? what do u guys think i should try? Injector cleaner? im also gettin bad fuel pressure heh
Here's a way to test for leaking injectors: Connect a rubber hose to the injector where the fuel rail would normally connect and apply compressed air to the rubber hose. I hook the whole thing up, apply compressed air to the injector and stick it in a paper cup of soapy water. If the injector leaks, it makes bubbles.
Second method is the 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 will shut off power to each injector, one at a time. When it has sequenced through all 8 injectors, it will flash 99 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.