Im troubleshooting my car (93 A4 T/A)- it pretty much falls flat on it's face over 2500rpm. Simply put- the more throttle I give it, the more it looses power, misfires & etc but holds a perfect idle, no SES light, and motor itself sounds great at the lower rpms w/ no abnormal noises. My economy fell to sub 14mpg. A new symptom Ive never had w/ any of my previous failing opti's is the tach jumping around in sync w/ the misfiring.

I checked the fuel pressure at the rails and it was only about 30 psi. I bumped it back up to 45 psi w/ my adj press regulator and that seemed to take care of 'some' of it's driveavility issues (idle & low rpm's). The injectors are stock and they are 160K old. Im not quite ready to buy new ones as I prob should due to thier age and mods done to the car, but want to find my exact prob before I start throwing parts at it. What impedance should the injectors read? Im sure the opti may also be part of the prob also, but I'll get there w/ that.

I did have the coil tested out already and it's ok and new plugs are installed.

thanks!

 

ideas?

 

John, sounds like a fuel pump issue...

You need to check the fuel pressure while driving and see if the pressure drops when the car "falls on it's face"...

Also, another thing is to check plug gaps and the ignition coil. As RPMs go up so does spark demand. A weak coil will show itself more at higher RPMs than idle.

 

Not to mention the fuel injectors could ohm out ok and have a bad spray pattern from being old and dirty or something. Try and take them out and clean them and see if it helps some too...after you check your fuel pump as "95TA-The Beast" suggests. It sounds like the pump to me based on what you've typed so far.

 

The stock injectors are 12 ohms, FYI.

 

If your tach is jumping around then that could be a sign of the opti going out. At idle my tach would be eratic, opti finally went south, installed a new one, Tach was fine...

 

Kill the opti.......... looks for hammer......