I was hoping I may draw on the helpful insight of owners who have perhaps unfortunately experienced this issue with their own vehicle before I mortgage my first born for the potentially unlimited EFI diagnostic fee.

Vehicle is a 2001 KJ Verada Xi, 85,000km fitted with K&N panel air filter, pacemaker extractors, Lukey type muffler and new battery recently fitted.

Problem is severe intermittent acceleration problems. At slight to moderate accelerator depression, symptoms range from surging to significant missing and at times backfiring with loss of power to neck snapping instantaneous restoration of full power. The issue occurs irrespective of speed, gear, or cruise on or off. Loss of power is so dramatic that when driving at highway speed with cruise on, speed will drop, the auto will drop gears only to have 4000 revs on the tacho but no acceleration.

At full accelerator depression the engine operates normally at all times and the revhead approach has become the only way to drive successfully atm - not so good in peak hour traffic.

At idle air con off or on in drive, idle speed varies from lumpy seat shaking near stalling low idle (near 0 on the tacho) to a corrected smooth 1000rpm + idle.

In terms of intermittence, I can have these issues and their correction many times while driving. Then there are times when I start the car and have a hassle free drive. All quite strange. Car always starts and idles well intially.

I have started with the basics and have replaced spark plugs and leads and inspected the dist cap and rotor with no obvious signs of arcing. I have purchased a uni fit oxy sensor but to date have not been able to decipher the wiring code (despite calling the distributor ACA and Autobarn where I got it from). I can't get any fault codes out of the ECU through probing with a test light as per instructions in Gregory's manual.

This is the best car I have ever driven to date, but I am growing to hate it atm. Your help would be appreciated. Your recommendations on EFI technicians in Brisbane would also be appreciated just in case this is a one off possessed vehicle that needs professional help.

Thanks for your assistance.

Cheers

Carl

Hi I doubt it’s the oxygen sensor, I never heard of faulty oxygen sensor causing such problems. Have you had you fuel filter changed recently, this can explain sudden power losses also the idle issue, blocked filter can do this ive had similar problems not in my magna tho, but the problem was just random power drop outs, I have pulled out my filter it was very dirty, so I replaced it & it was all good since. I know its along shot, if you can put it in yourself all its going to cost you is $20.

As said, will not be the O2 sensor. Severe cutting out sounds like a crank angle sensor or maybe even air flow sensor.