[jb92563]

I recently had an AOS failure and proceeded to replace the AOS.
After the replacement the engine idles poorly and has hesitation at various throttle settings it seems.
I cleaned the TB and got the new MAF installed and it seems a lot better and it has not thrown any codes yet but it has this odd hesitation.

I would be cruising at 4000 rpm and 50 mph with steady pressure on the throttle pedal and I can suddenly feel a hesitation and small loss of power for a second and then it carries on again with regular power for about 5 seconds(random interval actually) and then has this hesitation again.

Also when punching throttle it revs right up and at over 5k revs it hesitates momentarily.
It does idle fine, and I have reset the computer and done the DME adaptation thing with the ignition on for 1 minute and then off etc.

I did get a few P0507 codes the Idle Air control Valve but since the new MAF install have not gotten that or any other codes.

Seem now like the issue is with higher rev range.
I do have some suction at the oil cap but its not at all strong and the cap come off easy so I don't think its an AOS issue anymore.
I have tried but can not detect any vacuum leaks using TB cleaner spray around hoses.
The gas cap rubber ring does look like its a little cracked so I plan to change that as well since anything vacuum related is the only thing I can think of at this point.
It throws no codes since the new MAF is in place but I suspect a vacuum leak or something else perhaps, although I have not found it yet.

I decided i just dont want to blindly start replacing things and needed to determine how to figure out the problem and fix the actual cause of the problem.

After a bit of online sleuthing I found a series of excellent videos that explains how to use your Diagnostic tools like an ODBII reader or Durametic and determine the nature of your problem without replacing or testing unnecessary components.

I have a Durametric and now know how to use it to figure out what is going on.

Watch these videos and you will be able to save yourself a lot of time and cost and be able to verify repairs done by yourself or the shop.

The first 2 are about learning how the Fuel Trims work and what you can diagnose with them. Fuel Trims Part 1 Fuel Trims Part 2

The 3rd video takes a scenario from start to finish describing the technique to diagnose and verify resolution of an engine problem. Practical engine problem solving Part1 PEPS Part 2

I will do likewise this weekend with my own issues and document how I determined what the problem actually is and verify its resolution.

Wish me luck.