3500rpm hesitation

[yarnmx5]

I have just removed the aftermarket ECU from my NA6A and have put a reconditioned engine in too. The recon engine was done from the bottom up, new rings etc. The head was shaved 15thou as a clean up, valve reseated etc.

I now have the standard ecu and I am finding besides having less oomph, I have noticed a hesitation under heavy load in all gears between 3500 and 3800rpm....more pronounced when it is cold. It has been so long since I drive the car in standard form, but I can't remeber anything like this before.

I have advanced the timing to about 12 degrees, and will advance it ebven more once I have done more than 1000kms.

Anyone had similar problems.

Also, If you theorectically advacen the timing, does it mean you have less power at high revs....is there a trade off.

[Juffa]

Hesitation usually points to spark plugs and/or leads...or the O2 sensor. The plugs and leads are reasonable cheap and a Bosch O2 sensor can be picked up for under $200.

Re the timing, around 14 degrees should give you max power, at high revs. Moving the timing up to around 18 degrees moves the torque down the rev band, but you will need high octane fuel above 14 degress to fight the pinging.

J

[yarnmx5]

well its defintiely not the leads or plugs, plugs are new, leads are good too \"top gun 8mm\", so maybe the O2 sensor. I did have to have the ignition box replaced during the new engine fit....

[Babalouie]

May be a long shot, but try cleaning the ground strap to chassis connection...the one from the block to the chassis, behind the extractors.

[DanielB]

May be a long shot, but try cleaning the ground strap to chassis connection...the one from the block to the chassis, behind the extractors.

Funny you mention that..

My car hesitates heavily when cold, and just moments ago i noticed that this ground strap seems very dodgy in one section, has a very sharp bend in it which looks like it may be severed slightly.

[Babalouie]

May be a long shot, but try cleaning the ground strap to chassis connection...the one from the block to the chassis, behind the extractors.

Funny you mention that..

My car hesitates heavily when cold, and just moments ago i noticed that this ground strap seems very dodgy in one section, has a very sharp bend in it which looks like it may be severed slightly.

Easily fixed...just buy a short length of 8-gauge amp power cable from Jaycar, and a pair of crimp-on ring terminals to suit, and then make your own earth strap to go alongside the stock one. Should just cost a few bucks or so, and might fix the prob.