Hi guys,
I have a head-scratcher someone may be able to point me in the right direction with....
1989 FC JDM Series 5 stock standard apart form Trust BOV and exhaust.
Drove perfect for the first year of ownership. Faulted (below symptoms) one time. Fine after that for about 6 months.
Then faulted more regularly - about once very few drives.
Now its faulting all the time 100% without fail.

Symptoms
Starts and idles perfectly. Revs are smooth through the whole range while stationary. Will do this all day long.
Drives around at low speed (eg car park or driveway) no issues.
As soon as the car is under any sort of load/boost/acceleration/throttle input it misfires and bucks. It is undrivable almost.
Can drive it with about 20mm of peddle input under no boost to get you home. As soon as you introduce any sort if accelerator input it just misses and bucks again.
Turning the key off and on while driving will improve it for about 20 seconds but wont rev above about 5000rpm, before it happens again.
When misfire happens and while the car is stationary the symptoms are still there until switch off any on again and it again rev fine when stationary once again.

When it was doing this intermittently earlier on in the piece as soon as you turned the ignition off and on when it misfired it would come right for a period of time.
Now it wont.
Does this both hot and cold.
When it is doing it there are no other abnormalities like electrical power surges, strange noises etc.

Have just replaced spark plugs, fuel pump, fuel filter, inlet manifold gaskets, vacuum lines etc. TP sensor SEEMS to be working as it should. Compression good, never been hot, fresh fuel, clean tank.

Are the above symptoms pointing to ECU/AFM/OMP/fuel cut or a combo of them all?
Is this a known fault with the FC?
Any advice pin pointing the problem is appreciated.

Thanks

 

I am not certain about JDM vehicles, is there something like a MAF on these? Have you checked for ECU codes? If the JDM models have them. There are some pretty knowledgeable people here that can help.

 

first step is to check for codes, you need some kind of LED in the diagnostic port, as there is no check engine light.
there is a 2 pin green connector by the battery, LED goes there and then you ground the other 1 pin Green connector, and turn key on with engine off and the light should blink codes and you go from there

 

Check codes, but I would say making sure there isn't a major vacuum leak is going to be priority 1

 

Stinks of a TPS that needs some adjustment....