Thread: 3.9 no Power. Please help

Have you had the exhaust manifolds off? Sometimes people put the gaskets on upside down and half block the exhaust ports.

What plugs are you running?

Try adding an O2 sensor and a Jaycar mixture readout kit to see if it is too lean/rich.

Try running 10 degrees BTDC. I haven'tseen a petrol 3.9 with problems at 10.

lift your plenum cover and look for loose trumpets.

I remember reading on the pistonheads site a similar problem to this though it appears you have already checked it. the owner said he had tested the tps and it was fine and had full travel at the throttle body but that was when he was pulling on the cable in the engine bay. When the accelerator pedal was fully depressed and he checked the tps reading on the back of the ecu it wasn’t giving the wot reading even though the pedal was to the floor. Adjusted the cable properly and he had a new car with a top end.

Originally Posted by pibby

I remember reading on the pistonheads site a similar problem to this though it appears you have already checked it. the owner said he had tested the tps and it was fine and had full travel at the throttle body but that was when he was pulling on the cable in the engine bay. When the accelerator pedal was fully depressed and he checked the tps reading on the back of the ecu it wasn’t giving the wot reading even though the pedal was to the floor. Adjusted the cable properly and he had a new car with a top end.

Yes. something like this is my theory as well, I will check it out as your guy did, cheers.

I have posted how to adjust MAF and TPS in the files section.
Search for uploads under my name and you should come across it.
Would put the link up but I'm on my iPhone using tapatalk so can't access files...

It may well be a MAF issue. If the TPS is at fault, it will feel like a big miss or temporary stall. Any breaks in the tracks will effectively cut throttle signal to the ECU so only getting half throttle and it holding there would eliminate the TPS.

Cheers

Andrew


Sent from my mobile tellingbone using rock carvings.

Hi all, its a long time since I was playing with V-8 's , I suppose you have changed the fuel filter on rear of chassis, UK cars dont get these changed as the steel unions rust into steel filter and shear pipes when undone, ( pipes were no longer available )
as the filter is very fine, it can block restricting fuel volume,
The other thing is to take off the cat front pipes, and fit the earlier non cat front pipes, but you have to change the tune resistor, pluged into the loom nr ecu.
Anthony

In addition to all the other ideas...sounds characteristic of a vacuum leak. Every time I've done a work around the driver's side of the motor on my 90 3.9 I've knocked the vacuum pipe out of the valve on the charcoal canister - not much securing it. Still idles and runs smooth, almost no hissing, but flat throttle response.

Originally Posted by TOUTERRAIN

, UK cars dont get these changed as the steel unions rust into steel filter and shear pipes when undone, ( pipes were no longer available )

The other thing is to take off the cat front pipes, and fit the earlier non cat front pipes, but you have to change the tune resistor, pluged into the loom nr ecu.
Anthony

Luckily rust is not a huge issue in Australia. Australian spec vehicles didn't get cat pipes either.

Originally Posted by TOUTERRAIN

Hi all, its a long time since I was playing with V-8 's , I suppose you have changed the fuel filter on rear of chassis, UK cars dont get these changed as the steel unions rust into steel filter and shear pipes when undone, ( pipes were no longer available )
as the filter is very fine, it can block restricting fuel volume,
The other thing is to take off the cat front pipes, and fit the earlier non cat front pipes, but you have to change the tune resistor, pluged into the loom nr ecu.
Anthony

thanks, fuel filter done regularly and no cats and straight through muffler.