L98 rough idle????

[ftgcalaisv]

i was wondering if any one else has had a rough idle on their L98 v8 motor and what they did to fix it?

so far the things i have done:

Acdelco plugs which i gapped to 1.0mm.
Acdelco spark plug leads.
K&n Air filter.
engine oil and filter.
150k Auto transmission service with filter and fluid.
checked PCV.
cleaned throttle body.
Checked OBD and found no codes.

It seams fine when it is cold, but when it has fully warmed up and idles around 550rpm it is very rough in drive with foot brake on.

 

[Gaiter]

Fuel filter? Injector Cleaner?

 

[HSViCalais]

Fuel filter? Injector Cleaner?

+1 Injectors. If when the motor is cold it's flowing more fuel on the choke which will mask the symptoms.

When warm and the fuel is trimmed you'll notice a rough idle.

I'd recommend a replacement set rather than a clean unless you go to a trusted workshop who will replace the small filter screens and o rings

 

[MYVESSV8]

Fuel filter? Injector Cleaner?

fuel filter as such is in the tank on the VE, part of fuel pump assy, if its an early model 06 late 07 you can access under rear seat, if not fuel tank out.

 

[vr304]

fuel filter as such is in the tank on the VE, part of fuel pump assy, if its an early model 06 late 07 you can access under rear seat, if not fuel tank out.

What a stupid design lol

 

[ftgcalaisv]

i have put in Liquid-moly petrol treatment in to the tank, but it didn't smooth it out.

i reset the TPS today and it has made it better, but still not smooth. My Ve calais was built in july of 2007 so i will check the fuel filter under the rear seats.

 

[07GTS]

there is a strainer on the bottom of the pump and also the module part that surrounds the pump is also a secondary filter, make sure u have under 1/4 of a tank before removing it otherwise fuel will go everywhere, also if it was a fuel pump/filter issue then it would get worse if u drove with the added load so if its fine driving id keep looking, would be worth looking at the 02's see what they are showing if its miss firing or lean spots ect, check earth to engine ect may develop a poor connection once warmed up, does it start fine when warm..? had any mods or a tune..?

 

[MYVESSV8]

i have put in Liquid
its in the tank as 07GTS says, if you lift the seat you will see a disc approx. 150mm in dia, it is clipped and gooped into place, you have to remove this to access pump/strainer/filter in the tank, also requires tool to remove fuel tank ring to access the assy, my ve ss was built july 2006, (203,000klm) only reason I had the pump out was because the sender was failing, otherwise it was clean. One issue is to make sure plug leads are on properly this is known to cause poor idle (experience) if you had all the pipework disconnected to do the above-check for any leaks

 

[VrWagz1]

Sounds like its idleing too low, or running rich at idle for some reason. Just at a thought the emmision sersor thingys on exhaust(cant think of their name right now for some reason) might need replacing.

 

[ftgcalaisv]

everything else is fine, drives fine, responsive, revs out strong, starts fine when hot or cold, getting around 500km to 65litres of fuel. everything is standard apart from hsv cat back exhaust.

i double checked the spark plug leads to make sure that they are on right.