Call the doctor, Black Betty is sick!

[wheres my dizzy?]

Hi all!!

I'm a newbie so please be kind and understanding if I ask or say anything stupid (Dam! 2 Late, see my previous post/s)

My car is a 94 Black ED Futura Sedan with a 4 Litre fuel injected donk and auto trans.

It runs on petrol and Lpg.

Black Betty has been under the weather of late.

On LPG she runs great!!
On petrol, its not the same story.
Please help me to get her up and well again!

I suspect a blocked/choking fuel filter, please post with your opinions!

Symptoms:
1) runs very rough, only on petrol-but fine on lpg
2) when @ idle whole car shakes but it will idle
3) takes off very slowly, coughing and spluttering all the way, requiring a bit of throttle tickling to get it going a bit better
4) seems to run a bit better at +60Km/h but still lacks power a has a definite 1-1.5 second flat spot on accelerater depression
5) whilst at re 100km/h it feels like you are towing on an up and down undulating road
i.e. you feel the cars power continually fade for a moment each second or two
What I've Done:
1) run car very low on petrol previuosly
2) put in an injector cleaner chemical and driven it re 100kms since
3) bought new leads to put in(this weekend hopefully)
4) changed air filter
5) got a new fuel fiter to fit (this weekend)

Besides comments on possible problems can anyone tell me where the fuse for fuel pump is to be found?
Cant find it in dash fuse box! Are there other fuse boxes?

Someone told me that i have to pull fuse while running on petrol (and wait for it to stall)in order to depressurise fuel line prior to removing old filter.
Does this sound right?
And where is this fuse?
Should i also change plugs?

[back2back]

The fuse will most likely be near the battery behind the RHS headlight. Not sure which one though.
Your catalytic converter may be blocked. Take it off and give it a shake, crap might fall out.
And you should be able to undo the fuel rail cap to release pressure. Dont quote me on anything though