Monday, Oct 13, 2003 at 20:08
Rowen
I have a Datsun Bluebird (the 4 cylinder limosine- don't laugh) that I have had from new since early 1982.
I converted it to LPG in 1986 and have conducted a lot of R & D on it since.
One of the biggest problems that I had was valve recession into the seats.
Why am I telling you this,
well this causes rough idling like you wouldn't believe and no amount of 'tuning' will get rid of it.
I know you said you had yours tuned, but did they adjust the valve clearances.
I ended up having a special 'head job' done on it which included stelite exhaust valves and (I think they call them ) Serta seats put in. That Serta is spelt phonetically. It might have been Sertia of Certa, whatever, they are Italian and come in three grades A,B, & C for the most appropriate aplication.
Never had a problem with that again and as a matter of fact it has run on LPG only since 1987 when I had that special head thingy done. I just took off the petrol pump and blanked the port, adjusted the timing for LPG only ( It has a series II electronic igition) and it is still running A-OK at 330,000Km.
Also get this, I replaced the exhaust system in 1986 when the LPG was fitted and that whole, yes the same whole exhaust system is still on it today and it trundles around
Melbourne like the geriatric that it is every day.
Power wise, wouldn't pull the skin off a bannana. Who cares, costs me sweet F/A.
And those cootas of the 'flat earth society' (
Canberra) intend taking the so called LPG excise concession off in 2008. I think the rust battle will have beaten her by then though.
Speaking from a lot of experience with LPG I would definitely say its something to do with the head.
The other thing is that LPG setups are extremely sensitive to leaking Vacuum hoses and/or Vacuum air into and around whatever throttle body you are using or the inlet manifold.
This can give you rough idling as
well and is not as noticeable when switched petrol.
Thats about it, hope it gives you an idea or 2 towards fixing it.
Regards
Ken Robinson
AnswerID:
33647
Follow Up By: Rowen - Tuesday, Oct 14, 2003 at 23:47
Tuesday, Oct 14, 2003 at 23:47
Cheers Ken!
I appreciate the time you've put into this response. If u type as slow as me, you wouldve heard the paper boy's squeaky brakes as you finished typing.
I need to better 'process' what youve said & consider it. Anyone else have the same problems out there?
cheers
Rowen
FollowupID:
24317
Follow Up By: Member - Ken - Wednesday, Oct 15, 2003 at 19:31
Wednesday, Oct 15, 2003 at 19:31
Rowen
I forgot to mention one other thing that I should have and just because I was having a 'senior moment' at the time, didn't.
Another post jogged my foggy memory.
Do you have a EGR (Exhaust Gas Return) valve on your machine. If you do, these cootas can play havoc with the LPG. You really have to blank them off, because all they do is bleep a heap of exhaust gas into the throttle body when it opens and can upset the preset gas mix.
What tends to happen is that the tune up guy either gets it right for when its open (Hot) then everything is good, however when cold or warming up it either won't run, or runs like a dog.
Or vice versa, if he tunes the mix when cool or warming up and that valve hasn't opened then you are in the bleep .
All of the EGR'S I've seen operate on vacuum via heat sensors in the anti polution system. However it depends on what ever system has been installed in your machine
I blanked
mine off when the fuel pump was removed.
Another thing you can do is connect a vacuum guage to your manifold and see whats going on.
When I was having the problems the needle was only lifting about a third of the way around at idle and was jumping all over the place. i.e poor vacuum from the valve seating.
Now at idle it goes around to the max and sits steady.
Feel free to use my email site. ken_3149@yahoo.com
Regards
Ken Robinson
FollowupID:
24424