Car just serviced runs like junk.

Today I did my first oil, filters, radiator, plugs, leads and a few globes here and there on the new D21. When I popped the air cleaner off to get at the two rear plugs, I noticed the gas lines running into the inlet weren't sealed very well at all. After removing all the old goop and crap the previous genius had used, I sorted out a decent seal with Sikaflex before replacing the filter and lid.

I then discovered a vaccum hose that seemingly hasn't anywhere to connect to. It runs off a single brass barb coming up out of the forward half (1st & 2nd Cyl.) of the inlet manifold. From there it travels aft, under the air cleaner, over and around the valve cover and then just hangs down the firewall near the dipstick.

Where is this hose meant to attach to please? With the motor running, it leaks vaccum. Could this have anything to do with the LPG installation?

Also, the motor runs like a shocker now that I've serviced it. The higher rev range has the motor hesitating, surging, and even back firing. I'm hoping it may have to do with this stray hose, but everything was fairly good prior to servicing. When I try it on petrol, the motor runs less crap, but the symptoms are still there.

Maybe my mixtures are too rich now that the air cleaner is properly sealed. I still have to do my timing and dwell tomorrow. Any tips for a dual fuel set-up?

Ok block off any vacum leak you can find. If there is a vacum leak it will run lean not rich.
Need more info. That has the Z24 engine I think. Is it carburettored or injected? That vacum line could of been going to the distributor. Often it is removed when on gas and the engine is setup with more intial advance and less total i.e. removing the vacum advance hose.
With the vacum line coming off the inlet runner, that use to be an old trick for running on gas. Gave vacum at idle but none when you put your foot down.
I gather you run it mostly on gas?

That hose sounds like its for the vacumm advance on the distributor.

Helps the engine higher in the rev range.

No idea about the lpg system, sorry.

Good afternoon Tappet and good afternoon Dave,

Thanks for your thoughts. It is an 89 Z24 carby which I run primarily on LPG, only really using the petrol as a reserve for when the cylinder is empty.

The vaccum advance has already a hose connected to it, the only other available spot is on the dizzy cap which has a little rubber cap plugging it. Maybe I should put a T barb in and be done with it. Where the heck did this stray once connect to though?

I can barely even start the blasted thing today. I'll try removing the line to the advance and blocking it, as well as the stray one. Heading out now, fingers crossed.

Well it starts and idles like a dream with no hoses connected to the dizzy. Still sputters, surges and backfires a bit up in the higher revs though. There's still other stuff for me to do so I might go on with that instead as this has me shitty for the moment.

Have a good day yo'all!

Ok- if it needs the vacum line attached to the dizzy to run better I would say the timing is to far retarded. Forget what the intial (idle) advance was for them maybe 10deg. BTDC.
If your running on gas 97% of the time give it more advance, try like 12~15 and try blocking of vacum advance hose. Sounds like you need to richen up the gas mixture. Surging is usually a sign of a lean mixture and running on gas the backfiring can be to. It would have to be really, really rich to cause these symtoms and you would also smell it. One crude way of telling try holding the engine about a steady 2000 rpm or so and hold a finger or two over the air inlet if it picks up in revs you will know it's lean.
If your only using petrol for a back up use 98 premium as when you do switch to petrol your gas tune wont be so much of a comprimise. LPG is about 105RON
Best of all have LPG service shop set the mixture with a 4 gas, gas analyser. No hit and miss that way. It's quick to do and should not cost to much at all.
Good Luck

Now that I had a better read.

Did you move the dizzy ?

Get the LPG setup checked to, you dont want it running lean or you'll end up with melted pistons.

The advance on these distributors also gets a bit dodgy with age. As well as the vacuum, they have a mechanical advance below the points that relies on springs and weights - it can get stuck. If you have no joy with the vacuum line, the mechanical advance might be worth looking at. The vacuum line modifies the timing depending on load, the mechanical advance modifies the timing depending on rpms, so this might be more the culprit.

Hi Tappet, Dave and Pinelli,

Guys, it's all good now thanks a million. All of your advice, as well as phone calls to all my engine nutter brethren who have dabbled in the LPG caper has brought home the goods. Also, thanks to Repco for being open today and having the points assembly I needed (I haven't been satisfied with them since I was a boy watching Dad doing the servicing).

The ol' Z24 was way too lean, the timing was extremely advanced (now at 13 BTDC), points and advance needed refurbishment, vaccum leaks have been sorted, and I opened up the power valve ever so slightly.

Sorry for not coming back to you all sooner but we've had a greivance in the family and I only finished it all and tested it today. Schmicko to the power of Grouse! It's great that tinkering and fettling can distract us so much from other issues, and allow a methodical thought train to deal with them.

I'll get down to a gas tuner once they reopen later this month. For now I'll just drink some homebrew and fix the bowed and sticking speedo needle, tidy up some wiring and install the coconut air freshener I got for Chrissy. Ooh yeah, I also got some $5 floor mats to cut and shut.

Cheers very much, happy new year to you all! Thanks!

Don't stress about the time - glad to hear you got it sorted, and sorry to hear about the grievance in the family. Keep in touch.

The stray vacuum hose should have been running to a barb just forward of the shifter on top of the transmission. I just found it then, it's definitely it, as the hose length is perfect and the dust colour is the same on the hose and that part of the tranny. Sweet, finally!

That shouldn't be hooked up to vacuum, it should be open to atmosphere. It's just a breather.

Dion said:

That shouldn't be hooked up to vacuum, it should be open to atmosphere. It's just a breather.

Click to expand...

Party pooper.

Oh man, party pooper hell yeah! I haven't been sleeping soundly, knowing that a hose engineered by some Japanese guy to save the world, is lost and without a barb. Of course in time, I'm gonna dump the whole shebang and whack a breather tank on the motor. Would you happen to know where this stray hose should go then? Like I said, the dust colour is identical, and the length is spot on. A late eighties, Japanese motor/trans, with a breather venting to the atmosphere seems odd, vacuum seems to be where it was at back when the greenhouse effect was being taught to school kids.

Maybe this is a good case for my wife to understand why it's imperative for us to purchase a decent workshop manual. Does anyone recommend a particular publication? I use a fairly in depth Clymer for my '88 GSXR, but have no experience with them on cars.

This is the one I use.


Haynes. It's been pretty reasonable so far.

Not sure where the vac line is supposed to go. The transmission breather is to atmosphere because it's only to deal with the air and oil in the transmission expanding and contracting rapidly, for instance if you're brave enough to drive your 4x2 through floodwaters up to the doors. There's no emissions or anything

Thanks for the link Pinelli, I'll sort that out this evening.

As for the breather, I suppose it'd be better to not have floodwaters and muck entering the tranny on the offchance. Maybe it's in my head, but shifting does feel a lot smoother, especially into reverse, now that the line is connected. Ah well, I'll run with it for now, no offence Dion, in fact thanks for your insight.

Guiness should do a Book of Automotive Vacuum Hoses and Wiring, to help with differences of opinion in the automotive world. Speaking of which, it's midday somewhere in the Empire, I could sure go a pint. Cheers all!