4G32 odd misfires

[VGJONO]

So ive been plagued with misfiring issues in the higher revs (4000rpm-6000rpm) and wanted to get the opinion of some greater minds, I have no issues whatsoever below 4000-4500rpm and the engine runs smooth and has great power up untill the 4k mark, then sometimes i will get the odd misfired but it will continue to rev, then others it will just misfire like a pig and its useless to even try and keep up it past 5k rpm. I have brand new points, gapped to the specs in the manual (0.45 if i am correct) Brand new Topgun leads, rotor button is about 15,000 old, same with the condensor and plugs, I try to keep the timing at about 7-8 degrees advanced. any idea's as im just about out of them, and i need the car ready for a track day in 2 weeks time

Any help would be greatly appreciated
Cheers
VGJONO

[A112H]

Are you setting the timing hot, cold, idle, revs???

[VGJONO]

Setting it hot, Timing is at 7-8 degrees advanced at about 1000rpm idle

[SteveG]

Does it do it the first time you try and pull high revs or is it after holding in the high revs or repeatedly off and on the revs past 4500 ie good the first time or two but degrades each time after that?

Have you checked the fuel side? Sticky needle/seat not letting enough fuel in? Float set to low making it drain bowl? Crap in bowl, tank or filter creating intermittent blockage?

[VGJONO]

Its intermittent while revving past 4500rpm and onwards, sometimes better than the other times, Carby is a fully rebuilt 32/36 DFV and it was completely overhauled, ultrasonically cleaned, new needle and seat fitted all seals replaced and what not, never had a problem with it before, and its only 3-4 thousand kilometers since i fitted it.

I did some experimenting, set the timing to top dead centre, then advanced it a touch, by eye using the marking on the inside of the dizzy, ran like a bag of crap and started misfiring around 3000rpm, checked the timing and the timing mark was way advanced (off the scale and then some) turned it back to 7 degrees and now im back where i began, im really lost as to what could be going on

[davetrees]

Coil ? It's one thing you don't mention in your original post ... and they can cause those sorts of issues if tired (ie. fine until put under heavy load & having to regenerate spark very quickly at higher rpm)

[geezer101]

Coil ? It's one thing you don't mention in your original post ... and they can cause those sorts of issues if tired (ie. fine until put under heavy load & having to regenerate spark very quickly at higher rpm)

+1 on that. The higher the RPM, the more the coil struggles to deliver adequate spark. Once the coil starts breaking down, it'll cause misfires. Its probably causing it to run a little rich too if the spark is poor at lower RPM. I'd be getting a new coil (if you haven't already and you can cross this off the list as being a possible fault). Maybe it's time to upgrade to a Bosch "T" coil?

[VGJONO]

Coil was only replaced a few months ago with a Bosch GT40R

[davetrees]

Coil should be fine then if relatively new .... but might be worth getting it tested anyway ?

[VGJONO]

Possibly, My father seems to think its the points ignition being a points ignition and i need to drop in an electronic ignition setup, i have an electronic ignition from a G32B, i know the dizzy is different but will the internals all swap over the same?? has anyone tried this or am i going to have to give it a crack myself

Also would my points gab be an issue? im pretty sure ive set it around .45mm, but feel as though that is way too big

[geezer101]

O.k. time to go back to basics. What is your dwell angle? And what's the plug gap like? I know the 'book' tells you that the points gap must be blah blah blah but without a dwell meter, its still only a guess. Narrowing the gap in the spark plugs can help the coil deal with rapid charge/decay of spark. Also, what condition is the distributor in? If there's play in the shaft it can affect how everything works (the lobes actuating the points, contact between the distributor cap and the the rotor button) and how worn are the lobes on the shaft ?(and the driving gear on the end of the shaft?) I know - suddenly it gets complicated, but a collection of factors can make an impact on how it all works.

[VGJONO]

Think im going to pull out the dizzy and do a full investigative photo session with it, yes it has play, back and forth, not up and down, the lobes do seem to have seen better days, dwell angle, i have no idea on, no idea how to check it either. seems whenever i think im ontop of the points ignition the rug gets ripped out from under me

EDIT: Plug gap is 0.8mm but havent checked recently, going to buy new spark plugs tomorrow and gap them at 0.8mm again, should i be looking at going a smaller gap, or a better spark plug?? (not to solve this issue but just in general)

[geezer101]

A dwell meter is a pretty easy gadget to use. The real art is feeling your way into adjusting the points gap. I can't advocate enough to anyone using points ignition to learn about ignition tuning. Dwell meters are cheap and it doesn't matter if its digital or analog (mine is analog and it has served me faithfully), it will pay you back in horses and money saved in not paying someone else to do it for you (they also show rpm so you can set your base idle when tuning). When you get the hang of setting your own ignition tuning you will be surprised on how much of an improvement it makes in regards to your engine's performance.

[VGJONO]

got a dwell meter, chucked it on at running temp and idle (900rpm) and got a reading of 46 degrees, checked good old google and it said 48-55 degrees, is this correct, and am i better off aiming for 48 or 55 degrees for my aplication??

Cheers
VGJONO

[geezer101]

That base setting for the dwell angle doesn't sound right. It should be more like 45-55 degrees @ idle. If you're running 0.8 mm spark plug gap it'll be too narrow (IMO I wouldn't go below 0.85 mm). When I tuned the G32B engine (belt drive 1600) I would gap my plugs to 0.85 mm first, then adjust the dwell angle to 38 degrees and then ramp the advance a little on the timing until it starts to run rough and then back it off. Have a stab at bringing your dwell down to 40 degrees @ idle after regapping your plugs, and see how you go with setting your timing. This is a trial and error thing - it will be a case of set it, drive it and see how it performs and repeat.

[Jordan1249]

Im pretty sure i run like 12 degrees

[VGJONO]

fair enough, did a little digging around in the ignition system today, had a few facepalm moments, found the ground wire between the baseplate and the screw that holds the points in was loose, corrected that and then found i had the wrong line on the vacuum advance meaning it always had vacuum, not just under revs. after correcting that i dropped in some new plugs, gapped at 0.8 so i might take them back out and re-gap them to what you recomended geezer if the issue continues. here are the old ones


found cylinder 4 to be different from the rest


im not sure what the lobes are supposed to look like in here, so figured i would snap some pics as best i could



And chucked a new fuel filter in, cut open the old one to find this...


And the Dwell after doing all of this is much the same, points are .45mm, plugs 0.8mm

[tandanus]

Have you replaced the spark plug (or "suppressor") caps?
These are the first things I replace - cheap and notorious
T.

[LukeAussie]

Hey, I'm back from OS, so happy to help again :-)

Looks like many of the questions have been addressed. I was going to suggest checking the vacuum lines, and possibly also check the vacuum advance setting too (to see when it pulls in; there's a small amount of adjustment on there to play with). With the points gap and dwell angle, the dwell is always the best metric to work with (rather than gap), and as a general rule of thumb, a bigger gap is a smaller dwell. You'll have a lot of fun playing around with this, and it's interesting to see what kinds of differences things make!

A couple of other things to check are your fuel quality (has it been bought from a different servo? Different quality? I always run 98 RON, as anything less is rubbish!). And the other thing could be a vacuum leak, though you'd be more likely to get misfiring across the range of revs if this were the case (sadly, I've got a vacuum leak atm, but haven't tracked it down yet! Fun times! Ha ha!).

Good luck!

[geezer101]

Oh, and here's something else to check that often gets overlooked - the screw cap on the plugs. If these are loose it can mess with spark as well. It looks like you check the plugs when you pull them straight out of the packet, but a lot of guys don't. If they are handled roughly before they wind up on the shelf (or just aren't prepped properly in the first place) you can wind up with a less than accurate plug gap. It's best to gap them anyway...

[VGJONO]

i normally get 95 from the servo up the road, the woolies servo is only 5 years old, and ive always gotten fuel from there

Pulled the new plugs back out to see what they can tell me, and re-gapped them to 0.85, to me they look like the car has been running lean ?

[geezer101]

BEWARE OF WOOLIES FUEL. I had a really bad experience with it straight after doing the head and carby on my LB Lancer hatch. Tuned it that day, got it running beautifully and decided to take it for a night drive around the reservoirs. On the way up there I had to pull in for fuel as the tank was getting pretty low. The last spot I could get fuel was a Woolworths Express. Put in quarter of a tank and within a few k's it started running like a three legged dog. I've also heard of other people complaining about the stuff too. Might only be a coincidence - maybe tweak the main air/fuel needle and enrich the mix a little?

[webby]

I've had issues with Woolies fuel too. Took advantage of the 4c/L off thing once, ended up with 45L of 2-stroke mower fuel and four fuel filters full of water for my trouble

[VGJONO]

So might be an idea for me to fill up elsewhere for a week and see what happens, i have heard, and been victim of bad fuel via woolies, but for the most part the local one has never been a problem, its the ones closer to the city that end up with a few litres of water mixed in with a tank ect.

I have adjusted my dwell to around 42 degrees,will take the car for a run and see if its better or worse, if i still have problems then i will be opening up the carby, also thinking that running a secondary small clear filter between the pump and the carby might be an idea, incase the pump is on its last legs and is breaking down and sending stuff into the carby (pump is 40 something years old) before i do this however, does anyone have any reasons why this would be a bad thing??

Cheers
VGJONO

[geezer101]

I think a secondary filter is a cheap insurance policy - I've used one before and it will pose no issues with the carby.

[VGJONO]

[GLANT]

Ahhh what the?? Is that the needle valve loose in the float bowl?

[VGJONO]

no it isnt, everything is all good components wise, it is the lovely pools of brown rust particles that were concerning, now cleaned out.

[VGJONO]

Thinking my issue is fuel, still having problems, on the other hand, i did close the points gap and acheived a dwell angle of 40 degrees (somehow smaller than when i opened them right up WTF) so i gave it a drive and it went well, revved up to 5000rpm no problems, then slowly got worse and worse, pulled up and tested it again, dwell angle had changed to 46 degrees, re-gapped and checked the dwell, put it back to 40 degrees and all was well, then as i drove got worse again i think i am just having compounding problems. I gave it some loud pedal when it started playing up again, 2nd i got to 4500rpm before it started playing up, 3rd to about 4000rpm then 4th to about 3000-3500rpm, that suggest to me a fuel supply issue, so possibly that is my issue???

also sat down for a few minutes and made a 4G32 electronic ignition, i got given a G32B electronic ignition, and decided to swap all the insides over to a 4G32 dizzy, any pointers on anything i should look out for when i decide to test this, is there more to just the unit in the photo's that i should need?? im not sure, electronic ignitions are all new to me.



Cheers
VGJONO

[jvflash]

Twist the ignition leads. It is hard to tell, but from the pics it looks like they run neatly and parallel, this will cause misfiring as the spark jumps to a parallel lead to find the easiest path to earth.