engine missing at idle and more under load

[ckh]

On my 89 GQ TB42 carby model, with an auto transmission Had an annoying miss, when I drove around and was pulled over there would be a slight miss, so put it into park or neutral and would be even less noticable. Got sick of the loud tappet noise my truck was making so about a week ago adjusted the tappets, miss got worse, noticed at idle if I pulled off #6 spark plug lead no change to motor idle, but could tell it was only running on 5 when I gave it a rev... with the plug lead back on revs fine. I replaced the dist cap and leads, now at idle taking the same #6 lead off can hear a difference in the motor, but it still has a miss, have checked for vacuum leaks, can find any.
Loosened tappets off a bit idles a little better but the miss is still there, it doesnt have point have the pentrix ignighter and flam thrower coil.
Its more noticable when I have it in drive and or the aircon turned on...
Have searched the forums, some people saying miss is fluel related, so ran the tank to near empty, fill with BP ultimate, put several different fuel clearnwers and additived etc to clean system out, replaced fuel filter.

Am still getting same ecconomy as before but this rough idle and miss is driving me crasy.

Other sections on forums say my head or head gasket is stuffed..

So far have changed leads
changed plugs and dist cap
changed fuel filter.
readjusted tappets
readjusted timing. have tried to fiddle with fuel mixture.

have checked for vacuum leaks

What else can anyone suggest I hope and pray its not the head, as i only got this back in Aug and have emptyed my wallet already with doing a 2 inch lift and other things to her...

[threedogs]

Also try looking under the bonnet at night when its dark. you'll easily see any failing leads

[pearcey]

First thing do a compression test,if ok then start on the electrical side with a proper diagnostic check this can also show up some fuel faults as well

[ckh]

89 GQ TB42 carby model, with an auto transmission

[dahero]

hmm faulty inlet valve perhaps?
could even be the float in ya carby.. if its hanging to low you wont get enough fuel?

[taslucas]

What condition is your rotor button in?

[ckh]

What condition is your rotor button in?

bought a new one...

[Alitis007]

Do a compression test as said above to see if you have burnt out a valve or over adjust the tappets. They are a noisy motor to begin with so if your clearances are too small the valve might stay open causing your miss. Then you will need to put a Co2 meter on it and adjust the fuel mixtures to spec, it will miss more stoped in D coz of the lower RPM and while driving coz the engine is under load, but do those things and you should be able to pin point where the fault is. Oh the other thing is are your lead in the correct position?

[ckh]

Do a compression test as said above to see if you have burnt out a valve or over adjust the tappets. They are a noisy motor to begin with so if your clearances are too small the valve might stay open causing your miss. Then you will need to put a Co2 meter on it and adjust the fuel mixtures to spec, it will miss more stoped in D coz of the lower RPM and while driving coz the engine is under load, but do those things and you should be able to pin point where the fault is. Oh the other thing is are your lead in the correct position?
yes when replaced dist cap and leads, number 1 went to number 1 through to number 6 went to number 6

[ckh]

Now its starting to miss onn the highway every now and then feels like I've tapped the brakes, or it will cough and carry on then come good again.. I suppose if the damage is done its only going to get worse before i fix it and hopefully get better then....

[ckh]

1. its got an auto choke.
2. Timing has been set at 10 BTDC have tried it at 5 and at 15 made no difference.
3. no bubbles in coolant when radator cap off, not loosing any coolant either.
3.5 no using oil appart from the little usual bit of smoke when first started in the morning
4. have check oil filler cpa an clean as
have tried champion and another named brand plug, but dont want to spent a fortune on the iridium plugs yet, as if I have to replace the head its going to break the bank .
5 have replaced plugs, dist cap, leads, even tried going back to points yesterday incase it was the pentrix ignighter, but same miss
6 replaced fuel and air filters after running all the cleaning stuff mentioned below
7 yesterday arvo tacho was jumping all over the place, and car ran real bad, found bolt that holds dizzy in place when adjusting timing had stripped out, so replaced with another bolt and reset timing, tacho behaving now, except for the slight movement when it misses, but the miss is still there.

Thinking it was crap in the carbo or contaminated fuel last week as for the past month had been running cheap fuel from 7/11 in it, ran it near empty on friday, and filled with BP ultimate, and added every fuel cleaner, carby and injector clean and octane booster i could buy from repco and supercheap, over 120 dollars in additatives in total. since then been filling up with either bp ultimate or shell optimax, fuel consumption is now 20.49/100 on that first tank of good stuff, then 18.03/100 on the second and filling up this morning was 17.56/100, have been giving the aircon a bit of a hiding as its been very hot up here in Ipswich and brisbane..

One thing I have noticed as when I turn the aircon on the rev's dont go up like they used to if anthing it drops the revs a little...

[Alitis007]

You have either a bad earth some were and you might need to run a carby kit thru your carby, it may be gummed up inside and the diaphragms have dried a little with age. Have you done a compression test yet??

[ckh]

You have either a bad earth some were and you might need to run a carby kit thru your carby, it may be gummed up inside and the diaphragms have dried a little with age. Have you done a compression test yet??

Not yet a guy on a forum is doing a compression test on the weekend for me for a 6 pack of beer, another guy is getting me to go to his place tomorrow arvo, and try his coil etc in my car, he had simular problems.. So hopefully its not the head or valves after all

[dahero]

its always shit when there is something wrong with ya car. especially when you cant find it! good luck with it mate. hope it aint the head :(

[threedogs]

So this is an unleaded motor with no gas am I right ???

[ckh]

Correct unleadeed, no gas on it ever...

[ckh]

Just did the test a few people have said to to, started the car up in the dark and looked for sparks, none to be found or at least seen....

[Alitis007]

Just did the test a few people have said to to, started the car up in the dark and looked for sparks, none to be found or at least seen....

There wont be any sparks coz you put new leads and cap. Your fault sounds like earth, fuel or valve miss, so prey you have 150psi or there abouts in each pot and that will point you in the right direction and make sure you check the earths aswell.

[ckh]

have done as a few have suggested, pulled out the flame thrower and put origional coil back in, its still got a miss, did some googling. a test for a burnt valve is to put ya hand over the exhaust pipe and if there is any sucking rather than blowing its a sign of a burnt exhaust valve... tried that and was flat out keeping my hand over the exhaust, kept trying to blow hand off..

Am going to a guys place this arvo to try his GT40 coil and see if that makes a difference

[ckh]

have called around a few places around brisbane, a exchange head ready to bolt on is going to cost around the 1200 mark including gaskets, and for them to fit it and give me a full 12 month unlimited K warranty its going to cost around 2K in total... God I hope and pay its electrical or fuel..

[ckh]

Went to a mates place today tried his coil, his distributor, and still has a miss so its either head or carby
that mate said will put a perfectly running motor in mine, including ignition and carby, motor will cost me 1K but his mechanic mate says I should get at least ten years out of it if I look after it, so 1 K for the motor and for him and his mate to install it they want my motor to do up.... Considering its going to cost 1100 for a recon head for me to fit my self, and if that aint the problem a carby recon for god knows how much, they say this motor is good, new water pump, new fuel pump only fault with it is the power steering pump has a slight weep, so they are going to put my power steering pump on it, he said to turn up at his place on a sat morn in a few weeks and I'll be driving it home that afternoon/evening... So if there is no miss in the replacement motor now, there shouldnt be after the transplant considering I'm getting the motor, carby and ignition...

[happygu]

Hope your mate is a good one, as it will cost him more than 1K to fix yours up, so if he is giving you his for that he will be out of pocket.....

Do you know the history of the exchange motor?

[nissannewby]

Its not something as simple as the timing being 180 out is it??

[ckh]

Hope your mate is a good one, as it will cost him more than 1K to fix yours up, so if he is giving you his for that he will be out of pocket.....

Do you know the history of the exchange motor?

its done a 30k more thank mine but he said its been looked after, only reason the guy is getting rid of it is to put a diesel in

[ckh]

nope tried different dizzys yesterday, mad no difference, when putting mine back in it was 180 out and wouldnt srart, fix that..the donor motor is in good nic. this week end we are going to try just the carvy off it to see if that fizes my problems, he's doing a compression test on the donor motor tonight, and on the week end doing a compression test on mine, if the donor motor has better comptession we are going with it, if mine has better compression will look at doing the carby, but I'm betting money my compression will be crap, did some googling and did the burnt exhaust valve test of holding a piece og paper over the exhaust, when engine was warm tried sucking the paper up the pipe.. do my motor doesnt look promosing...

[rusty_nail]

Considering its going to cost 1100 for a recon head for me to fit my self

Hi mate not sure where u got you figures from, but I just replaced the head in my patrol same motor, an it was about 800 for a brand new head, reckon u should get another quote hey!


Tappin

[taslucas]

Hi mate not sure where u got you figures from, but I just replaced the head in my patrol same motor, an it was about 800 for a brand new head, reckon u should get another quote hey!


Tappin

I just saw a reco one on eBay for $400. Not sure how high the bids will go but worth watching

Tap, crackle, pop

[dahero]

yeah i agree with the above. look for a new head instead of a replacement engine! while your ad it you could see how the heart looks on the inside to.

[ckh]

Ok got the ruff idle and missing at speed sorted, turned out to be 2 bqad sets of plugs and a earth wire. runs smooth as now, but have been doing the trick where you put a piece of paper against the exhaust pipe and if it gets suckd in at allit meand a burnt or buggered exhqaust valve, I know I need to replace my exhaust and gasket as when a mate held his had over it yesterday you can hear it hissing around the exhaiust manifold, is there much credability to the piece of paper test? when I hold my hand over the exhaust I can feel presure trying to blow my hand away but cant feel it sucking.. so I'm hopeing I have fixed my engine problems, unless someone can varify the paper test means means a valve is shot. now just need to sort my car shaking at 90K's and I'll have a good truck.. unless my valves are shot and i got to replace the head!!!!

[taslucas]

Plugs and an earth wire........that's a damn lot better than replacing the engine!!
Good to see it's sorted.
What makes you think that your valves are shot? The reason you thought they were shot was because it was missing and now it's not missing.
Also, it is getting a bit confusing having two threads on the go and just cutting and pasting the same posts in both.

Tap, crackle, pop

[Alitis007]

Mate i'm in the trade and never heard of this paper test, exhaust gases swirl as they exit the tail pipe so to be sure that your valves or valve seats are sealing do a comp test or turn the motor till compression stroke on that cylinder and fill it with compressed air but for that you will need to make a tool. Its good you solved your issue easily and cheaply.

[ckh]

The tyre power guy said he did all that.. going to a mates placew tomorrow and trying a completely different set of rims and tyres, it that solves or improves things, I'll know my tyres or wheels are out of round.. Today when driving on a perfectly flat bit of freeway it felt like i was on a coragated dirt road,, my Mate is also going to have a look to see if anything else stands out like a sore thumb, I'm so glad I met "scaredgq " Andrew on a forum, he's a top block and knows his stuff when it comes to gq's, I'm still in awe as to what he has done to his and its only running on gas, would make most V8's be imbarrased...

if you do a google for exhaust sucking air you will find plenty of the yanks etc testing for burnt valves using paper or a dollar bill, from motor bike engines though to 4-6 and higher cylinder engines..

[ckh]

This is what Andrew and I got up to on Thursday arvo... "Hi matti- we spent about three hrs dickin around with electrics/timing,didnt swap plugs because mine are the 6's for gas.I would describe the issue as more of a hesitation at idle when warm and didnt miss under load when we drove it.has champion plugs atm and they were a tan colour.It did smell rich at idle.I am now thinking maybe a carby issue as today it is reportedly playing up worse-timing at about 12 deg,reved nicely from idle yesterday.Next thing we will do is leak test-will put about 100 psi air into each cylinder at tdc-valves closed and see if it has air coming from exhaust/carby or internally,will also check for bubbles in coolant.I dont think it is a valve issue but the head coming off or motor swap will be last on list.Motor and car seem in immaculate condition,looks like a well maintained vehicle,newish looking radiator,dosent look like its been offroad.I know this means nothing at all but makes me think its a small issue.Tappets are going to be reset warm at .40,plugs changed.have access to a carby on a running motor that runs perfect which will try after leak test.Another thought is manifold leaks but i think trying the leak test should point us in right direction.What is your views /opinion on this after yr experience with yr head change etc."

[happygu]

Good idea to change the rims and tyres to a known set where they are not out of balance.

You could then even try your rims and tyres on your mates car to see if they cause the same vibration on his.

Keep on going as you seem to be getting to the bottom of most of the problems

[fatboy-71]

This sounds exactly what mine is doing but mine is on gas, it does the same hesitation while driving on the highway and has the miss at idle with a hiccup under slight acceleration on either fuel, I was thinking mine could either be carbie fault or electrical haven't had it long so will be doing all things listed above to start with, it doesn't lose oil or water and never runs hot. Also can anyone enlighten me on why the tube from the snorkel that connects to the air box under the bonnet would have holes drilled in it? If I go into water it will just go straight into the air box/ cleaner then suck straight into the carbie, thinking I better change this item.
1991 DA maverick
Duel fuel, auto, 33's
2-3" lift
Snorkel.

[Robo]

Mate i'm in the trade and never heard of this paper test, exhaust gases swirl as they exit the tail pipe so to be sure that your valves or valve seats are sealing do a comp test or turn the motor till compression stroke on that cylinder and fill it with compressed air but for that you will need to make a tool. Its good you solved your issue easily and cheaply.

Paper test has been around since Adam was a boy.
You may find the suck backwards effect is just relaxed pressure as leaky cylinder cycles past.
cheers.

[Robo]

Any updates?.
as mine is playing up the same.
SUSPECTED BLOWN HEAD GASKET, thread.
Beginning to think it leaks between cylinders only.
Doesn't explain good comp, I'm at a bit of a lose at the moment.

Vac test showing up a leaky valve is the cause, and only a 6 psi drop max to min value.

[Pezzer]

Which earth wire?