Gq won't run properly

[Nozzle]

Hi guys,
I have an issue with my mates 88 gq it's on dual fuel I've set the timing to 10 degrees btdc idles perfect but farts and splutters when you rev it splutters so much you can't drive it
Replaced leads, plugs,rotor button put in a carby kit and still the same
Any ideas.

[mudnut]

Is it an rb30 or tb42? Is it running badly on both fuels? Have you checked the coil? Is the vacuum advance working? Is the distributor cap in good condition; no cracks, the centre brush not worn, the metal not corroded, or eaten away? check the wiring between the dissy and coil etc.

[Nozzle]

It's a tb42 both fuel are running exactly the same haven't checked the coil vacuum advance is working the cap looks clean and free from cracks the dizzy cam appears to be in good condition replaced and set the points.

I can get it to idle perfectly on both fuels but if I give it some revs it misses and splutters and occasionally backfires and if I try to drive it does the same and it won't go anywhere.

It's as though the timing is out this being said I have tried running it from 0 to 40 degrees in 2 degree increments with no luck it runs rough then a little better then rough.

[Lieney]

Are you certain you have the dizzy timed right?
It sounds like a common thing with both fuels, so I'd be looking at electrics or timing.
How good is the coil? Check at night to see if it's arcing somewhere as the increase in compression may be causing it to arc to the -ive terminal or ground somewhere.
Likewise with your leads. Check them all to make sure you aren't getting any 'tracking'.
What was the first thing you messed with, followed by the next and so on.
Then go back and re-set them.
Get engine to TDC compression No1 cylinder and check where dizzy button sits in relation to cap and contact point.
Another option would be both fuels playing up, but I'd be checking the static timing, electrics etc first

[mudnut]

Certainly sounds to be electrical, but could be the egr valve, vacuum leak. Have you got a multimeter?

[Nozzle]

Ok I am not sure about the dizzy,
A little more info.
From beginning he had no gas in the tank and was running on petrol and nearly had none of that either.
The car stopped just outside a servo (when he called me) by the time I got there he had taken off the fuel filter which was full of gunk and replaced it I jump started him cause he had run the battery down it took a lot of cranking to get it going.
It was running but like a sack. Missing under load. I checked for spark it appeared to be weak it was only jumping about .5 mm
I checked the distributor cap cleaned it the rotor had a bit of wear I replaced that while I was there anew set of points.
A slightly better spark but made no difference. New leads and plugs next still the same. Stripped the carby cleaned it put it back on no difference then put the timing light on it it was running at about 12-14 degrees at idle but still missing spluttering
I haven't had the distributor out but it's as though its a couple of teeth out. Adjusted it back to 10 degrees then round the clock bit by bit back to 10 with virtually no difference.

How big should the spark be from a plug lead testing with a screwdriver to an earth? It's about .5 mm and bluey orange.

[Nozzle]

Yeah got a multi meter

[Lieney]

Should be able to jump a few mm (4-7mm) easily out of the engine and be that colour.
I like what mudnut is saying regarding vacuum leak. Could be a hose come off somewhere
I'd be measuring the coil resistance to see if there is a short or open circuit.
The drive on the end of the dizzy could spin or turn, but I reckon unlikely.
I'd consider filling it with fuel and then playing with it.
Remove the inlet filter also to remove any other possibilities

[mudnut]

With power off, disconnect the coil, and measure between the pos and neg terminals = 1 and a bit ohms. From positive terninal to the high voltage = 9000 to 13400 ohms. If the system has a ballast resistor, check for a continuity between its terminals.

[Lieney]

Scratching my head from a few years ago while teaching, so please correct me if I am a little off.
Although you cannot 'load' the coil to simulate working condition, you should be able to check the basics.
Do not touch the negative terminal when voltage is connected.
+ive and -ve and centre terminal should all be connected via different internal coils or plates (centre), and have a resistance reading to each other.
All the terminals should be insulated from the body.
I think - to + is the highest ohm reading, + to centre is less, but not sure if it was less or more than centre to -.
Good luck
Just read what mudnut posted, so my readings might be off. The body should be insulated.

ADDED - Just remembered, mudnut would be pretty well right. As the points open, the magnetic field collapses in the primary (+ to -) which causes a field collapse. The collapsed field jumps to the core that connect to the centre outlet (secondary). So the resistance would be less between - and +. Cheers mudut

[Nozzle]

I'll check for vacuum leaks and test the coil tomorrow and let you know how I go. You wouldn't know the impedance for a bosch gt40 coil would you, can't find specs anywhere.

And thanks guys for your help!!!

[Nozzle]

Don't mind me I just read your posts
And thanks again.....

[mudnut]

I'm out of ideas any way, except for the small condensor on the side of the dissy.( if it has one, it is a small can with one wire connected to the points.) My old ford had points and the condensor would break down at high speeds. Good luck with it.

[Brisat]

Plug leads will be the problem. Get a good set, not superthief's cheap shit

[Mojo01]

My 92 GQ EFI petrol/gas did the same thing a while back, it was a vacum hose had fallen off where the previous dipshit owner had mouned a morleys oil bottle with a crappy plastic T piece

if yours is a carby... when you are standing @ the drivers side front wheel look at the carby there is a T piece ( metal ) that has 2 vac hoses that run to the front of the engine... if one is off they run like shit, my mates 89 carby dual fuel maverick had this issue, it idled fine, but ran like shit when ya hit the go pedal