[d1mitch]

hey guys,

im not happy with my zook right at this moment, it is running like a dog.

this started on friday night, i was driving along and on light throttle the car seemed like it was missing and surging, as i came up to an intersection i put the clutch in and it dropped revs to nothing and coughed and spluttered to stall.

it fired up again straight away obviously with a bit of throttle, but it wont hold idle so i resorted to having to brake with the handbrake and keep the revs up whenever i stopped.

now when i got home i was idling again albeit very roughly. i drove the car on the weekend again and it drove fine for part of the time but then started doing the same thing again. i looked under the bonnet to try to find anything out of order. i found the intake air hose between the filter and carby hat had split so i mended this with some 100mph tape buit couldnt find or hear anything more untoward.

i have been driving the car all this week with no sign of it flaring up again still idling a little rough but fine otherwise, until this morning. start the car up and it idles fine, i get 5 minutes down the road and it starts surging under light throttle, so i put the clutch in and lo and behold it stalls. so i drove all the way to work with it playing up like this as i had no other option really.

driving to work i was able to feel the symptoms more and hopefully help me work out the issue. i found that it had no light throttle response, if i came to a stop to keep the car running it had to be over 2k rpm anything below it would wildly flare up and down in revs till it eventually stalled, almost like it dies and fires up over and over again. under full throttle it seems to be fine.
when ever i would back off and accelerate while driving along it would lurch back under throttle once again no light throttle response as if it would realise you were accelerating again till you gave it more then it would jerk the power back on

i at first suspected dodgy fuel but have since gone through 2 more inputs of fuel with no real change

has anyone experienced a similar issue or knows what the problem is? this is on a standard g13ba with the standard carb

[tanshi]

needs a carby clean/rebuild.

[d1mitch]

hmm, i was thinking it would be the carb. any idea which part specifically what would be causing it, or how i can diagnose it?

[droverdave]

Spray the crap out of it with carby cleaner (supercheap, $15), while its off (hot) and then start it (it wont be easy to start) and keep spraying it in clean all the crap out. rev the guts out of it a bit while your spraying it.

Then see how it is.

[Reubs]

d1mitch wrote:

hmm, i was thinking it would be the carb. any idea which part specifically what would be causing it, or how i can diagnose it?

Idle jet sounds clogged. It sits underneath the top section of the carby and needs linkages/solenoids/choke/throttle cable etc., seperated from the main body of the carb to get access to it so the carb will need a partial teardown to fix the problem. It's about 45 minutes work for someone who has done them before. You will probably need a rebuild kit on-hand as the gaskets will be easily broken if they are 20 years old.

[Marko_SJ]

I've had that issue with both my zooks. On one It was resolved with a filter change and carby clean / kit, on the other I rebuilt the carby, changed the fuel pump and fuel filters, the new owner changed the carby from the one I rebuilt. It still did it. Ended up being a blocked fuel pickup in the tank.

Poor low end response and hunting at idle sounds like the carb itself might be starving or, like others have suggested, blocked idle circuit.

I'd change filters and absolutely make sure you are getting fuel to the carb before you tear it apart. My 2c.

[MadMuz]

Could be just bad fuel, or water in fuel.... sounds like you have checked for the obvious, so if I were you, I would put a bottle of carby/injector cleaner in the petrol tank and use good quality fuel. If you are using E89 or its equivelent, that could be your problem, ethanol eats rubber (lines and gaskets)

I use 95 in my vit and 89 shorty sierra, because I believe 95 is a bit better quality than 91 and I wont use ethanol in cars of my ones ages. A friend who works in the petrol industry tells me that E89 and the base ulp are usually the result of the rubbish (near to out of date or not up to standard) fuels being sold off to the public. So if a fuel company has a batch of premium that is not quite up to standard, it goes in.... so 91 can be made up of anything really, could be 98 octane, could be 90 octane or anything in between.

Other checks to think about is the pcv and egr systems, they can both give weird symptoms. Also, unplugging, cleaning and re-connecting engine electrical plugs is always a good thing to do.... many an intermittent problem caused by poor/dirty connections

One other thing to think about, I had an 87 barina and suddenly it began to not idle without a little bit of throttle, very annoying as it was an auto.... long story short, it turned out to be a micro switch on the throttle pedal had failed (to do with the engine run down/back off fuel cut off system) I had been told by various mechanics it was anything from the torqe converter full of crud and out of balance to the fuel pump failing.... to a problem with the ignition switch..... After I unplugged the pedal switch and bridged the wires, it was normal again....

[d1mitch]

^^ that was my first thought so i have already tried a few batches of fuel from different servos with much the same results, i always use BP98 in all my cars so its the best quality i can get from a servo. i have a weber sitting in my garage so i am thinking i will just chuck that on and see it it runs any better.

[droverdave]

Why are you wasting your money on bp ultimate?

[SuziBlu]

droverdave wrote:

Why are you wasting your money on bp ultimate?

Please explain why not.

I run 98 in everything, cars, mower, chainsaw, whippersnipper, would not use anything else, ever.

Please tell us why money is being wasted.

[jimny_timmy]

SuziBlu wrote:

droverdave wrote:

Why are you wasting your money on bp ultimate?

Please explain why not.

I run 98 in everything, cars, mower, chainsaw, whippersnipper, would not use anything else, ever.

Please tell us why money is being wasted.

X2

[d1mitch]

ok an update of how things went. on the weekend i swapped out the standard carby for a much simpler weber 32/36 and the stalling issue is gone! so its safe to say it was the carby not any of the other possible scenarios.

so all is well with the 32/36 the g13 feels so much quicker now.

now a question for any weber gurus, i am getting a bog down or hesitation when coming off idle. it happens just as im coming off the clutch taking off and easing on the accelerator (approx 1500-2000 rpm) it will just drop in a hole so you have to give it more gas and it screams to life, unfortunately it makes you look like an idiot with a big bunnyhop to take off.
it will do it if you just slow down in a gear aswell to a low enough rpm (1500rpm) as you come back on the gas it does the same.
although it doesnt seem to do it (or you cant feel it as much) if you just give it the herbs straight off the line or when coming back on the gas.

thoughts?

my initial thoughts were it could be the accel pump diaphragm meaning its getting a weak shot of gas and leaning out on the transition from idle? or i dont know maybe idle jets? im not an expert on carbs by any means so everyones help is much appreciated

[droverdave]

SuziBlu wrote:

droverdave wrote:

Why are you wasting your money on bp ultimate?

Please explain why not.

I run 98 in everything, cars, mower, chainsaw, whippersnipper, would not use anything else, ever.

Please tell us why money is being wasted.

Does it run any different in 98 octane than on 91?

If its not tuned for 98 octane (specifically the ignition timing) then there is no advantage other than the (apparent) cleaning abilities.

My WRX runs on 98, and if i run it on 95 or 91 it pings its guts out because the ignition timing is designed to take advantage of the octane of the fuel. My drover, ae112 corolla, lawn mower, wipper snipper all run on 91 (the cheapest i can buy) and it makes no differnce to driveability or fuel economy. (ive checked both the corolla an drover, within 10% fuel economy on 91,95 or 98).

Of course people are going to come back and say "oh but it runs alot better, i have 50kw more on 98", reality is, unless you change the ignition timing to suit, then there is no benifit of 98 to 91 (except the advertised cleaning ability, which i dont think is measurable). I did try an experiment where i put 98 in the drover and advanced the base timing until it pinged and backed it off a bit. It didnt really make much difference to the but dyno, and for the last year it has been 100% reliable and gotten 8-9L/100km daily driving on 91.

If the engine is in good condition, carby is working how its supposed to work, ignition is set to what suzuki recomend, then there is no reason to buy 98 over 91. (Afterall, suzuki and toyota specify 91)

re: webber.

Where did you get the webber? Was it specifically tuned for your engine? who fitted the jets?

[d1mitch]

i bought the weber from a member here, who never fitted it to his car but the guy who he bought it off supposedly had it running fine on his sierra.

i need to have a play around with the jets and such but would just like to get any ideas on what would be causing the flat spot

[SuziBlu]

droverdave wrote:

SuziBlu wrote:

droverdave wrote:

Why are you wasting your money on bp ultimate?

Please explain why not.

I run 98 in everything, cars, mower, chainsaw, whippersnipper, would not use anything else, ever.

Please tell us why money is being wasted.

Does it run any different in 98 octane than on 91?

If its not tuned for 98 octane (specifically the ignition timing) then there is no advantage other than the (apparent) cleaning abilities.

My WRX runs on 98, and if i run it on 95 or 91 it pings its guts out because the ignition timing is designed to take advantage of the octane of the fuel. My drover, ae112 corolla, lawn mower, wipper snipper all run on 91 (the cheapest i can buy) and it makes no differnce to driveability or fuel economy. (ive checked both the corolla an drover, within 10% fuel economy on 91,95 or 98).

Of course people are going to come back and say "oh but it runs alot better, i have 50kw more on 98", reality is, unless you change the ignition timing to suit, then there is no benifit of 98 to 91 (except the advertised cleaning ability, which i dont think is measurable). I did try an experiment where i put 98 in the drover and advanced the base timing until it pinged and backed it off a bit. It didnt really make much difference to the but dyno, and for the last year it has been 100% reliable and gotten 8-9L/100km daily driving on 91.

If the engine is in good condition, carby is working how its supposed to work, ignition is set to what suzuki recomend, then there is no reason to buy 98 over 91. (Afterall, suzuki and toyota specify 91)

re: webber.

Where did you get the webber? Was it specifically tuned for your engine? who fitted the jets?

I run 16degrees initial timing, in my G16A, runs sweet as, no pinging, imagine if I ran 95, or woe is me, 91.

I have to buy my fuel in jerrys, so why bother with different fuels, the amount I would save by buying cheap shitty fuel, for other than the car is negligible, so IMO use the 1 fuel in everything.

[droverdave]

Well its a bit different if you are buying in bulk i guess.

If you are standing at the bowser in suburbia with a choice between 98, 95 and 91 with a standard engine with oem ignition timing, then in my oppinion theres no gain to be had buying 95 and 98.

[SuziBlu]

Dave, I agree if it is a carby job, or if it is an old very early electronic computer controlled car, but these days, new computers can adjust to greater amount than used to be.

Part of the reason why 91 is shit is that it is never really 91, can be as low as 89, and also usually the older stale higher octane is put into the lesser fuel, so your modern computer is always chasing its tail trying to work out what the hell its spozd to do.

[henno]

I would argue that carby engines are far more picky about fuel than their EFI counterparts. Like you said, ECUs are far better at adjusting 'tune' (for want of a better word) according to the conditions (air temp, relative humidity/oxygen levels, fuel etc) whereas a carby is a static tune that can't retard or advance the timing accordingly.

I am no ECU expert (far from it) but from my limited knowledge in EFI engines and having had to retune many a carby to suit a change in fuel preferece (granted, for race purposes) EFI wins for adaptability hands down.

[droverdave]

Are thes "adjusting" ecu's proactive in advancing timing up to give maximum torque at those conditions? Or do they have set ignition timing and reactively retarding timing based on knock?

[JrZook]

droverdave wrote:

they have set ignition timing and reactively retarding timing based on knock

[henno]

Yeah, which is kind of my point. Unless your car is "tuned" (I dislike using that word) for high octane fuel, you will see no actual benefit, at least from an ignition point of view. A carby engine is certainly not going to be any better at taking advantage of being able to advance timing unless you have physically advanced the timing yourself at which point it (obviously) won't retard the ignition once it knocks if you decide to go back to 91ron.

[losfer]

regardless if your car is tuned or not , the higher the octane , the slower the burn rate , which in turns means a more complete combustion of the fuel .

[JrZook]

losfer wrote:

which in turns means a more complete combustion of the fuel .

That is if you advance the ignition to counter the reduction in burn rate.

[droverdave]

And if you do it, are you getting the improvement to match the price difference?

I paid $1.74 for bp ultimate the other day, 91 was $1.58 i think at the same time. Admitdly 15c over 40L is only $6 more. But if you are filling up every week (like i do), thats over $300/year. Better in my pocket than BP's.

Though if you can prove you can get better fuel economy with the 98, and the dollar value per 100kms is less than 91, then sure go the 98. When i tried it in my drover it didnt make financial sense. (my old 4age though did seem to get better fuel economy, it also went faster with ~20 deg base timing and 98)

[Gwagensteve]

It's generally more financially economical to run 98 in cars that are knock sensed than lower octane fuel. This has been from my personal experience with quite a few cars.

If that car isn't knock sensed or is carby and timing isn't adjusted to suit the higher octane, then running higher octane than the minimum recommended is a waste of money. The "extra power" offered by 98 octane is just burning down the exhaust.

Steve.

[fordem]

d1mitch wrote:

i bought the weber from a member here, who never fitted it to his car but the guy who he bought it off supposedly had it running fine on his sierra.

i need to have a play around with the jets and such but would just like to get any ideas on what would be causing the flat spot

I would start by increasing the size of the idle jet.

[JrZook]

fordem wrote:

d1mitch wrote:

i bought the weber from a member here, who never fitted it to his car but the guy who he bought it off supposedly had it running fine on his sierra.

i need to have a play around with the jets and such but would just like to get any ideas on what would be causing the flat spot

I would start by increasing the size of the idle jet.

I would also be checking the accelerator pump for unwanted play and slightly enriching up the idle mixture screw. Have you port matched the adapter to the inlet manifold?

[d1mitch]

yep will be changing jets on the weekend

JrZook wrote:

fordem wrote:

d1mitch wrote:

i bought the weber from a member here, who never fitted it to his car but the guy who he bought it off supposedly had it running fine on his sierra.

i need to have a play around with the jets and such but would just like to get any ideas on what would be causing the flat spot

I would start by increasing the size of the idle jet.

I would also be checking the accelerator pump for unwanted play and slightly enriching up the idle mixture screw. Have you port matched the adapter to the inlet manifold?

i am going to get a accelerator pump diaphragm and replace that as they can be know to cause problems too so a new one wont hurt.

i havent port matched the intake yet as i just need to get it running so i had a car. i will be port matching it over the christmas break. is enriching the idle mixture turning the screw in or out?

where is the best place to get jets and parts in perth?

[SuziBlu]

http://www.scuderiatopolino.com/Tuningo ... rsrev2.pdf

[JrZook]

d1mitch wrote:

i am going to get a accelerator pump diaphragm and replace that as they can be know to cause problems too so a new one wont hurt.

i havent port matched the intake yet as i just need to get it running so i had a car. i will be port matching it over the christmas break. is enriching the idle mixture turning the screw in or out?

where is the best place to get jets and parts in perth?

Turn the mixture screw out to richen. Non port-matched intake could also be causing a lot of grief with all the turbulence there