4k Stutters And 'lags'

[eiriksmil]

My 4K is fantastic, it's done 300k and the fuel consumption is great (6L/100km). It's only one thing that bothers me, and it's probably a simple fix. It stutters a bit when I floor it. Another car I have misfires, it's not like that, the Rolla's just hesitating a bit.. What's worse, when I've had the accelerator pressed for a while and go off, it pushes harder instead of slowing down. It doesn't last long, under a second, but it bugs me. Kinda crap when you've just overtaken and you're approaching the car in front of you... What could it be? It's almost like the car overfuels so it burns the remaining fuel when I release the throttle. Doesn't happen at all times, by the way..

I'm thinking the hesitation could be the fuel filter, but could that be the fault of the other problem too? Just wanted to hear around before I started replacing things :y:

[Falken_KE30]

Set ya points gap, set ya plugs, check timing, and clean ya carby out.

 

also replace all filters, and some fresh oil. should run like new.... or atleast better haha

[muzke30]

i got same problem with my 4k when i floor it and already change leads plus and still same thing it shutters a bit the weirds thing happend to me other day it went away for a good 15 min trip but on way back on freeway go to over take and i have to go 3 quater throttle just to gain speed. I have already opend a thread in regards to this pretty sure its a carby problem I'm going over seas for 6 weeks so will have to look into it when i get back hope this helps.

 

http://www.rollaclub.com/board/?showtopic=29662

[high_rpm]

could be accelerator pump on the carby

[corolla_bitten]

your fuel consuption sounds a bit unrealistic, only a few new models can acheive that. my standard ke70 with rebuilt factory carby only gets 7.8l/100k's. If it is what you are saying, its probably not getting enough fuel, tune carby

[Falken_KE30]

yeah i doubt 6L/100kays too actually.

 

I get an average on 8L/100kays on a mix driving, and some spirited driving...

[eiriksmil]

Not an average of 6, are you crazy. I'm not granny either :D I did manage it over of 300 kms during a road trip though, I thought it was pretty wild for a nearly 30 y/o carb'd car. Just had to get it down, so you didn't think this problem affected my fuel economy.

It could be that it's getting too little fuel, although I don't see how it gets an extra go when I go off the gas. Almost seems like the fuel is building up?

[KENut]

My KE70 had the same problem, especially the stutters when you push the load pedal down quick. If you have a look at the carbie you'll see that the accelerator pump linkage has a spring on it to sort of slow the application of the pump when the throttle is pushed. Start the car (when its hot) and hop under the bonnet. Hold the accelerator pump down at the linkage end and push the throttle at the same time. If the engine revs up quicker than normal you know its getting too much fuel. I fixed mine by getting a carbie kit ($45) for it and tuning it.

[rob83ke70]

vacuum leak or throttle nudger actually doing its job. probably vacuum leak though.

 

spray hydrocarbons (brake cleaner or carby cleaner) around the manifold/head joints with the engine idling (not too warm though) and see if it does anything, if it stalls or picks up revs then you have a leak.

 

best way i've found to seal manifold gaskets is to clean both surfaces thoroughly, and put a new gasket on coated both sides in silastic of your choice (the more expensive the better generally) and I used allen headed bolts (the O.D. of the bolt heads are the same as the genuine automotive spec 14mm head bolts, and they are readily available. this way (assuming bolts are correct length) there is no risk of the nut bottoming out on the stud or the bolt bottoming out on the thread and not squishing the gaskets tight.

 

ignore the last paragraph if you don't have a vacuum leak.

 

robert.