carb help

[toyo92]

got the 92 sedan with 5A-F engine
do mostly highway runs and the engine even though lacking some power gets the job done.
the problem is, the car has a run on idling problem.after the car is swtiched off and the key is out it still continues to run. i am forced to swtich off in a gear..which does not help much.i have tried treatments such as redline S1 and Techcron..helped a bit but the problem is still there

the other problem is that i notice that if i step on the gas pedal and suddenly take off my foot ...only at low speeds the car shuts off...

any ideas on how i can solve this ?

[canadianae92]

uh if its dieseling it could be too high of a compression because of carbon build up(unlikely, but it can get hot) or something is getting REALLY hot and that would lean mixture

does this happen only when it is hot or always?

dieseling is engine run on without ignition... is it getting spark while it continues to run? pull off the coil plug into the distributor and does it shut off or keep running?

[Createdtoburn]

Weird, never heard of an engine running without spark lol

[SCT]

Dieseling is when the engine continues to turn over on its own for a small moment after being shut off. No spark is involved; It's basically the heat inside the chambers that is allowing the air/fuel mixtures to ignite. Like a diesel car, when you turn off a diesel, it doesn't stop running right away (at least for the old cars).

Timing could be off, like mine is. It's off by a little and diesels for two seconds but it doesn't do it all the time.

Also, carbon build-up in the combustion chambers and/or a fast/ incorrect idle speed.

If any of those problems are there, if conditions are right, the engine can run on its own steams for a good amount of time which I've seen only once in an old diesel Mercedes-Benz but that was a diesel...

[90 GP]

If it's carbed it has a mass of vac lines. Check all for leaks.

[Flashmn]

Idle off solenoid, intake/carb gasket, intake leaks, stuck float (carb flooding), bad timing, etc, you got your work cut out.

Weird, never heard of an engine running without spark lol

Diesel engines run without sparks

[toyo92]

it only "diesels" when the car is hot..after a long run.. so i started using fuel treatmenst which seems to help for the carbon build up..has been a few months using stp fuel additive, crc carb cleaner, penray carb cleaner, the last two fill ups, i put the redline s1 and the chevron techron. the car still has run on but with the fuel additive seems to help a bit.

i decreased the idling alot, it is as low as possible, but the prob with this is the cold starts.

if the timing is too advanced.. what would i have to do ?

[toyo92]

also some of the vac valves were taken out by my mech...i would like to reinstall them eventually...dont know which vac valves were taken out...but i know the one by the dizzy is not hooked up and two or three around there

[90 GP]

The vac lines at distributor definitely need to be replaced. You need them to allow the vac advance unit on distributor to function. That accounts for your lack of power and more than likely is contributing to your dieseling. Don't know why the mechanic ever removed them in the first place.

[toyo92]

are there any diagrams available that migh show me how to reinstall the vac lines ?

[canadianae92]

timing could contribute to creating that much heat in the chambers, take out a spark plug and take a picture or describe how it looks like, is there pitting, broken insulation, is it mostly white, tan/brown, or black?

id definitely get the vac lines taken care of

[Flashmn]

Using too much fuel additives can cause other issues, since most of the so called fuel system cleaners are actually kerosene, they drop your octane number. Also modern fuels have really good detergents in them, I havent seen significant carbon deposits in modern fuels and modern engines that are maintained and have decent oils in them. Blackness and residue ontop of pistons isnt carbon deposits, thats normal.

I'd say theres an intake air leak, which is causing it.

[Ghostyman]

Originally Posted by Flashmn

Using too much fuel additives can cause other issues, since most of the so called fuel system cleaners are actually kerosene, they drop your octane number.

Shouldn't kerosene raise the effective octane?

To the original poster: if you are really seeing improvements from the gas cleaner, then it does sound like you've got excessive carbon buildup. My recommendation is to suck a bottle of ATF through a vacuum hose (exact same procedure as Seafoam) -- that should burn most of it out of your combustion chambers.

[Flashmn]

Kerosene doesnt have an octane rating, because its an light oil like diesel, it has a cetane number. Too much kerosene and your car will stop working properly, kinda like putting diesel in the fuel tank. Octane boosters are mostly kerosene, tho they have "unnamed" petrochemicals in them if you read the label, probably toluene is used to "bump" the octane, however fifth gear tested them out, the result was quite interesting.

You Tube

You Tube

[toyo92]

well the additives did work...i am not in the states
so there are no special additives in the gas..i think its about 92 ron for super and 95 for premium...
the preimum has helped the problem a bit, which is why i started using the fuel additives
btw wats ATF ?...and i do not think sea foam is here cause i was looking into that
read some old school method of drippin water into the carbs but too risky if done wrong
the other thing would be the carb cleaner into the gas filter...
forgot the add..i suspect as the car diesels and shuts off i think gas is shot out of the carb....will does a lil experiment weekend and find out... but i know the buttom of the air filter has a gas stain..jus one spot
i will try puttin the vac line in this weekend...