engine mis-firing during acceleration - Toyota Nation Forum : Toyota Car and Truck Forums

zturek · 10-26-2007, 10:33 AM

I have 89 toyota corolla with carb that misses during acceleration.
I seems to run ok when it is cold an the choke is on. It starts
having this problem during acceleration only but it does seem
to idle ok.

mopars&corollas · 10-26-2007, 11:11 AM

That can be so many things. If you manually rev you engine, does it miss? First guess would be a vacuum leak. Have you checked plugs and wires to make sure they are good and that you have solid spark?

zturek · 10-26-2007, 11:38 AM

Yes it does miss when I manually rev the engine. The sparks plugs
and wires were replaced about two months ago along with the fuel
pump and filter which was having vapor lock issues.

joeyicu · 10-26-2007, 11:45 AM

Quote:

Originally Posted by mopars&corollas

That can be so many things. If you manually rev you engine, does it miss? First guess would be a vacuum leak. Have you checked plugs and wires to make sure they are good and that you have solid spark?

an engine under load has little to no vacum compared to idle with the throttle plates closed

since spark is not the issue, i would have to lean towards having gunk in your carb, id take it off and clean it out making sure to be careful not to break anything and also replace all the gasketry as you go even if its reusable, that may help

its the 1.6L motor with the little 1 barrel right?

zturek · 10-26-2007, 12:06 PM

Yes it is a 1 barrel carb. Before I go pulling carb of I would
like to make sure that is the problem. Is there any thing
that I can try to verify that it is the carb?

mopars&corollas · 10-26-2007, 12:15 PM

Quote:

Originally Posted by joeyicu

an engine under load has little to no vacum compared to idle with the throttle plates closed

since spark is not the issue, i would have to lean towards having gunk in your carb, id take it off and clean it out making sure to be careful not to break anything and also replace all the gasketry as you go even if its reusable, that may help

its the 1.6L motor with the little 1 barrel right?

And yet vacuum was the problem I had with that exact same issue. Notice I did preface the comment with saying it could be a lot of things. Definitely take a look at the carb and maybe use a little carb and choke cleaner on it before you pull it off the engine. If something isnt sealed that should be, it will cause this issue. I have also experienced this issue on a big engine with poor wiring.

mopars&corollas · 10-26-2007, 12:21 PM

Quote:

Originally Posted by zturek

Yes it is a 1 barrel carb. Before I go pulling carb of I would
like to make sure that is the problem. Is there any thing
that I can try to verify that it is the carb?

If you had any idea where your vacuum leak was- hold an unlit propane torch in the neighborhood. If your engine revs up, you have a vacuum leak.

90 GP · 10-26-2007, 06:59 PM

Check your timing and the vacuum advance unit on the distributor. Check for leaks in the rubber vacuum lines that connect to the advance diaphram.

freakinbox · 10-26-2007, 08:08 PM

it could be the distributor, rings, headgasket, a crack, anything that can cause it to lose compression. Problems with the intake, a leak in it or such. Btw the 4af has a 2 barrel carb, not 1...

retiredat44 · 10-26-2007, 10:59 PM

I vote distributor,, you can go get a rebuilt with lifetime warranty... with core excahnge... I have been through this problem several times... it really turns the car into bucking bronco..

1989 Corolla SR5, carb, 5 speed manual,,

joeyicu · 10-27-2007, 08:34 AM

Quote:

Originally Posted by freakinbox

it could be the distributor, rings, headgasket, a crack, anything that can cause it to lose compression. Problems with the intake, a leak in it or such. Btw the 4af has a 2 barrel carb, not 1...

o ok i didnt know thats why i was asking, ive worked on that motor only a little bit in high school and i rember it being carberated, and i also rember dumping a couple gallons of water into the carb to clean the car up a little bit lol

it was a donated vehicle, it actually ran alot better after i circulated the h20 threw the system and smoked out the automotive courtyard

Awheet · 10-27-2007, 10:28 AM

Well me and my dad washed out my engine bay the other day and its been running gough and he couldnt figure out why. So he took off the spark-plug wires and there was water in one of the spark plug bays. It was missfiring during acceleration as-well. Now it doenst do it.

joeyicu · 10-27-2007, 03:06 PM

Quote:

Originally Posted by Awheet

Well me and my dad washed out my engine bay the other day and its been running gough and he couldnt figure out why. So he took off the spark-plug wires and there was water in one of the spark plug bays. It was missfiring during acceleration as-well. Now it doenst do it.

well there ya go my man

a tip i usually take my plug wires off completely and then when im done ill air out the plug holes with compressed air or something just to get the stuff outa the holes

zturek · 05-14-2008, 05:16 PM

A many months I have finally been able to look at this problem again.

I tried the unlit propane torch but no vacuum leaks found.

I different thing that I noticed is that this only runs rough
when I am under acceleration (throttle about a 1/3 down).

I can not get this problem in park or trying to power brake
and accelerate.

I looked at the boots for the spark plug wires they are clean
no oil or moisture.

I can not quite tell if it is a mis-fire or fuel Carburetor
acceleration issue.

I am going to try it again tomorrow morning to see if
it is different under cold engine conditions.

Any other inputs will be appreciated.
Thanks for your help.