hesitation remains

[Bills money pit]

Just returned from local mechanic who, for the second time, said he took out the stumble in the 81 by reducing accelerator pump charge and readjusting the fuel mixture. The stumble remains...Put ECM in diagnostic mode and received only the 12 code as expected, no other codes. I have now exceeded by expertise and need help.....

Any suggestions

Thanks!

 

[redvett]

Have you set the timing? If engine hasent had a new timing chain since new try advancing timing a couple of degrees. The ECM in that era were dumb and couldnt diagnose any thing. Check float level (too low) and check for vaccum leaks along with condition of rotor, cap and see if ign coil has carbon tracks on inside of cap where coil sits. Leaning out those cars is the wrong way to go they were way to lean from the factory to pass emissions.

 

[motorman]

Just returned from local mechanic who, for the second time, said he took out the stumble in the 81 by reducing accelerator pump charge and readjusting the fuel mixture. The stumble remains...Put ECM in diagnostic mode and received only the 12 code as expected, no other codes. I have now exceeded by expertise and need help.....

Any suggestions

Thanks!

take a voltage reading on the TPS

 

[redvett]

take a voltage reading on the TPS

I would hope that the mechanic used a scanner and looked at all the values available to see any discrepancys. Leaning out an engine without an exhaust analyzer is throwing darts in the ocean.

 

[Bills money pit]

Thanks for your reply. The timing was advanced to 10 deg and starts quick with no detonation. Have not checked tyhe distributor components you mentioned. It was running rough and what ever the mechanic did to try to fix it caused the stumble. I am starting to believe it is the idle mixture. What tool does it take to fit the idle screws and how should I set them. How many turns out them in I suppose. You recommendations are appreciated.

 

[Bills money pit]

I assume you are refering to the throttle position sensor. What should the voltage reading be and if it is low, what next? I am a novice and must ask, are both of the connectors on the front side of the carb the TPS?

 

[Bills money pit]

I am sorry but I do not know what he did...said he reduced the accelerator pump charge and messed with the lean/rich mixture. Should I screw in the mixture screws or turn them out???? I do not have an ega.

Thanks

 

[Bills money pit]

Another stumble issue

I failed to mention I found it necessary to route the hoses as indicated by the under side emission tag. Several hoses were not routed as indicated by the tag...Could this have an effect on the carb performance ie. stumble????

Thanks

 

[gmjunkie]

I failed to mention I found it necessary to route the hoses as indicated by the under side emission tag. Several hoses were not routed as indicated by the tag...Could this have an effect on the carb performance ie. stumble????

Thanks

Yes!!! and I know this should have a electronic Carb,But I don't think it has a TPS!!!!!!! I've got a Bone Stock 81 and it dose not have TPS!!

 

[AKRAY4PLAY]

is it a lag or intermittent stumble off idle?? if it is a dead lag when you hit the throttle hard, it is lean on the idle circuit. to correct, you need to turn out the idle air screws a 1/4 turn at a time until it's gone. if it stumbles and coughs and sputters from idle to 1/2 throttle, you need new spark plugs. it is not uncommon for the insulators on the plugs to hairline crack. this leads to misfires under load. it will idle fine, but stumble bad until rpms are over 3000. i suggest running cheap old copper core plugs in a stock motor. they are $1 each and hold up far longer. try some Autolite 25's or 26's if you find the carb alright.

 

[Bills money pit]

It is a stumble off idle..goes away toward midrange. If I roll on the throttle slowly, is does not hesitate. Only when you give it the gas rapidly does it stumble. Thanks for your help.....Also it only a momentary stumble, then it runs fine....

 

[Sensei]

I have been studying the E4ME carb for some time and feel I have a bit of expertise to offer. First off, my experience says that hesitation like you describe is seldom from too much fuel, it is almost always too little fuel. The way to tell is this: Use a small punch to drive the pin that the accelerator pump lever hinges on in toward the air horn, DO NOT drive it all the way against the air horn, leave enough room to put a screwdriver blade between the air horn and the pin to get it back in place later. Now remove the accelerator pump lever. This disables the accelerator pump. Now drive the car. If the stumble is better, it was too rich. If it is worse (as I'm betting), it was too lean. If there is no change, the accelerator pump is bad. Either way, let me know what happens. These carbs are not hard to fix, it's just hard to find someone who knows how! God bless, Sensei
PS. What you describe actually sounds like an accelerator pump or float problem. Look in the carb primaries and pull the throttle. You should see two full streams of fuel shoot out like twin squirt guns. If not, or if the fuel just sputters out, the pump has problems. Again, let me know what happens!

 

[AKRAY4PLAY]

It is a stumble off idle..goes away toward midrange. If I roll on the throttle slowly, is does not hesitate. Only when you give it the gas rapidly does it stumble. Thanks for your help.....Also it only a momentary stumble, then it runs fine....

sounds like you need open up your idle mixture screws a little to richen the idle circuit. that will fix your stumble, unless it from a bad accellerator pump. you can test the pump, remove the air cleaner and open the upper flapper by hand. with the engine off, look into the carb and manually actuate the throttle to full open. if it squirts a good amount, the pump is accel pump is good.

 

[Bills money pit]

Do I turn the screws our (counter clockwise to richen and what tool do I need to fit the idle screws????


Thanks for the advise

 

[Bills money pit]

If I screwed in the idle screws, how many turns out is a good starting point?

Thanks

 

[Bills money pit]

If the accelerator pump is to rich, what is the fix?

 

[motorman]

Yes!!! and I know this should have a electronic Carb,But I don't think it has a TPS!!!!!!! I've got a Bone Stock 81 and it dose not have TPS!!

yes they do have a TPS is is moved by the accelerator pump arm. it is inside the carb.

 

[motorman]

I have been studying the E4ME carb for some time and feel I have a bit of expertise to offer. First off, my experience says that hesitation like you describe is seldom from too much fuel, it is almost always too little fuel. The way to tell is this: Use a small punch to drive the pin that the accelerator pump lever hinges on in toward the air horn, DO NOT drive it all the way against the air horn, leave enough room to put a screwdriver blade between the air horn and the pin to get it back in place later. Now remove the accelerator pump lever. This disables the accelerator pump. Now drive the car. If the stumble is better, it was too rich. If it is worse (as I'm betting), it was too lean. If there is no change, the accelerator pump is bad. Either way, let me know what happens. These carbs are not hard to fix, it's just hard to find someone who knows how! God bless, Sensei
PS. What you describe actually sounds like an accelerator pump or float problem. Look in the carb primaries and pull the throttle. You should see two full streams of fuel shoot out like twin squirt guns. If not, or if the fuel just sputters out, the pump has problems. Again, let me know what happens!

do not loose the little green pin that is under the acellerator pump arm as that controls the TPS

 

[motorman]

Just returned from local mechanic who, for the second time, said he took out the stumble in the 81 by reducing accelerator pump charge and readjusting the fuel mixture. The stumble remains...Put ECM in diagnostic mode and received only the 12 code as expected, no other codes. I have now exceeded by expertise and need help.....

Any suggestions

Thanks!

computer controlled carbs have special adjustments that can not be made with out the gage tools.

 

[gmjunkie]

yes they do have a TPS is is moved by the accelerator pump arm. it is inside the carb.

Cool!! Ya learn somthing every day!!