951 bucking and backfiring
07-16-2002, 04:06 PM
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951 bucking and backfiring
87 bucking and backfiring
badly, started a few weeks ago, found a couple vacumm
leaks and the problem went away until last night.
I was VERY low on gas and it statred acting up, when I put some gas into it it seemed to clear up until today.
it seems to run fine until the engine is completley warmed up, then the longer you drive it the worse it gets.
seems to not be related to RPM or engine load
any ideas ?
Help !
badly, started a few weeks ago, found a couple vacumm
leaks and the problem went away until last night.
I was VERY low on gas and it statred acting up, when I put some gas into it it seemed to clear up until today.
it seems to run fine until the engine is completley warmed up, then the longer you drive it the worse it gets.
seems to not be related to RPM or engine load
any ideas ?
Help !
07-16-2002, 04:53 PM
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I think you've still got a vacuum leak. I had similar symptoms on mine awhile back, turned out to be a blown gasket on the front runner of the intake manifold. True test is to run a vacuum check - when I did mine I found ZERO vacuum! 
If one is blown out then you'll have symptoms similar to what your describing - car will run fine when first started, but once it warms up it will not idle at all.
Other possibilities might include water in your gas - causes backfiring and poor idle. Use one of the products available at the local automotive counter to correct. You can also just pour some denatured alcohol in. I've done this before and it works well.
One other possibility is crud in the tank. You mentioned the tank was low when the problem surfaced. You might have been "bottom feeding" from your tank and there may be lots of nasties in there.
But, I still think you need to run a vacuum check.
Disclaimer: Denatured alcohol can not be found in a can marked Bud! <img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" />
If one is blown out then you'll have symptoms similar to what your describing - car will run fine when first started, but once it warms up it will not idle at all.Other possibilities might include water in your gas - causes backfiring and poor idle. Use one of the products available at the local automotive counter to correct. You can also just pour some denatured alcohol in. I've done this before and it works well.
One other possibility is crud in the tank. You mentioned the tank was low when the problem surfaced. You might have been "bottom feeding" from your tank and there may be lots of nasties in there.
But, I still think you need to run a vacuum check.
Disclaimer: Denatured alcohol can not be found in a can marked Bud! <img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" />
Sorry, tried posting a link to Snap-On and whoa! Did that not work or what! 
07-16-2002, 06:36 PM
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Snap on has one listed for $160 on their site - But that's way high! It should come with a lovely young lady in short shorts at that price. Anyway, they look like this...
and plug into a your vacuum line with a "T".
Sorry for all the double posts! Seem a bit Dyslectic today! <img src="graemlins/yltype.gif" border="0" alt="[typing]" />
and plug into a your vacuum line with a "T".
Sorry for all the double posts! Seem a bit Dyslectic today! <img src="graemlins/yltype.gif" border="0" alt="[typing]" />
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07-16-2002, 10:36 PM
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sorry .. I meant what is the best way TO test for vac leaks.. I have a vac pump/gauge.
what is the best way to seal up the system, make a plate for the AFM and another for the throtle body
then test the intake manifold later ?
anyway I replaced few vac lines that "looked" leaky
cleaned the contacts on the AFM changed the plugs
put some fuel injector cleaner and some denatured alcohol into the tank (and some becks beer for good measure)
and it seems to be fixed (for now)
what is the best way to seal up the system, make a plate for the AFM and another for the throtle body
then test the intake manifold later ?
anyway I replaced few vac lines that "looked" leaky
cleaned the contacts on the AFM changed the plugs
put some fuel injector cleaner and some denatured alcohol into the tank (and some becks beer for good measure)
and it seems to be fixed (for now)
07-16-2002, 10:58 PM
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[quote]Originally posted by initzero:
<strong>sorry .. I meant what is the best way TO test for vac leaks.. I have a vac pump/gauge.
what is the best way to seal up the system, make a plate for the AFM and another for the throtle body then test the intake manifold later ?</strong><hr></blockquote>
See, here's where your supose to use the QUOTE button! <img src="graemlins/c.gif" border="0" alt="[ouch]" />
Some one correct me here if I'm wrong, but you shouldn't need to seal anything. You're testing to see if there is a leak under normal driving conditions. If you seal up anything then you're defeating the purpose of the vacuum check.
Glad to hear it's running better (those intake manifold gaskets are a bummer to replace)!
<strong>sorry .. I meant what is the best way TO test for vac leaks.. I have a vac pump/gauge.
what is the best way to seal up the system, make a plate for the AFM and another for the throtle body then test the intake manifold later ?</strong><hr></blockquote>
See, here's where your supose to use the QUOTE button! <img src="graemlins/c.gif" border="0" alt="[ouch]" />
Some one correct me here if I'm wrong, but you shouldn't need to seal anything. You're testing to see if there is a leak under normal driving conditions. If you seal up anything then you're defeating the purpose of the vacuum check.
Glad to hear it's running better (those intake manifold gaskets are a bummer to replace)!
07-17-2002, 12:16 AM
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I thought you were talking about
a not-running test.
I have a vac gauge in the car and the most vac I can generate is 20in is this a normal value ?
in theory, one could mount a plate in between
the throttle body and manifold and another between the AFM and airbox (in a stock AFM config)
and use a vac pump to apply vacumm (or pressure) to the entire induction system except for the actual intake manifold.
has anyone tried this ?
a not-running test.
I have a vac gauge in the car and the most vac I can generate is 20in is this a normal value ?
in theory, one could mount a plate in between
the throttle body and manifold and another between the AFM and airbox (in a stock AFM config)
and use a vac pump to apply vacumm (or pressure) to the entire induction system except for the actual intake manifold.
has anyone tried this ?
07-17-2002, 01:29 AM
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The road sign is located about 5 miles north of my new "ranch" in south central Texas! 
Bought 18 acres in June and plan on retiring there in about 15 years. Texas FM 951 is only about 5 miles long, but it's got lots of twists and elevation changes! Road surface is ok, but not perfect. Maybe we can get the state to repave it for us so we can do high speed runs! Yea - right <img src="graemlins/burnout.gif" border="0" alt="[burnout]" />
On the vacuum check, I was refering to the one that you use while the car is running. I don't recall what the correct reading was - sorry.
Bought 18 acres in June and plan on retiring there in about 15 years. Texas FM 951 is only about 5 miles long, but it's got lots of twists and elevation changes! Road surface is ok, but not perfect. Maybe we can get the state to repave it for us so we can do high speed runs! Yea - right <img src="graemlins/burnout.gif" border="0" alt="[burnout]" />
On the vacuum check, I was refering to the one that you use while the car is running. I don't recall what the correct reading was - sorry.
