runs rough
10-26-2016 | 09:47 AM
#1
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runs rough
my 87 was running rough...mis-firing so I changed the plugs & it ran perfectly for a few days & now is back to mis-firing...not as bad as before, but getting there...I replaced the coils in April of 2014 & plugs...have not put 5k mile on it since. It just started acting up again this fall....any ideas...the plugs I removed looked to be fine...clean & not oily...could it be fuel delivery, or maf problem?
Tom Taylor
Tom Taylor
10-26-2016 | 10:46 AM
#3
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Joined: May 2002
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From: Roswell, GA
my 87 was running rough...mis-firing so I changed the plugs & it ran perfectly for a few days & now is back to mis-firing...not as bad as before, but getting there...I replaced the coils in April of 2014 & plugs...have not put 5k mile on it since. It just started acting up again this fall....any ideas...the plugs I removed looked to be fine...clean & not oily...could it be fuel delivery, or maf problem?
Tom Taylor
Tom Taylor
Pull the new plugs and look at their condition.
10-27-2016 | 03:35 PM
#5
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Joined: Jul 2006
Posts: 5,199
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From: Bloomfield, MI
"..the plugs I removed looked to be fine...clean & not oily...could it be fuel delivery, or maf problem?".
Yes and yes.
However like Stan enquired, the ECU could be an issue w/ rough running, MAF usually but not always shows up as hesitation weak throttle response.
As it ran OK for a bit after changing the plugs I'd suggest:
Ohm out each Plug lead and note any drastic differences (check for cracks in the insolation).
For a good Idle mixture you need a fresh O2 sensor (less than 60k miles on it) and good (clean) MAF, rebuild it if it's old or never been done, won't hurt in the long run.
Check the TPS making sure its closed (o Ohm's) when the throttle is at idle.
Get a loaner LH and run it, the early 87 are known to have teething issues as they were a new design.
Edit: don't rule out a stuck / dirty Fuel Injector, but as you said the plugs all look the same, one of them should have looked different.
Dave K
Yes and yes.
However like Stan enquired, the ECU could be an issue w/ rough running, MAF usually but not always shows up as hesitation weak throttle response.
As it ran OK for a bit after changing the plugs I'd suggest:
Ohm out each Plug lead and note any drastic differences (check for cracks in the insolation).
For a good Idle mixture you need a fresh O2 sensor (less than 60k miles on it) and good (clean) MAF, rebuild it if it's old or never been done, won't hurt in the long run.
Check the TPS making sure its closed (o Ohm's) when the throttle is at idle.
Get a loaner LH and run it, the early 87 are known to have teething issues as they were a new design.
Edit: don't rule out a stuck / dirty Fuel Injector, but as you said the plugs all look the same, one of them should have looked different.
Dave K
Last edited by davek9; 10-27-2016 at 03:52 PM.
10-27-2016 | 11:10 PM
#6
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Joined: May 2004
Posts: 28,637
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From: Philly PA
I must be on ignore you never answered my questions in post 2
FWIW if your seeking wisdom the more info you provide,
the more accurate the suggestions will be.
That said please answer the questions I posted and describe exactly what was replaced on the intake refresh, or if it was even done , thanks
FWIW if your seeking wisdom the more info you provide,
the more accurate the suggestions will be.
That said please answer the questions I posted and describe exactly what was replaced on the intake refresh, or if it was even done , thanks
10-27-2016 | 11:40 PM
#7
Racer
Joined: Oct 2014
Posts: 402
Likes: 0
From: Columbia, Missouri
I must be on ignore you never answered my questions in post 2
FWIW if your seeking wisdom the more info you provide,
the more accurate the suggestions will be.
That said please answer the questions I posted and describe exactly what was replaced on the intake refresh, or if it was even done , thanks
FWIW if your seeking wisdom the more info you provide,
the more accurate the suggestions will be.
That said please answer the questions I posted and describe exactly what was replaced on the intake refresh, or if it was even done , thanks
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10-27-2016 | 11:51 PM
#8
Race Car
Joined: Apr 2010
Posts: 4,016
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If you have MrMerlins help here, take it. He knows his stuff.
How old are the plug wires? Run the car with the hood open in as dark a place as you can find and spray a fine mist of water on the engine near the front where the plug wires are. Check for arcing of the wires.
How old are the plug wires? Run the car with the hood open in as dark a place as you can find and spray a fine mist of water on the engine near the front where the plug wires are. Check for arcing of the wires.