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Engine misfire on acceleration!

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Old Oct 2, 2011 | 04:00 PM
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Default Engine misfire on acceleration!

Just started a week or two ago, would misfire under acceleration but when the pedal was released and applied again it would be fine. This started ever so often, not consistently. But it now happens more frequently, still depends on how hard the gas pedal is applied and reapplied.

No codes, no vacuum leaks, maybe Throttle position sensor?

Has anyone ran into this before?

Last edited by sfc rick; Oct 2, 2011 at 04:23 PM.
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Old Oct 2, 2011 | 05:50 PM
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Carefully follow your injector wiring harness (both sides) where they go to the rear of the manifold and makes a turn around the fuel rail stop bracket.

Tight fight + engine vibration/movement = 1 or more wires being rubbed through and intermittent shorting of an injector. Check your coil wiring harnesses as well.

Give it the close eyeball. The slightest little cut is all it takes.
HTH
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Old Oct 2, 2011 | 06:13 PM
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Will give it a look! I certainly have been doing a lot of work on the top end and could've done something. The start of many problems have been the result of fixing others.
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Old Oct 2, 2011 | 07:15 PM
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Originally Posted by sfc rick
Will give it a look! I certainly have been doing a lot of work on the top end and could've done something. The start of many problems have been the result of fixing others.
I'll definitely agree with you there.
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Old Oct 2, 2011 | 08:02 PM
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And you pulled the codes using the DIC?
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Old Oct 2, 2011 | 08:38 PM
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Originally Posted by dgrant3830
And you pulled the codes using the DIC?
No codes
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Old Oct 2, 2011 | 10:01 PM
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If the misfire was related to the throttle position sensor, I would expect it would throw a TCS code(s). I'm sort of wondering if you have a grounding issue with the fuel pump itself as it has its own ground. Another quick thought would be a sticking throttle plate.
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Old Oct 2, 2011 | 11:26 PM
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Originally Posted by dgrant3830
If the misfire was related to the throttle position sensor, I would expect it would throw a TCS code(s). I'm sort of wondering if you have a grounding issue with the fuel pump itself as it has its own ground. Another quick thought would be a sticking throttle plate.
I also would have expected a code for a tps or misfire if a coil was out, but alas no codes.

I'll work on the car in the morning.
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Old Oct 3, 2011 | 02:14 PM
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Found the problem, a sparkplug wire was jumping to the header pipe on the right of the dipstick tube. Really couldn't find a way to put more space between them, so I cleaned the sparkplug boot and brushed on some liquid tape. No miss now, but it's only a.temporary fix until I buy new sparkplug wires or find a better solution.

Last edited by sfc rick; Oct 3, 2011 at 07:33 PM.
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Old Oct 3, 2011 | 02:21 PM
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Glad to here you found the problem. The car will act the same way if one of the coil packs are going bad. They will misfire under load (acceleration) but be perfect under idle. Good Catch.
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Old Oct 3, 2011 | 02:44 PM
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Originally Posted by sfc rick
Found the problem, a sparkplug wire was jumping to the header pipe on the right of the dipstick tube. Really couldn't find a way to put more space between them, so I cleaned the sparkplug boot and brushed on some liquid tape. No miss now, but it's only a.temporary fix until I buy new sparkplug wires or find a better solution.
If they are MSD wires and low mileage, I can send you a used wire to replace the defective wire. I think mine have about 15k on them. I burned one and had to buy a whole new set. Now I have 7 spares.
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Old Oct 3, 2011 | 02:58 PM
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Originally Posted by Tech
If they are MSD wires and low mileage, I can send you a used wire to replace the defective wire. I think mine have about 15k on them. I burned one and had to buy a whole new set. Now I have 7 spares.
PM sent
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Old Oct 3, 2011 | 03:17 PM
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Replied
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Old Oct 3, 2011 | 03:49 PM
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wouldn't the Koolsox or similar brand wire cover help/prevent this?
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Old Oct 3, 2011 | 04:37 PM
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Originally Posted by redrckt97
wouldn't the Koolsox or similar brand wire cover help/prevent this?
They do. However, they are unnecessary and, in my personal opinion, ugly.

MSD wires have an end that will allow you to bend/shape them away from hot parts. I apparently missed double checking my wires after doing some work one day. I imagine the OP had a similar situation.
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Old Oct 3, 2011 | 04:49 PM
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Originally Posted by Tech
They do. However, they are unnecessary and, in my personal opinion, ugly.

MSD wires have an end that will allow you to bend/shape them away from hot parts. I apparently missed double checking my wires after doing some work one day. I imagine the OP had a similar situation.
Better Solution!
I found my oil dipstick tube was pushing the sparkplug boot onto the header pipe. I noticed the notch for the dipstick on the cover was further over so I pushed the dipstick tube over to the notch. It made plenty of room.


Last edited by sfc rick; Oct 3, 2011 at 07:34 PM.
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Old Oct 3, 2011 | 06:43 PM
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Originally Posted by sfc rick
I found my oil dipstick tube was pushing the sparkplug boot onto the header pipe. I noticed the notch for the dipstick on the cover was further over so I pushed the dipstick tube over to the notch. It made plenty of room.

Consider this quality, bonding-time with your car.
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Old Oct 3, 2011 | 07:19 PM
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Originally Posted by LoneStarFRC
Consider this quality, bonding-time with your car.
I bonded my finger to it.

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