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Discussion Starter #1
I hope someone can help. My 1997 Mustang GT recently started running horribly bad. I initially thought that i had cracked the intake manifold as it is a common problem. I pulled the top of the motor apart, and switched over to the Ford Racing PI Intake Manifold. No leaks... Vacuum is good, compression is good, and im showing no codes. I can pull spark from any cylinder on the left bank while running with no noticable difference, but the second i pull one from the right bank, I can hear a clear miss. I seem to have the same problem as this guy:

1997 Mustang GT 4.6L Removing spark plug wire does not change rythem of engine - Ford Mustang Forums

But im not trying to throw parts at my car, nor am i willing to give my car up for 2+ weeks and spend $1300 on the fix. Any help with ideas of what would fix this problem would be greatly appreciated!!
 

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Do a compression test , its the quickest indicator of an engines condition.
Have you tried disconnecting the fuel injectors one by one on that side to see if that affects anything?
How did you put the PI manifold on? Did you use rtv, or an adapter? Plug holes are dry?
No coolant leaking in?
 

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On the firewall passenger side there is a harness connector. check that it is plugged in right.

I would also double check your spark wire arrangement. there is a chance you messed or crossed it up some.
 

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Discussion Starter #4
Compression is good, Vacuum is good. I used rtv installing the PI intake between the PI gaskets and NPI heads around the water jackets - No Leaks... Pulling an injector in a cylinder on the left bank yields the same result as pulling a spark -No noticable difference.. Spark plugs and holes look great. Im not finding anything along the passenger side firewall that is not plugged in properley and securely. The problem appeared one day, it has not come on as a result of pulling the intake, that was an attempt at fixing the problem. I thought coolant was getting into the left bank cylinders.
 

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If its the whole bank that is dead, that rules out spark, fuel. Valve timing would be the next thing, chain jumping because of tensioner or guides.
Do the plugs on the dead side look wet/oily? Do all 4 look the same? How about compared to the good side?
Weird that out of the blue the whole bank would be dead. Please keep updating as progress is made.
 

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I dont see how you can say that rules out spark. It sounds like a Bad coil pack on that side. (ford designates these bank 1 pass side and bank 2 driver side) If the timing jumped he wouldnt have good compression like he states. My bet is bad coil pack if one bank is dead or like someone already stated a harness connection. Bad coil pack would not show any codes either as OP stated, but would eventually be picked up by the O2 sensor on that side and it would try to lean it out to compensate for the over rich on that side. Might have to be driven 10 miles for that code to show up though.
 

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Discussion Starter #7
I cant see the problem being a coil pack issue. They're MSD coil packs that were put into the car between a year and a year and a half ago. Each coil pack is responsible for firing two cylinders on each bank. So if it is a coil issue, it is both of them.-unlikely to be affecting only the left bank... Plugs were changed just before last summer, they're hardly showing any use. Im leaning toward it being one of the parts that fixed the car in the link from my first post:

"Replaced HEGO Sensor, Swapped CAT. Monitor Sensors, replaced PCM, replaced DPFE sensor, replaced PFE sensor and replaced timing sprocket....and $1,300.00 later it runs like a champ."

Timing was also checked on his car by the garage that he took it to. The timing was spot on. I AM VERY GRATEFUL FOR RESPONSES.... please dont stop chiming in. I will be sure to post the solution once the proper diagnosis is reached.
 

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Have you checked the cam sensor in the left side head? Try running with it unplugged.
Maybe they are not dead, just a misfire that is masking the change in idle when you unplug each plug. Swap coil packs around, unplug egr and dpfe, listen for vacuum leaks.
 

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Discussion Starter #9
I think ive gotten to the bottom of this one. I pulled the O2 on the drivers / (dead) side, and started the car. Hard to tell for certain under the noise, but the car sounded much better. It's pouring rain outside, but i backed it out and took it down the road. I'll have to make sure once the roads are dry again, but it felt like tons of power was back. When i dumped the clutch, the car responded like it should on wet roads, it rose and went almost no where.... but it didn't bog down.. Must be a melted cat.. Anybody recommend a good CATTed X pipe setup that will pass CA smog??
 
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