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Chris (aka- Moose)
Chris (aka- Moose), Technician
Category: Ford
Satisfied Customers: 45043
Experience:  16 years experience
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Ford Mustang GT: My son has a 98 Mustang GT 4.6L, manual transmission.

Customer Question

My son has a 98 Mustang GT 4.6L, manual transmission. Service engine light is on due to a P0303 code. Car runs fine for about 15 - 20 minutes, then it bogs down around 3000 rpm, but only when it is in gear. He said that last time it bogged down, he took it out of gear and was able to rev over 4000 rpm just fine - but as soon as he dropped it back in gear, 3000 was as far as it would go.
Submitted: 1 year ago.
Category: Ford
Customer: replied 1 year ago.
By the way, it seems not to matter WHAT gear the trans is in - it bogs around 3000 rpm in any gear (and whatever speed he's going in that gear at 3000 rpm).
Expert:  Chris (aka- Moose) replied 1 year ago.
For this 0303 code can you tell if a cylinder is misfiring through this event?I would like to know if you have cleaned the MAF sensor, checked the fuel pressure, and checked for restricted catalytic converters. You want a excellent 5 star answer & I would like to be rated the same for providing it. Consider I don't know your skill level & I can't see, smell, hear, or touch the vehicle. It may take a few back and forth replies. Try your best to respond with good detail so I can do the same. I normally log in at 3pm and work late. A rating is required. Your rating me, what I type. I am not an employee of this website, nor have control over the fees or the time it took to get a response. If you rate negative or not at all you still paid, but I get nothing. I want you pleased with me and my efforts, so let me know if your experience here has come up short.Thanks Chris
Customer: replied 1 year ago.
It doesn't seem to be misfiring - but I can't tell by listening to it. (The car has some kind of racing cam in it and idles unevenly.) The code has been cleared and it comes back, so I guessed there must be a misfire, unless there's something wrong with the chip that gives the code. We have changed the camshaft position sensor, based on a suggestion; no change. Other than that, we have done nothing. The spark plug is going to be a challenge to get to: there's some aftermarket supercharger hardware in the way. (No, we did not do the mods; he bought the car this way.)We did not check any of the things you asked about. I'm a casual backyard mechanic who usually relies on books and logic to get through whatever I have the tools and time to tackle. Why would the MAF sensor or catalytic converter cause this to happen only when the car is in gear? I could see maybe a fuel issue (more energy needed to move the weight of the car than when it is not under load...), but then why the code? I was leaning about a coil pack, but then again, why just when the car is in gear?
Frankly, I was hoping for a more definitive answer, given the symptoms I provided. We don't want to spend a lot of time checking those things or trying to replace a spark plug that is hard to get to -- or part-swapping to get to the answer. I don't even have the capability to check fuel pressure or for a restricted catalytic converter. We might just have to take it to a mechanic.
Expert:  Chris (aka- Moose) replied 1 year ago.
Sorry I did not realize the car was modified. I do not work on modified cars. I will opt out and get you back on the list for another to help you.

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