Car's running poorly (see details)


Old 11-21-10, 02:57 PM
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Car's running poorly (see details)

I have a 94 Ford Mustang V6 3.8L Automatic AODE. The car as a whole is not running optimum. It has 217,000 miles on it, and it starts acting up after I've driven it for a while especially, but the transmission will start shifting around erratically, and if I punch the gas, the shift in gear sometimes is way late. Also I've noticed that while the car ideals, the rpms fluctuates sometimes. The rpm indicator will bounce up and down 500-1000 rpms like the car wants to die. I was thinking maybe the computer is possibly on its way out (it's the original computer in the car). Any ideas?
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Old 11-21-10, 04:26 PM
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Clearly the basics haven’t been addressed.

You must rule out the common issue (s) before focusing on a major issue (s).

Rule out the following and post back the results

Engine vacuum leaks (confirm with an engine vacuum pressure tester).

Engine misfires (Ignore the “MIL”. Scan even if “MIL” is off. Post any misfire codes (or any non-misfire codes).

Are all the injectors firing? (Confirm with a “Noid Light”)

Is spark reaching all the plugs? (Confirm with an inline spark tester).

Is there an issue with fuel flow or volume? (Confirm fuel psi and volume) with a fuel system pressure tester, and post the stats.

Has the fuel filter been changed recently?

Given the mileage you should at least post the results of a compression test.

If you’re interested, and desire to take this to the next level, post the results of a compression and cylinder leak down test.

Diezel or Chandler
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Old 11-21-10, 04:29 PM
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Routine maintenance items or sensors; computers are generally pretty reliable and when they go they're usually gone, not intermittent. I still have the original computer in my '94 wrecker with a Chevy 5.7L @ 580,000 miles.

How long since it had plugs, plug wires, and dist cap & rotor (if equipped; can't remember what the set up is on that age 'Stang).

O2 sensor another possibility, but I wouldn't condemn it without checking it. On the other hand if it has a couple of hundred thousand miles on, might not hurt to replace.

Tranny serviced on a regular basis? At 217,000 miles it could very well just be worn out.

Some of the pros will be along to play more 20 questions.
Old 11-21-10, 04:31 PM
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You must have been already almost done typing when I started, Devil Dog; I was wondering why no one else was lurking out there.
Old 11-21-10, 09:23 PM
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my first guess is air leaks. either in form of worn out gaskets, or bad vacuum hoses. they used to have way too many of those back in those times. (he-he, will always remember 87 accord, had 96 vacuum lines just on the valve cover.).
as of trannie shifting poorly, regular tuneup can do miracles. plus, if engine lacks power, trannie may choke with shifts. one leads to another.

what you need to do, buddy, is to sit down and compile precise list of what exactly was ever done to this vehicle. it plain sounds neglected on basic maintenance. it's not towguys wrecker, those are made to last.
Old 11-27-10, 10:49 AM
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I'll get all that checked out this week. Thanks for your help! I'm pretty methodical with my car maintenance. I change my Fuel Filter every 9,000 to 16,000 miles, the transmission is flushed every 33,000 miles. The transmission has already been rebuilt just 60,000 miles ago, they replaced everything include the valve case and put a shift kit in. It definitely only does it when its either hot out, or its been run for a while on a long trip, then it starts acting up. Can any of those minor problems really effect both the engine and the transmissions performance? Cause like when the transmission shifts up and then down erratically, I'm coasting on a level surface with no change in speed with the car or change in my application of the gas pedal. And the ideal rpm speed doesn't really shift, but it bounces up and down like it feels the car wants to die.

I also had a problem with my electrical system previously. Ford detected at 177,000 miles via PID scan that voltage had spikes as low as 0.012 volts, and they weren't sure what it could be. They said whatever it was should have been addressed, as those spikes would have played havic with my computer. Since then I replaced the alternator, and I also found my one-touch window module had fallen off the interior door panel into the bottom of my door interior, and got soaked with water and was fried. I've replaced those two things. and ensured there are no diodes that are worn through. Could this give any insight into what this problem might be?

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