1988 Mustang GT Convertible - Shifting hard

I'm hoping someone can point me in the right direction here.
The car seems to shift "hard" when going between gears (it's an automatic). Regardless of speed the car seems to "jump" into the next
gear. I had the idle speed lowered as it was "jumping" when moving from park to drive.
I've never owned a Mustang prior to this and I've had this one for 3 weeks now. It's a nice car with the exception of this shifting issue. Now the garage adjusted the shift indicator (little pin near the left gasket cover) and that helped a little (it was shifting at almost 4000 RPM in overdrive).
If I drive and let go of the gas pedal it seems to shift ok. If I do not let go of the accelerator it will shift at approximately 2800 RPM at a low speed. I think this is still a little high but like I said I don't know these cars.
Any suggestions as to what the problem might be.
Just in case someone asks. The idle RPM is currently near 750 now. It was brought up to about 1000-1100 and it started to "jump" when going from park to drive so I lowered it again. The shift indicator pin is now set a the "line" on the pin. Should I play around with this.
Also any suggestion on what can be done to improve performance on the car would be appreciated. I've bought a FlowMaster exhaust (not yet installed) and a BBK Air flow kit. Are there any other "minor" changes that can be suggested?
Thanks, Marc
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On Tue, 14 Aug 2007 08:08:54 -0700, battlefield

Bad move. Idle speed cannot be adjusted. Only set the base idle. IAC control actual idle speed. Never screw with that "adjustment" unless you know what you are doing with a very good reason. It sounds like someone was covering another problem with a false high idle.

I believe what they may have adjusted the nuetral switch. Not likely a problem on an AOD for the problem you describe as the AOD is not electronic.

Sounds like a bad trans throttle adjustment or worn connector bushing.

See below

No. Don't touch that for now. It was slamming the hell out of the drive train. You may have a broken engine mount if that went on for long.

I love the sound of the Flowmaster on a healthy 'Stang. You are probably better to spend your money on something other than either until you get it healthy "stock" and understand exactly what you have now.

As you say, you don't appear to know the car. No big problem as long as you are willing to learn.
First, have you done any modification away from "stock" at this point? You mention the BBK air flow kit which I believe is a throttle body. Maybe not. In any case, you should stay away from it for now and make sure it is performing properly in it's stock form before you start modding.
The '88 year model used the AOD automatic trans. One of it's weaknesses was the bushing for the trans throttle cable at the throttle body connection. They tend to wear out or break allowing the cable adjustment to get off. If you continue to drive in this condition, the trans will be operating with low line pressure which also controls the shift points and quality in the AOD. This will destroy the trans in short order. You need to get to a dealer pronto - today - and get the new type bronze bushing for the cable connection. It is not expensive. It is easy to install but, the adjustment is a bit tricky especially if someone has monkeyed with the throttle idle stop adjustment to correct engine idle speed. The base idle speed has to be set using a very specific procedure very carefully. Actual engine idle speed is controlled by the IAC. If you do not have a manual, get one now. Once that is done, the transmission throttle cable can be adjusted. If you drive the vehicle with low line pressure, the trans can destroy itself within very few miles. You should not drive the car until this problem is corrected unless you are ready to invest in a new transmission.
Once this is done and the ECM reset, you should drive the vehicle a couple of days to watch for any engine fault codes. You can buy a scanner for that one very cheap or go to the site below for a cheap way to read it along with the codes if you have a good helper. If you have codes, post them back here with the description.
As far as the air flow kit(s), they are pretty much useless on an otherwise stock application. Your exhaust system will help but, only well above normal operating speeds. The best thing about the exhaust is the sound quality and the illusion of more power via being louder. The best thing you can do before you start anything is get it running right in stock form if for no other reason than to make sure the engine is healthy enough to be modified reliably. Many engines that old are just plain tired just like people when they get old. It will do it's job but, may not take well to being leaned on without a rebuild. This may be the start of your best-bang-for-the-buck education. You can run out of bank account long before you get anywhere near what you want if you are not careful.
Cheers and good luck Lugnut
http://www.troublecodes.net/Ford /
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On Tue, 14 Aug 2007 08:08:54 -0700, battlefield

I also meant to mention there is a Mustang group with a wealth of knowledge if you can tolerate the condecention, bullshit and flaming. Once you figure out which are willing and capable of helping and which just like to stir up the s**t, you can learn a lot specific to your Mustang.
Cheers
Lugnut
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Thanks Lugnut. I'll bring the car into another dealer as the one I've visited here is not helping at all.
I'll have them check the items mentioned above. The BBK unit I have is a replacement for the stock air filter.
Thanks again, Marc
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On Tue, 14 Aug 2007 16:01:38 -0700, "88 Mustang GT Conv."

Thanks for the info on the BBK. If the air filter is the oiled mesh type, I am generally not in favor of them in any mass flow system. IIRC, the 1988 Mustang was a mass flow EFI system - not speed density. If your vehicle has a MAF sensor in the air intake, you must be extremely careful not to over oil the air cleaner element as it will contaminate the MAF sensor making it inaccurate or malfunction completely. Another aspect of these filters is that they do tend to pass more particulate abrasives than a paper element introducing the prospect of accelerated engine wear. The ability to flow more air is usually accomplished while reducing filtering efficiency. There are only a few ways to increase air flow thru a filter. In an EFI system, the fuel mix is controlled by the electronic sensors with the EGO sensor having pretty much the final say. The ability to pass more air to the engine ultimately has no effect at less than about 80% power operation in most cases. Not to be critical of the BBK or any other system in particular but, most are simply eye candy and increase the sound level to give the illusion of more power. Some even reduce actual performance.
Lastly, if you want to give the 'Stang a big boost in around town driving punch, a 3.73:1 rear gear will do wonders with not too great a hit on fuel economy. This will give you a immediately recognizeable kick. Cost to make the switch will run around $600US including parts by a tech competent to do the job. Do not install used gears or bearing off eBay. This is not a driveway job for a beginner nor anyone else who doesn't have some experience unless, of course, you are will to pay for their experience. Done right, it is the best performance gain for the buck in a stock vehicle. You will also need to change the spedometer gear in the 'Stang which is a cheap easy swap for a novice.
Good luck
Lugnut
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wrote:

88's are speed density except for a few sold in CA. They had the most power from the factory but are more difficult to mod then the MAF equipped ones.
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On Sat, 18 Aug 2007 23:03:18 -0700, Ashton Crusher

Thanks. I don't remember when they changed. The Mustang was one of the first to switch. The speed density is less capable of handling modifications than the mass air system. The speed density can be updated with an overlay harness and an ECM from a later model mass air system for a few hundred bucks unless you can get it from a doner vehicle and don't mind a little extra work.
Lugnut
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Check the U-joints for sure.
Brad

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