JimRockford

Hi everyone,hope I am posting this in the right section,I looked but couldn't find a general discussion forum.
I am considering buying an 1988 Trans am with 305 TPI and digital dash. The car has some problems however, the first is that the owner said they had the ECM replaced recently, and now the tachometer no longer functions. The other thing that I have noticed is that the car seems to idle very high, I turn the engine off and restarted it after driving it for a while and it still idled high. another issue is an electrical gremlin concerning the electronic ac control panel. The fan keeps turning on seconds after it's turned off,it will keep doing this over and over no matter how many times you turn it off. Also when the ac is turned on the compressor will engage,but then rapidly cycle the clutch on and off every second. The owner claims the ac system was recently repaired,.rebuilt compressor,etc and the switch was acting up before but issue was resolved. Apparently it started up again when they showed me the car. Does this sound a like bad electronic hvac control panel? If so how much would it cost find another or have this one repaired? Another issue with the car is that both power window motors are extremely slow they literally move slower than a snail,barely at all. I was talking to a friend who is a mechanic and he claims that perhaps the ECM they replaced is not the correct one for the car and that's why the tachometer is not working? Is there a specific ECM for the digital dash cars? Forgive all my questions, I hope somebody here will help me make a decision as to whether I should buy this car or not. I really like it, but I would hate to wind up thousands of dollars in the hole chasing down electrical gremlins

JimRockford

I wanted to also add that the car has less than 100,000 miles on it, and that the owner apparently had an overheating issue with the car, the fan was not kicking on and it ended up blowing the head gasket. They spent nearly $4000 in repairs having the valves redone the head gaskets replaced,etc. The car still seems to run too hot on my opinion,around 220 or so,over 195 on digital gauge,and the fans only kick on for a bit then shut off again. Is this like a throttlebody car where you can replace a fan switch in the engine with a 180° one and lower the temperature?

Tuned Performance

iTrader: (92)

The tach signal comes from the ign coil to the tach.
Sounds like a vacuum leak or stuck iac causing the high idle.

JimRockford

Thanks for your advice. What/where is the iac so I can check it if I go look at the car again? What color is the tach wire?
Are tuned port cars fairly reliable? I've only had carb and tbi cars in the past

Tuned Performance

iTrader: (92)

Tune ports are reliable but are known for older style injectors to fail. The tach wire is white.

JimRockford

Thanks "tuned perfomance",I really love the car,just afraid of the more "modern" technology. Glad to hear they are reliable as I plan to use this as my daily driver. I would just need to get all the issues sorted out,like the high idle,non working tach and intermittent ac controls.
How hot are these cars supposed to run? The electronic dash temp gauge ran around 210-200,over 195,which is kind of scary seeing the indicator so near to the red.

Is it possible to change the fan sensor switch to a lower temp unit like on a tbi car or does the ECM control when the fans turn on?

Tuned Performance

iTrader: (92)

The cars do run hot and the primary fan is ecm controlled and turns on around 226f.
I set mine to on at 200f and off at 185 with a 195 thermostat it stays close to 200f.
The secondary fan has a fan switch in the passengers head like tbi it can be changed to a lower on setting bye changing out the thermal switch.
https://www.thirdgen.org/forums/cool...le-switch.html

JimRockford

Sorry for all the questions but how do you change the ECM settings to turn on sooner like you did? Would changing the secondary fan to a cooler temp switch be enough?

Tuned Performance

iTrader: (92)

You would need a moates.net burn2 a sst27c512 eeprom and a moates g1 . Is one way of doing it I uv erased my old prom and used a old programmer. I do think changing the secondary fan switch would be enough to make it run much cooler . Just a reverse of what I did.

JimRockford

Thanks for the wealth of info! I will go back and make an offer on the car. Hopefully the electronic dash problems can be resolved. Where is the IAC and how do I check it for causing the high idle?

Tuned Performance

iTrader: (92)

The iac is idle air control. It's located under the throttle body a square four pin connector. To see if it's moving in you can jumper the plug under the drivers side dash pin a to b this is called the aldl connector. Turn the key to the accessory position. The fans will come on. You can go feel the iac and listen to it. If it's clicking it's more than likely working. I would really suspect a vacuum leak since someone had the tpi apart not to long ago. I hope the digital dash isn't to costly to repair.

JimRockford

I will go back and make an offer and if I get it will check it out as you said. Any chance you can give me a part number for the 180 cash switch for the 88 trans am 305 tPi?
I will buy that right off too.
Thanks again for all your help. This is a great site

Tuned Performance

iTrader: (92)

The lowest I know of 195 on 185 off
https://m.summitracing.com/parts/jet-60600
Or if you can find a Hypertech 4026
On 200f off 185f

Tootie Pang

iTrader: (2)

I am just now emerging from a similar situation.

I wouldn't hesitate to pick it up. All of the things you mentioned are solvable.

These cars are actually the lowest tech for "modern" engine management systems beyond carburetors.

JimRockford

Thanks for all the advice,I've bought the car! Now the fun begins,lol. I I'm going to do what tuned performance suggested and get the low temp fan switch right away. So hopefully it will run cooler and change the thermostat. Then the power windows and air conditioning controls need to be addressed.

JimRockford

Anybody here have any advice dealing with the electrical issues of the heating and air conditioning control? When I shut it off it keeps turning the fan back on and seconds later.I am thinking because it has the electronic air conditioning controls that maybe that unit is bad

JimRockford

The one thing that scares the hell out of me is the fact that these tpi cars have and electric fuel pump in the tank which I've read is a pain in the *** to get to. What I've heard is that in order to get the tank down, you have to drop the rear suspension, cut the exhaust away, then drop a heatshield, and then wrestle the tank down. Are there any easy ways to replace the fuel pumps In these third gens? Asides from cutting a hole in the hatch floor that is.
I wonder why General Motors didn't think ahead and add an access panel? I was told by someone that owns a 2007 mustang that Ford actually has an access panel for the fuel pump under the rear seat cushions so you don't need to drop the tank. Why didn't General Motors do something similar? Was it that these bodies were designed for carburetors originally so they didn't bother to upgrade them with an access panel when TPI and TBI came into use? I know carbs were used until 87 on third gens.

2012sergen11

iTrader: (1)

Fuel pump sounds like a tremendous amount of work but it isn't half as bad as people make it out to be. I have done mine the right way more than once. Cutting into the floor to replace it is the first sign of a future parts car, just my opinion

JimRockford

Agreed,and given the beautiful condition of this trans am I don't want to destroy it. I guess I would just pay a shop with a lift to do it right.
Is it necessary to cut the exhaust down in order to do this? And what pump is the absolute best longest life pump that you can get so that if you have to do this it will last you a long time?

OrangeBird

iTrader: (1)

If your gonna own an antique car and pay "shop rates" to get the work done , your gonna $pend a whole boatload of $$$ doing things that really aren't all that difficult to do for the average mechanically minded sort .

PS , make damned sure any "shop" you take it to fully understands you want the pump done using GM's procedure and NOT to go and cut a hole like some shops have been known to do to these cars .....

JimRockford

Hi Orangebird,I own mostly 50's and early 60's cars. I don't consider 1988 to be an "antique",but yeah,that's almost 30 years ago now! I'm not rich and given to tossing money around to shops to do something I can do myself,I do most all the work on my cars,except auto trans stuff myself,but they are all pre-smog carbureted cars that are straightforward and easy to work on. In my honest opinion,it's ludicrous to design a car with a fuel pump in the tank that necessitates dropping the rear axle,cutting the exhaust away,removing a heatshield and then taking the tank down to replace a part they know will need service.
Why not engineer an access panel straight from the factory to make them easier to service? Is it deliberately done for planned obsolescence? Figuring that the car is not supposed to last more than 130,000- 150,000 miles anyway?
That would suck to be 100 or more miles from home and have to have it towed to a shop and wait a day or two for them to get it done.
I love these cars and think they are stunningly beautiful,much more so than the fourth gens,but there are certain aspects of the engineering that should have been more well thought out.

If I did take it to a shop,I would be very sure to discuss precisely how I want it done. I am not going to pay to have someone do a hack job on the car.

GeneralDisorder

iTrader: (1)

Dropping the tank is not that bad *on a lift*. You do not have to drop the rear axle completely out. Just remove the pan hard bar and swing it down. You do not have to cut the exhaust with a lift either. It unbolts and comes out. The heat shield is to prevent the exhaust from heating up the tank. It's not at all difficult to remove and install. The whole job takes maybe two hours.

It's because inexpensive, unibody sports car. Compromises must be made. Production costs either go to your fancy fuel pump access panel or they go to make the car faster or handle better. Your choice....

Rick

2012sergen11

iTrader: (1)

Not terrible without a lift either, my earlier opinion was based off using a jack and jackstands (and a bit of language)

JimRockford

Thanks for the input. Obviously a lift would be the way to go,but I don't have one. I've read some other posts on thirdgen with people saying it took them 8+ hours without a lift.
Correct me if I am wrong,but these cars were not "inexpensive" back in the day,the 1988 trans am was something around $14,413 and the GTA a whopping $19,713. ($40,592.95 in today's money). How much more would it have realistically cost to add an access panel from the factory when they started going to fuel injection? Ford finally did it on the 2005-2009 mustangs. I have heard several other manufacturers do it now too. Something so simple makes service so much easier. It beats having to have your car towed if you're on a long trip,and having it in the shop for days.
There are other design issues like the steering gear mount cracking too,but I think they later addressed that by adding a brace.

Yes,I understand that GM didn't expect people to be driving them 30 years later,but I am sure some of the fuel pumps went out a few years into ownership causing the owners a headache. A little thoughtful engineering to make service easier earns a lot of brand loyalty.

Does anyone remember the 1982 Trans Ams equipped with the terrible th200c auto trans that was also used in the chevette? Those darn things would fail behind a 305 at 40 to 60,000 miles.

Tootie Pang

iTrader: (2)

1. If my fuel pump goes, so does the floor. No one will ever notice and it make the job a lot easier going forward. I've done in tank pumps before by dropping them and I always feel like I'm dealing with a bomb. Which I am.

2. The electric fan have a lot of devices that control them. It may not be the AC switch. I bought this thing: http://www.autozone.com/cooling-heat...267187_69565_0

Works great so far.

Lots of good info in those forums!

GeneralDisorder

iTrader: (1)

I get what you are saying. I work on Subaru's every day and they have had access panels in every model that has an in-tank pump. Since 1990. It makes it nice.

GM has never done it on anything other than the vette that I'm aware of.... Guess they just don't care. In tank pumps *should* last the life of the car. They do in most cases on Subaru's even with the access panel. GM doesn't seem to have such luck with theirs.

Rick

OrangeBird

iTrader: (1)

Jim , if you want to see one of these access hatches done right search out the member here named Tibo and find the thread where he fixed his . I say fixed because he didn't cut the hole as I remember , he bought a very nice third gen that happened to have already been cut in it's previous ownership (if I recall) , and when he was faced with the already cut hole he did a 100% totally professional looking job of making someone else's mess into a damn near factory looking hatch .

Thing is , to properly install a hatch like Tibo did , the tank has to come out because to do it right you must have full access to both sides of where the hatch is gonna go (rustproofing & all) and well , , if the tank has gotta come out anyway , and the car ain't already cut , might as well just go and install a decent brand of pump (I think Bosch and Walbro are the two current favorites) and skip the entire hole cutting side journey in it's entirety .

PS , put a cheap "Airtex" or such in and you will be doing it again in a year or so , like Baretta used to say "You can take that to the bank" ....

GeneralDisorder

iTrader: (1)

Walbro pumps are loud. We switched to Deatschwerks fuel pumps on all our turbo builds and have been very happy with them. I used a Corvette kit on my 86 TPI and a Dorman pickup assembly. Worked great and completely silent. The DW65 I used is rated up to 840 HP at 40 psi. Plenty for me. Frankly anything over that would need dual pumps and bigger lines than stock.

Rick

JimRockford

Hi Rick,that's interesting that makes with the access panel from the factory usually have the pumps that last the longest. Whats the most mileage you've seen a Subaru pump last? I really don't understand General Motors,the leader of the big three,not doing simple things other companies have been doing for years.

JimRockford

I'll check that out Orangebird,I have seen several third gens in the junkyard with access panels in the hatch floor. The Trans Am that I got has really been well preserved by the original owner, it has never been hacked into. It's just honestly amazing that they wouldn't engineer and acess panel like other makes have done to make life easier for everyone.
I've heard good things about the Walbro pumps to, I definitely will never buy anything made by airtex. I had to replace an air text pump on a friends 2002 Mustang twice, because the first one was defective

JimRockford

The fan I am in reference too is the blower motor that blows the air through the ducts in the interior of the car to cool or heat the passenger compartment. I didn't mean the radiator cooling fans.