1987 Mustang GT 5.0: Huge Help Needed - Mustang Evolution

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Old 01-14-2012, 02:40 PM   #1
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Unhappy 1987 Mustang GT 5.0: Huge Help Needed

To start this off I will be posting to many, many forums my problem. First off,

Details Of Motor:

Block: 302 bored 30 over
Crank: Stock
Pistons: Stock
Cam: B-303
Heads: Aluminum Gt-40 SVO
Rockers: Stock
Intake Lower: Gt-40
Intake Upper: Gt-40
EGR Spacer: 70mm
Throttle Body: 70mm
Intake Tube: Aftermarket Cold Air
Mass Air Meter Housing: 70mm
Headers: BBK Shorty 3/4
Cats: None
Exhaust Pipe: Off-Road H-Pipe
Mufflers: Flowmaster
End Tips: Dumps
Computer: ’93 A9L Mass Air Computer
Fuel: Stock Fuel Pump
Injectors: Stock 19lb
Fuel Lines and Tank: Stock

Problem(s):

First two problems interchange but first problem is more present:

1) Surging Idle ( 1500 rpms to shut off ):

When cruising at rpms higher then 1500, letting of the gas and pushing the clucth, the car’s idle will drop till it cuts off.

If cruising at the same rpm as above then slowing the car down to where it should it, then 50% of the time, it will stay there or it may surge till it cuts off.

If at idle the car will idle if cold but after a few minutes the car will start to surge till it cuts off.


Parts Tested To Find Problem:

Throttle Postion Sensor: Set to .97 Volts

Parts Tested But Not Sure If Bad:

Stock Mass Air Sensor: 12 Volts to + and - Wire, 12 volts to 3rd wire,
Signal Wire is the problem wire. It is suppose to stay at around the same idle at idle. It changes erratically at idle and when the throttle is pushed. Please give opinion.

Vaccum Lines:

All visible vaccum lines have been checked with cleaner to check for vaccum leaks. Advise if all lines should just be replaced.


Parts Replaced To Fix Problem:

Idle Air Control

2) Hanging Idle:

When starting the vehicle it will hang to around 2000 rpms then drop slowly to 1100 rpms.

As I push the throttle to gain speed then shift, it stays at that rpm for 2 to 3 seconds then drops to around 1100 rpms.

Parts Tested To Find Problem:

Throttle Postion Sensor: Set to .97 Volts

Parts Tested But Not Sure If Bad:

Stock Mass Air Sensor: 12 Volts to + and - Wire, 12 volts to 3rd wire,
Signal Wire is the problem wire. It is suppose to stay at around the same idle at idle. It changes erratically at idle and when the throttle is pushed. Please give opinion.

Vaccum Lines:

All visible vaccum lines have been checked with cleaner to check for vaccum leaks. Advise if all lines should just be replaced.

Parts Replaced To Fix Problem:

Idle Air Control

3) Whining/Whistle Noise:

Vehicle as a whining/whistle noise coming from the engine compartment at idle and cruise. Noise does increase as rpms increase. All gaskets and suppected hoses have been sprayed for leaks.

Parts Tested To Find Problem:

Vaccum Lines/Gaskets

Parts Tested But Not Sure If Bad:

Vaccum Lines:

All visible vaccum lines have been checked with cleaner to check for vaccum leaks. Advise if all lines should just be replaced.

Not the Problem:

Pulleys

My Note:

Please post on the thread or send me an email at stj_1993@yahoo.com. I need help with this problem really bad. This is my daily driver and I have no clue what else to do. I need you to list what you think I should replace, test, or do to find the answer to my problem(s). Thank you so much everyone.
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Old 01-14-2012, 02:59 PM   #2
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did these problems occur after your upgrades? also did you check your intake manifold for vacuum leak or just the lines?i would say if your lines look ok then they dont need replaced:no holes,kinks collapsing etc.

this is located in the stickies. http://www.stangnet.com/mustang-foru...cklist.698148/
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Old 01-14-2012, 03:17 PM   #3
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Re: 1987 Mustang GT 5.0: Huge Help Needed

The whistle could be in your intake tract or it could be a vacuum leak in your intake itself or other vacuum powered accessories.
There are more possibilities for vacuum leaks than just the hoses.


Do you have a Chilton's or Haynes manual?
You need to follow the procedure in one of those to properly set the idle.


Have you checked and set the timing?


You mentioned pulleys, are they under drive pulleys?
If they are and you have not upgraded your alternator, then low voltage could be part of your problem.
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Old 01-14-2012, 03:31 PM   #4
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Re: 1987 Mustang GT 5.0: Huge Help Needed

To dreamstang:

Problems happened after cam and mass air system was installed.

I sprayed the intake for signs of leaks and did not find any.

Lines look ok from what I can see.

To Trojan Horse:

All the intake tract has been sprayed.

No I do not have a manual.

Timing is 13 degrees.

No underdrive pulleys just stock P/S, A/C, Crank, W/P, and Alternator pulleys.
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Old 01-14-2012, 03:40 PM   #5
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13 should be ok as long as there is no signs of detonation.i would try setting the idle with the proper technique like TH described.you may find that in the stickies also.you may just need to get a tune.
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Old 01-14-2012, 09:11 PM   #6
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Re: 1987 Mustang GT 5.0: Huge Help Needed

To dreamstang:

Timing is good. No detonation.

I set the timing by using an online step by step process.

If you could check the part about the MAF Sensor reading. Should I get a new MAF and get a tune?
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Old 01-14-2012, 10:34 PM   #7
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Quote:
Originally Posted by Trojan Horse
The whistle could be in your intake tract or it could be a vacuum leak in your intake itself or other vacuum powered accessories.
There are more possibilities for vacuum leaks than just the hoses.

Do you have a Chilton's or Haynes manual?
You need to follow the procedure in one of those to properly set the idle.

Have you checked and set the timing?

You mentioned pulleys, are they under drive pulleys?
If they are and you have not upgraded your alternator, then low voltage could be part of your problem.
What exactly do u mean by upgrading ur alt.?? For u/d pulleys
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Old 01-14-2012, 10:42 PM   #8
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What brand is the mass air? And any reading on the signal wire for the mass air over 5 v is bad, your mass air is saturated..
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Old 01-15-2012, 12:23 AM   #9
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Re: 1987 Mustang GT 5.0: Huge Help Needed

To Cobrarunnin9s:

Professional Products 70mm MAF Housing

Whenever the car is at idle it jumps around haywire like.
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Old 01-15-2012, 12:50 AM   #10
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If you have the stock one still, put it back on and see what happens. If that was the problem you should be able to
replace both with a meter from from the lightning it's a 90 mm piece and it's factory
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Old 01-15-2012, 01:16 AM   #11
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Re: 1987 Mustang GT 5.0: Huge Help Needed

I don’t have it anymore. I think the size is ok. I think I just need a new mass air sensor.
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Old 01-15-2012, 01:36 PM   #12
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Re: 1987 Mustang GT 5.0: Huge Help Needed

Quote:
Originally Posted by mystang50 View Post
What exactly do u mean by upgrading ur alt.?? For u/d pulleys
Under drive pulleys are infamous for causing charging problems because they do not spin the stock alternators (pre- 94-95) fast enough to keep the battery charged and the voltage up at idle.
Low voltage in your electrical system can cause all sorts of weird problems.
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Old 01-15-2012, 01:46 PM   #13
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Quote:
Originally Posted by Trojan Horse

Under drive pulleys are infamous for causing charging problems because they do not spin the stock alternators (pre- 94-95) fast enough to keep the battery charged and the voltage up at idle.
Low voltage in your electrical system can cause all sorts of weird problems.
stupid u/d pulleys! agreed
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Old 01-15-2012, 02:20 PM   #14
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Quote:
Originally Posted by Trojan Horse

Under drive pulleys are infamous for causing charging problems because they do not spin the stock alternators (pre- 94-95) fast enough to keep the battery charged and the voltage up at idle.
Low voltage in your electrical system can cause all sorts of weird problems.
What bout 9495 I have u/d and mine drops to can I "upgrade" a alt for my 95?
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Old 01-15-2012, 02:32 PM   #15
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Re: 1987 Mustang GT 5.0: Huge Help Needed

Quote:
Originally Posted by mystang50 View Post
What bout 9495 I have u/d and mine drops to can I "upgrade" a alt for my 95?
You can, but the 3G in your car should be up to the task.
Maybe you should have it tested?


I ended up buying a 200 Amp alternator for my 86 GT, because I am going to be running so many electrical mods on it.
Electric fan, electric water pump, MSD ignition.....
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Old 01-15-2012, 02:51 PM   #16
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Quote:
Originally Posted by Trojan Horse

You can, but the 3G in your car should be up to the task.
Maybe you should have it tested?

I ended up buying a 200 Amp alternator for my 86 GT, because I am going to be running so many electrical mods on it.
Electric fan, electric water pump, MSD ignition.....
Test said it was good
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Old 01-15-2012, 02:57 PM   #17
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Quote:
Originally Posted by mystang50

Test said it was good
how did u test it?with u/d pulleys the alternator can be in perfect shape but still not charge efficiently.the best way is to use a volt meter on the alt leads while running.it should be at least 12 volts at idle and up to 14 ish with throttle.
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Old 01-15-2012, 03:09 PM   #18
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Quote:
Originally Posted by dreamstang

how did u test it?with u/d pulleys the alternator can be in perfect shape but still not charge efficiently.the best way is to use a volt meter on the alt leads while running.it should be at least 12 volts at idle and up to 14 ish with throttle.
I tested it at auto zone it goes low with headlights on and when fan comes on, and when I go to a stop cause idle drops
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Old 01-15-2012, 03:19 PM   #19
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Quote:
Originally Posted by mystang50

I tested it at auto zone it goes low with headlights on and when fan comes on, and when I go to a stop cause idle drops
If they tested on the car that should be ok.but testing off the car will not tell how it charges with your u/d pulleys.that's why I said the best way is the volt meter.
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Old 01-15-2012, 03:35 PM   #20
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Re: 1987 Mustang GT 5.0: Huge Help Needed

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Originally Posted by mystang50 View Post
Test said it was good
Did they test it with the U/D pulley and at what RPM did they test?


When you first start the car, hook up a voltmeter and see if the voltage jumps up to around 14.5 volts.


Then turn the car off, disconnect the battery cables and test your battery voltage.
The voltage on the battery should be at 12.5 volts or slightly more.
Any less than 12.5 volts and it means that the battery needs to be charged or it is defective.
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Old 01-15-2012, 07:27 PM   #21
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Quote:
Originally Posted by Trojan Horse

Did they test it with the U/D pulley and at what RPM did they test?

When you first start the car, hook up a voltmeter and see if the voltage jumps up to around 14.5 volts.

Then turn the car off, disconnect the battery cables and test your battery voltage.
The voltage on the battery should be at 12.5 volts or slightly more.
Any less than 12.5 volts and it means that the battery needs to be charged or it is defective.
Yes with u/d pulleys and it was at idle
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Old 01-15-2012, 08:53 PM   #22
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Re: 1987 Mustang GT 5.0: Huge Help Needed

I did not get to the car today with my 11 hour work day but tomorrow afternoon I will be working on it. I will post soon.
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Old 01-17-2012, 11:13 PM   #23
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Re: 1987 Mustang GT 5.0: Huge Help Needed

Mass Air Flow tested good. I had a bad volt meter. So if TPS, IAC, and MAF good. Now I have another computer on the way. A new computer and vaccum leak to check.
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Old 01-18-2012, 09:12 AM   #24
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Forgive me if I missed a post but have you had a dyno tune yet, just kinda curious cause you have a pretty good bit of performance parts so I was wondering if it's been on a wide band or anything. Not to keep adding to your frustration but I've seen you have already checked a lot of parts, I've never had this issue but depending on when you have this issue it could be something like a temp control sensor maybe?
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Old 01-18-2012, 09:19 PM   #25
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Re: 1987 Mustang GT 5.0: Huge Help Needed

Never looked at the temp control sensor. I am taking the upper intake over in a couple days. And no I have never put it on a dyno. I have never tuned it or anything. Think that might help?
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