87 mustang gt surging idle/stalling

[87 GT]

Hi Group

I have a completly stock 87 mustang gt. I am having problems with it.

1. stalling as soon as i start it, when i start it again the idle
will drop almost to stalling then catch it self and try to stableize.
If i have the air off it will uually idle fine, but with the air on it
surges up and down.
2. When driving and i push the clutch in the RPMS take a few secounds
to drop. If i am driving fast and shifting fast its as if im power
shifting for the RPMS do not have a chance to drop.
3. From about 3800 RPM and up i have a bad hesitation/stumble.
4. Intermitantly the car will stall after idleing at a stop. My wife
has said that it has stalled when coming to a stop, I have not had
this happen yet, but she drives the car more than i do.
5. I have taken the car to a mechanic and after doing some adjustments
and replaceing some vacum line tells me the the car is old and it will
run this way. I donot believe this.

I have replaced numerouse parts:
Tps sensor and adjusted to .98 V
Idle bypass valve.
Ignition moduale
Distributor
Distrubutor cap and rotor
New Wires and plugs
Cleaned throtle body, spacer intake
Cleaned Egr valve
Have checked solinoid for egr and seams to be working fine
new thermostat
Air filter
Aftermarket flex fan
Reset computor according to repair manual

I have ran a self test on the car and the only codes that come up are
for the thermactor system.
Also after each part was replaced the car ran fine for a while then
would act up again.
Any help would be apprieciated

[Carver]

Check the timing , with spout unplugged see what the timing is set
around. Spout is a plug near the distributor wire harness. I would
set it around 14 deg. Super Unleaded, 13 deg Plus... Every car is
different. Set it high , if it pings back it down a degree, if it
pings after that back it down another degree and so on till you find
your cars sweet spot. Of coarse type of gas you run effects this.

Cheak the fuel filter and fuel pump. Normally a bad fuel pump humms
really bad.

Check you Map Sensor , make sure that the Manafold vaccume line is
hooked up to it and that it does not have any holes in the line. 87-88
really depend on the Map sensor. MAP sensor is mounted on the firewall
on a bracket near vaccume tree.

Replace the Temp sensor, the sensor that lets the computer know what
temp the engine is. (not the temp sending unit) Check or replace the
sensor that that is screwed into the black tube that runs under the
throttle body to the heater hoses. Sensor costs around $30.00

Have you replaced to O2 sensors?

What does the motor idle at?

Disconnect the vaccume line that goes to egr and see if it changes
anything. Plug the vaccume line with your finger after you
dissconnect it.

Have you checked the fuel injectors to see if one may be plugged or
leaking (bleeding off pressure) ?

I cases like yours, it is best to go through a proccess of
elimanation. I have no doubt that the problem you have can be fixed,
the comment that the mechanic made was a cop-out. If he really knew
what it was or knew how to fix it he wouldnt have said that.

Dont feel bad everyone that has had a fox body has gone through the
idle surging bs, Keep looking and you will find it.

One last thing I just thought of. What temp themostat was installed?
If it was too cold of a thermostat like a 160 that would make it
surge.

Let us know !!

[87 GT]

The timing is set at 13 deg. I use reg. unleaded gas.
The fuel pump was replaced about 6 months ago and the filter was again
replaced 2 days ago.
All of the vacum lines on the carhave been replaced and all of the
ones going to the map sensor are good. How do you check the map
sensor?
I have not changed the temp sensor, but will doso this weekend.
The o2 sensors were changed last year.
The engine idles at about 800 rpm with the air off and when it stops
surging it idles at about 900-1000 with the air on.
The thermostat is 180 deg.
I have not checked the injectors. I will do that this weekend as well.

Thanks for your response

Carver <Car...@Carver.com> wrote in message news:<ttb8i05lvjaohvi6q...@4ax.com>...

[Mr. Ford]

> I have a completly stock 87 mustang gt. I am having problems with it.
>
> 1. stalling as soon as i start it, when i start it again the idle
> will drop almost to stalling then catch it self and try to stableize.
> If i have the air off it will uually idle fine, but with the air on it
> surges up and down.
> 2. When driving and i push the clutch in the RPMS take a few secounds
> to drop. If i am driving fast and shifting fast its as if im power
> shifting for the RPMS do not have a chance to drop.
> 3. From about 3800 RPM and up i have a bad hesitation/stumble.
> 4. Intermitantly the car will stall after idleing at a stop. My wife
> has said that it has stalled when coming to a stop, I have not had
> this happen yet, but she drives the car more than i do.
> 5. I have taken the car to a mechanic and after doing some adjustments
> and replaceing some vacum line tells me the the car is old and it will
> run this way. I donot believe this.

At first thought it sounds like a vacume leak. Are you hearing any type of
sucking noise from any of the hoses?

[Mr. Ford]

"87 GT" <b...@bellsouth.net> wrote in message
news:abcba7bc.04081...@posting.google.com...

> The timing is set at 13 deg. I use reg. unleaded gas.
> The fuel pump was replaced about 6 months ago and the filter was again
> replaced 2 days ago.
> All of the vacum lines on the carhave been replaced and all of the
> ones going to the map sensor are good. How do you check the map
> sensor?
> I have not changed the temp sensor, but will doso this weekend.
> The o2 sensors were changed last year.
> The engine idles at about 800 rpm with the air off and when it stops
> surging it idles at about 900-1000 with the air on.
> The thermostat is 180 deg.
> I have not checked the injectors. I will do that this weekend as well.
>

Any help would be apprieciated

Well stupid me for not reading the whole thread. Since you have replaced all
vacume hoses have you had the fuel pressure regulator tested to see how much
pressure you are pumping? Ford uses a closed fuel delivery system to the
engine and back to the tank. The fuel pressure regulator delivers fuel to
the injectors, if the pressure is low boost is compromised. Any dealer or
Firestone or garage can check the pressure for you.

[Snake1]

Got an 88 mustangthat was doing the same thing,unplug the commpressor and
see if it idles properly,mine idled at a steady 750 after I did that.if it
does you're low on r12.I got rid of my condenser and all the lines and used
the compressor as a pulley only so I didn't have to screw around finding a
new snake belt.
gained a couple of horsepower and another couple of miles to the
gal.
My wheels.click on thumbnail
[URL=http://img34.exs.cx/my.php?loc=img34&image=DaveFrontStore.jpg][IMG]http://img34.exs.cx/img34/1428/DaveFrontStore.th.jpg[/IMG][/URL]

[Backyard Mechanic]

very thorough ... and that mechanic is a lazy idiot.

the idle bypass valve itself may be clean, but the valve and/or ISC motor may
stick... this would be the first thing i would look at.

you adjusted the tps to the right voltage but was the throttle stop adj screw
at the right point when you did it? warm engine and disconnect (key off)
idle control sol and set it to idle at 550 or 600 rpm.. or 50 below nominal

block and disconnect all vacuum lines to accessory parts, incl heater.

run vac leak test on those and power brake booster vac.

vac gauge on egr valve actuator, see if engaging, on and off.

check egr flow, vac directly to actuator to see change in engine when vac is
applied - tests flow and ops.

block thermactor air to manifolds, to see if it affects the problem.

87 GT opined in news:abcba7bc.04081...@posting.google.com:

[87 GT]

Thank you for all of your responses.

The air bypass assembly is new and i believe it is working correctly.

I adjusted the tps after adjusting the throttle stop according to one
of the threads posted for it is not in any of my repair books.

Which solinoids are for the idle control, and how do you adjust the
idle on the car. I thought and read that it was computor controled.

I did a vacum check and found that there is no vacum coming from the
egr solinoid, but there is vacum to the solinoid. So i have ordered a
new solinoid and it should be here in a week.

Again thank you all for your help

I will post a follow up when the new part comes in

Backyard Mechanic <pett...@Yaywho.com> wrote in message news:<Xns954D9BA4...@207.115.63.158>...

[Gary Vitagliano]

Look into a engine idle air kit part number F2PZ-9F939-A. It goes
between the idlemotor and the spacer.

[87 GT]

Hi group,

Thanks for all of the replys.

I have got the car running pretty decent right now.

I replaced the egr vacum solinoid and the car is idleing pretty steady
at about 800 rpm with or without the air on.

The only problem im having now is that the car will stall the first
time i start it, once i restart it will run fine until the next time i
try to restart.

I am having the fuel pressure check to day and hopefully this will
solve the problem if parts need to be replaced.

I have a couple questions and hopefully someone can tell me the
answers.

What is the correct idle for this car, i have read several different
specs and they seem to range from 600-900 rpm.

How can i adjust the idle if it is indeed lower than what it is
running at. Will the idle air valve spacer do this?

Again thanks for all of the help.

Chris