Someone PLEASE help???

[lib88stang]

I have a 88 5.0 speed density car. It has had a miss or hesitation for over a month. It is getting worse and my gas milage went down 50miles and I can smell gas like it is running rich sometimes. It used to miss just sometimes but now it is frequent. If you are driving the car at normal speeds you can feel it start to miss then you get into the gas and the car bogs likes its not geting fuel(but the fuel pres gauge don't drop neither does the RPMS) then when its gets to about 4500rpms it cuts loose like it has a power band. Now if you are slowing down with your foot off the gas you can also feel the car hesitating.

Here is what I have done-checked TPS,TFI,MAP,O2's,IAC. I have changed the dist.,cap,rotor,coil,plugs,wires,rotor,ACT sensor. Took it to a garage and they checked for vac leaks and they changed the fuel filter, and its still doing it and its getting worse. I disconected the MSD box and it still does it. I scaned for codes and it has none. The Fuel pres reg is only a year old as is the fuel pump.

If you run it hard like you are racing it it runs great.The pedal feels like it has a dead spot until it gets to a certain RPM then it takes off. No mechanics want to work on it and Im tires of just changing parts for no reason.

Someone had to have had this prob. please help, or tell me where to take it,(southwest PA) Thanks

 

[bmorrisj]

have you checked the 10-pin salt n pepper shakers? try opening up the heads on the pins with a small flathead, and put on a new coating of dielectric grease....

 

[lib88stang]

My mechanic said if something was wrong with them or if it was EGR, to just unlpug the EGR and take the vac. off and it will bypass it. I did that and the car still did it.

I don't know what to doi with it???

 

[jrichker]

Use an analog voltmeter to check the TPS. With the ignition switch on, engine off, probe the black & green wires. At the idle postion the TPS should read less than 1 volt. As you open the throttle, the voltage should increase slowly in a smooth linear fashion. When you get to WOT (Wide Open Throttle) you should see 4.6- 4.9 volts. You should not see any flat spots or places where the voltage drops as you open the throttle.

 

[JB66]

How's your CTS? Coolant Temp. Sensor. If it feeds wrong info to the computer, it will make the car run rich all the time. Also, do a vacuum check. How many inches Hg are you running?

 

[lib88stang]

The TPS is fine, I've already checked that. There are no flat spots in the voltage range.

I already did a vacuum check. All lines are fine, no leaks.

Is the CTS the same as the ECT sensor(engine coolant temp)?

Any additional info would be helpful and greatly appreciated.

 

[ss93cobra]

ECT=CTS

 

[jrichker]

The ACT & ECT have the same thermistor, so the table values are the same

ACT & ECT test data:

Use Pin 46 on the computer for ground for both ECT & ACT to get most accurate readings.

Pin 7 on the computer - ECT signal in. at 176 degrees F it should be .80 volts

Pin 25 on the computer - ACT signal in. at 50 degrees F it should be 3.5 volts. It is a good number if the ACT is mounted in the inlet airbox. If it is mounted in the lower intake manifold, the voltage readings will be lower because of the heat transfer.

Voltages may be measured across the ECT/ACT by probing the connector from the rear. Use care in doing it so that you don't damage the wiring or connector.

Here's the table :

68 degrees F = 3.02 v
86 degrees F = 2.62 v
104 degrees F = 2.16 v
122 degrees F = 1.72 v
140 degrees F = 1.35 v
158 degrees F = 1.04 v
176 degrees F = .80 v
194 degrees F = .61

Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter.

Ohms measures at the computer with the computer disconnected, or at the sensor with the sensor disconnected.
50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms

 

[lib88stang]

it is at a garage right now getting checked for bad injectors or injector harness.

It will prob. come back not fixed, Im about to sell it.

 

[jerry beach]

My 88 SD car ran very much like you are describing. Is it popping through the intake when the miss occurs? Mine had 100,000 mi. on it and the injectors took a crap. I have read of this happening alot to the 88 cars. I had a dead miss at first. One injector was not firing, and two others were leaking. I was going to buy set of 8, but someone told me it is common to just replace the bad ones. So I put 3 inj. on it and it ran as you describe. I replace the other 5 after that, no change. I bought a set of 8 Ford racing inj. and put them in, car has run great ever since. That was about 3 yrs ago when I was totally new to working on EFI stuff. Look for gas starting to seep out of the injectors, that is the first sign I saw before mine acted up.

 

[bryanrevans]

my stock 86 was doing same thing.I did everything!!!except map sensor.But I kept gettin rich fuel code and map sensor code!!!!I unplugged map vacuum line(speed density)And it idled steady just low.Then threw in new Map sensor.Pay attention to Jricher and Dagger especaily for S.D issues!!!!

 

[jerry beach]

Someone wrote in here a little while back that there is an orifice in the MAP sensor vacuum line on the SD cars. I replaced that line years ago and never thought to look in the old one before I threw it out. My car runs fine without it though. Just something you might want to check out since there was work done in that area. Does that line look new?

 

[lib88stang]

I changed the MAP and the vac. line to the MAP is new.

Also how do you check the injector harness for voltage to see if they all are getting the right amount??

 

[Daggar]

Someone wrote in here a little while back that there is an orifice in the MAP sensor vacuum line on the SD cars. I replaced that line years ago and never thought to look in the old one before I threw it out. My car runs fine without it though. Just something you might want to check out since there was work done in that area. Does that line look new?

The lack of the orifice wouldn't cause the problem described here. If anything, removing the orifice would make for quicker throttle response. On some cars, removing the orifice makes for really unstable idle and surging issues. I've seen two Stangs react poorly to it's removal but most folks never knew it was even there and have swapped out that line with no ill effects. Mine is gone too with no problems (only benefit). So in this case I don't think it's causing your problem.

 

[lib88stang]

anymore ideas??

I ve put alot of money in it over this and still no fix.

Should I just buy a complete motor and put it in and if it still does it get anouther wiring harness????????????

No mechanics know wtf is wrong with it. Any shops in southwest PA??

 

[bryanrevans]

Im surprised you have no codes.I get crazy codes even when car is running slightly off!!!And its a 86 gt.