rough idle, losing hope.

Check out this thread.
http://forums.stangnet.com/showthread.php?t=534062&highlight=surging+idle

SoCal89GT said:

Ill give you the backround first...
This car is new to me and she needs some serious lovin.
89 GT 5 speed.
new plugs, wires, cap, rotor, TFI module, air/ oil filters, cleaned EGR valve.

and the Problem...
It idles like total garbage. It will rev from 600-1500 rpms when its just sitting at idle almost all the time. sometimes it will idle smooth but thats pretty random and rare. after replacing what i have I am not sure where to go next. The car also has an H-pipe on it and its throwing a code but i really dont want to have to pay the $65 people want around Orange County to scan it. But if someone knows a good place to go around Irvine please share. I am getting very frustrated with this thing and need to direction so PLEASE give some advice.

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My did the same thing a few years back I replaced all the vacume lines and it still did it. It ended up being the intake plenum gasket was blown out and wouldnt seal up. I had the same thing happen later on with my GT-40 intake. The car wouldnt idle for crap but once it got going it drove fine till it had to idle again. I went through all the steps you already did before I found out what it was also.

SoCal89GT said:

Ill give you the backround first...
This car is new to me and she needs some serious lovin.
89 GT 5 speed.
new plugs, wires, cap, rotor, TFI module, air/ oil filters, cleaned EGR valve.

and the Problem...
It idles like total garbage. It will rev from 600-1500 rpms when its just sitting at idle almost all the time. sometimes it will idle smooth but thats pretty random and rare. after replacing what i have I am not sure where to go next. The car also has an H-pipe on it and its throwing a code but i really dont want to have to pay the $65 people want around Orange County to scan it. But if someone knows a good place to go around Irvine please share. I am getting very frustrated with this thing and need to direction so PLEASE give some advice.

Click to expand...

no need to pay for a scan. you can do it yourself for free, with virtually no tools. here is How to Check for Codes . good luck, let us know what codes you get.

If you don't want to do the free method of checking codes, you can buy a code scanner at an auto parts store for about $40.

Jeff

JChalfan said:

If you don't want to do the free method of checking codes, you can buy a code scanner at an auto parts store for about $40.

Jeff

Click to expand...

Or you could just head on up to your local parts store and have them scan it for free.

millhouse said:

Or you could just head on up to your local parts store and have them scan it for free.

Click to expand...

good luck with that...99% of the time those parts store guys are idiots.

Yeah, those are the guys who told me my car didn't have a V8, because it was an LX. That's what their computer told them.

I bought one of the code scanners just so I would have it and could use it whenever I needed. It's easier than the "do it yourself" method, but you get the same results either way.

Jeff

I think part of getting a car scanned is how cute you are. I once asked (just cuz I was there) and was told no, but my sis (also with an EEC-IV car) was able to get codes run and the dude wrote down all of them along with nomenclature and possible fixes.

You don't need a scanner, all you need is a paper clip...

Dump the codes and see what the computer says is wrong… Codes can be present without setting the Check Engine Light.

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.

See http://www.troublecodes.net/Ford/
OR
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html

IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Walmart.

Or for a nicer scanner see http://www.midwayautosupply.com/detailedproductdescription.asp?3829 – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $35.

SoCal89GT said:

I had a guy i work with take a lot at my car last night, he used to race an 88 a while back. He thinks that it is a vacuum leak somewhere towards the bak of the motor. He checked the voltage across the TPS and that read out fine. when we sprayed brakeleen all over the rear of the manifold by the firewall, the idle would jump them plummit. he suggested trying to find a vacuum leak and pray that I do not have to tear the manifolds off. A buddy of mine will be getting his hands on a scanner that I can use thursday so i will know the codes then. BTW the MIL is on and off a lot, when I romp it, it comes off then goes away. its wierd... thoughts?

Click to expand...

It sounds like you have a vacuum leak from what you said about the brakleen. Maybe check and make sure your pcv valve didn't pop out of the rear of the intake. Also check the vacuum lines that plug into the rear of the upper intake. I believe there are two small ones on a stock 5.0, reach around the back of the upper intake and you will feel them. Also make sure the vacuum line didn't pop off the fuel pressure regulator, since that's around the back of the intake too.

Even if you have to pull the intake and reseal it, it's not that big of a deal.

Good luck!

Jeff

I got 2 on-demand codes; 67: Clutch open, AC on, Trans in gear.

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I imagine that you checked you check those things and that the A/C is NOT on and the tranny is IS NOT in gear. With those out of the way, there's a wire harness that goes into the front of the tranny. Locate it and disconnect the harness at the connector pig tail (the pig tail is about 6 inches long). DO NOT disconect the pigtail from the tranny. You only want to remove the the rest of the harness from the pigtail. Then jumper the two connections in the pigtail together. This will likely remove that code and allow you to proceed.

Code 35 EVR - EVP sensor signal is/was high – Bad sensor, or possible missing ground for EVR circuit. With the power off, measure the resistance between the black/white wire and battery ground. You should see less than 1 ohm. Check the same black /white wire on the TPS and MAP sensor. More than 1 ohm there and the wire is probably broken in the harness between the engine and the computer. The 10 pin connectors pass the black/white wire back to the computer, and can cause problems.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif

See http://fordfuelinjection.com/index.php?p=6 for more wiring help & 10 pin connector diagrams

Code 41 or 91 - O2 indicates system lean. Look for a vacuum leak or failing O2 sensor.

The computer sees a lean mixture signal coming from the O2 sensors and tries to compensate by adding more fuel. Many times the end result is an engine that runs pig rich and stinks of unburned fuel.

The following is a Quote from Charles O. Probst, Ford fuel Injection & Electronic Engine control:
"When the mixture is lean, the exhaust gas has oxygen, about the same amount as the ambient air. So the sensor will generate less than 400 Millivolts. Remember lean = less voltage.

When the mixture is rich, there's less oxygen in the exhaust than in the ambient air , so voltage is generated between the two sides of the tip. The voltage is greater than 600 millivolts. Remember rich = more voltage.

Here's a tip: the newer the sensor, the more the voltage changes, swinging from as low as 0.1 volt to as much as 0.9 volt. As an oxygen sensor ages, the voltage changes get smaller and slower - the voltage change lags behind the change in exhaust gas oxygen.

Because the oxygen sensor generates its own voltage, never apply voltage and never measure resistance of the sensor circuit. To measure voltage signals, use an analog voltmeter with a high input impedance, at least 10 megohms. Remember, a digital voltmeter will average a changing voltage." End Quote

Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear. The computer pins are 29 (LH O2 with a dark green/pink wire) and 43 (RH O2 with a dark blue/pink wire). Use the ground next to the computer to ground the voltmeter.

Most of the common multimeters have a resistance scale. Be sure the O2 sensors are disconnected and measure the resistance from the O2 sensor body harness to the pins on the computer.

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. Do not attempt to measure the resistance of the O2 sensors, it may damage them.

The O2 sensor ground (orange wire with a ring terminal on it) is in the wiring harness for the fuel injection wiring. I grounded mine to one of the intake manifold bolts

Code 51 Engine Coolant Temperature (ECT) sensor signal is/was too high -
Possible bad ECT sensor, or wiring. Possible missing signal ground –
black/wire wire broken or bad connection. With the power off, measure the
resistance between the black/white wire and battery ground. You should see
less than 1 ohm. Check the same black /white wire on the TPS and MAP
sensor. More than 1 ohm there and the wire is probably broken in the harness
between the engine and the computer. The 10 pin connectors pass the
black/white wire back to the computer, and can cause problems.

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

Voltages may be measured across the ECT 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


Code 53 Throttle Position sensor too high – TPS. Set the TPS according to the following tech tip.
Try this... Currently there is some dispute about setting it at .99 volts being worth the effort, but anything less is probably OK. All you need is less than 1.0 volt at idle and more than 4.25 at Wide Open Throttle (WOT). You'll need a Digital Voltmeter (DVM) to do the job.

The Orange/White wire is the VREF 5 volts from the computer. You use the Dark Green/Lt green wire (TPS signal) and the Black/White wire (TPS ground) to set the TPS

Here’s a TPS tip I got from NoGo50

When you installed the sensor make sure you place it on the peg right and then tighten it down properly. Loosen the back screw a tiny bit so the sensor can pivot and loosen the front screw enough so you can move it just a little in very small increments. I wouldn’t try to adjust it using marks. Set it at .97v-.99v, the closer to .99v the better.

(copied from MustangMax, Glendale AZ)

1. Always adjust the TPS and Idle with the engine at operating temp. Dive it around for a bit if you can and get it nice and warm.

2. When you probe the leads of the TPS, do not use an engine ground, put the ground probe into the lead of the TPS. You should be connecting both meter probes to the TPS and not one to the TPS and the other to ground.

3. Always reset the computer whenever you adjust the TPS or clean/change any sensors. I just pull the battery lead for 10 minutes.

4. Check the procedure for your year, on my 90 I have to turn the idle screw until it just touches the tab, then insert a .010 feeler gauge and give it about one more turn. Then you adjust the TPS voltage to .98v, reset the computer. Start it up, if the idle is to low then turn the screw in until it is just right, then readjust the TPS voltage to .98v and reset the computer and start it up. The key is to adjust the TPS voltage and reset the computer whenever the idle screw is changed.

Clear the codes by disconnecting the scanner while it is turned on or remove the jumper once the computer starts to dump the codes. Or disconnect the battery for 10-20 minutes.

Once you have cleared the codes, retest for them. If you still get a code 53, then check the resistance between the black/white wire and the negative battery terminal. Disconnect the battery before making any resistance measurements. You should see less than1.5 ohms between the black/white wire and the negative battery terminal. More that that means wiring problems or bad connections.

Code 54 – ACT sensor out of range. Broken or damaged wiring, bad ACT sensor. Note that that if the outside air temp is below 50 degrees F that the test for the ACT can be in error.

Check the resistance of the black/white wire to battery ground. If it is less than 1 ohm, it is good. If it is more than 1 ohm, the black/white wire has bad connections or a broken wire. Always take resistance measurements with the circuit powered off.

Then check the resistance of the ACT sender located in the #5 intake runner on most 5.0 stangs.

ACT & ECT test data:

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

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. 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

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

You have a missing signal ground on the ACT, ECT & TPS sensors. The black/white wire, Pin 46 on the computer serves as signal ground for all the sensors. The 3 sensors you show codes for pick up that signal ground on the black/white wire in the 10 pin salt & pepper shaker wiring connectors behind the upper intake manifold.



Pin #1, white connector is the one to check. It is likely that you have either a broken wire or bad connection in the engine side of the fuel injection harness.

Daggar said:

...there's a wire harness that goes into the front of the tranny. Locate it and disconnect the harness at the connector pig tail (the pig tail is about 6 inches long). DO NOT disconect the pigtail from the tranny. You only want to remove the the rest of the harness from the pigtail. Then jumper the two connections in the pigtail together. This will likely remove that code and allow you to proceed.

Click to expand...

or you could run the KOER with the clutch pushed in