EEC-IV GUYS

[allballsmustang]

I am trying to troubleshoot an issue I am currently having with my car. I was told by several reputable sources that the EEC-IV will run open loop if one of the 02 sensors is unplugged, which I can use to establish if I am having a sensor(ie: tps, maf, ect...) issue. Anyone use this method before? Any reputable insight would be greatly appreciated. Thanks

Jim

 

[2BADSTANGS]

Never heard of that, should throw a code if you unplug an O2 sensor though...

 

[TheRedBlur]

I see what you're getting at, but running a car on open loop will make the computer ignore a lot of the driveability sensors. It's really just gonna read the tps and run the timing according to that. So if your maf is bad, on open loop it might ignore that since the engineers at ford know about how much air a 5.0 will consume at any given rpm and throttle level. Also, the IAC and EGR will probably be closed.

Anyways, what's the issue that you're having?

 

[jrichker]

Disconnecting the O2 sesnors will probably put you in Failure management mode with reduced performance and economy.

Dumpuing the codes will provide information on what sensors are misbehaving.

Dump the codes and see what the computer says is wrong…Codes may be present in the computer even if the Check Engine light isn’t on.

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. You watch the flashing test lamp or Check Engine Light and count the flashes.

See Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical

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.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

Do not jumper anything to the single black connector. It is the power for the under the hood light. It is in another bundle of wires near the windshield wiper.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems.

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.

Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see EQUUS DIGITAL FORD CODE READER (3145) – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

 

[joel5.0]

I see what you're getting at, but running a car on open loop will make the computer ignore a lot of the driveability sensors. It's really just gonna read the tps and run the timing according to that. So if your maf is bad, on open loop it might ignore that since the engineers at ford know about how much air a 5.0 will consume at any given rpm and throttle level. Also, the IAC and EGR will probably be closed.

Anyways, what's the issue that you're having?

Open loop does not cause the EEC to ignore sensor inputs...... it turns adaptive strategy off, but all the sensors are used for fuel/spark trimming. A failing circuit does cause a type of the FMEM strategy to be used as shown below.........

 

[allballsmustang]

well heres the trouble...at idle i have no issue, when the car runs in open loop i have no issue whether its at idle, part throttle or wide open throttle. when the car is hot and its running in closed loop it idles fine too. where my problem lies is in closed loop at part throttle or wide open throttle...it cuts up bad... as it cuts up the rpms drop out and come back... also if you leave it in gear and bring it up to 3000 rpm and then let off as it slowly drops you can see the tach drop a couple hundred rpm and then recover to where it was...it looks to me from the best of my knowledge to be cutting spark? i mean, the tach is connected to the coil and if you see the rpms dropping out like that it could be related?

as for the codes, yes i know i do need to get a code reader and check em... i will try to do that sometime this week...

i thought someone may have ran into a similar situation, and i can really narrow down when its happening so i think that must be indicating something, or atleast a certain system(ie: ignition, sensors, fuel)

any input is appreciated!

thanks guys
jim

 

[jrichker]

No code reader is needed, save some money: all you need is a paper clip if the car has Mass Air.

 

[allballsmustang]

thanks for the advice, yea i have used the jumper method... i just have access to a code reader that a friend has and it makes it nice and easy...


oh, and i also forgot to mention that i have a superchip... the egr is turned off in the tune too...

 

[allballsmustang]

ok so i did a key on engine off and i got a 67 and an 84... the 84 i can understand because i have the egr turned off with the chip but whats up with the 67? maybe because it was in gear or something? anyway, neither lead to any conclusion as to whats going on

i didnt have time but im going to do a key on engine on test tonight, but i assume that since i have my problem in closed loop i should probably get the engine good and hot first...

 

[TheRedBlur]

do you have a timing light? check your plugs too, see what's going on in the cylinders.

 

[stang&2Birds]

Without any O2 sensors, then the A/F is open loop - it is that simple.
The EEC "closes the loop" with the O2 sensor feedback. So, without O2 sensors, there is no way you could have a closed loop on the A/F ratio. So, by definition, the A/F is open loop.


You will still have a closed loop on the idle speed. That's because the idle speed closed loop feedback is the RPM from the distributor (and the IAB/IAC is the control).


I have sigs turned off. So, let me guess, you either have a POS C&L and/or a POS cone filter? If that's the case, then my guess is that a code scanner won't show any problems. Also, feel free to shove those POS parts up the *** of who ever sold them to you and/or suggested them to you. .


If you have 19's, go with a 94/95 70mm MAF, adapter, and stock filter setup with a K&N.
http://forums.stangnet.com/616246-94-95-maf-install-completed.html

BTW: Your symptoms cry of POS C&L and/or POS cone filter.

Good Luck!

 

[jrichker]

Code 67 - clutch not depressed (5 speed) or car not in neutral or park (auto) or A/C in On position when codes where dumped. Possible neutral safety switch or wiring problem. This code may prevent you from running the Key On Engine On tests. You can generally ignore this code, since it has no effect on engine performance.

The computer wants to make sure the A/C is off due to the added load on the engine for the engine running tests. It also checks to see that the transmission is in Neutral and the clutch depressed (T5, T56, Tremec 3550 & TKO)). This prevents the diagnostics from being run when the car is driven. Key On Engine Running test mode takes the throttle control away from the driver for several tests. This could prove hazardous if the computer was jumpered into test mode and then driven.

The NSS code 67 can be bypassed for testing. You will need to temporarily ground computer pin 30 to the chassis. Computer pin 30 uses a Lt blue/yellow wire. Remove the passenger side kick panel and then remove the plastic cover from the computer wiring connector. Use a safety pin to probe the connector from the rear. Jumper the safety pin to the ground near the computer.
Be sure to remove the jumper BEFORE attempting to drive the car!!!

Code 84 EGR Vacuum Regulator failure – Broken vacuum lines, no +12 volts, regulator coil open circuit. The EVR regulates vacuum to the EGR valve to maintain the correct amount of vacuum. The solenoid coil should measure 20-70 Ohms resistance. The regulator has a vacuum feed on the bottom which draws from the intake manifold. The other vacuum line is regulated vacuum going to the EGR valve. One side of the EVR electrical circuit is +12 volts anytime the ignition switch is in the run position. The other side of the electrical circuit is the ground path and is controlled by the computer. The computer switches the ground on and off to control the regulator solenoid.

If you are having idle problems, see the "Surging Idle Checklist for help with all your idle/stall problems. The first two posts contain all the updates to the fixes. At last count there were 24 possible causes and fixes] for surging idle/stall problems. I continue to update it as more people post fixes or ask questions.