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Author
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Topic: check engine light keeps coming on!!
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drews50
CAFords OG
Member # 2670
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posted
 
 
so, when the car is cold, or i haven't been driving her long, the check engine light will come on under hard throttle, not full, but putting it pretty deep. then after i let off the gas, it'll go away, but come on the next time i gas it. i'm gonna check out my o2 sensors today, but i wondered what else would cause this problem.
thanks in advance guys
drew ![[patriot]](graemlins/patriot.gif)
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*shiftylx*
2013 Race Red 5.0 "Lucy"
1967 Lime Gold 289 coupe "Ethel"
Posts: 2457 | From: phoenix | Registered: Apr 2003
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FasterDamnit
Bad Attitude
Member # 442
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posted
Pull codes. All you need is a paper clip, pencil and paper.
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'92 LX T5
Looked stock, went 11's 11.90 at 115mph.
'65 Mustang 347
www.fordmuscle.com
Livin' in the Carolina Pines
Posts: 2971 | From: NorCal | Registered: Sep 2001
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drews50
CAFords OG
Member # 2670
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posted
i've never known how to pull codes...how do you do it?
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*shiftylx*
2013 Race Red 5.0 "Lucy"
1967 Lime Gold 289 coupe "Ethel"
Posts: 2457 | From: phoenix | Registered: Apr 2003
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graylx
¯
Member # 3919
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posted
You could buy a cheap scanner from Autozone. I had a similar problem awhile back. The "Check Engine" light would come on under throttle but would disappear once you let off the gas. It turned out to be the EVP (EGR Valve Position Sensor). Located right behind EGR Valve. It was inexpensive. Around $50 or so, I think.
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2012 Mustang GT
1989 Mustang LX 5.0 Notch
1995 Impala SS
Posts: 891 | From: Fresno | Registered: Dec 2003
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drews50
CAFords OG
Member # 2670
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posted
how much are the scanners?
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*shiftylx*
2013 Race Red 5.0 "Lucy"
1967 Lime Gold 289 coupe "Ethel"
Posts: 2457 | From: phoenix | Registered: Apr 2003
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graylx
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Member # 3919
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posted
quote:
Originally posted by shiftylx:
how much are the scanners?
It's been awhile but it wont break the bank. I think I spent around $30 or so for a cheap one at Autozone. It's handy to have around anyway.
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2012 Mustang GT
1989 Mustang LX 5.0 Notch
1995 Impala SS
Posts: 891 | From: Fresno | Registered: Dec 2003
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drews50
CAFords OG
Member # 2670
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posted
where do you put the paperclip to read the codes?
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*shiftylx*
2013 Race Red 5.0 "Lucy"
1967 Lime Gold 289 coupe "Ethel"
Posts: 2457 | From: phoenix | Registered: Apr 2003
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FasterDamnit
Bad Attitude
Member # 442
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posted
"You just need a piece of wire, and maybe a voltmeter if your car has no Check Engine light, and you can run the EEC-IV Quick Tests in the privacy of your own garage. These can give you an amazing wealth of information on the machine's health, without getting your knuckles dirty, and without pulling one plug or reaching for the leakdown tester. There are two tests you can do- the Key-On, Engine Off test (KOEO), and the Key-On, Engine Running (KOER).The two tests tell you different things, and each has its place.
In order to run either test, the car has to be fully warmed up to operating temperature, and the car must be in neutral (both these steps are critical, or the only codes you will get will be the codes for "coolant too cold" and "transmission not in neutral"! Also make sure that the heater and A/C are off, or you'll get the code for "AC is on", which is the same as the code for "tranny not in neutral"...
To run the tests, you must locate the EEC-IV test connectors. In the late model Mustang, these are in the engine compartment, right in front of the driver's side hood hinge. There are two connectors of interest- one is a 6-pin connector, and the other is a single pin connector. Both use 1/4" quick disconnect-style terminals, so you'll probably want to make yourself a jumper about 8" long with a 1/4" male QD terminal on each end, if you mean to do this often. Otherwise, any random chunk of wire will do.
Here's the pinout for the EEC-IV connector, looking at it from the working side (looking into the female terminals). Note that only these three pins may actually have terminals in them- the other positions may be empty:
Signal Return
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V
_________________
/ ___ ___ \
/ \
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|___________________|
^ ^
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STO FP test
The left pin in the center group of 4 pins is the Self Test Output pin (STO). The single terminal hanging loose is the Self Test Input pin (STI). To run the test, you must either have a Check Engine light, or hook up an analog voltmeter. If you have the Check Engine light ('87 and later cars), just watch it during the tests- it will flash the codes. Otherwise, hook up your voltmeter between the positive terminal of the battery, and the STO pin above- you'll count its needle sweeps to get the codes. The FP test pin, when grounded, runs the fuel pump continuously- but that's just FYI. You won't deal with that pin for these tests.
To enable the KOEO test, connect your wire jumper between the STI pin (dangling off by itself) and the Signal Return pin above. Then, turn the ignition on, but don't crank the starter- the EEC-IV will enter the KOEO test. During this test, 5 things will happen.
First, you'll hear a bunch of clicking for a few seconds as the EEC-IV exercises its valves and actuators, and takes readings from its sensors.
Second, if you're using a voltmeter, you'll see a series of very fast pulses go by- they may register a volt or two. These are the "fast codes" that the real STAR scan testers use, but they go by too fast (100x the normal scan rate) to be of any use to us. If you're watching the CE (Check Engine) light, you won't see anything.
Third, you'll get the on-demand codes- these indicate what the EEC box has found problems with _at the moment of the test_. They will be presented to you as either flashes of the CE light, or sweeps of the needle on the voltmeter. The code 21 would be presented as flash-flash, pause, flash. The on-demand codes will be presented twice- if the EEC-IV has found nothing wrong, it will give you code 11, twice:
flash, pause, flash, longer pause, flash, pause, flash.
The flashes and pauses for a given digit are each 1/2 second. The longer pause between digits are 4 seconds. The longer still pauses between codes are 6-9 seconds. If you'd like to see a code just to see what they look like, leave the trans in gear (MT) or drive (AT), or push in the clutch- and you'll get code 67 repeated twice. If there is more than one code detected, they will be presented in sequence, twice: 22, 47, 22, 47.
Fourth, you'll get the separator code. The Ford manuals call this code 10, but you can't see the _absence_ of a pulse for the 0- you'll just see a 6-to-9 second pause after the last "on-demand" code, then a single flash.
Fifth, you'll get the "continuous" codes- these are the codes that the EEC-IV has stored in its non-volatile memory from events that have occurred while you were driving in the past. Another 6-to-9 second pause after the separator code, and you'll get another sequence of 2-digit codes that will look exactly like the on-demand codes. If all is well, you'll once again see 11,11.
So for example- if at some point in the past your throttle position sensor has wigged out while driving, you'll get a 23 in the continuous codes. If it's still wigged out at the time you start the test, you'll see it as a 23 in both the on-demand and continuous codes.
One last item is how to clear the continuous codes, so that you can see if new ones crop up. This is simply done by disconnecting and then reconnecting your jumper after all the tests have been run and the codes have been received.
Pretty simple, _very_ powerful. Unquestionably your friend. Perhaps there's something to this computer stuff, after all.
To do the KOER test, set the car up as above. Then with the STI/signal return jumper disconnected, start up and run it at 2000 RPM or so for two minutes, to thoroughly warm up the EGO sensors and get everything stable. Shut down, reconnect the jumper, and immediately restart, and the EEC-IV will go into the KOER test.
Several things will happen. The first is that you'll get the engine ID code- 2 pulses for a 4-cylinder, 3 pulses for a 6, and 4 for a V8.
Then the EEC-IV will begin playing with its actuators and sensors, trying to fool them into going to the extremes of their ranges. During this interval the car will run very poorly at times- it may go rich, lean, stumble, buck, and do all manner of unpleasant things. This will last from 6 to 20 seconds.
After this interval, the motor will smooth out and begin an even idle. You will then see a single flash or sweep of the needle. This is the Dynamic Response code, which is your cue. After this code, you have 10 seconds to snap the throttle wide open, just long enough to get above 2000 RPM. Once the engine gets above 2000 RPM (it won't take long at WOT with no load!), release the throttle, and let the engine go back to idle. This part is lovingly called the "goose test". The EEC-IV needs to see what happens at high throttle settings to make sure all of its sensors and actuators work properly, so you get to help out by goosing it. This test will last from 4-15 seconds.
The goose test is followed by fast codes (which only those of us stuck with a meter will be able to see, and we can't do anything with them), followed by the KOER on-demand codes exactly as above. If all was well, you'll get 11-11. If you didn't goose it enough, you'll get a 77 and get to do it over again.
At this point you can optionally run the SEFI or Cylinder Balance test. If you have an '87 or later, lightly tap the throttle (it only takes a small movement) WOT), and release it. Owners of '86s will have to go WOT briefly. After a little while, the EEC-IV will begin cutting the injector to each cylinder in turn, and looking for a drop in RPM. If there is no drop associated with any individual cylinder, then there is some problem there (that may or may not be related to the injection system- you could have a valve problem, or a fouled plug, or a shop towel stuck in the intake runner, and get the same effect). This test takes about 90 seconds. If a cylinder is found by this test to be weak, a single-digit code will be flashed telling you which one (1-8). If all is well, the code will be 9. If it gives you a 77, it got confused (perhaps you bumped the throttle) and you need to start over and rerun the test.
'87 and later cars can then rerun the SEFI test after it finished, again by just tickling the throttle (saves having to go back through the whole KOER test). It also relaxes the criteria for "fail" with each retest, so if one cylinder fails the first time but passes the second, it's only a little weak- whereas if it fails 3 times in a row, it's profoundly dead. Those of us with '86s have to go back to Square 1 to rerun, and we don't get this progression of thresholds to help us troubleshoot. "
from Mustangworks.
edit: the damn board reformats the metadata so the pucture is screwed up- I will try to find a pic. Two grey plugs loose right by the drivers side hood-hinge.
[ January 15, 2005, 03:26 PM: Message edited by: FasterDamnit ]
Posts: 2971 | From: NorCal | Registered: Sep 2001
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ShiftyGT
¯
Member # 3862
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posted
shiftylx on shiftygt's comp:
![[worship]](graemlins/worship.gif) Fasterdamnit
thanks man, i ran the codes and i got a 63. i can't figure that out, it tells me thats the throttle position circut, but my tps is good. i blew out the tps of dirt and put it back and the check engine light hasn't come on, so i'm gonna run it again after i cleared it. thanks again.
drew
[ January 15, 2005, 05:03 PM: Message edited by: ShiftyGT ]
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1990 GT, Back in action
Posts: 396 | From: Chico CA | Registered: Dec 2003
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FasterDamnit
Bad Attitude
Member # 442
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posted
Is it below 1.00 volts at idle?
Posts: 2971 | From: NorCal | Registered: Sep 2001
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