stuttering at low rpm's

[tording]

Hey guys. I have a question about my 92 LX coupe. Over the past couple of months I have developed a clutch chatter when I take off in 1st gear. It seems to be worse after I have been driving for a few minutes and the clutch and everything gets hott. Now just last night I was in 4th gear at about 1500 rpm and pressed the pedal to the floor pretty far and the whole car started shaking and it feels very similiar to clutch chatter but this was at 50 mph. Once I climb up above 1800 or so rpm it stops and the car pulls hard with no problems.

Is this like I said clutch chatter or is it an actual hesitation in my motor below 2k rpm do you think?? Other than this the car seems to run fine and I have no check engine lights or anything on. What do you guys think?

 

[jrichker]

You have a low speed miss or hesitation. Time to dump the codes & do a tune up. A tune up includes, plugs, wires, cap, rotor, fuel & air filter.

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.

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.

 

[tording]

Ok well just about a month ago I did new dist cap, new UR45 NGK plugs and new MSD 8.5mm wires. I will check the codes in the morning as well as the air filter and fuel filter. Is there no chance this could be clutch chatter cause I know I have some clutch chatter in first gear when I take off.

 

[tording]

Ok I pulled the codes and got code 15 which is Read only Prom failure so not real sure what that means. The ECU seems to work fine as the car runs good. I also got a code 67 which is the A/C clutch and that is because I have no A/C compressor anymore as I did the A/C removal. In the continuous memory codes I got a 33 which is EGR valve not opening properly but I dont think this would have anything to do with my problem but I could be wrong. Anybody else shed some light on these?? thanks in advance

 

[jrichker]

Code 15 - No Keep Alive Memory power to PCM pin 1 or bad PCM (Memory Test
Failure). The voltage to the Keep Alive Memory (KAM) is missing (wiring problem)
or the KAM is bad. The KAM holds all of the settings that the computer "learns" as
it operates and all the stored error codes that are generated as a result of
something malfunctioning while the engine is running. Use a voltmeter to check
the voltage to the pin 1 on the computer - you should always have 12 volts. No
constant 12 volts = bad wiring. If you do always have the 12 volts, then the KAM is
bad and the computer is faulty.

If the computer has to "relearn" all the optimum settings every time it powers up,
the initial 5-30 minutes of operation may exhibit surges, poor low speed performance and
rough idle..

Note that some aftermarket chips will cause code 15 to set. Remove the chip,
clear the codes and retest.

Before replacing the computer, remove the battery ground cable for about 20
minutes. This will clear all the codes. Retest after several days of running. If the 15
code is gone, then don't worry about it. If it is still there, then you get to do some
troubleshooting.

Wiring diagrams for the proper model years are next…

For 86 models see http://www.autozone.com/images/cds/gif/large/0900823d80167158.gif

For 87 models see http://www.autozone.com/images/cds/gif/large/0900823d8016715e.gif

For 88 models see http://www.autozone.com/images/cds/gif/large/0900823d80167162.gif

For 89-90 models see http://www.autozone.com/images/cds/gif/large/0900823d8019595f.gif

For 91-93 models see http://www.autozone.com/images/cds/gif/large/0900823d80195960.gif

Ditch the chip. clear the codes and recheck in a week. If you still have a code 15,
either the computer's KAPWR (pin 1) is losing power when the ignition switch is off
or your computer is bad.

See the following website for some help from Tmoss (diagram designer) & Stang&2
Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/

Diagram courtesy of Tmoss & Stang&2birds

http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

 

[tording]

Is there a fuse or anything that could be bad that could be causing this PCM to get no power?? I noticed at the top of the one wiring diagram that Pin 1 at the ECU is a yellow wire that goes up to fuse Link G. Is there a way this fuse link G could be bad and causing the power to not get there?? If so where is fuse link G located??

I also have a question about the color of the wire. On the one Diagram by Tmoss and Stand&2bird it shows that pin 1 wire is black/orange and is 16 guage and on the other diagram that you posted it says it is yellow. Do you know which one it is?

 

[jrichker]

There is no fuse, there is a fuse link. If it blows, the computer gets no power and the engine will not run at all.

Get out your voltmeter and a safety pin. Remove the passenger side kick panel and the plastic cover over the computer connector. Ground one voltmeter lead and use the safety pin to probe the back of the connector where the black/orange wire is. Connect the other voltmeter lead to the safety pin. You should see 12 volts: no 12 volts and you have wiring problems in the EEC relay socket. Wiggle the wiring and make sure the voltage doesn't come and go.

If the 12 volts is solid and never changes, there is no add on chip on the computer, then the odds are that the computer is bad.

 

[tording]

There is no fuse, there is a fuse link. If it blows, the computer gets no power and the engine will not run at all.

Get out your voltmeter and a safety pin. Remove the passenger side kick panel and the plastic cover over the computer connector. Ground one voltmeter lead and use the safety pin to probe the back of the connector where the black/orange wire is. Connect the other voltmeter lead to the safety pin. You should see 12 volts: no 12 volts and you have wiring problems in the EEC relay socket. Wiggle the wiring and make sure the voltage doesn't come and go.

If the 12 volts is solid and never changes, there is no add on chip on the computer, then the odds are that the computer is bad.

when you say to remove the plastic cover over the computer connector do you mean to actually take out the bolt and remove the harness from the ECU?? I have never taken off any cover before except for removing the harness from the ECU by loosening that bolt in the middle.

 

[jrichker]

when you say to remove the plastic cover over the computer connector do you mean to actually take out the bolt and remove the harness from the ECU?? I have never taken off any cover before except for removing the harness from the ECU by loosening that bolt in the middle.

Remove this cover...

Then you can get to the back side of the wiring to check it out.

 

[tording]

I checked my spark plug wires and because I put a set of MSD plugs on it the boots are not angled so I had one boot that had been resting on the header primary just a bit and it burned a small hole in the gray rubber part but not the actual plug wire. Anyway I swapped this wire back out for one the old ones that was in better condition and the stutter went away. I will for sure take care of the code 15 though. Thanks for all your help.