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Discussion Starter #1
How can a check-engine light problem be diagnosed when there is no readout at all on the code reader?

I just bought a 91 LX 5.0 5spd with 150,000 miles. CK engine is on. It runs extremely rich and rough at idle....almost stalling, then sputters or misses if reved.

I found the TPS was disconnected and reconnected it. No big difference.

Bought a code reader at Auto Zone, plugged in to the left firewall connectors, the code-reader light came on solid. When the reader was turned on (with key on and engine off), I heard a click near the mid firewall, the code-reader light turned off and that was all. No flashing codes, nothing. Waited 5 minutes...still nothing. Tried the key on, engine on....same results.

With the motor running, if the code-reader is turned on, there is a drop in rpm, so I think there is some connection. Why can I not get any reading and what do I do next? Could the ecm or the reader be shot?

My plan is to pull and rebuild the motor anyway. It has very low oil pressure and I hate to run it more than I have to...I was hoping to fix the codes BEFORE I pulled the motor.
 

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I would take the code reader back! My friend picked one up at WalMart for around $75 that has an LCD screen and a memory. He came over and did my scan told me the codes, what they ment, and reset the ECU.
 

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Nermal said:
How can a check-engine light problem be diagnosed when there is no readout at all on the code reader?

I just bought a 91 LX 5.0 5spd with 150,000 miles. CK engine is on. It runs extremely rich and rough at idle....almost stalling, then sputters or misses if reved.

I found the TPS was disconnected and reconnected it. No big difference.

Bought a code reader at Auto Zone, plugged in to the left firewall connectors, the code-reader light came on solid. When the reader was turned on (with key on and engine off), I heard a click near the mid firewall, the code-reader light turned off and that was all. No flashing codes, nothing. Waited 5 minutes...still nothing. Tried the key on, engine on....same results.

With the motor running, if the code-reader is turned on, there is a drop in rpm, so I think there is some connection. Why can I not get any reading and what do I do next? Could the ecm or the reader be shot?

My plan is to pull and rebuild the motor anyway. It has very low oil pressure and I hate to run it more than I have to...I was hoping to fix the codes BEFORE I pulled the motor.
OK, the code reader might be shot but, you don't need it to verify your codes...just follow this AVOM, CEL or test light procedure...if it doesn't work, something is definetely wrong in the EEC-IV system (wiring, connections, ECM) and the code reader is not the problem. LUK what you find out. GL
 

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If you follow the directions in Joel's link, you can omit the test light and volt- meter, and instead, watch the CEL for code flashes. Connect the jumper wire from STI to SIG RTN, get in the car, turn the key to "run". You'll hear a few clicks, and the fuel pump will prime another time, and it should start flashing the codes shortly. You'll get KOEOs, they'll repeat, then a single flash, then the Constant Memory codes, which will also repeat. Then you start the motor and wait for the KOERs.
Make sure you follow the directions for the scanner. It might have to wait for the slow-flash sequence, to read the codes.
Make sure that the car is in neutral, and that the motor is warmed up. You can also try holding the clutch pedal to the floor, before you turn the key, to scan, and throughout the scan.
.Don't change your O2s until you're sure everything else is ok.
 

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Discussion Starter #5 (Edited)
Thanks for the feedback. I'll try that and let you know.

I just found a vacuum connector at the right firewall with screws jammed in where vacuum hoses should be.

Since the motor is going to be pulled anyway, do you think it's a bad idea to pull it now and figure the vacuum / CK engine problem once the new motor is in? I wonder if starting from scratch would be easier than untwisting this existing mess.
 

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Nermal said:
I just found a vacuum connector at the right firewall with screws jammed in where vacuum hoses should be.
Sounds like emissions stuff.
 

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Hey Gents, I just tried this and well I am not sure what the hell happened. When I connected a jumper from the STi to the sig return I could hear something clicking near the 10 pin connectors. It was a few clicks then a wrrring motor noise. From inside the car it sounded almost like the intake pump coming on but a higher pitch. I sat in the car and I could hear the pump coming on and off and on and off. Let me back up...I just bought this car. It runs really fat. I checked the tps sensor and it seems fine. The seller told me the mass air was going bad, or so he was told. I took another known good one and installed it. Now the car runs better but still very fat. SO I decided to see what codes are showing up. I cleared everything by letting the car sit for a few hours with the batt disconnected. I installed everything drove the car for a few minutes of suburbia stop and go driving, the check eng light came on and I headed back home. Now the door ajar chime is almost impossible to hear as the check eng light is very hard to see. I didnt think much of this at all. Now I try and do this self test and the light didnt go out, it would flash brighter. Then after 25 seconds it went out. Completely. I shut the key off, waited 2 min and tried again. No chk eng light. So I figure I will go for a spin. Now the car wont start. Its always started right away. What does this sound like to you gents? I have my own ideas but i want to hear your opinions....please shed some light on the subject for me!!!!
 

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Sounds to me you have a computer problem more than an underhood problem now.
 
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