In need of some help here, not sure where else to turn!
Before I get into my 'story' and problem and my diagnostics, here is my build:
Stock block 302
TFS-1 Cam
GT-40 Heads
Trickflow Street Heat Upper/Lower Intake
42-lb injectors
Pro-M 80-mm MAF calibrated for 42-lb injectors
Vortech V-1 Supercharger (non-intercooled)
Dyno-Tuned with a SCT chip
255lph Fuel pump
My 1992 5.0L has, what appears to be, a progressive engine issue. It started out about this time last year - I would be cruising on the highway, when the car would "hiccup" or, mis-fire, it would seem. I didn't think too much of it at the time because it really only occurred occasionally during cruising at highway speeds. Before I started noticing this mis-firing, I had changed my cooling setup to a larger 3-core Champion radiator and dual mishimoto fans. I also upgraded to a 3G alternator (and yes, I upgraded the rear ground wire to 4Ga.). I didnt think the mis-firing and these new components were related, though. The codes I pulled when i first noticed the mis-firing were KOEO: 15, CM: 66, KOER: 11.
I then started to really get into trying to solve my issue this spring, after the problem came back to life in full form. I had driven an hour away to a friend's shop to have a Panhard bar installed. The drive out there was absolutely fine - no problems. 8 hours later after the install, I drove home, and almost immediately starting my trip, the car misfired/cut-out/hesitated (whatever you want to call it) big time. What happened at this point in time is I would be driving on the highway in 5th gear, just cruising, when all of a sudden I would feel the hiccup. At the same time as the hiccup, my air/fuel gauge pinged at full lean (17.0 on my gauge). I would continue to try and drive the car (by this i mean, keep on the accelerator), but the car would not accelerate - instead it would act as if you were completely off the pedal and decelerate. If I were to keep my foot into the accelerator, a few moments into it, I would hear what I think are lean pops from the intake. After a few moments of this behavior, the car would "come back to life." The codes pulled at this time were still the same, but with the addition of 96 during CM.
So at this point, I really got into diagnosing everything. I will try to "list" everything below for easier flow of events. I will also be as thorough as possible. The way I have been operating my test procedures is as such: I will plug my digital multimeter into a new circuit/component and tape my DMM to my dash so i can monitor it while driving. I drive the car up I-95 20-min and then back 20-min. The issue almost always arises on the return trip after power cycling at my turn around point.
- Code 66 is MAF signal below min test voltage so i checked out the MAF per this --> https://www.stangnet.com/mustang-for...m-help.826120/
VPWR & Ground KOEO ---> 12.07V
MAF Sig & MAF RTN ---> 129.4 kilohms
MAF Sig & GRND ---> 100.8 kilohms
Pins C and D at idle ---> 0.54V
- TPS measures 0.938 V at KOEO
- IAC red wire reads 14.37V at idle
- Fuel pump relay:
Green/yellow ----> 12V with fuel pump running
red ----> 12V w/ fuel pump running
orange/black ---> 12V with fuel pump running
light blue/orange --> 12V w./ fuel pump off and 0V w/ fuel pump on
- inertia switch: 10.5V both wires with fuel pump on
- I hooked up a multimeter to pin 19 on the fuel pump relay and ground to make sure it was getting constant 12V. I also hooked up a 2nd multimeter to the 12V switched power that goes to the pump to verify that the relay was switching power and providing constant 12V with koer. I monitored both these voltages via my multimeter throughout 30min of drive time. I was hoping that when the problem arose, the voltages would tell me something. But... the problem arose, and the voltages stayed true to their 12V. The code 96 went away... i wonder if it had something to do with me just simply cleaning up the relay and pushing in all the wire pins. EVER SINCE THIS, I have not seen code 96.
- I also hooked up a fuel pressure gauge to the car to see how that's doing at idle, under load, WOT
44PSI at idle with vacuum line connected to regulator
51 PSI at idle with vacuum line not connected to regulator but plugged with screw
blipping the throttle with vacuum line disconnected from regulator did not affect fuel pressure
- Monitoring fuel pressure during driving...the issue came up yet fuel pressure stayed true >>> fuel pressure is not cutting out
- I hooked up a test light to the #1 fuel injector harness to see if the ECU was still sending a signal to the injectors to fire during this driving issue..... during the issue, the test light still pulsed >>> ECU is sending signal to injectors.... I think at this point it's safe to say that the engine is getting fuel (fuel pressure + fuel signal)
- I hooked up a multimeter to the MAF Sig and MAF RTN (pos & neg) and monitored these during driving to see what happened during the driving issue.... issue occured and there was no sharp drop or spike in the MAF Sig voltage
- MAF SIG voltage is around 0.50 V during idle... I believe this is throwing the code 66... but I also believe the code 66 is partially due to my tune (tuner not using Pro-M Transfer Function). But, let's assume the tune is not the root cause here because since it was tuned many years ago, this problem only came to fruition recently.
- I backprobed my computer with my dmm at pins 50 (+) and pin 9 (-) for the MAF. Here are my findings:
First startup and idle: 0.65V
After driving a bit, idle: 0.45V
(Saw it dip instantaneously to 0.22V once)
Blipping the throttle at idle max voltage I saw was 2.5V
WOT on highway I saw max around 3.1V
- I borrowed a friend's A9L ECU and swapped it out with mine to see if the MAF SIG would read a different voltage.... with new ECU, MAF SIG read same voltage.... ECU not problem
- with DMM hooked up to MAF SIG and MAF RTN while cruising in 5th on the highway i was able to keep my foot steady enough to have the DMM output a constant voltage of about 1.35V. When the issue occurred, i saw an immediate drop in voltage to about 1.0V. I'm not sure if this is significant or not.
- No voltage drop between MAF SIG at ECU and MAF SIG at MAF component
- At idle, spark plugs are sparking and coil plug sparks. With this, I can assume that the engine is receiving spark at idle. I'm not sure how to monitor SPARK during driving.
- Distributor was pulled to check for shaft play. No shaft play. I ran into some difficulty with this step as this was the first time i have pulled a distributor. It wasn't until a week later that I found out I had re-installed the distributor a tooth off from TDC... so for a week the car wouldn't start. With the help of a friend, the distributor was re-installed with engine assembly at TDC compression stroke, and rotor pointing towards #1 spark plug wire... then set to 10° BTDC.
It's after all this testing that I start to replace components to try and isolate the issue.
- I first started at my MSD 6AL box. I took this out of the system by disconnecting everything to see if this was the cause of the problem. Issue still arose >>> MSD not problem
- I replaced the distributor with a remanfuactured one from NAPA and Motorcraft TFI module from Rockauto. I installed both of these and could not get the car to idle properly even after correctly setting base timing to 10 deg btdc. It would start up, idle high, slowly come down, and then die once below 1000 rpm... normally only after a minute of runtime. I put my OEM TFI module back on the car and it will idle. So i sent my TFI module back and for a replacement. New TFI module shows up and I install it. It idles fine and got up to operating temperature. It showed no signs of dying on me so i decided to take the car out for the first time in months for a test drive... I didn;t make it more than 100 yards before she died on me... RPM just dropped instantaneously to 0. I couldn't get the car back in my garage. So, I installed the OEM TFI module again and again it would idle. I took it for a test drive and it loses power above 3k RPM and starting around 2.5k RPM, the RPM needle will start bouncing around.
So, here I am... stuck, having tested what I believe to be most critical (and some non-critical) functions/sensors/components on my car with no clue as to why the engine is acting up. I mentioned above that this has been a 'progressive' issue because it all started with just a 'hiccup' or mis-fire during 5th gear cruising... and now the car can't be driven more than 100 yards without dying.
I would appreciate any and all help to get this Fox running correctly again.
Thank you,
Ryan
Before I get into my 'story' and problem and my diagnostics, here is my build:
Stock block 302
TFS-1 Cam
GT-40 Heads
Trickflow Street Heat Upper/Lower Intake
42-lb injectors
Pro-M 80-mm MAF calibrated for 42-lb injectors
Vortech V-1 Supercharger (non-intercooled)
Dyno-Tuned with a SCT chip
255lph Fuel pump
My 1992 5.0L has, what appears to be, a progressive engine issue. It started out about this time last year - I would be cruising on the highway, when the car would "hiccup" or, mis-fire, it would seem. I didn't think too much of it at the time because it really only occurred occasionally during cruising at highway speeds. Before I started noticing this mis-firing, I had changed my cooling setup to a larger 3-core Champion radiator and dual mishimoto fans. I also upgraded to a 3G alternator (and yes, I upgraded the rear ground wire to 4Ga.). I didnt think the mis-firing and these new components were related, though. The codes I pulled when i first noticed the mis-firing were KOEO: 15, CM: 66, KOER: 11.
I then started to really get into trying to solve my issue this spring, after the problem came back to life in full form. I had driven an hour away to a friend's shop to have a Panhard bar installed. The drive out there was absolutely fine - no problems. 8 hours later after the install, I drove home, and almost immediately starting my trip, the car misfired/cut-out/hesitated (whatever you want to call it) big time. What happened at this point in time is I would be driving on the highway in 5th gear, just cruising, when all of a sudden I would feel the hiccup. At the same time as the hiccup, my air/fuel gauge pinged at full lean (17.0 on my gauge). I would continue to try and drive the car (by this i mean, keep on the accelerator), but the car would not accelerate - instead it would act as if you were completely off the pedal and decelerate. If I were to keep my foot into the accelerator, a few moments into it, I would hear what I think are lean pops from the intake. After a few moments of this behavior, the car would "come back to life." The codes pulled at this time were still the same, but with the addition of 96 during CM.
So at this point, I really got into diagnosing everything. I will try to "list" everything below for easier flow of events. I will also be as thorough as possible. The way I have been operating my test procedures is as such: I will plug my digital multimeter into a new circuit/component and tape my DMM to my dash so i can monitor it while driving. I drive the car up I-95 20-min and then back 20-min. The issue almost always arises on the return trip after power cycling at my turn around point.
- Code 66 is MAF signal below min test voltage so i checked out the MAF per this --> https://www.stangnet.com/mustang-for...m-help.826120/
VPWR & Ground KOEO ---> 12.07V
MAF Sig & MAF RTN ---> 129.4 kilohms
MAF Sig & GRND ---> 100.8 kilohms
Pins C and D at idle ---> 0.54V
- TPS measures 0.938 V at KOEO
- IAC red wire reads 14.37V at idle
- Fuel pump relay:
Green/yellow ----> 12V with fuel pump running
red ----> 12V w/ fuel pump running
orange/black ---> 12V with fuel pump running
light blue/orange --> 12V w./ fuel pump off and 0V w/ fuel pump on
- inertia switch: 10.5V both wires with fuel pump on
- I hooked up a multimeter to pin 19 on the fuel pump relay and ground to make sure it was getting constant 12V. I also hooked up a 2nd multimeter to the 12V switched power that goes to the pump to verify that the relay was switching power and providing constant 12V with koer. I monitored both these voltages via my multimeter throughout 30min of drive time. I was hoping that when the problem arose, the voltages would tell me something. But... the problem arose, and the voltages stayed true to their 12V. The code 96 went away... i wonder if it had something to do with me just simply cleaning up the relay and pushing in all the wire pins. EVER SINCE THIS, I have not seen code 96.
- I also hooked up a fuel pressure gauge to the car to see how that's doing at idle, under load, WOT
44PSI at idle with vacuum line connected to regulator
51 PSI at idle with vacuum line not connected to regulator but plugged with screw
blipping the throttle with vacuum line disconnected from regulator did not affect fuel pressure
- Monitoring fuel pressure during driving...the issue came up yet fuel pressure stayed true >>> fuel pressure is not cutting out
- I hooked up a test light to the #1 fuel injector harness to see if the ECU was still sending a signal to the injectors to fire during this driving issue..... during the issue, the test light still pulsed >>> ECU is sending signal to injectors.... I think at this point it's safe to say that the engine is getting fuel (fuel pressure + fuel signal)
- I hooked up a multimeter to the MAF Sig and MAF RTN (pos & neg) and monitored these during driving to see what happened during the driving issue.... issue occured and there was no sharp drop or spike in the MAF Sig voltage
- MAF SIG voltage is around 0.50 V during idle... I believe this is throwing the code 66... but I also believe the code 66 is partially due to my tune (tuner not using Pro-M Transfer Function). But, let's assume the tune is not the root cause here because since it was tuned many years ago, this problem only came to fruition recently.
- I backprobed my computer with my dmm at pins 50 (+) and pin 9 (-) for the MAF. Here are my findings:
First startup and idle: 0.65V
After driving a bit, idle: 0.45V
(Saw it dip instantaneously to 0.22V once)
Blipping the throttle at idle max voltage I saw was 2.5V
WOT on highway I saw max around 3.1V
- I borrowed a friend's A9L ECU and swapped it out with mine to see if the MAF SIG would read a different voltage.... with new ECU, MAF SIG read same voltage.... ECU not problem
- with DMM hooked up to MAF SIG and MAF RTN while cruising in 5th on the highway i was able to keep my foot steady enough to have the DMM output a constant voltage of about 1.35V. When the issue occurred, i saw an immediate drop in voltage to about 1.0V. I'm not sure if this is significant or not.
- No voltage drop between MAF SIG at ECU and MAF SIG at MAF component
- At idle, spark plugs are sparking and coil plug sparks. With this, I can assume that the engine is receiving spark at idle. I'm not sure how to monitor SPARK during driving.
- Distributor was pulled to check for shaft play. No shaft play. I ran into some difficulty with this step as this was the first time i have pulled a distributor. It wasn't until a week later that I found out I had re-installed the distributor a tooth off from TDC... so for a week the car wouldn't start. With the help of a friend, the distributor was re-installed with engine assembly at TDC compression stroke, and rotor pointing towards #1 spark plug wire... then set to 10° BTDC.
It's after all this testing that I start to replace components to try and isolate the issue.
- I first started at my MSD 6AL box. I took this out of the system by disconnecting everything to see if this was the cause of the problem. Issue still arose >>> MSD not problem
- I replaced the distributor with a remanfuactured one from NAPA and Motorcraft TFI module from Rockauto. I installed both of these and could not get the car to idle properly even after correctly setting base timing to 10 deg btdc. It would start up, idle high, slowly come down, and then die once below 1000 rpm... normally only after a minute of runtime. I put my OEM TFI module back on the car and it will idle. So i sent my TFI module back and for a replacement. New TFI module shows up and I install it. It idles fine and got up to operating temperature. It showed no signs of dying on me so i decided to take the car out for the first time in months for a test drive... I didn;t make it more than 100 yards before she died on me... RPM just dropped instantaneously to 0. I couldn't get the car back in my garage. So, I installed the OEM TFI module again and again it would idle. I took it for a test drive and it loses power above 3k RPM and starting around 2.5k RPM, the RPM needle will start bouncing around.
So, here I am... stuck, having tested what I believe to be most critical (and some non-critical) functions/sensors/components on my car with no clue as to why the engine is acting up. I mentioned above that this has been a 'progressive' issue because it all started with just a 'hiccup' or mis-fire during 5th gear cruising... and now the car can't be driven more than 100 yards without dying.
I would appreciate any and all help to get this Fox running correctly again.
Thank you,
Ryan
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