Intermittent miss

[black5.0lx]

I've got an irritating miss that starts after the car warms up. It's an '87 LX 5.0 with Mass air conversion. If I cut the car off and restart it immediately the miss disappears but returns a short while later. Does this sound like a TFI or PIP? I haven't really started troubleshooting yet I was just looking for a direction from the experts out there. Still daily driving it but it's really aggravating when it starts up in traffic. It just started last week and I checked the plug wires, plugs and coil this past weekend. I had my timing light on the coil wire and when it starts the miss I could see it as an unsteady flicker in the otherwise almost constant light. Could only get it to do that once and then it wouldn't repeat.

Tom

 

[black5.0lx]

Ok, I replaced the TFI last Friday and it ran good all week until today. Damn miss started again. I had a spare coil so I replaced it and no difference. Still missing. It runs really sluggish now. After the TFI was replaced it ran like it's supposed to but all of a sudden it's back to the way it was. I have no codes when I checked. Driving me crazy because I have good fuel pressure and the plugs look good. Any thoughts?

Tom

 

[hotcobra03]

look here anything might help,,,,,,,,,,,,,,2003 PCED OBD SECTION 3: Symptom Charts
Procedure revision date: 06/30/2003

--------------------------------------------------------------------------------

Step 3: No DTC(s) Present Symptom Charts

Chart 1
Starting Concerns: Stalls After Start
Stalls/Quits: Idle, Acceleration, Cruise
Runs Rough
Misses
Buck/Jerk
Hesitation/Stumble
Surge
Unique Idle concerns: Rolling Idle
Note: For stalls on passenger car applications, engine may stall if left running while refueling. Advise customer to turn engine off while refueling to avoid contamination or damage to the EVAP system.



SYSTEM/COMPONENT REFERENCE (Section 5 Pinpoint Test unless noted)
Check The Following PIDs:
DPFEGR (if equipped) (hot idle value within 0.15V of KOEO value)
LONGFT1 / LONGFT2 (value between -20 and +20)
VPWR (value between 10.5 and 17.0 volts, and within 0.5 volts of battery voltage)
DPFEGR PID value not within 0.15V of KOEO value:
For vehicles equipped with ESM EGR: GO to HH33
All others: GO to HE100
LONGFT1 / LONGFT2 value low (-):
Continue diagnosis.
Concentrate checks in areas that would cause the engine to run rich.
LONGFT1 / LONGFT2 value high (+):
Continue diagnosis.
Concentrate checks in areas that would cause the engine to run lean.
VPWR not between 10.5 and 17.0 volts:
Go to the Workshop Manual, Charging System Section 414.
VPWR between 10.5 and 17.0 volts, but not within 0.5 of battery voltage:
CHECK B(+) supply to PCM power relay (or CCRM). CHECK VPWR circuit between PCM and PCM power relay or CCRM. CHECK PWR GND circuits.

For vehicles that run rough at idle:
With the key on, engine off, check the INJxF PIDs (the "x" indicates the injector number, there will be one INJxF PID for each engine cylinder). All INJxF PIDs must indicate no fault (or NO).
INJxF PID(s) indicate a fault (an injector circuit fault is indicated):
Natural Gas applications:
GO to HA60
All others:
GO to H56

Mass Air Flow (MAF) Sensor
GO to DC25

Secondary Ignition System
GO to JB1

Fuel Delivery System
Natural Gas Applications:
GO to HB1
All Others:
GO to HC1

Exhaust System
GO to HF1

PCV System
For 4.6L Mustang, Aviator:
GO to HG1
All Others:
GO to HG4

Natural Gas applications with rough idle:
Injector circuits between NG module and injectors.
GO to HA57

EVAP System
Check for EVAP system blockages (engine stalls) or leaks (other symptoms). REFER to Evaporative Emissions, Section 303 in the Workshop Manual (Section 310 for LS, Thunderbird, Explorer, Aviator and Blackwood).

Automatic Transmission
Automatic Transaxle/Transmission - Section 307 of the Workshop Manual

Base Engine
Engine System - General Information, Section 303 of the Workshop Manual

Intake Air System
GO to HU1

Applications with A/C Pressure Sensor (3 wire sensor):
A/C pressure (ACP) sensor input to PCM
GO to DS22

Additional Testing
GO to Z1

Additional Checks:
NOTE: Some applications have a PID that will indicate whether the PCM is reducing torque (TQ_CNTL)(#095E b0), and if so, why the torque is being reduced (#095Eb1-13) (0 = No torque reduction requested; 1 = Torque Truncation. Cuts fuel to protect when line pressure fails to minimum limit; 2 = Traction Control Event. Cuts fuel and/or spark for traction control; 3 = Vehicle Speed Limit - Cuts fuel).

Correct PCM vehicle identification (VID) block information (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM)
Be aware of engine RPM/speed limiting functions of the PCM (look for incorrect high vehicle speed signal from ABS, VSS or OSS)
Verify fuel cap is properly tightened, and not physically damaged.
Drivelines
Manual transmission/clutch
Charging System
Traction control system (if equipped)
A/C system (for surge with A/C on)
Speed control system (for surge with speed control on)
A/C compressor diode, if equipped (for rolling idle

 

[HISSIN50]

Run a cylinder balance test.

 

[hotcobra03]

hission50 sent you straight to fuel control,,,,,,,,when he does his C.B.t should he do all quick test also????? only thing i can add is note from ford ,,,to prvent the replacement of good components,be aware that the following non-eec areas may be at fault:::::::::ignition coil,,,,,,,,dist,cap:rotor,,,,,foulded spark plugs ,,,,,,,plug wires,,,,,,canp problems,,,,,,pcv,,,,,,egr valve and gasket..........air filter,,,,,,,,,fuel contamination,engine oil:: poor power ground,,,,,,,,fuel pressure,,,,manifold leaks,,,,,intake/exhaust....engine not at normal operating tempertures,,,,,,,i will watch and follow along to hission way of diagnostic ......

 

[black5.0lx]

Thanks guys. I ran a cylinder balance test when it reared its ugly head originally but got the 9 code every time. I'll try again today when I get off from work. I think I'm going to unplug the MAF and see what happens as well.

Tom

 

[hotcobra03]

cbt test

Thanks guys. I ran a cylinder balance test when it reared its ugly head originally but got the 9 code every time. I'll try again today when I get off from work. I think I'm going to unplug the MAF and see what happens as well.

Tom

when you ran it the first time .did you record all of your codes,,what if any and now did you check for codes????????

 

[2000xp8]

What brand TFI did you buy?
The ones from chain stores are crap, and it wouldn't suprise me at all if it already went bad.

 

[HISSIN50]

hission50 sent you straight to fuel control,,,,,,,,when he does his C.B.t should he do all quick test also????? only thing i can add is note from ford ,,,to prvent the replacement of good components,be aware that the following non-eec areas may be at fault:::::::::ignition coil,,,,,,,,dist,cap:rotor,,,,,foulded spark plugs ,,,,,,,plug wires,,,,,,canp problems,,,,,,pcv,,,,,,egr valve and gasket..........air filter,,,,,,,,,fuel contamination,engine oil:: poor power ground,,,,,,,,fuel pressure,,,,manifold leaks,,,,,intake/exhaust....engine not at normal operating tempertures,,,,,,,i will watch and follow along to hission way of diagnostic ......

You bring up a good point that a lot of people miss. I use the CBT as a quick test to narrow down which cylinder(s) is acting up, but I make NO inference as to the cause simply from the CBT results themselves (read another way, all the CBT does is tell you if one cylinder is not contributing as much as it should, NO matter the reason).
In my experience, it's seldom a fuel issue that causes a miss. The CBT does tell me which cylinder upon which to check the plug, plug wire, compression, injector wiring connection, etc.

 

[black5.0lx]

Ok. I had some errands to do but I ran the code check and cylinder balance test. Nothing useful other than codes for the air pump solenoids that are unhooked because I have no cats. I took the TFI with me and had it checked. It checked out ok as did the one I replaced. I read the voltage on the MAF and it came out to be about 1.1 to 1.2 at idle on a digital Fluke meter. I know it's supposed to be ~.6 volts. I tried a spare meter and got the exact same reading. Still missing but runs good when at WOT. I'm going back to square one and run through the checklist to see what I can find.

Tom

 

[hotcobra03]

fords quick test 1.0 thru ,6.0 and self tests

Ok. I had some errands to do but I ran the code check and cylinder balance test. Nothing useful other than codes for the air pump solenoids that are unhooked because I have no cats. I took the TFI with me and had it checked. It checked out ok as did the one I replaced. I read the voltage on the MAF and it came out to be about 1.1 to 1.2 at idle on a digital Fluke meter. I know it's supposed to be ~.6 volts. I tried a spare meter and got the exact same reading. Still missing but runs good when at WOT. I'm going back to square one and run through the checklist to see what I can find.

Tom

hission50 when i read fords procuedures on quick test it shows C.b.T. TEST..HIS 9 CODE can i assume it was a 90 which is a pass in the first half of cbt test,than leads to part two of cbt test,perform 2nd/3rd level cylinder balance test......when failed goes back to injector test and if passed goes to hego sensors,which would have codes 41/91 or 42/92.It seems to me that the internet is not telling the whole story to ones who search for answers vs ford books... with obd1 i have an otc 2000 and never done the jumper way, sounds like you really need to pay attention

 

[I_AM_CANADIAN]

Have you done a compression test?

 

[black5.0lx]

Thanks guys for all your help! Problem solved!!! I've been working in the dark until today so this morning in the daylight I finally saw that I had a bad ground. Fixed it and its running like it should. I'll save the spare TFI for my wife's 347.

Tom