1991 5.0 missing when hot

R

roc-e

New Member

Jun 23, 2008

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May 21, 2010

#1

• May 21, 2010

• #1

My 91 5.0 runs fine at first startup and until it gets warm. Then, under, load, from light throttle to full, it'll stutter/hesitate/sputter/miss. It's not violent, just noticeabe, annoying, and power-sapping.

If I turn the car off and then restart it, it'll run okay again for a very short time before the miss rears its head again.

I have an intermittant check engine light. The only code I get is a code 94.

I've done the following to it already:
Replaced coolant temperature sensor (got rid of my code 21)
Cleaned MAF
Cleaned TB
Cleaned IAC
Checked and reset TPS
Tried driving with the EGR unplugged (no difference)
Changed both upstream oxygen sensors

So to me, the stutter seemes to be happening only in closed loop and/or when the engine is hot.

Any ideas? I'd really appreciate it.

 

2000xp8

SN Certified Technician

Aug 8, 2003

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NJ

May 22, 2010

#2

• May 22, 2010

• #2

Problems when hot are usually a sign that TFI module has had it.
Although first i'd check your cap and rotor.

Do not replace the cap, rotor or Tfi module with any chain store crap parts, or you will be doing this again in 6 months if it fixes the problem.
Motorcraft or ford cap and rotor, and Definetely a ford TFI module, don't be tempted by any aftermarket module upgrades, they are garbage too.

 

N

nthorpe01

New Member

Jan 15, 2011

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Jan 16, 2011

#3

• Jan 16, 2011

• #3

What was the result? I am having the same problem on my 92 LX.

 

jrichker

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Jan 17, 2011

#4

• Jan 17, 2011

• #4

The TFI module mounted on the distributor is usually the culprit for a high speed miss on a warm engine. If the problem does not occur when the engine is cold, the TFI module is definitely suspect. You may need a special socket to remove the TFI module, but most auto parts stores will have one for $5-$7.

Be sure to use plenty of the heat sink grease on the new TFI and clean the old grease off the distributor.

View attachment 198938

See Automotive Tools Specialty | Auto Mechanic & Technician Diagnostic, Testing Equipment | Thexton

 

C

crickifur

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Dec 18, 2009

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Jan 18, 2011

#5

• Jan 18, 2011

• #5

Tfi could be it true, but any faulty ignition part will misfire when hot, plugs, shorted wires, cracked cap, corroded wire, bad coil... RPM goes up, dwell time is shorter. Ign circuit resistance doesn't allow the voltage to build up in the coil or transfer properly in the secondary... just my $.02

 

347STROKER50

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Dec 19, 2010

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New England

Jan 18, 2011

#6

• Jan 18, 2011

• #6

replace your ignition module when things get hot they expand thats whats happening inside your module causing your miss when it cools off it retracts making good contacts again

 

S

SlamminGears

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Nov 14, 2010

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Jan 22, 2011

#7

• Jan 22, 2011

• #7

jrichker said:

The TFI module mounted on the distributor is usually the culprit for a high speed miss on a warm engine. If the problem does not occur when the engine is cold, the TFI module is definitely suspect. You may need a special socket to remove the TFI module, but most auto parts stores will have one for $5-$7.

Be sure to use plenty of the heat sink grease on the new TFI and clean the old grease off the distributor.

View attachment 198453

See Automotive Tools Specialty | Auto Mechanic & Technician Diagnostic, Testing Equipment | Thexton

Click to expand...

What exactly do you mean by a high speed miss? Mine sputters at 4k at WOT, once at 5k its stops.

 

jrichker

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#8

• Jan 22, 2011

• #8

SlamminGears said:

What exactly do you mean by a high speed miss? Mine sputters at 4k at WOT, once at 5k its stops.

Click to expand...

Start your own post and I will try to help. Hijacking someone elses post is bad manners.

 

B

BlackFox93

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Mar 26, 2010

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Greenbrier, Alabama

Jan 22, 2011

#9

• Jan 22, 2011

• #9

Mine was doing the exact same thing when I first bought it, turned out it was the distributor itself. Replaced it and havent had a problem since

 

S

SlamminGears

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Feb 1, 2011

#10

• Feb 1, 2011

• #10

jrichker said:

Start your own post and I will try to help. Hijacking someone elses post is bad manners.

Click to expand...

well i'm pretty sure I'm having the same problem the OP is. I'm not jacking anyones thread. Why should I start ANOTHER thread for the SAME thing. I'm sorry for inquiring as another fellow mustang owner. I'm not trying to start any crap, nor do I want to recieve it. Now if anyone else has suggestions, I'm curious if a solution was found and what fixed the problem, which is the origional reason I posted to begin with.

 

globaltefl

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Aug 2, 2009

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Grand Junction, CO

Apr 21, 2011

#11

• Apr 21, 2011

• #11

My 90 5.0 craps out at about 4500rpm. It has a new Mallory ignition and new MSC coil. Could it be the wires? What else, unless the new TFI on the Mallory isn't good?

 

2000xp8

SN Certified Technician

Aug 8, 2003

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NJ

Apr 21, 2011

#12

• Apr 21, 2011

• #12

globaltefl said:

My 90 5.0 craps out at about 4500rpm. It has a new Mallory ignition and new MSC coil. Could it be the wires? What else, unless the new TFI on the Mallory isn't good?

Click to expand...

Any aftermarket distributer and/or tfi is always suspect.
None of them are as good as original ford units.
I'd take a junkyard original over an aftermarket new any day.

 

globaltefl

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Aug 2, 2009

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Grand Junction, CO

Apr 21, 2011

#13

• Apr 21, 2011

• #13

Except it's the original equipment that failed.

 

2000xp8

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Apr 21, 2011

#14

• Apr 21, 2011

• #14

globaltefl said:

Except it's the original equipment that failed.

Click to expand...

Ya, after what 150,000 miles?

 

globaltefl

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Aug 2, 2009

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Grand Junction, CO

Apr 21, 2011

#15

• Apr 21, 2011

• #15

No, actually under 100 mi.

 

smokin joe

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Sep 30, 2000

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Apr 21, 2011

#16

• Apr 21, 2011

• #16

Hate to sound basic here but I had a similar problem with my 86 GT. I had platinum plugs and when I went back to copper plugs it ran much better.