Rough Idle (again) :(
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Laughing Gas
Joined: Oct 2014
Posts: 787
Likes: 22
Rough Idle (again) :(
1994, 5.8 V8. Club Wagon
Since repairing the computer, replacing the ignition control module, the
Ignition coil, the idle air control valve, cleaning the throttle body, replacing
the radiator (more recent)and hoses and a few other things The van has
been running very good the last few months but It has just developed a
minor rough idle in the last few days, then today It had a slight hard time
starting (when hot) and then felt like it would stall when coming to a stop.
This is similar to what it did before I replaced the ignition control module,
When its hot it would not want to start and would stall and the wheather
here in So. Cal. has been much hotter in the last few days than a few days
ago. These are also the symptoms It had when one of the battery cells
died.
Any Ideas?
I am thinking of having the battery checked first, to make sure its good.
Its a Interstate that is aboug 1.5 years old.
Thanks.
Since repairing the computer, replacing the ignition control module, the
Ignition coil, the idle air control valve, cleaning the throttle body, replacing
the radiator (more recent)and hoses and a few other things The van has
been running very good the last few months but It has just developed a
minor rough idle in the last few days, then today It had a slight hard time
starting (when hot) and then felt like it would stall when coming to a stop.
This is similar to what it did before I replaced the ignition control module,
When its hot it would not want to start and would stall and the wheather
here in So. Cal. has been much hotter in the last few days than a few days
ago. These are also the symptoms It had when one of the battery cells
died.
Any Ideas?
I am thinking of having the battery checked first, to make sure its good.
Its a Interstate that is aboug 1.5 years old.
Thanks.
Elder User
Joined: Mar 2013
Posts: 847
Likes: 4
From: In my house..
okay, if it's a repeat performance of a previous malfunction then we know the same problem still exists and we know it's related to heat and the ignition module so that would lead me to believe that the module is being subjected to excessive heat but even more likely you are using a TFI module manufactured from someone other than FoMoCo and that's a mistake lot's of people make so don't feel bad, there are lot's aftermarket components that work just fine but the TFI module is not one of them and I'm not too sure about the coil UNLESS you measured the primary and secondary resistance and compared those figures with factory specs to see if they are within tolerance, if they're not it can cause premature failure of your TFI module so check the coil and replace if it's not in tolerance, then replace the module with genuine overpriced motorcraft parts.
Cheers, George
Cheers, George
Thread Starter
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Laughing Gas
Joined: Oct 2014
Posts: 787
Likes: 22
Yes, When I replaced it I had originally purchased a Motorcraft but then
found (so I thought) out it was the wrong one even though it was for my
year and motor but a different color , but then got really bogged down by
the color designations
supposedly it must be black or must be grey/green and after reading many
posts on the subject I was totally confused
so I opted to go with
the non motorcraft with the correct color designation, it had been
working fine, even in the heat after I installed it.
I ll have to go back and look at my posts to find the exact month I
installed it.
Thanks.
found (so I thought) out it was the wrong one even though it was for my
year and motor but a different color , but then got really bogged down by
the color designations
supposedly it must be black or must be grey/green and after reading many
posts on the subject I was totally confused
so I opted to go with the non motorcraft with the correct color designation, it had been
working fine, even in the heat after I installed it.
I ll have to go back and look at my posts to find the exact month I
installed it.
Thanks.
Thread Starter
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Laughing Gas
Joined: Oct 2014
Posts: 787
Likes: 22
I just checked and I guess the TFI is the ICM that was mounted on the distributor, mine is mounted on the inside drivers fender behind the battery. It doesnt seem like much air flow through there.
Elder User
Joined: Mar 2013
Posts: 847
Likes: 4
From: In my house..
Try relocating the ICM to get better airflow and see if that doesn't help.
this may help..
http://easyautodiagnostics.com/ford/...module-tests-1
this may help..
http://easyautodiagnostics.com/ford/...module-tests-1
Senior User
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From: boston
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Laughing Gas
Joined: Oct 2014
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I have already replaced the coil. I did not replace the plugs because they
had been replaced fairly recently, I just pulled the ones I could
access to look at them and they all looked like new and were all gapped
properly.
It idled rough on the way home today and felt like it wanted to stall a couple
times while in traffic but it did not.
had been replaced fairly recently, I just pulled the ones I could
access to look at them and they all looked like new and were all gapped
properly.
It idled rough on the way home today and felt like it wanted to stall a couple
times while in traffic but it did not.
Elder User
Joined: Mar 2014
Posts: 906
Likes: 1
I have already replaced the coil. I did not replace the plugs because they
had been replaced fairly recently, I just pulled the ones I could
access to look at them and they all looked like new and were all gapped
properly.
It idled rough on the way home today and felt like it wanted to stall a couple
times while in traffic but it did not.
had been replaced fairly recently, I just pulled the ones I could
access to look at them and they all looked like new and were all gapped
properly.
It idled rough on the way home today and felt like it wanted to stall a couple
times while in traffic but it did not.
I looked through the list of parts replaced/tested and did not see a TPS sensor. If the TPS is "noisy", the output to the computer makes it difficult to keep the idle steady. The reference voltage on the sensor is 5V so the output signal is very sensitive. I had a short circuit in my electrical system that affected the reference voltage and the idle got so rough that if was almost stalling at the stop light.
Check the voltage on the output of the TPS while moving the throttle (engine OFF) to see if the voltage smoothly changes with throttle opening. A needle type voltmeter is best for this but even a digital readout will jump around indicating a problem. jim
Thread Starter
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Laughing Gas
Joined: Oct 2014
Posts: 787
Likes: 22
Hi NICKSAN,
I looked through the list of parts replaced/tested and did not see a TPS sensor. If the TPS is "noisy", the output to the computer makes it difficult to keep the idle steady. The reference voltage on the sensor is 5V so the output signal is very sensitive. I had a short circuit in my electrical system that affected the reference voltage and the idle got so rough that if was almost stalling at the stop light.
Check the voltage on the output of the TPS while moving the throttle (engine OFF) to see if the voltage smoothly changes with throttle opening. A needle type voltmeter is best for this but even a digital readout will jump around indicating a problem. jim
I looked through the list of parts replaced/tested and did not see a TPS sensor. If the TPS is "noisy", the output to the computer makes it difficult to keep the idle steady. The reference voltage on the sensor is 5V so the output signal is very sensitive. I had a short circuit in my electrical system that affected the reference voltage and the idle got so rough that if was almost stalling at the stop light.
Check the voltage on the output of the TPS while moving the throttle (engine OFF) to see if the voltage smoothly changes with throttle opening. A needle type voltmeter is best for this but even a digital readout will jump around indicating a problem. jim
Elder User
Joined: Mar 2014
Posts: 906
Likes: 1
Fuel Injection Technical Library » Strategies
The throttle body where the TPS is mounted is heated by coolant so it gets heat cycled with every cold start. If the TPS develops a "bad spot", the output voltage signal to the computer will signal the wrong position of the throttle. Also, if anything disturbs the 5 Volt reference on the TPS, the output will be wrong. If the signal ground connection is bad, the output will be wrong.
The good news is testing it is simple and the wiring is easy to reach. You might test it hot and cold just to see if temp is a factor. jim
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