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N* question... by jediperk
Started on: 08-23-2014 09:46 PM
Replies: 13 (188 views)
Last post by: Will on 08-26-2014 08:40 AM
jediperk
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Report this Post08-23-2014 09:46 PM Click Here to See the Profile for jediperkSend a Private Message to jediperkEdit/Delete MessageReply w/QuoteDirect Link to This Post
Well, my N* fiero is acting up. It seams to not want to start up every couple days. It turns over fine and starts to fire like its getting air and spark but then dies like its not getting fuel. When it does start, which is most of the time, it runs fine. Any one have experience with this? My first thought is maybe the fuel pump is going bad or I have a bad ground or something. My brother thinks it might be b/c the computer is reading low oil pressure and cutting the fuel. I'm not sure about that though b/c the guage reads good pressure....
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Will
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Report this Post08-23-2014 10:22 PM Click Here to See the Profile for WillClick Here to Email WillSend a Private Message to WillEdit/Delete MessageReply w/QuoteDirect Link to This Post
The computer doesn't read oil pressure.

Does it have this problem when cold, or on hot restart?
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Dennis LaGrua
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Report this Post08-24-2014 10:36 AM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
You really can't diagnose without doing a thorough scan of the pcm. This may not be the answer that you were looking for but there is no way around it. Either
you keep guessing or do it the way the pros do.

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jediperk
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Report this Post08-24-2014 10:59 AM Click Here to See the Profile for jediperkSend a Private Message to jediperkEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Will:

The computer doesn't read oil pressure.

Does it have this problem when cold, or on hot restart?


Hot restart every time...
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phonedawgz
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Report this Post08-24-2014 11:09 AM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
When it happens try flooring the gas and cranking to see if it then starts. If it then starts but starts by running rough and then clears out look for a leaking injector.

When you first turn the key on do you hear the fuel pump run for two seconds? Bump the starter - does the fuel pump come on again for two seconds. It should for both. Then start the engine and turn it off after 10 seconds. Does the fuel pump run for a while even with the engine off?

Finally get this to happen again and then listen for the fuel pump. Is it running when this problem occurs?
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Report this Post08-24-2014 07:03 PM Click Here to See the Profile for jediperkSend a Private Message to jediperkEdit/Delete MessageReply w/QuoteDirect Link to This Post
Got on the cadillac forum and it looks like it might be the fuel pressure regulator. We'll see...
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phonedawgz
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Report this Post08-24-2014 08:36 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
You are going to check this with a fuel pressure gauge instead of just replacing the FPR right?

Yes it could be the FPR. It could be many other things also. Guessing parts, replacing them and then seeing if the problem still exists is a frustrating, slow and expensive way to solve problems.
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Will
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Report this Post08-25-2014 07:43 AM Click Here to See the Profile for WillClick Here to Email WillSend a Private Message to WillEdit/Delete MessageReply w/QuoteDirect Link to This Post
What computer are you running?
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jediperk
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Report this Post08-25-2014 02:07 PM Click Here to See the Profile for jediperkSend a Private Message to jediperkEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Will:

What computer are you running?


Stock 93 ecm with fast chips prom.
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Will
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Report this Post08-25-2014 08:58 PM Click Here to See the Profile for WillClick Here to Email WillSend a Private Message to WillEdit/Delete MessageReply w/QuoteDirect Link to This Post
Auto or stick? (not relevant, just curious)
Have you watched a fuel pressure gauge while it's experiencing the problem?

Stainless or nylon fuel rail?

[This message has been edited by Will (edited 08-25-2014).]

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jediperk
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Report this Post08-25-2014 10:00 PM Click Here to See the Profile for jediperkSend a Private Message to jediperkEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Will:

Auto or stick? (not relevant, just curious)
Have you watched a fuel pressure gauge while it's experiencing the problem?

Stainless or nylon fuel rail?


It's an auto (4T80). The fuel pressure gauge is next. Based off what I learned on the Cadillac forums it is most likely the Fuel Pressure Regulator or the fuel pump. Based on the sporadic nature though, its looking more like the FPR and that appears to be a common problem on the N* when it goes over 80K miles, which mine recently did. Fortunately, its a cheap part which I am going to replace regardless of what the fuel pressure gauge says just to be safe...
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Report this Post08-25-2014 11:57 PM Click Here to See the Profile for IXSLR8Click Here to Email IXSLR8Send a Private Message to IXSLR8Edit/Delete MessageReply w/QuoteDirect Link to This Post
It could also be your IAC unit on your throttle body.

Make sure it has a clean seat and pintle head from carbon deposits. Doesn't hurt to put a new one in place or to have a back up for its future failing.
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Will
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Report this Post08-26-2014 08:36 AM Click Here to See the Profile for WillClick Here to Email WillSend a Private Message to WillEdit/Delete MessageReply w/QuoteDirect Link to This Post
'93 doesn't have IAC... it uses an ISM like the 4.9.
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Will
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Report this Post08-26-2014 08:40 AM Click Here to See the Profile for WillClick Here to Email WillSend a Private Message to WillEdit/Delete MessageReply w/QuoteDirect Link to This Post

Will

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quote
Originally posted by jediperk:

It's an auto (4T80). The fuel pressure gauge is next. Based off what I learned on the Cadillac forums it is most likely the Fuel Pressure Regulator or the fuel pump. Based on the sporadic nature though, its looking more like the FPR and that appears to be a common problem on the N* when it goes over 80K miles, which mine recently did. Fortunately, its a cheap part which I am going to replace regardless of what the fuel pressure gauge says just to be safe...


Good. Step through the troubleshooting tree and be patient. Throwing parts at it without a solid diagnosis is a waste of money.

Also, the Fiero tends to end up with a very warm fuel tank after extended drive times. Old fuel pumps don't like that and can allow the pressure to sag on a restart.
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