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1999 STS - diamond white
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Discussion Starter #1
So what's wrong this time? The STS doesn't always start right away. Cranks fine, just takes a few seconds to fire up once in a while. It has backfire/popped a couple times while trying to start. Today the car stalled as i was coming off of the highway and on to a right hand clover leaf exit.
I replaced the crank position sensors a year or so ago. Had a bad coil a couple weeks ago. Cleaned the TPS, throttle body and MAF. Has new Motorcraft plug wires. Also replaced the FPR. Could it be a fuel pump? No codes. No CEL.
 

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1999 STS - diamond white
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5,229 Posts
Discussion Starter #3
Yup. :yup: Check your fuel pressure.
I'd be happy if a pump fixed it, but I wouldn't want to find out it didn't. I have about 1\2 tank of gas to drain. I'm going to check the pressure and replace the filter first. It's original.
 

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1999 STS - diamond white
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Discussion Starter #4
Here's a related question: The local AC Delco reseller has an AC Delco fuel filter for $21 and a Hastings for $13. I always thought Hastings was a good brand. Is AC Delco worth 40% more in price?
Autozone has Fram for $13 and Duralast for $10.50
 

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White Diamond '03 DHS (with DTS floor shift)
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86,785 Posts
I don't know what to say about the fuel filter. I would guess one is as good as the next.
 

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1999 STS - diamond white
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5,229 Posts
Discussion Starter #6
I ended up with Fram. The STS filter is about half the size of the one I just put in my Focus!
I'll see how it goes this weekend. If it still acts up I guess a fuel pump is next. At least there's an access panel in the trunk so I don't have to drain and drop the gas tank.
Interesting AC Delco video on Rockauto about their pumps. Shows the quality difference between them and aftermarket parts.

 

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1999 STS - diamond white
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5,229 Posts
Discussion Starter #7
Replaced the fuel filter and so far it starts right up. Hasn't stalled yet. The wife called today to say it "popped" when she started it. Sounds like timing or does it? No codes. Dirty injectors?
 

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White Diamond '03 DHS (with DTS floor shift)
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No, that's not timing. Timing is controlled electronically by the PCM.
I have found that if I released the key to quickly I could get that "pop" now and then.
Seems to me a vacuum leak can cause that as well if I remember correctly.
 

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98 DeVille, 97 DeVille d'Elegance
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I get the occasional pop from my 98. Like Ranger said not unusual and i believe i have a vac leak also.
 

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1999 STS - diamond white
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Discussion Starter #10
I still have the hard starting. Wouldn't a vacuum leak affect the idle? Mine is smooth once it starts.
 

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White Diamond '03 DHS (with DTS floor shift)
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86,785 Posts
Yeah, usually a vacuum leak will affect the idle.
Rule it out anyway. Spray some Brakleen around the manifold base, TB mount and vacuum line connections. Simple and easy. If you get no RPM increase, you can rule out vacuum.
 

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1999 STS - diamond white
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Discussion Starter #12
I removed the fuel pump tonight. It wasn't very hard with the trunk access panel. The pump looked okay. The fuel looked clean. No rust in the tank as far as I could tell.. I couldn't bring myself to ordering a new one. It doesn't exhibit the usual fuel pump symptoms; surging, lack of power under hard accell etc. Maybe it's something like an EGR. I'll keep looking. Maybe it's the FPR I replaced recently when it was running bad. It turned out to be a bad coil instead. Maybe now I created this problem with the new FPR. <sigh>
 

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White Diamond '03 DHS (with DTS floor shift)
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You can't tell a bad fuel pump by looking at it. Fuel pressure test is the only way. Did you ever check yours?
 

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1999 STS - diamond white
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Discussion Starter #14
Yeah. It was good. I just wanted to be sure the pump wasn't getting clogged up or there was rust in the tank. It only stalled once when driving. otherwise it drives smooth up and down the power range. Frustrating.
I'm going to replace the rusted up lockring and close up the trunk space.
 
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