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1995 Cadillac STS
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46 Posts
Discussion Starter · #1 ·
Hello, this seemed to start a couple months back and the problem seems rather intermittent. It's always there to a small degree but probably not noticeable to anyone who hadn't driven the car before the issue. But today it was worse than usual and it is rather balmy now in Houston so I now know it isn't a temperature issue.

Basically, when under light acceleration or just a steady coast at low speeds, you can feel and visually see on the tach it hesitate for a millisecond. Almost like it isn't getting any gas for just a moment. The car starts and idles fine and does not have this issue on heavier acceleration (or at least it isn't enough to be noticeable, yet). It doesn't seem like a fuel filter or pump issue to me because of the perfect idle and problem disappearance under heavier accel, but I'm no expert. Plugs and wires were changed less than 5,000 ago and had ran fine with them for 4 months.

Thanks for any help!
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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72,798 Posts
Codes ??? Throttle position sensor, throttlebody cleaning, ISC motor, check all the vacuum lines attached to the throttlebody and the PCV system at the front and rear cam covers. Air filter ? Re-check all the plug wire connections at both ends. EVAP control solenoid and vacuum line just under the rear run of the fuel rail. FPR (Fuel Pressure Regulator) OK ? No gas in the nipple when the vacuum line is pulled off ? Fuel pressure OK ?? (40 - 45 psi at idle - test port on rear of fuel rail, passenger side). Run a 20 oz. jug of Chevron TECHRON through a tank of 93 octane Shell, Texaco,or Chevron gas: powerful fuel system cleaner.
 

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Registered
1995 Cadillac STS
Joined
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46 Posts
Discussion Starter · #4 ·
Codes ??? Throttle position sensor, throttlebody cleaning, ISC motor, check all the vacuum lines attached to the throttlebody and the PCV system at the front and rear cam covers. Air filter ? Re-check all the plug wire connections at both ends. EVAP control solenoid and vacuum line just under the rear run of the fuel rail. FPR (Fuel Pressure Regulator) OK ? No gas in the nipple when the vacuum line is pulled off ? Fuel pressure OK ?? (40 - 45 psi at idle - test port on rear of fuel rail, passenger side). Run a 20 oz. jug of Chevron TECHRON through a tank of 93 octane Shell, Texaco,or Chevron gas: powerful fuel system cleaner.

What brand plugs and wires did you use?
Damn, I meant to answer both of those questions in the original post. AC Delco wires and plugs (I remembered reading that was the best bet). As far as codes - a month ago when I checked I didn't have any getting thrown out at me except for a S071 for the front right accelerometer but I haven't quite located that yet to check the connection (saw on a post from 5 years ago stating "It is located at the rear top, of the right strut tower.
It is a small square unit with a black cover on it." - but I can't see what he was talking about) but I will check again when I get home for any new codes.

I have a 20oz bottle of Techron in the garage I was planning on throwing in with some tier one supreme on top of it. Figured that would help possibly rule out some things.
 

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99 STS, White Diamond
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792 Posts
Run a 20 oz. jug of Chevron TECHRON through a tank of 93 octane Shell, Texaco,or Chevron gas: powerful fuel system cleaner.
I'll second that idea to use a jug of Techron!

My fuel gauge was beginning to wander too much and at Submariner's suggestion I used the Techron.

Not only did it help the fuel gauge, but the very occasional, momentary feeling of hesitation under light acceleration has disappeared.

My throttle body is nicely cleaned, fuel pressure regulator OK, no leaks in the air intake or in vacuum.
 

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2000 Seville SLS
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37 Posts
Bump. Exactly the same problem, 2000 SLS.

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Going to try Techron with some Shell/Chevron premium.
 

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2000 Seville SLS
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37 Posts
Tried Techron, then changed out fuel filter and cleaned the throttle body. Problem stopped (seemingly) for about 3 hrs of driving then reappeared, and now it still does it fairly regularly. Another gearhead who drove it said it felt like the transmission.

Any ideas?
 

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2000 Seville SLS
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37 Posts
Shore did! Got a PCM P0101 and thought I might clean the MAF. I used the whole can of CRC MAF cleaner (why not?) and it seems like it fixed it. Mileage has dropped a little, I think it's because it was running lean because it wasn't seeing the air come in.

Edit: I had previously checked the fuel pressure regulator, checked fuel pressure, and run Techron cleaner several times.
 
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