Yet another fuel problem; specifics inside - TCCoA Forums
 
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post #1 of 10 (permalink) Old 03-23-2011, 09:15 PM Thread Starter
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Yet another fuel problem; specifics inside

1997 T-Bird, 4.6/automatic. Plugs look ok, no fouling or obvious signs of anything strange.

Ok, It's been doing this for a while now so I really started to pay attention to the symptoms before asking.

How it started:
No problems at all before this day, none at all. Filled the tank and had to go for a long drive. On the expressway I darted right onto an offramp and felt the car buck. After getting on a straightaway I swerved the car back and forth. Every time I did this the car would buck and skip, then clear up. It would only do this when the fuel was sloshed in the tank (apparently)

How it is now (after 2 months):
When the car is cold, no problems. Swerve the car back and forth; nothing unusual. Floor it, goes as it should. Lug the engine, it goes as it should. Now, when the car reaches normal operating temperature if the engine lugs it bucks and skips. If I leave the car in second gear to keep the RPM's up it will never buck. I can get it well over 3,000 RPM without a problem as long as it's held in a lower gear and the throttle isn't opened enough to cause big vacuum drop.

Haven't checked the fuel pressure yet but that's on the list. What's the correct pressure? With vacuum connected and disconnected?

White 1997 LX Sport 4.6
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post #2 of 10 (permalink) Old 03-30-2011, 05:11 PM Thread Starter
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Hooked the code reader up to it today. Got "Cylinder 6 misfire detected" and an "O2 sensor, bank 2; sensor 2" codes. Searched around on the net and looked into the EGR valve diagnosis. Unhooked the vacuum line and plugged it off, no change while driving. Still skips when warm. Will look at the plugs tomorrow, and also check the wires for resistance. Next will be warming the car up and pulling the coils to have them tested. If they are good I will test the fuel pressure, but at this point I am thinking it's a firing issue.

Out of disgust with this car it has sat parked since I started this thread. I started it today and pulled it into the shop to check the EGR. Saw that the rear view mirror had fallen off. Big surprise. While driving it to warm it up I noticed that I now have a rumbling sound when I hit the brakes. I am REALLY beginning to hate this car.....

White 1997 LX Sport 4.6
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post #3 of 10 (permalink) Old 03-30-2011, 05:29 PM
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Plugs and wires is where I'd start; I doubt it's EGR related. What were the actual codes you got?

-Brandon
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post #4 of 10 (permalink) Old 03-30-2011, 06:43 PM Thread Starter
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Well, I got the EGR idea from quite a few other websites that said a malfunctioning EGR system could cause a lean condition and result in cylinder misfires. So with that I figured I'd try the easiest and cheapest (free) troubleshooting that I could. I thought of doing the plugs/wires/coils first but had read many reports of people replacing them, only to have the same problem recur in only a few hundred miles, so the problem was never actually fixed, only masked for a while. The actual code numbers I got were:

P0156
O2 Sensor Circuit Malfunction
Bank 2 Sensor 2

P0306
Cylinder 6
Misfire Detected

I do all of my own mechanical work and this car has had me working overtime since I have had it. It's in great condition body and interior wise, save for a couple of small imperfections, and when it runs well it is an absolute blast to drive. But here lately the problems, whether self-inflicted or not, have driven me up the wall and make me want to throw in the towel on this one. I've never owned a car that has given me this many problems; it's becoming almost comical

White 1997 LX Sport 4.6
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post #5 of 10 (permalink) Old 03-30-2011, 07:16 PM
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If the EGR was causing a lean condition it would "theoretically" throw banks 1 and 2 lean codes or ping.

Plugs and wires on these cars are somewhat notorious. Coils do go bad on occasion but usually as a result of having to fire through bad wires for prolonged time periods.

According to the O2 code, you either have a short in the wiring harness to that sensor or the sensor itself is bad. That section of the wiring goes through the transmission harness in the event you have to search for shorts.

-Brandon
97 Laser Red Thunderbird LX 162k, Stage 2 4.6L 2v N/A | 300 BHP (255 RWHP, 290 RWTQ) | 13.95 @ 97.58 | Build details | Pics at the Lorain Assembly plant
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07 Redfire Fusion V6 SEL 178k, for the wife
Gone but not forgotten: 96 Mark VIII, 94 Cougar XR7, 93 Mark VIII

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post #6 of 10 (permalink) Old 03-30-2011, 07:35 PM Thread Starter
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Okay, thanks for the heads up on the wiring. One thing I did read, and I *think* it was actually on this site somewhere, is that a guy had bought a set of plug wires at his local parts store and they fixed the problem for a while, then it returned. Well, after replacing numerous pieces and parts he revisited the plug wires. He replaced them with either FRPP or Motorcraft wires and it fixed the problem for good. I just checked on Summit Racing and the Motorcaft wires are $100. Quite a bit more than I was expecting, but if it fixes the skipping problem it will be money well spent.

And as an aside note, the car was throwing the O2 sensor code for a couple of months before the skipping started. I know, I'm a slacker for not checking into that problem sooner lol.

White 1997 LX Sport 4.6
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post #7 of 10 (permalink) Old 03-30-2011, 07:45 PM
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When it comes to wires you'll be glad you went with Motorcraft. Boots getting ripped out upon removal is are a common issue with aftermarket wires, in addition to a few brands known to start arcing out of the box.

FWIW the most common EGR problems on this engine include carbon plugging the passageway into the plenum or the DPFE sensor going bad.

-Brandon
97 Laser Red Thunderbird LX 162k, Stage 2 4.6L 2v N/A | 300 BHP (255 RWHP, 290 RWTQ) | 13.95 @ 97.58 | Build details | Pics at the Lorain Assembly plant
98 Black Mark VIII 160k, stock daily driver
07 Redfire Fusion V6 SEL 178k, for the wife
Gone but not forgotten: 96 Mark VIII, 94 Cougar XR7, 93 Mark VIII

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post #8 of 10 (permalink) Old 04-04-2011, 09:08 PM Thread Starter
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OK, the wires seemed to have fixed the problem. I also went ahead and replaced the strut rod bushings at the control arm end while I was working on it. Still have a strange clunking/vibration under braking. I believe it's coming from the front. Everything has been replaced now so I'm suspecting the caliper pins. After replacing everything almost all of the clunks are gone, which is great because when I first got it it sounded like the front end was about to fall out from under the car, and I'm used to driving ratty 4x4's, so that's saying a LOT lol

White 1997 LX Sport 4.6
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post #9 of 10 (permalink) Old 04-04-2011, 09:28 PM
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Vibration under braking is usually warped rotors. If you're spending less than, say, $40 on one rotor you might be getting the thinner rotors that heat up faster and warp more easily. You say "everything" was replaced; how are the wheel bearings, sway bar endlinks and ball joints? These all can make noises...

-Brandon
97 Laser Red Thunderbird LX 162k, Stage 2 4.6L 2v N/A | 300 BHP (255 RWHP, 290 RWTQ) | 13.95 @ 97.58 | Build details | Pics at the Lorain Assembly plant
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07 Redfire Fusion V6 SEL 178k, for the wife
Gone but not forgotten: 96 Mark VIII, 94 Cougar XR7, 93 Mark VIII

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post #10 of 10 (permalink) Old 04-04-2011, 09:35 PM Thread Starter
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The only thing I haven't replaced is the wheel bearings. They make no strange noises when cutting right or left so I suppose that's a good sign. I'll check the rotors with a dial indicator this week sometime and also check for free play at the calipers. Also, the rotors are the ones that were on the car when I bought it, so there's no telling what brand they are or how cheap they were.

White 1997 LX Sport 4.6
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