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laura796
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Jun 30, 2012, 8:09 AM
Post #1 of 36
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Hello,
I have a 1995 Buick Lesabre 3.8 that is bucking at aprx 45-55 MPH. It started off at lower speeds as well and eventually just quit running all together. I changed the fuel pump and it started right back up, but its still bucking at 45-55 MPH. I have changed the MAP sensor, fuel filter, and a couple other parts but it didn't help. the only thing I have not done is a tune up. do you think that could help? People keep telling me that its a fuel related problem, but I dont know how it can be, after I have changed out so many parts. (they were all new parts except the MAP sensor-was a used part from another car we had) if you floor the car and pass the 55mph mark the car is fine and drives normal. Just the speed limits around me are all pretty much 45mph so its a real a pain to have to drive just under the speed limit to avoid the bucking. it kind of feels like a new person learning stick shift..how it bucks when they arent fully in gear or dont have enough gas. DO you think it could be a transmission problem?
there was no check engine light on, but I did try to scan it just in case and for whatever reason it couldn't be scanned (said error scanning) so maybe I have a fuse out somewhere that I didn't know about. So another mystery to add to the problem.
thanks for any help you can provide 
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Discretesignals
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Jun 30, 2012, 9:15 AM
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Re: 95 lesabre bucks
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Sounds like an ignition problem to me. Usually ignition problems show up around those speeds when you crowd the engine before the transaxle downshifts. It's more apparent when there is a lot of load being put on the engine when the TCC is engaged.
If the plug wires are worn out, that can cause those symptoms. Also inspect the ignition coil posts for corrosion. If you have any rusted out coil king pin posts, you need to change the coil.
95 was the change off year between OBD1 and OB2, so even if it has the OBD2 connector you need a enhanced scan tool to get into it.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Jun 30, 2012, 9:17 AM)
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Sidom
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Jun 30, 2012, 12:56 PM
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Re: 95 lesabre bucks
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Take it out of overdrive and see if that helps........could be a problem the clutch locking up & disengaging.....That speed is right around where it will lock up
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laura796
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Jul 2, 2012, 6:20 AM
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Re: 95 lesabre bucks
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ok, so here's an update.
I checked the coils, it was running on 5 cylinders not 6, so instead of messing with it, I changed the whole coil pack. it started right up and ran good. took it for a test drive and it ran like crap. stalled out once and managed to get it restarted then we got stopped at a red light and the car completely died. (had to push it off the the road)
Put the old coil pack back on-thinking it would start-NOPE nothing. listened to the fuel pump and nothing... how do I test the voltage of the wires to make sure there is power going to fuel pump? (there are a bunch of different wires in a cluster so Im not sure which ones power the fuel pump) also would you know where the relay is for the fuel pump? (my owners manual does not show a diagram or there isnt nothing labeled "fuel pump" does it run with something else that I could look for?
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Discretesignals
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Jul 2, 2012, 8:28 AM
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Re: 95 lesabre bucks
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Best place to check for power and ground to the pump is down at the fuel tank. There is a connector you can access to take your voltage readings.
Grey wire is the fuel pump power feed and black is the fuel pump ground.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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laura796
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Jul 2, 2012, 9:47 AM
Post #6 of 36
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Re: 95 lesabre bucks
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Ok, thats where it was checked and nothing... no power
Could it be the security system? VATS? That shutdown the fuel pump and stops it from turning over? It cranks but wont turn over completely to run....
(Just a side note: got the key read for Ohms and have resistors to bypass the system if need be)
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Hammer Time
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Jul 2, 2012, 9:53 AM
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Re: 95 lesabre bucks
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That's not how Passkey works Are you checking that power while cycling the key or cranking the engine?
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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laura796
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Jul 2, 2012, 11:01 AM
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Tried it both ways and nothing....
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Hammer Time
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Jul 2, 2012, 11:36 AM
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Then you need to troubleshoot the rest of the circuit to determine why.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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laura796
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Jul 2, 2012, 12:01 PM
Post #10 of 36
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Re: 95 lesabre bucks
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Im at a loss as how to check everything.
After changing the coil pack it started, then quit and now nothing at all. now the fuel pump has no power. are these two linked somehow? the fuel pump and the coil pack?
is there anything else someone could recommend I try? I tested relays, fuses and everything fine. (the fuel pump was just put on in FEB.- which I know they can still be faulty even though its fairly new)
Im just at a loss as where to go from here? 
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Hammer Time
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Jul 2, 2012, 12:35 PM
Post #11 of 36
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Re: 95 lesabre bucks
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You don't try things. You diagnose problems systematically. If you don't have fuel pump power, you first need to be sure about that with a fuel pressure gauge and then you have to follow a wiring diagram to find the fault.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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laura796
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Jul 2, 2012, 1:59 PM
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Sorry... Im not wording things correctly for you. "try" means DIAGNOSING! you
"try" testing things to diagnose right? I KNOW I have no fuel pump power, I cant hear it come on, no pressure with gauge.
I dont have the schematics (yet) for the wiring so Im just going to hold off testing that. Ive tried different suggestions of wire colors and still cant get voltage/power to show up on a tester.
I just thought I would ask if it "MIGHT" be the VATS, because it shuts down the power to the fuel pump. I know the VATS in these cars give people a lot of problems. (had to bypass 2 other cars, for different reasons though)
Would the car even try to turn over if it was the VATS or would there be nothing at all once you turned the key on?
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Hammer Time
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Jul 2, 2012, 2:02 PM
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It doesn't have VATS. It has Passkey and that locks out the starter.
GENERAL DESCRIPTION
The personal automotive security system (PASS-Key) is standard vehicle equipment. The system prevents vehicle theft by disabling the engine unless a key with a specific electrical resistance is used in the steering column ignition switch. The system components are the ignition key, the steering column lock cylinder, the PASS-Key II(R) module, the starter enable relay, and the power control module (PCM).
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Jul 2, 2012, 2:04 PM)
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laura796
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Jul 2, 2012, 2:59 PM
Post #14 of 36
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Re: 95 lesabre bucks
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Sorry.. I thought the passkey was called the VATS (vehicle anti theft system)
Thanks for the wire schematics and for the help I do appreciate it!
do you think because the car turns over but doesn't start I can rule out the passkey? and just focus on finding out the power issue with the fuel pump?
Is there relay's on the passenger side as well for the fuel pump? I know there are some in there, but I have no way of knowing what they are for (no labeling that I can see..?) maybe I missed a relay somewhere that sends power to it...
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Hammer Time
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Jul 2, 2012, 3:12 PM
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You would have a flashing security light if you have a problem with Passkey. VATS is a legit system, just not on your car.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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laura796
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Jul 2, 2012, 3:45 PM
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The light does flash but it goes out after a couple flashes. If I leave the key on for a minute it flashes for aprx 2 seconds and never comes back on.
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Hammer Time
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Jul 2, 2012, 3:49 PM
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As long as it goes out, the module is satisfied with the key. Besides, I told you numerous times that it locks out the starter.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Discretesignals
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Jul 2, 2012, 3:51 PM
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Even if it was a passkey problem, passkey won't kill the engine after it is running. It wouldn't even crank if the passkey system was in inhibit mode.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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laura796
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Jul 2, 2012, 4:13 PM
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ok, well I was hoping to get it up and running today, but its not looking like it will happen. Ill work on it again through out the week, but I will keep you posted.
Ill double check fuses/relays and check the wires with a tester (thanks again for the diagrams on both of those)
if there is no power in the wires what would you recommend I do then? (I have no idea how to split/jump wires but I would give it a try if I had the right instructions.... or is there more to test/diagnose after that to rule out other possibilities?
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laura796
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Jul 9, 2012, 9:24 AM
Post #20 of 36
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Re: 95 lesabre bucks
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Ok, so I changed the fuel pump again (incase it was a faulty even though it was only 5 months old) I changed the relay and checked the fuse with a tester. I didnt have a fuel pressure gauge, but I checked it at the valve and it had no pressure. (Checked it with the key on and off)
Coils have spark (now that its been changed), battery is good...
Im lost as to where to go from here?
Do I just continue to look at the wiring And try to find out where the connection has possibly gone bad ? Can I follow the wiring schematics you sent me or is there more advanced ones that could show me more.
detail as to where the wires lead to/from.
If its not wiring whats the next thing to diagnose? (If anything)
My dad and I are giving it one more look over this weekend and if we cant figure it out its going to become a parts car and then scraped at the local junkyard.
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Hammer Time
Ultimate Carjunky
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Jul 9, 2012, 9:27 AM
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You need to get a fuel pressure gauge before throwing any more parts at it.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
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Jul 9, 2012, 9:44 AM
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Ditto + arggh! You did all that before testing fuel pressure!
~ $60. +/- could save you tons of wasted bucks,
T
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laura796
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Jul 9, 2012, 10:45 AM
Post #23 of 36
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Normally if I press on the fuel valve it squirts out really strong. This time it was a VERY tiny tiny drip. If I get a gauge and it says no pressure where do I go from there?
(The fuel pump was replaced for free-so no added $ came out of my pocket, but I still didnt hear it come on)
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Tom Greenleaf
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Jul 9, 2012, 10:53 AM
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Didn't re-read whole thread but now a tiny drip of fuel is NG but may not be ready with new fuel pump yet. If no power to it and power is sent that way it still needs ground. No matter what you should want to test a new pump. Specs not in front of me but how would you tell 15 PSI from 60 PSI which may be in spec for this without both measuring pressure and that it holds?
T
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laura796
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Jul 9, 2012, 11:43 AM
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I understand what youre saying, about not knowing the psi measurements. But my dads worked on cars for a very long time (hes no master mechanic) but he knows that a drip coming out of the fuel valve is not enough to start a car. We tried it a bunch of times so the fuel pump could fill the lines back up with fuel (even lowered the jacks/stands so the car would be level)
Heres the post in a nut shell.
Started with bucking at low speeds, then around 45-55mph it eventually quit all together. No fuel pressure-checked with the valve again-no gauge) so changed the fuel pump/filter and it started right up. No more bucking at low speeds but still there at 45-55. Drove it for 5 months-trying to figure out the bucking cause. The other person on here said check coil pack-checked it and found it was running on 5 cylinders not 6. So, changed the coil pack. Took it for a test drive- it stalled and we got it started again. Then it completely died on us and here we are now...trying to figure out what happened. (We even put the old coil pack back on hoping to get it to start so we didnt have to tow it home...but it didnt work)
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