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Author
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Topic: Miss/Buck in a 5.0L 89 Crown Vic
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gotstang68
Journeyman Posts: 12
From: Williamsport, PA
Registered: Jun 2001
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posted 07-19-2001 05:45 PM
   
History: In the past, A head gasket seemed blown. Turned out a head bolt had cracked and bent in two places. Recently replated plugs, wires, cap, roter and coil. I was having a problem with my EVP sensor. It was telling the computer that there was a problem and my check engine light would flash. We checked it out and the voltage at idle was fine. Under loads while driving it would semi-randomly flash on and right off again. We tried to plug the hole and trick the Computer into think it was working with some resistors and relays. Almost worked too but a signal was then out of range (when measured and compared to specs it was fine). so we put an old EGR valve back on and grinded some of the pin off that moves the EVP sensor until it was right. No more check engine light. Now the problem: My car used to randomly buck around when maintaining a steady speed. Well it mysteriously stopped. I found that the vacuum line to the EGR had come off. I put it back on and the random bucking at steady speeds started again...BUT!!! The check engine light hasn't flashed nada once. I find that wrong and suspicious. The other problem I'm having is that when I accellerate or if it's under any amount of load (higher the gear the worse it gets) it will buck in a similar manner. Not a miss..like something pushing backwards somewhere. Someone suggested the cats and I'm gonna maybe poke them out to see if they're the problem next. Any ideas on what is causing all this crap? I'm pretty sure the EGR valve has a SLIGHT...VERY slight leak...but not much. If it workes unplugged, I think I'll just slap a solid plate over the holes and call it fixed there...but the buck under a load is still left...and I believe they might be related. If anyone can offer anything, please do. I'm running out of ideas fast. It is a completely stock 5.0L EFI 1989 Ford LTD Crown Victoria. The part that makes me worry about all this...is the odometer. It reads 182,000 miles. The teardown for the head gaskets went well and showed everything inside to be in relatively good condition for its mileage so I'm not so sure it's mileage related. Maybe something with the tranny?? HELP ME!!!!!
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cpmaverick
Moderator Posts: 927
From: Auburn, AL.
Registered: Jan 2000
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posted 07-22-2001 06:41 PM
Bottom line is, you've tricked the computer with your rigging. Fix the original problem the right way. EGR system is a common cause of surging/bucking. Obviously you have a problem with it that you have not fixed, only covered up. I'd hate to have to work on that car in my shop.
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gotstang68
Journeyman Posts: 12
From: Williamsport, PA
Registered: Jun 2001
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posted 07-22-2001 11:31 PM
It's more weird than that though. I noticed that when we changed the cap we pulled the vacuum line off the EGR valve that goes to the selenoid. The rigging is no longer in place, nor has it been since we tried it. Odd thing is, with the Vacuum line to the EGR valve being off, no codes have been set! It just doesn't make any sense.
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cpmaverick
Moderator Posts: 927
From: Auburn, AL.
Registered: Jan 2000
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posted 07-23-2001 08:15 PM
quote:
Originally posted by gotstang68:
so we put an old EGR valve back on and grinded some of the pin off that moves the EVP sensor until it was right. No more check engine light
-----So the EVP has been replaced with a new unit? You shouldn't have to grind on it; Ford recommends replacing the EGR with the EVP as a unit.
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gotstang68
Journeyman Posts: 12
From: Williamsport, PA
Registered: Jun 2001
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posted 07-26-2001 07:19 PM
No No No. . Again I say, The rigging is no longer there. It was removed because it did not work properly. When I created my circuit, I created it with relays and resistors to put the correct voltages on the Sensor Signal wire at the EVP and the relays were in place of the selenoids. That was just so the computer thought I was using an EGR valve and so it didn't trip a code and/or the check engine light for no good reason. Also when I had the mentioned circuit connected, the EGR valve and sensor was replaced with a solid plate. With no holes to let ANYthing through. Now it has a legit EGR and vacuum line selenoids, but the sensor was readin way higher than it should have when the valve was closed. We did check the valve. With the vacuum line that would normally OPEN the EGR Valve disconnected my car runs fine. There is no miss/buck-ish type of thing happening at steady speeds. But if I reconnect the vaccum line to the EGR selenoids, no check engine light is tripped, no codes...yet I have a screwy miss/buck. And the buck not only feels like a split second loss of power...it feels like something is actually resisting the power. If you're as befuddled as myself, don't hurt your brain over it. The car is high mileage (183,000) and may just need rebuilt. seals and all that good stuff...I was just asking in here because I figured a lot of those in this topic would be running either identical or similar 5.0L's and may have encountered a problem like this before. Do you think a leaky EGR valve could be responsible for a buck/miss when under a load/accelerating? Maybe the cat. converters? Meow. Any other ideas even? I don't want lectured for disabling emmissions equipment. Save the pay Ford money for trees crap. I paid them 13 dollars for a 6 inch piece of hose once. They wanted, if I recall, over $100 for that whole assembly. Screw that, I'd rather plant a tree myself and disable the EGR valve.
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cpmaverick
Moderator Posts: 927
From: Auburn, AL.
Registered: Jan 2000
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posted 07-26-2001 07:55 PM
I'm not lecturing you on emissions equipment, I'm saying that everything works as a system and I have had to retrace many problems on cars like yours back to a disabling of a circuit or system just to make it run right.I think that you shouldn't have had to grind the EVP, and something is wrong with the EVP, EGR, or both. And that is contributing to your problem. Another possibility: Obviously the problem is EGR related. Do you have vacuum at the EGR line at idle? You shouldn't; if you do then you probably have a bad EGR solenoid. Unplug the EGR solenoid and if you still have vacuum through it replace it. -Charlie
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cpmaverick
Moderator Posts: 927
From: Auburn, AL.
Registered: Jan 2000
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posted 07-26-2001 07:57 PM
quote:
Originally posted by gotstang68:
Do you think a leaky EGR valve could be responsible for a buck/miss when under a load/accelerating?
Absolutely. In fact it is common. Good luck on finding your problem.
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gotstang68
Journeyman Posts: 12
From: Williamsport, PA
Registered: Jun 2001
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posted 07-31-2001 08:54 AM
I have removed the vacuum line from the EGR Valve and plugged the vacuum line supplying vacuum to the solenoid. No codes. I am going to replace the modified EVR assembly with the one that has the exhaust gas path welded closed. This will assure me that there is no leaky EGR valve. I'm going to see what happens after this change. Hopefully, I get a chance to do it this weekend. I will post the results.------------------
'89 Crown Victoria LX - Daily Driver
'71 LTD Convertible - Current Project
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