My 86 GM (94000 miles) bucks hard when I let off the gas going around 30-65. It does this some days and other days it drives fine. I also noticed a surging idle when I start it and every once in a while it idles way down and clears up after a while. I've cleaned the egr valve and iac, replaced plugs, wires, coil, cap and rotor, fuel filter, tps, ect, air filter and cut off the ac/smog belt and muffler. I also checked the timing and had to advance it to get it to 10-11. When it's in overdrive, it also likes to slow down when I press the gas so it can downshift to 3rd. It doesn't have very good throttle response in od. The things I noticed was that there are a couple of wires on the alternator that are bare in places and when I cut the muffler off it seemed to stop bucking as much. I thought it was dirty gas or a bad fuel pump or strainer but I had someone drop the tank and it looked brand new without one little piece of dirt. Should I spend time trying to chop off my converters or change the wires on my alternator? Or are there other things that can be wrong here?
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"It is the soldier, who salutes the flag, who serves under the flag, and whose coffin is draped by the flag, who allows the protester to burn the flag."
-Father Dennis O'Brien, USMC -
vac leak?sigpic
- 1990 Ford LTD Crown Victoria P72 - the street boat - 5.0 liter EFI - Ported HO intake/TB, 90 TC shroud/overflow, Aero airbox/zip tube, Cobra camshaft, 19lb injectors, dual exhaust w/ Magnaflows, Cat/Smog & AC delete, 3G alternator, MOOG chassis parts & KYB cop shocks, 215/70r/15s on 95-97 Merc rims
- 2007 Ford Escape XLT - soccer mom lifted station wagon - 3.0 Duratec, auto, rear converter delete w/ Magnaflow dual exhaust
- 2008 Mercury Grand Marquis Ultimate Edition - Daily driver - 4.6 2 valve Mod motor, 4R75E, 2.73s. Bone stock -
Did you check the timing with the SPOUT unplugged or plugged in? It needs to be unplugged to properly set it.
What kind of wires and plugs? What does the terminal on the ignition coil look like?86 Lincoln Town Car (Galactica).
5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley
91 Lincoln Mark VII LSC grandpa spec white and cranberry
1984 Lincoln Continental TurboDiesel - rolls coal
Originally posted by phayzer5
I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousersComment
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I checked everywhere for vacuum leaks and can't hear or find any. I did have the problem with the vent going to defrost under heavy acceleration but that stopped when I took the rusty vacuum reservoir out and replaced it with a plastic one. The codes I pulled were for the ect sensor which I replaced and saw an improvement in mpg from 16 to 18, and for running lean on both sides. I forgot all about the new fuel pressure regulator I bought for it and never put in. The upside down screws on it are hard to deal with. Is there a trick to taking the regulator off?"It is the soldier, who salutes the flag, who serves under the flag, and whose coffin is draped by the flag, who allows the protester to burn the flag."
-Father Dennis O'Brien, USMCComment
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The timing was checked with the spout unplugged, I followed the procedure from this site. The plugs are motorcraft copper core and the wires are msd street fire with the dielectric grease. I've pulled the plugs a few times and they all have a black burn spot on the part where it's usually white. The terminal on the coil looks like new."It is the soldier, who salutes the flag, who serves under the flag, and whose coffin is draped by the flag, who allows the protester to burn the flag."
-Father Dennis O'Brien, USMCComment
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You wont be able to hear vacuum leaks for the most part. You'll have to closely inspect the lines. Bend them around your finger. Sometimes you find cracks that aren't obvious. Look at the back side too. I've seen hoses on my own car that looked fine from one side, but on the back they were shot.
If all of them have black spots, its running rich. A major leak, especially one on the MAP sensor will do that. A bum MAP will also do that, but those fail less often than vacuum hoses do.86 Lincoln Town Car (Galactica).
5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley
91 Lincoln Mark VII LSC grandpa spec white and cranberry
1984 Lincoln Continental TurboDiesel - rolls coal
Originally posted by phayzer5
I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousersComment
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That sounds like a bad map/ loss of vacuum to the map sensor as Gadget said. I have had this problem, and after I replaced the vacuum line going to the MAP sensor and it was working fine. If the line is original, it's probably cracked to high hell and leaks.Comment
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I checked the vacuum line going from the map sensor and it is cracked in a few places. I followed it as far as I could under the intake and lost it. Does the intake have to come off to replace it? I might just try covering the hose with gasket maker if that's the case because the cracks are in spots where the line is still visible."It is the soldier, who salutes the flag, who serves under the flag, and whose coffin is draped by the flag, who allows the protester to burn the flag."
-Father Dennis O'Brien, USMCComment
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it doesn't HAVE to come off, but unless you have short and skinny arms, you're not about to be able to get that line off without taking the upper plenum off (I've already done this once). Get a new plenum gasket and go to town. once the upper plenum is off it's super easy to change. I didn't even bother removing anything else from the plenum other than the 5.0L plate.
Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
Originally posted by gadget73
... and it should all work like magic and unicorns and stuff.
Originally posted by dmccaig
Overhead, some poor bastards are flying in airplanes.Comment
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For all practical purposes, yes the upper needs to come off. No, I don't know why they didn't use some common sense and extend those steel nipples out to where you can actually replace the rubber lines wirthout having to remove the intake. Either way, its not that hard to unbolt the upper. Do the PCV stuff if its needed while its off, its much easier.86 Lincoln Town Car (Galactica).
5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley
91 Lincoln Mark VII LSC grandpa spec white and cranberry
1984 Lincoln Continental TurboDiesel - rolls coal
Originally posted by phayzer5
I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousersComment
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Sorry I didn't get back with the results right away. I covered the rear hose with gasket maker and it didn't do anything. Since then I've sold the GM to my brother and right after he bought it, the right hose in front of the intake below the plenum cracked in half and it really started bucking bad on him. He replaced the hose and there's been no problems with it since. It was that hose that was causing all of the intermittent problems. It didn't look cracked but after I moved it around a little, a bunch of little cracks showed up. Thanks for all of the advice and help."It is the soldier, who salutes the flag, who serves under the flag, and whose coffin is draped by the flag, who allows the protester to burn the flag."
-Father Dennis O'Brien, USMCComment
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