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Author
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Topic: Mustang Engine Cutting Out (Bucking/Surging)
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Casey90GT
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Member # 6175
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posted
 
 
Hey guys...I just bought a new (to me) 1990 LX Mustang. The car is 100% stock with just 100,000 miles on the clock and everything is in great shape.
I bought the car last night and it was driving just fine and then tonight out of nowhere it just started cutting out while driving. You will be cruising at a steady rpm (any rpm) in any gear and all of a sudden the car will start falling on it's face, with the rpm dropping 200-500 rpm making the car buck wildly. It does this so bad that you can't drive the car.
The car had a full tune up with Motorcraft parts right before I bought it. I figured that the cause of the problem might have been a bad coil, and I had a known good coil off of another foxbody, so I swapped it out. I also disconnected the battery while swapping the coil. After the swap the car ran perfect for about 15 minutes, but then went back to it's occasional bucking, and then quickly and completely degraded again to the point of not being driveable.
I was planning on replacing the TFI module, but wanted to ask on here before I did. Any help would be greatly appreciated.
Thanks,
Casey
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Some day I'll finish it.
Posts: 1064 | From: Santa Rosa | Registered: Nov 2005
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SHORTSHIFTER89
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Member # 7810
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posted
my car is doing the same thing to the tee and i changed a few things with new parts did not help my next move is to pull out the distributor msd and put my stock one back in and go from there. Also my buddy that works with me stang is doing the samething and he just changed his fuel pump but nothing yet so hope you could get it right so you can tell me cus im pretty much stuck ![[Smile]](smile.gif)
i havent checkt my tps yet or fuel lines. but i have check just about everything else. so good luck and please let me no how it go's
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1989 Mustang 5.0 HCI NOW SUPERCHARGED
2013 Range Rover Sport
2011 Bmw 5501 twin turbo 530HP
1998 silverado c1500 cheyenne
Posts: 923 | From: 707 hillside | Registered: Jul 2007
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N8
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Member # 6048
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posted
Yo Casey sounds similar to what my was doing (your isn't backfiring tho ![[Wink]](wink.gif) ). Here is what fixed it for me.
Removed the IAB cleaned it well. Then ran the idle reset process
Check voltage on the TPS
But this was the golden ticket. Fuel pressure was low. Regulator was on the way out. Replaced it and now the car runs beautiful.
But first thing I would say is dump the codes and let us know what those are. If you have a CEL you can use a paper clip to do it. Give me a call if you need a lil help.
Edit
Forgot to add I checked the fuel pressure prior to replacing my regulator. But definitely run the codes. Keeps you from swinging in the dark at problems. And the dude below me has a point. I would actually check the gap plus check the firing order. Sounds stupid, but I have done that before too (reversed a wire).
[ July 21, 2008, 01:38 PM: Message edited by: N8 ]
Posts: 11638 | Registered: Sep 2005
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Cobraboy
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Member # 7826
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posted
Check the gapping on your plugs. Your car will run like shit if the plugs are gapped to wide. My car had this same problem.
Did you do the work yourself when you changed your plugs? Also, your car will do this if it's running too lean... Or even worse, running too lean with your plugs not gapped properly (which was what mine was doing)
Posts: 552 | From: California | Registered: Aug 2007
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Casey90GT
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Member # 6175
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posted
Ok everybody...here's the scoop. The car runs amazing, really strong, actually one of the faster 5.0's that I've driven, and then WHAM!!! Out of nowhere it starts falling on its face. It's like somebody shut off the motor, but only for a split second (just enough to drop the rpms by about 200-500) and then it kicks back on, but every time you try and accelerate it goes for a second and then falls on its face again, only to kick back on a split second later. It's so bad that you can barely maintain 15 mph. Then shut it off overnight, turn it back on and it's fine for about 15 minutes before it starts acting up again.
At this point I have checked every plug under the hood, checked the main ground at the back of the block, replaced the ignition coil and the TFI module. I have checked the TPS voltage and it is right on the money (no erratic readings, etc). My friend 306notchback510 did the tune-up and I know that he checked all the plug gaps, because he is a perfectionist. Plugs, cap, rotor and wires are all new, all Motorcraft.
N8, I will check the fuel pressure tomorrow. That's an interesting idea and it may be the cause of my problems...regardless, I'm glad to know that you figured out what was up with your ride.
Anybody else have any ideas...the problem seems to be directly related to engine temperature, and it's getting progressively worse everytime I drive the car.
Thanks in advance!
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Some day I'll finish it.
Posts: 1064 | From: Santa Rosa | Registered: Nov 2005
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threethirty1
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Member # 7814
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posted
sounds like a miss. when my fuel pump relay went bad it did that. like it shut on and off. everytime i hit any imperfection in the road.
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1987 Black GT
factory zero option car
Posts: 777 | From: North Bay | Registered: Jul 2007
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Casey90GT
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Member # 6175
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posted
This will do it sitting in the driveway though too...but only when it's hot.
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Some day I'll finish it.
Posts: 1064 | From: Santa Rosa | Registered: Nov 2005
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N8
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Member # 6048
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posted
Run the codes.
A paper clip jumping the connection will do it (red line).
[ July 22, 2008, 10:19 AM: Message edited by: N8 ]
Posts: 11638 | Registered: Sep 2005
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Casey90GT
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Member # 6175
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posted
Ok...so I still haven't checked the fuel pressure, but I did run the codes. I used both methods of running the codes KOEO (Key On Engine Off) and KOER (Key On Engine Running). Made sure the car was good and hot and it was actually cutting out while the computer was doing it's little diagnostic in the Key On Engine Running test. The only code I got was code 11, which means that everything is fine...FINE MY ASS! ![[Mad]](mad.gif)
For what it's worth, this is the first time that I have experienced the engine cutting out without even moving the car from my driveway.
I will report back after I put a fuel pressure gauge on it tomorrow. In the meantime, does anybody else have any ideas? I would really love to drive my new car!!! ![[Frown]](frown.gif)
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Some day I'll finish it.
Posts: 1064 | From: Santa Rosa | Registered: Nov 2005
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N8
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Member # 6048
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posted
hhmmm....now that is weird no code and it is running that bad. Does it have smog equipment? Just thinking a little test you can try to see if your computer is acting right is maybe disconnect one of the vac lines on one of the pots after the smog pump (you should get a code 49/94 or something like that) and see if you can get the car to throw you a code.
Anyway my guess would have been fuel pressure or the regulator or something. but no code so that is probably not the issue.
Posts: 11638 | Registered: Sep 2005
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Casey90GT
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Member # 6175
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posted
I had the car in gear the first time I ran the codes and I got a code 67, which means that the car is in gear...so it's working. I'm really pulling my hair out here!
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Some day I'll finish it.
Posts: 1064 | From: Santa Rosa | Registered: Nov 2005
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Cobraboy
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Member # 7826
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posted
Typically if your car is running like shit and your computer knows nothing of it, it means the problem is something that has nothing to do with the computer... vacuum leaks, exhaust leaks, etc etc... maybe you are looking for the wrong thing by checking for codes because maybe the problem is something that will not trip one?
Just a thought.
Posts: 552 | From: California | Registered: Aug 2007
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Casey90GT
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Member # 6175
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posted
That's what I'm thinking...
ALSO-When it cuts out, none of the lights flicker, or and the voltmeter reads consistently. I have checked the grounds that I can see, but this leads me to believe that it is not a bad ground anyway.
Any other thoughts? I'm running out of things to check.
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Some day I'll finish it.
Posts: 1064 | From: Santa Rosa | Registered: Nov 2005
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Cobraboy
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Member # 7826
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posted
What kind of mpg are you getting? Does it burn anything funny looking or funny smelling out the exhaust? Like white smoke or something?
Does it burn a lot of oil? Anything somewhat unusual other than the hesitation/bucking?
Posts: 552 | From: California | Registered: Aug 2007
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Casey90GT
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Member # 6175
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posted
23-25 mpg...plugs are a little bit more brown than ideal (running a tad rich), but out the pipes it smells like it's running right and there is no excess condensation or smoke of any color.
ALSO-I may have led people astray when I called it a miss. It's not a miss, because a miss would tend to suggest it's dropping a cylinder. This acts like somebody is intermittently hitting a kill switch. You cannot accelerate or maintain speed. IT FALLS FLAT ON IT'S FACE.
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Some day I'll finish it.
Posts: 1064 | From: Santa Rosa | Registered: Nov 2005
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Cobraboy
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Member # 7826
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posted
It sounds like a vacuum leak
Posts: 552 | From: California | Registered: Aug 2007
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Casey90GT
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Member # 6175
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posted
I really don't think a vacuum leak could do that, but I will go spraying around with my carb clean.
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Some day I'll finish it.
Posts: 1064 | From: Santa Rosa | Registered: Nov 2005
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threethirty1
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Member # 7814
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posted
Fuel pump, fuel filter, inertia switch in trunk.... Follow your fuel pump hot wire from the engine bay to the trunk. Its pink and blue i think? I had a short in my trunk where that wire was exposed and grounding out my fuel pump. Maybe a bad MAF sensor....or coolant temp sensor... did u check your timing? ....just some ideas man. Sounds like this car had been worked on just prior to you buying it. Was this problem disclosed?
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1987 Black GT
factory zero option car
Posts: 777 | From: North Bay | Registered: Jul 2007
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Cobraboy
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Member # 7826
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posted
quote:
Originally posted by threethirty1:
Fuel pump, fuel filter, inertia switch in trunk.... Follow your fuel pump hot wire from the engine bay to the trunk. Its pink and blue i think? I had a short in my trunk where that wire was exposed and grounding out my fuel pump. Maybe a bad MAF sensor....or coolant temp sensor... did u check your timing? ....just some ideas man. Sounds like this car had been worked on just prior to you buying it. Was this problem disclosed?
I think he would trip a check engine light if any of those were the problem... with the exception of the fuel pump grounding out..
[ July 23, 2008, 03:28 PM: Message edited by: Cobraboy ]
Posts: 552 | From: California | Registered: Aug 2007
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N8
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Member # 6048
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posted
Oh yea I clean my MAF with some MAF cleaner a while back and that helped my surging idle. I cant think of many vac leaks that would cause this issue and the computer not pick up. but that is based on my experience and not any trained knowledge. But yea I would agree at this point with running through your fuel system.
Posts: 11638 | Registered: Sep 2005
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Cstang5.0
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Member # 4925
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posted
I had the same problem it ended up being a fuel pump..
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88 VERT slow sold
89 coupe stock ; )
02 yukon
05 focus
Posts: 1638 | Registered: Oct 2004
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Casey90GT
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Member # 6175
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posted
Bad PIP was the culprit...problem solved...now for the modifications! ![[Big Grin]](biggrin.gif)
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Some day I'll finish it.
Posts: 1064 | From: Santa Rosa | Registered: Nov 2005
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threethirty1
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Member # 7814
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posted
what is pip.
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1987 Black GT
factory zero option car
Posts: 777 | From: North Bay | Registered: Jul 2007
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1bdpone
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Member # 6708
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posted
Does anyone know what a PIP is. That is what casey posted as the solution & my sons is having the exact same problem while on a road trip.
Posts: 182 | From: Tri Valley | Registered: Apr 2006
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SLOWSN95
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Member # 8269
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posted
my buddys 90 notch had the exact same problem
cleaned the salt n pepper/10 pin connectors behind the intake manifold and problem was fixed
clean the grease out of them, spread out the male connectors just a hair with a sewing needle or something small enough to squeeze between the prongs, and use a little bit of dielectric grease if you have some (if u dont thats ok too)
those connectors have been related to many different types of problems such as surging idles, rough idles, cars cutting out, inaccurate check engine lights, etc
hope this helps u out ![[patriot]](graemlins/patriot.gif)
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94' GT
347 Stroker
MM Suspended
2003 SB SVT Lightning
Pullied and Lowered
89'Hatch-SOLD
Posts: 2214 | From: 510/east bay | Registered: Mar 2008
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