Engine stumbles and shakes when I give it open throttle under load - Ford Mustang Forum
 
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post #1 of 12 (permalink) Old 06-19-2007 Thread Starter
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Engine stumbles and shakes when I give it open throttle under load

My 5.0 LX has 285,000kms on it now but the engine has always been like a rock. Out of nowhere it just started having this weird problem where it stumbles and bumps and shakes when I step down on the gas all the way. It feels like an electrical problem or a sensor that's malfunctioning.

It seems to happen in any gear, especially when the rpm is low and I try to give it open throttle. When the rpm is at like 2,000 and I step down hard it really shakes and bumps around. If I just give it a little gas and accelerate like a grandma it doesn't show the problem at all. It's not fuel pump is it? It never stalls out.

Another important point is that the shaking etc. doesn't seem to happen if I'm in neutral and rev it up. It seems like it's only when it has to move the car that there's a problem.

I haven't had too much time to fiddle with it yet, but I did find a loose connection on the positive terminal at the battery. I thought that would have been it but tightening it didn't seem to fix it.

Any suggestions would be much appreciated. Thanks!!!
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post #2 of 12 (permalink) Old 06-19-2007
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check your TPS sensor.
Bet ya its bad.

Pick up a new one set the voltage for .99 with a multimeter.

j

2004 mustang gt: JLT CAI, SLP LM2 catback,
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post #3 of 12 (permalink) Old 06-19-2007 Thread Starter
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Ya that was one thing I was going to check... I set it to .99 last spring with my multimeter. Will it for sure need replacing or just need to be reset back to .99
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post #4 of 12 (permalink) Old 06-19-2007
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ussually the tps dont go bad, i would just reset it to .98-.99, kinda sounds like a bad fuel filter too, check your maf wires too, if you see no improvment with resetting the tps and a new fuel filter i would replace the tps

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post #5 of 12 (permalink) Old 06-19-2007 Thread Starter
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I put a new fuel filter on last spring when I was doing a lot of those tune-up things. Unless something clogged it up it should be good. I'll try resetting the TPS tomorrow and I'll let you guys know how it goes. Thanks for the advice... I actually hadn't thought about the fuel filter. Now I'm wondering if it's clogged up by something.... naw, it's probably just the TPS.
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post #6 of 12 (permalink) Old 06-20-2007 Thread Starter
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So I made sure the TPS was set to .99 stock today and it didn't do anything. I checked as much wiring as I could to make sure there were no problems. Everything seemed fine... it's just weird because the problem happened totally out of the blue. I guess my next step would be to spend the $76 on a new TPS and see if that solves the problem. Do TPS's just randomly go bad?
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post #7 of 12 (permalink) Old 06-20-2007
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Also check your distributor cap and rotor and plugwires, coil and sparkplugs.
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post #8 of 12 (permalink) Old 06-21-2007
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check your U-joint it might be going to bad. Mine shakes but it feels like the whole car is shaking when it hits 3000 rpm
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post #9 of 12 (permalink) Old 06-21-2007
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Check for an arcing plug wire. Look at the engine as it idles in a really dark place. Especially if you have equal length headers.
Maybe pull the plugs and read them, see if one looks different.

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post #10 of 12 (permalink) Old 06-21-2007 Thread Starter
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I FIXED IT! I put new plugs in today after spraying the wires down with water to see if they were arcing. I put in a new set of Autolite 25's ($26) and it totally solved the problem. No more sputtering along... just lots of power and acceleration, Woohoo!

Thanks for the help guys! I appreciate it as always.
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thats funny i was just about to tell you i had the same problem on a escort and changing the plugs took care of it . i'm glad that you got it figured out, and have fun.
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Engine shakes

check your Harmonic Balancer the rubber starts to come apart and makes the engine shake/vibrate. Look at the balancer while the engine is idling and see if its whobbling.
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