Lacking power and misfiring

fgtmustang95 · Jul 17, 2006

For the past month my car wouldnt spin above 3k rpms. It was running so bad I couldnt pick up enough speed to get on the damn freeway. Two days ago I changed the oil, oil filter, pcv valve, o2 sensors, and fuel filter. The car would run ok now as long as I didnt push it cuz it would start to bog out again. Yesterday I installed a cold air intake and a new coil and now I can redline it, however it still slightly hesitates to get there. My spark plugs are fine but i bought new ones anyway along with another set of wires cuz i tore one on my wire loom. I wont install the new plugs till the wires get here on tuesday though. The codes that im pulling still deal with the o2s and tps. I checked the distributor and it seems fine and the ignition module is working properly too. All i can think of next is fuel injectors. If anybody has an idea on what it could be I would surely appreciate it. I also replaced the tps about two months ago by the way and made sure it is still working properly now. thanks fellas

ProKiller · Jul 17, 2006

get some fuel injector cleaner and run higher octane fuel for a while and see if that helps at all. wait till you get the new plugs and wires on before you try to much more. it sounds like its a spark problem to me.

94-302-vert · Jul 17, 2006

Get the plugs and wires on there... the O2 and TPS codes will keep coming up since you are not gettign good spark and the computer is trying to compensate....

KK6695GT · Jul 17, 2006

This sounds similar to the problem I'm having. Is it a rough jerky popping type of miss like a short or is it more of a smooth bog type of miss as in loosing power like it's not getting fuel or a rev limiter kicking in?

Here's the thread I already have in this section:

Loosing power @ WOT above 3000 - need help

Looking for some diagnostic help on my ’95 GT 93,000 mile 5.0 motor with a stock intake system (except for K&N filter) and a Mac shorty / Flowmaster cat-back exhaust. In other words, a basically a stock original motor w/o many mods.

The car runs great except above 3000 RPM at wide open throttle. About 2000miles ago I had some intermittent stating problems so the fuel pump, idle air control valve, ignition control module (not the computer), ignition coil, and fuel filter have all been replaced. (Replacing the ignition switch finally fixed the problem….). The car has been fine up to about a month ago.

For normal everyday driving the car is fine. If you run it up to 4500 at part throttle it’s fine and it will run continuously (cruise) at 4500 without a problem. It’s when you punch it and try to rev it above 3000 RPM that it has a problem. In other words, it will run up to 4500 fine with a part throttle but if it’s WOT (floored from a take off) it will run up to 3000-3500 RPM and then act like it’s running out of fuel above approximately 3000 RPM. It will start to die and loose power at 3000-3500 but momentum will carry it up to about 4500 (starts acting up about 3000 but will still rev up to 4500) but by then it’s dying enough to slow itself back down. If you hold it WOT it will continue to slow itself back down just like it’s running out of fuel. If you back off to part throttle at any point it’s fine and will run at 3000, 3500, 4000, what ever you want, but as soon as you step back down to WOT it acts like it’s loosing it’s fuel flow and begins to die again.

No check engine light is showing and the fuel pressure regulator seems to be operating ok (I have a fuel pressure gauge mounted on the rail and at idle the PSI bumps up with the vacuum line disconnected like it should). With a new fuel pump and fuel filter, new ICA, and new ICM in the car and the regulator appearing to work I don’t really know where to go from here. It strikes me as a computer control/signal issue or some sensor like maybe the throttle position sensor type issue. I just hate to just throw money at new parts (particularly the computer) and hope something fixes it.

Anyone had this problem and know how to fix it!

Thanks.

Follow up coment: This feels more like a definite cut out though, more than just a miss. Like a loss of fuel or the timing is being pulled waaay too forward or something. Almost like a rev limiter is kicking in earlier than it's supposed to be. Seems like either an RPM, vacuum, or computer controlled thing because letting off the gas will allow it to pick back up but as soon as you go back to WOT it will want to die again.

__________________
95 GT w/ stock 5-Speed and 3.55 FRPP gears. KB underdrive pulleys. MAC unequal length headers with Flowmaster catback and stock cats/H pipe. K&N filter. Aluminum clutch quadrant. Hurst Billet Plus shifter w/ HD clutch. Stock heads, intake, and TB. 95 Cobra 17x9s w/ Toyo Proxes. Pioneer 550 watt w/ 10" sub.
66 Mustang Convertible. Owner since 1979. Original code 76C bench seat convertible. 289 4 barrel. Automatic. 3.25 Trac-Loc. P/S. P/B. A/C. Power top. Rally Pac. S/S wheels.

Does my problem sound the same as yours or similar but not exactly the same?

Just wondereing, still haven't figured mine out........

95Vert · Jul 17, 2006

subscribed

fgtmustang95 · Jul 17, 2006

KK6695GT said:
This sounds similar to the problem I'm having. Is it a rough jerky popping type of miss like a short or is it more of a smooth bog type of miss as in loosing power like it's not getting fuel or a rev limiter kicking in?

Here's the thread I already have in this section:

Loosing power @ WOT above 3000 - need help

Looking for some diagnostic help on my ’95 GT 93,000 mile 5.0 motor with a stock intake system (except for K&N filter) and a Mac shorty / Flowmaster cat-back exhaust. In other words, a basically a stock original motor w/o many mods.

The car runs great except above 3000 RPM at wide open throttle. About 2000miles ago I had some intermittent stating problems so the fuel pump, idle air control valve, ignition control module (not the computer), ignition coil, and fuel filter have all been replaced. (Replacing the ignition switch finally fixed the problem….). The car has been fine up to about a month ago.

For normal everyday driving the car is fine. If you run it up to 4500 at part throttle it’s fine and it will run continuously (cruise) at 4500 without a problem. It’s when you punch it and try to rev it above 3000 RPM that it has a problem. In other words, it will run up to 4500 fine with a part throttle but if it’s WOT (floored from a take off) it will run up to 3000-3500 RPM and then act like it’s running out of fuel above approximately 3000 RPM. It will start to die and loose power at 3000-3500 but momentum will carry it up to about 4500 (starts acting up about 3000 but will still rev up to 4500) but by then it’s dying enough to slow itself back down. If you hold it WOT it will continue to slow itself back down just like it’s running out of fuel. If you back off to part throttle at any point it’s fine and will run at 3000, 3500, 4000, what ever you want, but as soon as you step back down to WOT it acts like it’s loosing it’s fuel flow and begins to die again.

No check engine light is showing and the fuel pressure regulator seems to be operating ok (I have a fuel pressure gauge mounted on the rail and at idle the PSI bumps up with the vacuum line disconnected like it should). With a new fuel pump and fuel filter, new ICA, and new ICM in the car and the regulator appearing to work I don’t really know where to go from here. It strikes me as a computer control/signal issue or some sensor like maybe the throttle position sensor type issue. I just hate to just throw money at new parts (particularly the computer) and hope something fixes it.

Anyone had this problem and know how to fix it!

Thanks.

Follow up coment: This feels more like a definite cut out though, more than just a miss. Like a loss of fuel or the timing is being pulled waaay too forward or something. Almost like a rev limiter is kicking in earlier than it's supposed to be. Seems like either an RPM, vacuum, or computer controlled thing because letting off the gas will allow it to pick back up but as soon as you go back to WOT it will want to die again.

__________________
95 GT w/ stock 5-Speed and 3.55 FRPP gears. KB underdrive pulleys. MAC unequal length headers with Flowmaster catback and stock cats/H pipe. K&N filter. Aluminum clutch quadrant. Hurst Billet Plus shifter w/ HD clutch. Stock heads, intake, and TB. 95 Cobra 17x9s w/ Toyo Proxes. Pioneer 550 watt w/ 10" sub.
66 Mustang Convertible. Owner since 1979. Original code 76C bench seat convertible. 289 4 barrel. Automatic. 3.25 Trac-Loc. P/S. P/B. A/C. Power top. Rally Pac. S/S wheels.

Does my problem sound the same as yours or similar but not exactly the same?

Just wondereing, still haven't figured mine out........

Thats sounds right on the money. It cruises ok but as soon as you floor it, it hesitates and im forced to let off the throttle. Tomorrow brown is supposed to deliver my wires along with the pulleys, which i will put on tomorrow with the new plugs. Internally my engine is still stock and I have never had a problem like this before. Im wondering if the dizzy might have something to with it. I might just buy a new one cuz I still have the original one. Other than that Im clueless

SMOOTHIE95GT · Jul 17, 2006

fgtmustang95 said:
Thats sounds right on the money. It cruises ok but as soon as you floor it, it hesitates and im forced to let off the throttle. Tomorrow brown is supposed to deliver my wires along with the pulleys, which i will put on tomorrow with the new plugs. Internally my engine is still stock and I have never had a problem like this before. Im wondering if the dizzy might have something to with it. I might just buy a new one cuz I still have the original one. Other than that Im clueless

My 95 is doing the same thing. I have worked on it for a month now and can't figure it out. I have replaced oil/filter,plugs/wires,fuel filter, and cleaned the MAF sensor. I noticed in the previous threads though somebody said they replaced the "ignition switch"? Mine is busted right now but I do not understand what that has to do with it acting like it has a rev limiter My car also cruises great at 2-3 grand. I have found one difference though. When I first start mine I can bounce it off the redline. As long as I keep it bouncing above 4 grand it will stay well alive but once I let it idle back down that's it until you start it again.

BlackVert · Jul 17, 2006

mine has acted similar to what you are describing twice, both times it was spark related. it was spark plug wires.

SMOOTHIE95GT · Jul 17, 2006

BlackVert said:
mine has acted similar to what you are describing twice, both times it was spark related. it was spark plug wires.

Could you actually see a light show or was it just inside the wire itself?

BlackVert · Jul 17, 2006

SMOOTHIE95GT said:
Could you actually see a light show or was it just inside the wire itself?

i never saw any arcing

95five-oh · Jul 17, 2006

had a similar problem with mine a couple years ago, ran fine up to around 3200 rpms then felt like it lost everything. i had a new timing chain installed and now it runs great even with about 150k on the block..

SMOOTHIE95GT · Jul 17, 2006

95five-oh said:
had a similar problem with mine a couple years ago, ran fine up to around 3200 rpms then felt like it lost everything. i had a new timing chain installed and now it runs great even with about 150k on the block..

Same boat.... I have 176,000 on mine. From what I have read it can be soooo many different things it is crazy. I love to drive my vert but I hate not having full throttle.

fgtmustang95 · Jul 17, 2006

SMOOTHIE95GT said:
Same boat.... I have 176,000 on mine. From what I have read it can be soooo many different things it is crazy. I love to drive my vert but I hate not having full throttle.

I know what you mean. Hopefully new plugs and wires will take care of this. Ive spent so much money on replacement parts that I could have used on performance ones. If I can get it running 100% again it would be worth it though.

fgtmustang95 · Aug 1, 2006

My car is still doing the same crap. Yesterday I installed a MSD pro-billet dizzy and it runs MUCH better but still misfires slightly when I gun it. My ignition system SHOULD be working fine. Plugs, wires, coil, and dizzy are all new. I tested the ignition module and thats working fine too. Injectors? MAF? My check eng. light doesnt come on and Im still pulling the same O2 sensor lean code and TPS lean code. What else should I check for? I need my car 100% soon cuz Im taking her to the track against my uncle and his Bowtie buddies. I Really, REally, REALLY want to whoop their asses, or atleast keep up. If you guys have any input I sure would appreciate it. Thanks

fgtmustang95 · Aug 2, 2006

I just noticed how much fuel my car is burning up since I got the new dizzy. I filled up on monday and now I have half a tank. Its still misfiring so I havent even been pushing it for fear of messing something else up. This isnt some kind of break in cycle right? I dont know where the gas is going. Anybody have a clue?

BlackVert · Aug 2, 2006

if an o2 sensor is reading lean, the computer will try to add fuel to compensate.

how old are your o2 sensors? i suppose that might be worth a try, they are not too expensive, i guess.

when i was having my problem, i replaced the rotor, coil, dizzy and tfi unnecessarily. i hate throwing parts at a problem ...

fgtmustang95 · Aug 3, 2006

BlackVert said:
if an o2 sensor is reading lean, the computer will try to add fuel to compensate.

how old are your o2 sensors? i suppose that might be worth a try, they are not too expensive, i guess.

when i was having my problem, i replaced the rotor, coil, dizzy and tfi unnecessarily. i hate throwing parts at a problem ...

I just replaced the O2 sensors a month ago. All the other stuff you mentioned is new too, expect the TFI. It happens when I floor it suddenly. If I slowly rev the engine it will do okay, but when you open up the throttle you can hear it misfire, however there are also times when it kicks pretty good. My timing is set at 12deg if that helps any. Thanks guys.

1994Vib.RedGT · Aug 3, 2006

you could go to the dyno and do the wideband a/f ratio check

davidspeer2 · Nov 19, 2011

I have many of the same problems, and then I remembered I had a car that acted like that and It was a blocked CATALYTIC CONVERTER, crack the connection between the exhaust manifold and the tail pipe on both sides and relieve the back pressure, start it and see if it revs up! If it does it is a blocked exhaust system.
Hint you can see fire at night if your spark plug wires are arching!

tomc3 · Nov 24, 2011

this type of issue seems common - my fix - Coil!

bad miss starting at about 3500-4K - turned out to be the MSD coil. Stock replacement and car runs fine now.

Lacking power and misfiring

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