Help please, low RPM miss


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Help please, low RPM miss

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All Forums >> [Off-Road Vehicles] >> Truck Discussions >> Help please, low RPM miss

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Help please, low RPM miss - 11/23/2008 7:59:58 AM

ARK_SWAMP_RIDER

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Joined: 7/23/2005
From: AR
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My 96 Ford Mustang Cobra (I know, not a truck, but maybe you guys can help) is missing/sputtering at low RPM's. In a drag race situation (go all out from a stop) it runs great. If you're driving along and downshift then punch in, runs fine (dropping into the 3-4k RPM range). However, when just taking it easy, say cruising in 4th at 2-3k RPM and then flooring it to go, it just falls on its face. You can ease into it and it works fine. It has been going on for about a month or so, but hasn't been bad until recently (colder weather, could be a coincidence though). It's not something just when the engines cold or hot, pretty much all the time. I have a CEL, and had it scanned when the problem first started. Only codes were rear o2 sensors (no cats, MIL's went out). I'm thinking plugs/wires should fix it, but also have heard similar symptoms when the front o2's need replaced. The guy that I have always used for mechanic work has quit doing it for a while, so I'm left out in the open. Car has 127k miles, not sure how long it's been since a tune up. I'm thinking I will take it by the local tire/wheel shop (also do tune ups, brakes, etc) and see what their "tune up" consists of, and probably have them do it if priced reasonable. I'm not mechanically inclined, every time I work on the car something goes wrong, so not really wanting to get into this myself, I'd rather pay someone to do it then put up with the headache. If it's something like o2's, they should be easy to replace without taking it anywhere. What do you guys think it is? Thanks for any input.

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2005 Honda Foreman 500 S 4x4 with 4 26x12x12 bear claws on itp c series type 6
93 Honda 300 4x4-Mostly stock
90 GMC-6" superlift, 315 buckshot mudders (sold)
96 Ford Mustang Mystic Cobra
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Post #: 1

RE: Help please, low RPM miss - 11/23/2008 5:21:14 PM

1meanforeman450

Posts: 1387
Joined: 4/10/2006
From: Vicksburg MS
Status: online

im thinkin its a problem with the 02 sensors... i cut the 2 rear cats out of my 97 GT and it ran great at first, actally for about 1 1/2 years then it started running rough, it would actually somtimes stall out at a red light. car would still run great when at full throttle but low RPM it would go to crap. i say check the 02's and also check your front cats, they could be getting clogged, 127,000 miles doesnt seem much but if i drive anything with over 100,000 the cats come out or in a case like this where you had 4 of them, i would replace the 2 front ones and hack the rears off. honestly i would have a good mechanic diagnose the problem before getting any work at all done... most mechanics can tell you what it is just by driving the car. i would just hate to see you spend money on a complete tune up when it could be somthing real simple and cheaper.

< Message edited by 1meanforeman450 -- 11/23/2008 5:22:47 PM >

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my "thrillcraft"
07 brute force (it beats stuff up) 650i silver
28" mudzillas on ss112s, HMF pipe, dynatek, jet kit, snorkeled, relocated radiator, 2 rear ape's, clutch kit

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Post #: 2

RE: Help please, low RPM miss - 11/23/2008 7:21:01 PM

camogrizz51

Posts: 3819
Joined: 1/31/2006
From: Louisiana
Status: online

I had the same problem with my f150 with the 4.6 V8 and it was a 02 sensor cant remember what one though.

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RE: Help please, low RPM miss - 11/23/2008 7:41:26 PM

ARK_SWAMP_RIDER

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Joined: 7/23/2005
From: AR
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I've got a friend that will help me do plugs/wires next weekend, so shouldn't be that expensive. From what others have told me, it is most likely those, and if not, that's the cheapest place to start. I'm gonna go by Autozone tomorrow and have them scan it to see if there are any new codes, and also pick up the new plugs/wires. If that's not it, well I think it needs them anyway.

_____________________________

2005 Honda Foreman 500 S 4x4 with 4 26x12x12 bear claws on itp c series type 6
93 Honda 300 4x4-Mostly stock
90 GMC-6" superlift, 315 buckshot mudders (sold)
96 Ford Mustang Mystic Cobra
My Pics

honda4trax.com

(in reply to camogrizz51)

Post #: 4

RE: Help please, low RPM miss - 11/23/2008 11:53:27 PM

1meanforeman450

Posts: 1387
Joined: 4/10/2006
From: Vicksburg MS
Status: online

if it is plugs and/or wires it will bring up a mis fire code. if you do end up buying plugs and wires, dont go cheap with them. the ones that say lifetime warranty and are on like $30-40 bucks, do not buy them, they will go bad real fast.

_____________________________

my "thrillcraft"
07 brute force (it beats stuff up) 650i silver
28" mudzillas on ss112s, HMF pipe, dynatek, jet kit, snorkeled, relocated radiator, 2 rear ape's, clutch kit

(in reply to ARK_SWAMP_RIDER)

Post #: 5

RE: Help please, low RPM miss - 11/24/2008 4:59:09 PM

ARK_SWAMP_RIDER

Posts: 2989
Joined: 7/23/2005
From: AR
Status: offline

Took your guys word and had it scanned. P0420 code as described here:
http://www.obd-codes.com/p0420
Any ideas? I know it has an exhaust leak, but it's been there for a year or two no problems. Thanks.

_____________________________

2005 Honda Foreman 500 S 4x4 with 4 26x12x12 bear claws on itp c series type 6
93 Honda 300 4x4-Mostly stock
90 GMC-6" superlift, 315 buckshot mudders (sold)
96 Ford Mustang Mystic Cobra
My Pics

honda4trax.com

(in reply to 1meanforeman450)

Post #: 6

RE: Help please, low RPM miss - 11/26/2008 1:13:44 AM

1meanforeman450

Posts: 1387
Joined: 4/10/2006
From: Vicksburg MS
Status: online

ok first imma ask a few questions before i go and mis-inform you... have you added any type of programmer or basically any othe kind of performance part to the car lately? have you used cheap gas? like gas from a kroger, walmart or anything like that? second i would have the cats checked, they could be clogged, making them bus open and leak slightly, my f-150 is doing it right now, that would definantly be my first look. if it is a clogged cat, cut it off and order some o2 simulators, ive found some pretty cheap online before, that will cause the computer to "think" that the cat is still there, turns off you check engine light and car runs great with better performance and sound IMO. if you added a programmer, listen for any pinging, a programmer messes with your timing and could change the octane fuel you run. ive found in my own study that the kroer, sack and save, wal mart, etc.. gas isnt quite as good as kangaroo, chevron and places like that, my fuel mileage dropped wayyy down when i switched the places i buy gas. i only use kangaroo or chevron now. my 99 chevy extdcab 2wd with a 5.3 went from getting well over 300 miles on a tank to getting right at 200 miles to a tank when i used kroger or walmart gas and you could tell a slight difference in performance. pay attention to a few little things next time you drive it and let me know how it goes...hope this help and im still here to help if i can

_____________________________

my "thrillcraft"
07 brute force (it beats stuff up) 650i silver
28" mudzillas on ss112s, HMF pipe, dynatek, jet kit, snorkeled, relocated radiator, 2 rear ape's, clutch kit

(in reply to ARK_SWAMP_RIDER)

Post #: 7

RE: Help please, low RPM miss - 11/26/2008 9:46:53 PM

ARK_SWAMP_RIDER

Posts: 2989
Joined: 7/23/2005
From: AR
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After a week of waiting and giving up all hope my mechanic called me today. I'm gonna have him look at it and scan it next week sometime. No recent modifications, no programmer, or anything of the sort. The car doesn't have Cats, it has MIL's (o2 simulators) but they went out. I built a new set, haven't got them put in yet, should do that this weekend. I'm on hold right now, but I have the feeling I'll end up with new plugs/wires to fix the problem. My mechanic can use his scan tool to see how each plug is firing to determine if there is a problem with one or more of them. Thanks!

_____________________________

2005 Honda Foreman 500 S 4x4 with 4 26x12x12 bear claws on itp c series type 6
93 Honda 300 4x4-Mostly stock
90 GMC-6" superlift, 315 buckshot mudders (sold)
96 Ford Mustang Mystic Cobra
My Pics

honda4trax.com

(in reply to 1meanforeman450)

Post #: 8

RE: Help please, low RPM miss - 11/30/2008 12:13:06 PM

AKHNTR

Posts: 2557
Joined: 8/26/2003
From: Chugiak, Alaska
Status: offline

    Older Fords do great with carbon cleans (motor vac etc..). This has solved a lot of minor missfire problems on engines around 100,000 miles. It couldn't hurt even with a tune up.

    The po420 code will set if you do not have cats. That is what the rear O2's job is. The rear O2 is supposed to read basically one voltage after warm up(this tells you if the cat is working). It is not supposed to "switch" like a front O2.

   For what it is worth,

                  Dan

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RE: Help please, low RPM miss - 12/2/2008 7:10:46 PM

ARK_SWAMP_RIDER

Posts: 2989
Joined: 7/23/2005
From: AR
Status: offline

It still isn't throwing a misfire code, but while driving around my mechanic watched the scan tool, at low RPM's plugs 1 and 8 were missing. I've got my new plug/wires ordered, will be ordering a new fuel filter in a couple days. Anything else while I'm at it? Thanks.

_____________________________

2005 Honda Foreman 500 S 4x4 with 4 26x12x12 bear claws on itp c series type 6
93 Honda 300 4x4-Mostly stock
90 GMC-6" superlift, 315 buckshot mudders (sold)
96 Ford Mustang Mystic Cobra
My Pics

honda4trax.com

(in reply to AKHNTR)

Post #: 10