sputtering during acceleration

jslomax · 07-29-2005

I am having a little difficulty isolating this problem which has crept up. The engine sputters on acceleration and some backfiring is occuring on deceleration. I have changed the fuel filter, distributor cap and rotor, spark plugs. I also checked the timing and it is proper. The plug wires are about one year old.

Any ideas?

Thanks
Steve

92 convertible, 5.0L LX, automatic, 100K miles, no engine modifications

green91 · 07-29-2005

pull the mass air meter off and make sure there isnt any dirt or debris of any sorts on the filaments... if there is you can clean the filaments with a good brake clean and let it air dry. then unhook the battery for about 15 mins to clear the Keep alive memory (to reset the barometer). i just fixed a 94 crown vic today with your exact problem... (acts like it has low fuel pressure)

if your mass air is fine then i would check your fuel pressure

PEPE · 07-30-2005

jslomax what is base or full timing readings??Did this occur after your tune up or before??? Best way to clean mass air sensor is with rubbing alcohol and Q tip. Spraying brake cleaner clean good but as most brake container come with alot pressure when you spray could possible bend or damage the heating wire sensor.

green91 · 07-30-2005

you just spray lightly, its actually a Ford approved repair.. to use brake clean.

jslomax · 08-08-2005

cleaned the air mass sensor with isopropyl and left battery disconnected for about an hour - problem still exists.

the problem occurred before i replaced any of the components in previous post. base timing is at 10 deg btdc.

one of my friends suggested it could be an oxygen sensor problem.

i am leaning toward just taking it in to the Ford dealer and let them tell me what is wrong.

meangreen92 · 08-08-2005

It's easy to bend the MAF filiment with a Q-tip too, I've done it. I suspect the fuel pressure might be declining, you can check it at the schrader valve behind the alternator. Also, the harmonic balancer pieces can slip, causing erronious readings with the timing light. But I'd check the fuel pressure. I wouldn't do new O2s until you're sure everything else is fresh and functioning correctly.

jslomax · 08-08-2005

do you know the range and a recommended pressure gage for the measurement?

is there a fuel management computer module that might be contributing to this problem?

Alex Dring · 08-09-2005

What would happen if you cleaned the MAF and didnt unhook the battery to clear the memory?

green91 · 08-10-2005

technically if you floor a couple of times (while driving) it'll reset the baro (barometer), but in some cases with older vehicles, you'll need to disconnect the battery to clear the KAM which will reset the baro.
your fuel pressure should be somewhere in the mid 30's to low 40's

jslomax · 08-15-2005

thanks for your help everybody. it really gave me things to check out. turns out the car would not stay running which prompted me to replace the ignition switch/lock cylinder. Once I had access to the steering column, I found the plastic components with copper traces operated by the lock cylinder were not properly seated. This makes sense with the indications I had, sputters during acceleration - poor contact in the run position, occassional backfires - raw fuel from cylinders that did not get spark because engine was technically off when the ignition switch was not made.

thanks again for all the suggestions.

Alex Dring · 08-15-2005

So you just checked your ignition switch huh? I am having almost identical symptoms with mine. Sunday I got to see it idling for the first time, it almost looks like it is the exact same thing, the motor just (quits or stalls) with a very strong smell of fuel like it was flooded.

So you changed the switch or lock cylinder and it doesnt do it anymore?

jslomax · 08-18-2005

My daughter normally drives the car. It had been giving the indications as listed in this thread. She called me one evening and told me it would turn over but would not stay running. I figured it may be the ignition switch so changed it out (actually the lock cylinder was changed out, not realizing it actually actuated the plastic pieces with copper runs). Once the cover was removed from the steering column I noted the plastic pieces not in their mounting bracket. I just put them back in the mounts, installed the new lock cylinder since I had it, put the trim back on and vroom!

Sometimes it is better to be lucky than good http://allfordmustangs.com/forums/im...ies/winkie.gif

Alex Dring · 08-19-2005

All right that does it, the switch is coming out for review. It seemed like such a simple fix that I kept denying it could be something so simple. If the switch works you will be able to hear me beating my head on the wall for miles............

'95.0 stang · 08-19-2005

There's so many different things that can all cause the same symptom you NEED to be lucky when you're working on our cars.

Alex Dring · 09-02-2005

Well I am sort of at a lost. This is what I have done so far. I replaced the stator, cleaned the MAF, AIT, TPS and IAV. Cleaned, buffed and polished throttle body and air meter body. Changed fuel filter, ran injector cleaner and installed BBK CIA fenderwell system. Replaced plugs, wires, caps and rotor with MSD, installed MSD blaster coil.

It still has the problems, when it is hot it starts then dies immedialty after I shut it off to get gas or something. About after 20-30 times of this it finally starts but keeps spitting and sputtering wanting to die. Immediatly afterwards on the road if I slowly let into it, nothing, but if I take my foot off and stab it, hesitation and sputtering then acceleration, although this goes away after about ten miles. Now sometimes i have noticed it revving high when I get home for work, push in the clutch and it sits there at 1500 or 2000 slowly climbing down after about 30 seconds. This symptom is new and leads me to think its for sure fuel related. My next step is to change the fuel pressure regulator and injectors.

The thing is all these problems are sparatic expect the starting and dies after it is hot. I am about to drive this thing off a cliff if my wife doesnt kill me first for spending all this money on a "dont worry about it work car"