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'98 cobra losing power, even dying

doc stang

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O.K., long post but i have no idea which little clue may help someone figure this out. So get some milk and cookies.


'98 SVT, with :

long tubes, NEW oxygen sensors, o/r h-pipe, flow masters, turndowns.

New plugs, wires are fine.

K&N filter and shield,

Steeds UDPs,

Smog filter gone, and some of the EGR stuff removed

Steeda battery relocation box, to the trunk.

Dyno tune yielding ~286


Car ran FINE, after all this, roughly back in October last year, and even the first few events of road course /open tracking, this year.


Did 8-10 track days w/o issue.


~3 weeks ago, we gutted the interior, deleted the a/c compressor and condenser, and installed the rear half of a roll cage.

By gutting, i mean carpet, rear seat, sound deadening, headliner, insulation, door panels, windows, window motors, stereo and speakers, passenger airbag.


First trip to the track, after these mods, problems began.

Track is 2 hours away, 90% interstate, 10% highway. Was 3/4 there, cruising down I-20, foot steady, doing 75 in a 70, flat terrain, with rare undulating hill.

Following my buddy who is towing his '95 gt/cobra CMC car, and my car suddenly DIES.

It got quiet, i depressed clutch, rpms fell to zero over 1-1.5 seconds. I turned ignition to off position, then cranked it up, and it cranked easily, 1st try, and ran fine the rest of the way.

It did have a few scattered spells of hesitating /losing power, for <1second at a time.


At the track, it ran fine, most of the time, except for these occasional brief hesitations. As the day went on, they got a little longer, 1-2 seconds at a time.

One time, coming out of turn 7, there was a 3-5 second hesitation/ loss of power, and a LOUD backfire. Another time, it died coming out of turn 7 (done with the turn, already straight and accelerating down the straight).

Theree is no pattern to it. Not always in a turn, not always just after a turn, not always at WOT. It is usually just cruising, 5th gear, 60-70mph, partial throttle.


Alternator has good output, battery has good juice. I even replaced the entire MAF unit (gotta remember to go take the core back), to no avail.


Missing a track day right now because of this, (and my interminable procrastinitis).


Went for a ride with a local tuner/dyne guy this am, who was data logging with an SCT and his laptop.


Over the 40 mile ride, it hesitated briefly a number of times, <1second, a few times 1-2 seconds, DIED twice, and had a few 2-3 second hesitations / losses of power.

It threw a few codes which i will list in a second or two, but the more curious thing is that he lost OBD II connection with the hesitations and with the shutdowns.


Yesterday, and early today, it would always crank back up, 1st try.

If i simply engaged the clutch, and then released it, to push start the engine (@60mph, it wouldn't start)

If i turned ignition to off, then to on (withOUT cranking the engine, and THEN tried the 60 mph push start without the clutch, it fired right up.


It seems like at some potions in time i have seen the theft light come on with these spells, (maybe not, i may be just thinking of when i open the door), i am 99% certain that today and yesterday, the only time i saw the theft light was when i reengaged ghe ignition, after turning it off.


I bring this up, because the other dyno tuner guy mentioned he was having trouble with some antitheft codes, when tuning it, and this made the tune take 2 days instead of one.

That being said, it ran fine many times, after the dynotune, these problems all just began.


The car's computer has been loose for a while, due to the screw which secures it (at the passengers right foot kick plate) is broken off in the EEC. It has been this for a while, at least at/before the time of the tune.

It has run fine since then.

Today he jostled it and the wiring harnesses with his foot, during our data logging trip, and it had no effect.


Back at his shop, he removed the EEC, removed the diablosport chip, checked the contacts, cleaned them with a razor blade, despit not being dirty, reinstalled them, and when he went to plug in his scat again, fuse #8, under drivers footwell, blew.


Replaced the fuse, he could not come up with any other ideas. He felt that it has something to do with the PATS anti-theft system.

He thought that even though the fuse wasn't blown, before, it may have been bad, and was the cause of the problem.


After leaving the shop, it is still doing it, with even greater frequency.

Even did it one time on I-385, where i couldn't restart with the ignition, on three attempts, and i had to pull over on the shoulder. I waited just a few seconds, restarted, and was able to take off.

However, as soon as i got going, it still lost power MUCH MORE FREQENTLY ove the next few miles, and even died twice more but easily restarted.

Yesterday, and yesterweek, it did pretty good after it died and restarted.


So in summary:

it died once on the way to the track a few weeks ago, and once ON the track.

THEN, after a new MAF it has increased from 3 times in 40 miles yesterday,

To 2-3 times in 40 miles of data logging this morning,

To 5 times in 5 miles, after having replaced that fuse, and taken the EEC and chip out and back in.




Heading back to the dyno guy who tuned it, on Monday.

He says he thinks he knows what to do, and if he can't fix it, he knows someone else who WILL.


I am not so optimistic. Hence here i am trolling for ideas.

Should i go ahead and scare up a replacement EEC, in case it comes down to that, and a new chip?

Other ideas?



If anyone made it this far,


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Obd II codes thrown, were :

1260 theft detected, vehicle immobilized.

1516 gear change neutral/drive fault

1519 intake manifold runner control stuck closed, bank 2




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is your battery in the trunk ? if so , how did you ground your battery in the trunk? you need to run a ground from that batery in the trunk back up to the motor. not just ground it back in the back.


if you haven't done that then do it regardless. If that doesn't fix it then have your tuner turn off the pats system. It can be done.That should take care of pats


If it still does it, I would head to the crankshaft position sensor.


check your other grounds as well.




After all that and it's still doing it I would get a fuel pressure gauge on it . get a long enough hose and tape the indicator to your windshield so you can see it while driving.

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also, when you welded the back half of your roll cage in did you take the battery loose killing power to the car before welding on it ?

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If it still does it, I would head to the crankshaft position sensor.




The crank trigger wheel inside the timing case can crack as well. I have now seen TWO fail on cars in our region in the last year. Once cracked in half, the other broke the center out. Similar symptons as you described.


Good luck.

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Had a similar problem with my 97 cobra. Turned out to be the canister purge valve. Its tough just to throw parts at it though! I agree with Steve, check grounds and other basics first.


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Grounds all checked out, tight. Good contact.


No shorts, skinned wires found from wire-brushing the sound deadening away.


ecu WAS disconnected while cage was welded in


car permanently died on way to race shop yesterday

died and restarted 3-4x in 0.3 miles, running rougher and a shorter time with each restart.

Eventually got dead and wouldn't restart at all.


Tried to restart with BOTH keys

to no avail


"THEFT" light even more active and flashing


How does one remove/disable the PATS??

Does it have to be done with the whole car at the tuner/dyno shop?

Just the chip??

Just the chip AND ecu??


Should I start looking for a reman. ecu yet???




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Back to basics:

1. check for spark while cranking

2. check for fuel at the cylinder


Electronics suck but make sure you eliminate the basic fuel /spark / ignition / coil simple issues.

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Have you removed any electronic type items since the time it was running good? Tge PATS is tied into several items that complete the circuit.


Edit: read the post again, could be some of the items you removed like airbag. May try hooking some of the stuff back up if possible. Another edit...lol I found my 97 electrical troubleshooting book. If you removed anything to do with door or trunk locks, they are tied into PATS or TATS. I didn't see where the airbag was involved. PATS= PITA. If I can look at anything for you in this book LMK.

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pats is cluster, key /key ring in column and ecu. it can be taken out with a hand held t box if you know what your doing. spray some strating fluid down the tb. see if it hits. pats controls fuel.

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I have yanked the airbags and airbag modules from my 1994 GT and 2004 GT without causing any engine problems, so you can likely rule that out. But, I have only worked with the first and last SN95 cars, and since yours is in the middle, YMMV.


My buddy runs a Mustang shop, and I had him install a program that turned off the PATS, rear O2 sensors, EGR system, and evap system, although all systems were (and still are) intact at the time.


I removed the theft and airbag bulbs from the gauge cluster so I don't have to keep looking at the warning lights.


This might be "too late" to mention here (although it might save somebody in the future), but when I gutted all non-essential wiring in the dash of my 2004 GT, I removed a circuit, then fired up the car; removed another circuit, fired up the car again. I cut very few wires, and unpinned individual wires from the harnesses whenever possible. It took forever, but it kept me from chasing small problems later on.


If your theft light is flashing, then you likely fubarred something in the PATS. But, if the engine fires at all, then it's something intermittent in the PATS (not like you cut a wire or left something unplugged).



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after it permanantly died, and wouldn't crank at all.

And, after reading these and other posts,

we reattached the door lock harnesses to the door lock motor

and it cranked right up!!!


Ran for 2-3 minutes, till my buddy slammed the passenger door shut

very minimal cranking success since


finally got the original dyno/tuner guy to reflash chip/ecu and DISABLE the PATS

and it's running beautifully (albeit for a short drive).


Thanks for the help, posts, and ideas.


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  • 5 weeks later...

after disabling the PATS,

it drove from greenville to CMP (2 hours) rand three 20-30" sessions on track, and drove back home.



then, . . .


~2 weeks later at Road Atlanta,

1st session of instructor clinic it started sputtering, and missing 15 miles in,

2nd session, it started sputtering sooner, and even DIED passing under the yokohama bridge (started right back up, with a crank of the key)

3rd session, it sputtered BEFORE I GOT PAST THE BLEND LINE!!!


we removed the diablosport chip, with the custom tune . . .

and it tested just fine out on the road.


saturday and sunday it drove all sesions WITHOUT A SINGLE MISS OR HICCOUGH.


not sure how many hp /ft.lbs. i left on the table by removing the chip.

but at least i didnt haev to cancel the weekend.


thanks to all the ideas and help.


unsure what to pursue next.

may leave well enough alone, untill i put in a 5.0 coyote motor


Edited by Guest
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So, are (were) you using an old-school plug-in chip? If so, then a common problem with them is that the ECU terminals haven't been properly cleaned, and others are just plain crap. Back when I installed a Powerdyne blower on my 1994 GT in 1996, the Hypertech chip that came with the blower kit would cause the car to intermittently shut off at random intervals. Removal of the chip and manually tuning it via fuel pressure and timing allowed it to run just fine.



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