View Full Version : engine cuts out when supercharger engages

09-22-2003, 09:14 PM
anytime i run the supercharger past 0 on the gauge it cuts off (kind of bucking) in any gear. many new parts tryin to get it to run perfect but no luck. also it doesnt seem to have the power the old motor did after it broke a rod.
any help will be appreciated

Duffy Floyd
09-22-2003, 09:16 PM
What new parts?

09-23-2003, 12:30 PM
When that happened to me, I sprayed the Air Bypass butterfly (behind the supercharger) with WD40 and it solved the bucking problem. Good luck

09-23-2003, 05:08 PM
What kind,... and when was the last time,... you replaced the Plugs AND Wires??

09-23-2003, 06:37 PM
off the top of my head..... Electronic Module, coil pack, plugs, wires, cam sensor, crank sensor. i know im forgetting something but thats it for now.

I was told that maybe my fuel pump isnt pumping enough fuel when its engaged... any thoughts?

also the old motor did this,, then when i replaced it it didnt do it for about a month and half. now its back.

09-25-2003, 11:39 AM
I've got the same problem. I've had it for two years.
I've basically changed the parts you have...plus o2 sensors,
motor mounts, tps+ maf sensor.
I'm in the process of trying to get a cheap computer.
Do me a favor?
Put a timing light on it....watch the light.....rev the motor
and see if the light stops blinking.
That is the case with mine....proving to me that it's a weak
spark as the rpm climb. Same thing with several other I've talked to. What's causing it, I'm not sure.
Good luck


09-25-2003, 04:36 PM
i appreciate the help but still havent got my problem pegged

09-26-2003, 08:10 AM
If you are worried about fuel pressure, then buy a fuel pressure guage and hook it up to the Shraeder Valve next to the SC. Most of them you can leave hooked up. and take the car out for a spin and note the pressure as you hit boost. A weak pump or pressre should be obvious. If not then you can rule out the pressure/pump. Sounds like bad wires, but your sure they are good? Most people and myself have had probs with bucking/missing at boost turned out to be bad wires/plugs.

09-26-2003, 05:37 PM
This is probably trivial but what kind of wires & especially plugs did you install?

09-26-2003, 05:41 PM
I've had this prob on both my sc and my old xr7. On the SC, the hose clamp that connects to the bypass valve mysteriously came outward, thus, causing the valve to get stuck and making the car run n/a. At first, I figured my blower had seized. Took me about a day of looking to notice it. On my old xr7, I had defective plug wires which caused a bucking condition under boost conditions. Also, on the SC, I used some Bosch plugs and experienced the same thing, bucking under boost.

09-27-2003, 04:48 PM
i got the wires recently i beleive theyre magna tech, plugs also new and are motorcraft.

today i took the belt running the supercharger and it dont buck...still not a lot of power but it dont buck.

09-27-2003, 08:08 PM
Where are you located in PA?

09-29-2003, 06:50 PM
i still need help

09-29-2003, 06:52 PM
Originally posted by Brandon
Where are you located in PA?

Punxy is a little far for me.

09-29-2003, 08:30 PM
I'm currently having the same problem, seems like alot of SC's are. Mines going to the garage to get checked for vacume leaks. Because if it was the plugs or wires ( which are new from SC Performance.com installed by Ford) wouldn't it buck or miss all the time.
I'll post again on Thursday with results of the test and other possibilities.

Please keeps this going 'till it's solved

09-30-2003, 11:19 AM
I don't believe the vacuum leak theory.....at least not in my case.
The only possibility that I could think of is leaks around the intercooler. (which I don't have)

It is a textbook case for 'misfires under load' which is what people seem to be describing. It usually points to an ignition problem. (plugs-wires ect)

Can anybody humor me and put a timing light on it.....rev it past 2000 and watch to see if the light stops blinking.
That's what my case is...which says weak spark. I'm still working on it.
Let me know


09-30-2003, 08:44 PM
DIS good? Got heat sink under it? Good wiring from DIS to the coil? And most overlooked - CORRECT order for your plugs? Have you ran any codes?

MIKE 38sc
09-30-2003, 10:04 PM
Yes if the timing light stops lighting when you rev the engine you are loosing spark. Of course it could be the plug or the wire on that cylinder as well causing the problem. After eleminating those 2 items take a look at the coil and associated wiring, if these things check out OK take a look at the DIS module and wiring.

10-01-2003, 05:06 AM
All parts were new...and motorcraft.
Grounds, wiring, and supply voltage all good.
(coilpack-dis mod-eec)
A set of new plugs cures the problem for a month or
It's a weak spark for sure. (all plugs)
I'm just wondering who with the same symptoms
has the same problem.

10-01-2003, 05:07 AM
Oh....no codes.
There never have been.
Nothing that the computer has picked up on.

ben m
10-01-2003, 11:21 AM
there seems to be alot of this going around. i got a new motor from Hesco and not long after that this same thing started, i too have replaced the entire ignition system short of the entire harness, this includes the ECU, PCM, or whatever you want to call it. it wasn't the fuel pump either, but whatever it was it destroyed my engine! it threw a rod out the side of the block a couple of weeks ago and Ford and Hesco are screwing around and trying not to cover it under waranty. anyway, the purpose of that is saying DON'T DRIVE YOUR CAR WHILE THIS IS HAPPENING!!!!!!!!!!!!!!!!!!!!!!!! it blew mine up, and lucky enough it's under waranty, if they cover it. i hope you guys figure it out.
ben m

10-02-2003, 07:22 PM
sorry to keep the thread going but this seems to be really important to alot of guys. mine seems to have the same problems - bucking under boost (usually around 5-7 psi). One thing i noticed is that the lights on the car flicker slightly while it is running, inlcluding diagnostic lights onthe dash. I also found that if you take the car out dead cold and run it hard the bucking doesnt happen. It usually only works well for a minute or two. It only started happening when the weather started getting cold in the morning.

anyone experiencing any of this?
someone else try a cold run and see if it helps


10-03-2003, 12:00 AM
Mine did that, it turned out to be a cylindar filling with coolant =)

10-03-2003, 05:07 AM
I would change the cam sensore for starters. The cam sensor actually tells the engine where top dead center is.....

If this sensor is bad the car will buck like mad under the smallest amount of boost, (had it happen if just getting into the throttle.

The part is only like $25 and can be done yourself with simple sockets. The bolts are 7/32" I believe.

This is what I would try before wires and all that.


10-03-2003, 09:54 AM
one cracked spark plug insulator could cause this problem. it would run fine until under boost/ load conditions. as hard as they are to get to it would be real easy to break a spark plug when installing it.

ben m
10-03-2003, 10:57 AM
right, but the only problem has been that all this has been done to no avail. a shop even hooked up a scanner that reads what the ECU was "seeing" from the sensors, everything was nominal, there wasn't even glitches in the readings when the engine was bucking. they did find that i had blown a headgasket, but that was fixed and no changes until my motor blew.

10-03-2003, 04:04 PM
its not the fuel pump, bypasss valve didnt help.
any other ideas?

10-04-2003, 09:45 PM
Ignition problem plain and simple. You have to remember to check things like making sure the plugs are fully "clicked" on same with the coil pack. Maybe a bad wire EVEN if it's new.


ben m
10-06-2003, 10:49 AM
true, but after 3 sets of new wires and plugs, plus checking their resistance with a multimeter, you would think that you could rule that one out. i personally think there was something wrong internally with mine, it was wierd. i hope that we can find a solution to this problem!
ben m

10-06-2003, 02:59 PM
Started bucking at the transition from vaccum to boost.
Turned out to be a plug wire (NEW) laying against dip stick, it was cut by the bracket on the dip stick tube.
Open the hood at night in a dark area and look for arcing. Rev the motor.
Hope its only something this easy.
Good Luck

10-08-2003, 09:21 PM
Mine still has this problems, it's going in on Friday for new plugs and wires so we can start from scratch, i'll post again with the results, but i fear that it will be just a bandaid and that the problem will return and i'll be stuck searching for answers here again. Please keep this running.

Thanx again for everyone's input thus far


10-08-2003, 09:37 PM
Interesting, I havn't been keeping tabs on this thread but mine has been doing the same thing. It isn't only under boost though. For instance just tonight as I was comming home from work I was cruising at about 80mph @ 2000rpm when all of a sudden my engine dropped to ~1500 rpm, bucked, then ran fine the rest of the way home. It does this in all gears & it seems to be competely random. As soon as I get paid this Friday I'm taking her in to get a tune-up. I'm hoping this solves my problem.

10-09-2003, 05:05 AM
In my case......new plugs used to cure it......for 3-4
weeks. It was almost as if the lessened resistance of the
new plugs compensated for the low current of the ignition system.
Another 'fix' : Gap the plugs at 20-25 thousand.
( again lessened resistance for a sick spark system)
Great way to 'cure' the symptoms without curing the problem.
I'll soon swap out my computer to prove it out.
After that, I've got an oscilloscope that I'll borrow to actually
look at the square waves off the crank ps, cam ps, pip,
and dis coil triggers.
I've already verified good DC voltage and grounds to all components.
I'll keep you all posted.

ben m
10-10-2003, 12:43 PM
a shop hooked my car up to one and it showed nothing out of ordinary, EVEN WHILE IT WAS BUCKING! thats what i dont understand. of course it might have been something else. i hope your test shows something.

also, would faulty wiring show up on an oscilloscope?:confused:
probably but im just curious.

10-10-2003, 12:50 PM
The scope will show clean square waves or not.
My new computer showed up yesterday...
We'll see

10-10-2003, 08:45 PM
I just had my plugs and wires replaced and the problem was fixed. After she warmed-up i got on it several times a few quick launches and punched it few times cruising at 50mph. And NO bucks at all, no missing, no stumbling what so ever.

I just hope the problem doesn't come back like you guys have said. If it does i will certainly reply again to this post, and if it's not active i'll start it up again. I've saved most of the info posted thus far. And will use it in the new thread if needed.

Thanx again for all your input !


Ford did the work factory plugs and wires total cost $ 264.00

10-10-2003, 08:51 PM

10-14-2003, 08:51 AM
New plugs and wires used to cure mine too......
It cured it for 3-6 weeks.
I put a 91 computer in my 92 over the weekend.
What a total failure. Skipping...coughing...smoking and
stalling. I'm still tryin'

ps The 92 computer is back in-
91 computer anybody??????

10-14-2003, 09:30 AM
I had this same problem it would idal ok but under load major miss it turned out to be 2 switched plug wires check them thats free

10-19-2003, 08:46 PM
well everyone ihad new wires on mine, and enough people said it so i did it and checked my wires again (of course in the dark) and i found a spark. i taped it up and its running great now.

so take a long hard look at the wires, i would have sworn the wires were good

10-19-2003, 10:48 PM
cool glad you found it!!

10-20-2003, 12:27 AM
A buddy of mine had the same problems...Changed all of that (cam and crank sensor, plugs and wires...) Turned out that he needed some thermal compound under his DIS module. Lemme know if that helps!

Tim Groth
11-17-2003, 02:34 PM
Oh these cars are such a pain sometimes! Glad I found this thread for I'm having these problems now after I replaced my crank sensor and Harmonic Balancer (BHJ unit).

Anyways my car has a new Cam and Crank Sensor, plugs and wires are less than a yr. old...they are magnacore wires and Double Plat. Autolites.

I guess I will check the connections like all have suggested, I guess there are just to many variables in the ignition of these cars. Seems to me as a TPS problem but who knows.

Thanks again for some tips.


After further inspection I found that one of the plug wires had come loose...she runs great now... DUH!:rolleyes:

11-17-2003, 03:31 PM
on mine it was the bap map sensor same damn part two names

11-18-2003, 09:55 AM
i had new wires on mine too. the problem was 1 wire was touching exhaust manifold and burnt leaving a bare spot. the only time you could see it was when it would arc at night and alot of throttle

11-18-2003, 09:58 PM
Changed the plugs and wires and she ran great for about a month, and still does after she's warmed up. but when it's cold going into boost causes missing and bucking just like before.

Any thing i should look at that would cause this problem when she's cold... ?

Thanx Mark.