Car Is Hesitating Only Under Full Throttle

ericlp007

Registered User
I HAVE A 93 SC 5 SPEED. I'M LOOSING MY PATINCE WITH THIS CAR. THE CAR RUNS PERFECT IN THE MORNING WHEN IS COLD. THEN IT STARTS HESITATING UNDER MAX BOOST. IT WILL DRIVE LIKE A NEW CAR UNDER NORMAL DRIVING CONDITIONS. PLEASE HELP!

I HAVE CHANGED, SPARKPLUGS, WIRES, O2 SENSORS, CAMSHAFT SENSOR, PUT IN 255 LPH WALBRO FUEL PUMP WITH NEW FILTER, TPS SENSOR.
CAR HAS BEEN SCANNED AND HAS NO CODES. WILL A BAD DIS CAUSE THIS PROBLEM OR CRANKSHAFT SENSOR?

PREVIOUS OWNER INSTALLED A BRAND NEW COIL PACK AS WELL.

PLEASE HELP?
 
Crank sensor and dis could be causing your heistation. Check for the yellow upshift arrow while cranking the engine and make sure the crank sensor connectinos are ok. You might want to try putting a fresh coat of heatsink compound on the base of the DIS before tryign to replace it.
 
Vac leaks, IC tube leaks, low compression in a cylinder, or try fuel pressure. Wife's Mustang ran fine unless you got on it. Fuel pressure low and finally went out all together in a few weeks. New pump all is well. Might put in new filter and check pressure again though don't think it will matter. I know little of the elc end the others refer you to.
 
MY MECHANIC CHECKED FOR LEAKS ON THE IC TUBES AND CAME UP WITH NOTHING. HE IS TELLING ME THAT IT IS EITHER MY DIS MODULE OR CRANK SENSOR.
 
ericlp007 said:
MY MECHANIC CHECKED FOR LEAKS ON THE IC TUBES AND CAME UP WITH NOTHING. HE IS TELLING ME THAT IT IS EITHER MY DIS MODULE OR CRANK SENSOR.

Well please post if that takes care of it.
 
HOW DO I CLEAN THE MAF? ALSO DOES ANYONE KNOW A LINK TO INSTALLATION OF CRANK SENSOR WITH PICS FOR ILLUSTRATION.
 
What brand plugs did you install???

Anything other that AutoLite or MotorCraft Double Plats can cause problems (missing, sputtering, loss of power) under boost. Iridiums may be OK, but I know the AutoLites (MotorCraft) are preferred. Never use Bosch.....
 
Someone else said it...Check your fuel pressure reg. Is the car blowing black smoke? If so it may also be the MAP sensor. You did not state if the car was giving any codes. Usually if there was a DIS problem the check engine light will come on. If it is a bunch of goofy codes...running rich, running lean, misfire codes, you could suspect the MAF. You can bypass the MAF by unplugging it and keying the car up two times. You can not bypass the MAP though. If you have a buddy you can swap it to see if it is running better but they are specific to year and model. Let us know.
 
I WILL CHECK THE REGUALATOR OUT. THE CAR HAS NO TROUBLE CODES WHAT SO EVER. NO BLACK SMOKE EITHER. SOMEONE TOLD ME THAT THE IC TUBES CAN CAUSE PROBLEMS SO I'M GOING TO CHANGE THOSE AND THE DIS. I GOT THE DIS CHEAP FROM E-BAY. I CHECKED THE CRANK SENSOR BY LOOKING FOR THE ARROW ON THE DASH. IT DOES NOT STAY ON SO I CAN ASSUME THAT THE CRANK SENSOR IS GOOD. IF THOSE TWO THINGS DONT WORK I'LL START TO LOOK AT MY MAF.
 
After you check out the IC tubes, use throttle plate cleaner to clean the MAF. I seriously doubt it is the DIS module causing you this trouble as you would have serious bucking no matter how you were driving the car, i.e. cruising at 35 in non-boost conditions. I've had a DIS go out and you'd think you're going to get whiplash it bucks so hard.

And there are several different sparkplugs that work wonders on these cars. I personally am using NGK Iridium's in mine and have not had any complaints at all. And I peg my boost guage pretty easily (now that I have my IC gaskets from tbird88)
 
I've also seen coil packs cause this. They go bad internally and jump around under heavy demand. Try having a friend hook it up on a lab scope and watch the fire underload. Just to make sure it's not some kinda of firing problem.
 
The thing with the DIS module that 007 stated is correct. USUALLY it causes a bucking or what happened in my case is it felt like a couple of plug wires were off. When you clean your MAF, use carb cleaner and make sure it is DRY when you plug it back in. It needs to be absolutely DRY. So let it sit as long as possibel. Do you have any SC buddies near you? If so try the MAP swap. Its clamped to the cowl on the pass side and has a plug and a nipple that is exposed to open air. Both the plug and nipple are facing forward. If I knew how to post pics I would send you some of what it looks like. In the past when I have seen theese go bad (never on a SC) it is usually only at full throttle that the car runs. Let us know what fixes it.
 
If you can get hold of him I highly recomend tbird88 seals for the IC tubes. After using the other 2 methods it is only thing that worked for me. They are reusable and improved the boost on every SC I have installed them on whether running bad or not.
 
Sounds like you are having the same problem that I am having with my 94 SC. Now I do not know a lot about everything in a car, but in my car the hesitation is only coming when I gas it while I am driving, it does not happen if I rev up the engine at a stand still which leads me to belive that it is my clutch that is slipping and that is what is causing the hesitation because it also does it when I have 4 people in the car and I am starting out at a stop light. My car has 120,000 on it nad it still has the original clutch, so just from my deductive reasoning I narrowed it down to the clutch. This could be the same situaiton with you. I am just offering my thinking, I could be wrong but I know how frustrating it can be trying to figure what is wrongg with your car when you think you have checked everything. Hope this helps some.
 
ITS NOT MY CLUTCH, BECAUSE IF I STAND STILL AND REV IT MAX BOOST IT STUDERS. I'M WAITING FOR MY DIS TO ARRIVE. I HOPE IT DOES THE TRICK. HOWEVER I'M SELLING THE CAR FOR 2800. I LIVE NEAR LOS ANGELES AREA. THANKS FOR TIP
 
Not to be the barer of bad news. But mine did the exact samething. Would drive excellent under normal condition, soon as I would put it to the floor, it would start cutting out under full boost. Within 20 miles later, the HG's blew on me. Also the fuel pump was on its way to dieing.
Do you have any detonation or pinging going on when you get into boost?
I am not rying to say that is your problem, but definatly be a consideration from experience.
 
Back
Top