mustang has the stutters

[lazy j]

Hey guys! I bought a '02 gt about 9 months ago with 78,000 verified miles. It had a ton of bolts ons when I bought it- the only thing Ive added is BBK thottle body/ plenum about a few months back. About a month ago the car developed a stutter under medium to heavy throttle. Never has thrown check engine light or anything. Took it to a shop to check for codes and no codes have been thrown. I had them change the fuel filter (since the car is lowered and can't fit my big ass under there even on jack stands to change it) and had no change. One thing that comes to mind is, I bottomed the car out leaving a friends house and the problem seemed to start around that time- maybe a week or two after. Could be a coincidence but I had the mechanic inspect under the car while he had it up on the lift and he said he didn't see any damage. The car runs great during normal driving.
My question to you guys is: what would cause the issues Im having and not throw a code?? Bad injector, fuel pump, spark plug or COP's??
Thanks for the help!

 

[blacksheep-1]

Fuel filter was a good call, I guess it didn't help however. Any possibility of crappy gasoline? although that might show up in the O2 sensors. BTW it does have them right? because that might be the next call.

 

[lazy j]

I've thought about the O2 sensors but I thought for sure those would throw a code if they went bad right? I've also thought about junky gas but I've put a few tanks of gas threw the motor since the problem started. I may pull the air filter and MAF this weekend and clean those just to be sure before I start buying expensive replacement parts that I can't afford.... One dumb theory I had was when I bottomed the car out, could I have hit and knocked something loose in the cats that's plugging up the exhaust?? Or can that not really happen?

 

[blacksheep-1]

It's possible, those cats don't last forever, could you pull the exhausts off and take a look?
I've also seen where the pipe is composed of an inner and an outer piece, and the inner pipe has collapsed

 

[pmanchin]

I would start with a plug change. Start cheap and work your way up.

PDM Designers

 

[blacksheep-1]

I would start with a plug change. Start cheap and work your way up.

yeah, good call as well

 

[Seclusioned]

I just had the same problem. From my research the computer will only throw a misfire code if its extreme. I had one code for number 4 cylinder. Changed all plugs, no change. Changed number 4 COP. Ran alot better but not fixed. Took the car to a shop that had a better computer. He actually hooked it up, started the car, held it at 2500 rpm and the computer showed misfire in 7 and 8! Changed those 2 COPS, Problem solved. The misfire after I changed the number 4 was so minimal, you would only know if you know the car. It had great power and sounded normal. But I could tell there was still a sputter. The computer should throw a code no matter how minimal the misfire is IMO. But my advise is find a shop that has something other then the Auto Zone OBDII reader. The mechanic at this shop said his cost almost 10k$. It was 90$ for him to run the diagnostics and took him 10mins..... It showed alot of info on what was going on with the car though. I asked him if it had paid him back for buying it. He said it has trippled his investment lol. CRAZY!!!!

 

[lazy j]

The mechanic I took it to supposedly has the super expensive diagnostic reader but I wasn't around when he hooked it up. I know he has something way better than what they have at Advance and Auto Zone.
I think I'll just have to pick something to start with and it will probably be the plugs and COP's. I've had to change the plugs and wires on my '99 F150 and it was a treat to say the least. So I think while I've got the COP's off to change the plugs, I might as well change them so I only have to do it once. Do you guys know if the coil itself normally goes out or is it usually the boot with the spring/ plug wire inside? And do you know if you have to pull the fuel rail to change the plugs and COP's? Thanks for the help guys!!

 

[pmanchin]

Removing the fuel rail makes it easier but you do not need to.

PDM Designers

 

[lazy j]

slight update: I've bought some new E3 plugs but have to wait a week or so til I can afford to order new COP's I'm hoping they will help but in the meantime I've noticed that it doesn't seem to do the stutter when the car is cold. After I've driven it for a few minutes it starts to develope the stutter at heavy throttle- any ideas?

 

[pmanchin]

Have you put the plugs in yet? My Pontiac did that same thing when one of the plugs were bad. It was horrible sounding once she warmed up. Made the supercharger sound like gun fire on a futuristic video game.

PDM Designers

 

[lazy j]

Finally ordered new Accell Coil on plugs from Summit and installed those with new plugs. Seems to have fixed the problem! All the plugs had similar wear and the boots and springs on the COP's looked fine so maybe it was one of the coils.... Thanks for all the help guys!