massred98gt

what can cause the car to sputter during normal driving. when i'm just cruising barely touching the gas the car runs like garbage. as soon as i give it some gas it seems to disapate. i was thinking the tps but i got a new one a couple years ago and its in spec of the voltage reading. any other suggestions???

cliffyk

At what engine speeds is the sputtering happening?

I don't see a tune/tuner on your list of mods, and with the intake mods you have made (especially the stage-2 cams), without a custom tune it is not surprising that it would run like crap at lower loads and rpms--the OEM tune cannot cope with closed-loop operation and the intake mods.

Do you have a wideband O2 system? With those mods you should as you will never get it tuned correctly without one...

massred98gt

ya i have a tuner and just got a dyno tune a couple weeks ago. car has ran even worse sinse then. the problem was there before the tune and now it has gotten even worse. it all started when i put new heads on last year with pi cams/ intake. car hasn't been running right sinse then. what the heck is going on??? and it does this around 1500-3000 rpms. only when i'm barely touching the gas

cliffyk

Bring it back to the dyno shop and have them tune it properly.

Without your having a wideband it's hard to be exact, however I'd look at AFR while it's stuttering, and would suspect the MAF transfer function first. Then make sure the injector high and low slopes, and breakpoint are properly set.

Are you running the stock MAF, also what injectors?

tHedinGo

I am having the same issue with my stock (cai only) 1999 GT. You can't really feel it sputter through 1-3 but anytime I get below about 2k in 4th or 5th it will do it. Any news on the TPS?

massred98gt

haha thought this post was long gone...

i know for a fact that it wasn't the tps because retarded me i went out and bought a new one dispite my old one checking out within spec. made no difference. its not the tune because i got it retuned at another shop, still does it. don't know what it could be? i really think its because of an exhaust leak. i have many so i'm leaning towards that. i'm just to lazy to fix em to be sure.

cajungt

Same issue here. I just bought new plugs, not in car yet. Thinking maybe COPS,OEM Ford next. Tried snake oil,the pour in fuel injector cleaner on last 4-5 tanks. Switched gas stations. Still happens under light load conditions, at maybe 1/8 to 1/4 throttle. Passengers do'nt seem to notice, but I do.....

mdrich02

I have a 99 GT (basically stock) and I am having the same exact thing happen to me. It did not start until recently and it only studders if I mat it. If I ease into the pedal it does fine. Anyone know what I can try?

tHedinGo

I have been cured for two days. All I did was change out spark plugs reset ecu and clean MAF,IAT and all COP and injector connections and put some electric grease on the COP ends after they dried. To clean the electronics I used CRC QD electronical cleaner got both sides of MAF and IAT good then sprayed up in the springs of the COP's. After I finished I reconnected the neg. cable on the bat let it idle for about 20 minutes and then went and drove it casually for another to make sure it was settled down and so far so good. I think the largest part of this is that the plugs in my car appeared to be the motorcraft originals and them being like 88k old was the problem lol.

cliffyk

I don't know how many times this needs to be said.

The very first thing to check/replace when any sort of random misfire pops-up are the spark plugs, and while you are changing them inspect the COP boots for hardening and/or signs of high voltage arcing.

Also understand that when the spark plug gap doesn't fire it means the HV from the COP went someplace else; at a much higher voltage (45kV+) than that that would be required to fire the plug (10kV to 16kV). Typically the "someplace else" is down the plug's insulator to the head, or through the rubber boot to the plug well.

This makes the COP work harder and heat up more; have this happen often enough and the COP may overheat and burn out.

However, the COPs are actually rather robust units and because they stick up like they do they are reasonably well-cooled. So, if you continue to run the car with the bad plugs a more likely scenario it that eventually the errant discharge paths to the head and/or through the boots will develop a higher resistance than the internal insulation of the COP's windings.

When this happens the COP will discharge internally and short out the windings.