Unless you have a Diablo chip or another type of chip, don't use high octane fuel. It's only messing up your timing and it's causing your hesitation and misfiring. Go back to 87 and use a higher grade of fuel. Stay away from surplus fuel and mom & pop gas stations. 76 or Conoco/Sunoco is the stuff I only use. Your car should go back to normal. If the problem doesn't go away, disconnect the battery ground and let the computer reset. Drive it normally to let it relearn the shift patterns and timing.

 

occurs 95% of the time when in idle at a stop lite. happed only 2times during take off so far been using same gas for last two years.

 

Originally posted by sameboy@Mar 30 2006, 12:49 PM
occurs 95% of the time when in idle at a stop lite. happed only 2times during take off so far been using same gas for last two years.

Your PCM is programed to run on 87 octane. A common myth is that adding a higher octane fuel to a vehicle's engine will increase its performance and/or lessen its fuel consumption; this is mostly false—engines perform best when using fuel with the octane rating they were designed for and any increase in performance by using a fuel with a different octane rating is minimal.

Using high octane fuel for an engine makes a difference when the engine is producing its maximum power. This will occur when the intake manifold has no air restriction and is running at minimum vacuum. These conditions are present only when the accelerator is totally depressed.

If the reason you went to a higher octane to get rid of the knocking or hesitation, then your knock sensor may be defective or you have some sort of air restriction problem or it could be you live at a higher altitude and the air is thin.

Does all this make sense?

 

ok i apriciate that information but it has nothing to do with my problem, since i have been running same grade of gas since i bought car.
its not a knock. its a slight engine shudder when at idle in drive. at stop light. it does not occur if i put it into park. is it posible idle adjustment has become to low. its like the engine is running fine then it shudders shakes for a second and then returns to normal operation

 

Could be a vaccum leak or an Idle Control Valve problem. When the cars running and the hood up, listen for a whistling sound. Check all the lines to the upper intake. A lot of times, if you press the area of concern, the sound will increase or decrease. If it does there's a possible vaccum leak. It may be a rubber boot or a plastic line that has a crack in it.

Don't use STP fuel treatment anymore. There's a harsh chemical that can damage parts and seals in the fuel pump. There are only a few fuel additives are Ford friendly.

 

Does the Check Engine light go on? Mine did not.

I have a 24V 3.0L 96 LX that ran like it was going to stall at a stop sign, then ran fine on acceleration. The lower intake gets a ton of oil residue almost backing up into the upper intake. The Idle Air Control (IAC) passage had a residue too. The passage is labeled with warnings that it has a coating on it and not to use cleaners. I cleaned the passage with an intake spray from an autoparts store and the car runs fine. I sprayed into the tube DOWNSTREAM of the Mass Air Flow sensor while I idled the car with the other hand.

Good luck!

 

ill try that

 

If you have COPs instead of plug wires I bet one is bad.

 

I don't think he has coil on plugs, but it's possible to have a bad one or a bad coilpack and that's the problem.

If you use a spray, Deep Creep is an excellent intake cleaner and it's safe on the Trottle body. You just spray a 1/3 of a can directly into the intake manifold and wait 5 minutes then start it up.

To reduce the amount of oil residue, I use 2 oil catch cans. I never had to use the Deep creep again after I installed the catch cans.

 

M.Y. 2000 and later should have COP (my 2000 does).
My 2000 has done a similar thing as you describe and has been doing it for about three years now (car only has 34,000 miles).
I checked Alldata for TSB's at my local library for free and found a TSB about COP's possibly going bad and creating the symptoms described. I recommend you check out the TSB also (I did not make a copy).

later,
r

 

tried spary did not help, forgive my ignorance but what is cop

 

Originally posted by sameboy@Apr 3 2006, 12:09 PM
tried spary did not help, forgive my ignorance but what is cop

Coil On Plug

What kind of spray did you use?

 

throttle body cleaner