Rough idle help, PLEASE!!!

suprared89

Registered User
Guys,
I have posted about this before. I really need help. I will post everything i can about the car. I really need some expert help here.
It is a 95 sc auto. The problem is a rough idle mostly in gear. I have no codes. I have replaced motor mounts, egr valve, oxygen sensors, cam sensor, cleaned the maf sensor. My fuel pressure is approx. 36lbs at idle with regulator connected. I have replaced the fuel filter, spark plugs, wires, and even swapped out the coil. Fuel pressure increases accordingly with acceleration. I have gone over all the vaccuum leak possibilities with carb cleaner. Meaning all vaccuum lines and intercooler conections. I have even gone so far as to try seafoam 2-3 times. I thought it might have been carbon build up on one of the valves. I have run cylinder balance test and passed. I have tried fuel system cleaners. The only thing I notice that is out of the ordinary is that my temp gauge will read a little cool at times. It gets to th N in Normal. The car seems to be running rich. I drive approx. 50 miles a day, and have to fill up every 3 days. When I pulled the plugs I noticed the 3 on the drivers side seemed to be black(rich). That led me to replace the oxygen sensors. The odd part is that it was only the 3 on the drivers side. The others had normal color. The car runs well and has good performance while driving and seems to have plenty of power. The vac gauge shows approx. 18 at idle in park, goes to approx. 12-15 in gear.
I am desperate PLEASE HELP!!!!
 
This may be a long shot, but given what you have tried already, try turning your air/idle screw about 1/8 of a turn. I just recently replaced mine with a jet engine bolt and a washer to keep the car running at idle. I did notice with the old screw that if it was off by just a touch the engine would run rough at idle.
 
I have tried that also, I appreciate any advice from you guys. I am just beating my head against the walls. This is so frustrating!!
 
suprared89>The problem is a rough idle mostly in gear.
  • I have no codes
  • I have replaced motor mounts
  • egr valve
  • oxygen sensors
  • cam sensor
  • cleaned the maf sensor
  • My fuel pressure is approx. 36lbs at idle with regulator connected

I have replaced the
  • fuel filter
  • spark plugs
  • wires
  • and even swapped out the coil

  • Fuel pressure increases accordingly with acceleration
  • I have gone over all the vaccuum leak possibilities with carb cleaner Meaning all vaccuum lines and intercooler conections
  • I have even gone so far as to try seafoam 2-3 times
  • I thought it might have been carbon build up on one of the valves
  • I have run cylinder balance test and passed
  • I have tried fuel system cleaners

  • The only thing I notice that is out of the ordinary is that my temp gauge will read a little cool at times. It gets to th N in Normal.
  • The car seems to be running rich.
  • I drive approx. 50 miles a day, and have to fill up every 3 days.
  • When I pulled the plugs I noticed the 3 on the drivers side seemed to be black(rich). That led me to replace the oxygen sensors. The odd part is that it was only the 3 on the drivers side. The others had normal color.

  • The car runs well and has good performance while driving and seems to have plenty of power.
  • The vac gauge shows approx. 18 at idle in park, goes to approx. 12-15 in gear.

rough idle...poor fuel mileage...slightly low vacuum
  • Does it start easily or take a few tries?
  • Will it idle without being nursed?
  • Any smoke out the exhaust?
  • Did you put the 3 black sooted plugs back in or were they replaced?
  • What type of plugs, exactly?
  • How many miles on the engine?
  • What repairs have been done recently?
  • How many volts at the battery...key off and engine running at idle...?

Do the basics: check firing order of plug wires. Check all grounds/ground paths. Start with the ground strap on the passenger side of the engine, from the motor mount to the body. Consider doing a compression test. Gotta say, in general, it sounds a lot like just a worn out engine.
 
Last edited:
I noticed the black plugs(drivers side) when I was replacing the plugs. They were soot black, definetely not oil. It has new plugs they are motorcraft awsf 34pp's I believe. I got them from Ford along with the wires. The car has approx. 165k.
I think you may have hit on something with the ground on the passenger side mount. It seems to have started after replacing the motor mounts.
Could it really be that easy?
I appreciate the help. Please keep thinking about this. I have burnt MY brain with this car.
 
>Could it really be that easy?

Grounds/ground paths are critical with these cars. Never ignore or underestimate the role they play.
 
Ok, I have checked the ground at the pass side mount. I have also pulled all connectors and cleaned and reinstalled. i also applied dielectric compound to all connections. I am still experiencing this rough idle. Is it possible that all 3 injectors on the drivers side are leaking? I checked for fuel pressure drop and found nothing. Anybody have any other ideas. I am lost!
 
Gotta say, in general, it sounds a lot like just a worn out engine.

Again, might be time to do a compression test.
 
Ive been doing a little work to a local SC owner's 95 5 speed SC .. when it gets Warm / Hot, it will run a little rough in idle ( shaked enough to make the power steering loose ) .. motor mounts are new, checked for vac leaks, everything seems ok .. same symptom, it just runs a little rough at idle when warmed up ( w/ clutch in our out ). Not really sure since Ive only had about 1 hour trying to diagnose the problem.

- Dan
 
injectors possibly stuck open on the driver side?

this happened to my car last year. I just replaced them with some 36 lb. injectors and it was all good to go (mines an 89)
 
re: Rough idle

I have been fighting a rough idle/ lean idle condition for some time. I notice a slight oil leak from my right valve cover. When my car idles for a while it goes really lean and shows "lean" on my air/fuel mixture guage. When decellerating with the throttle body closed it actually goes past lean to "air". I am in the process of replacing that valve cover gasket right now! I think it will solve my problem.
 
temp. gauge mentioned

Guys,
I have posted about this before. I really need help. I will post everything i can about the car. I really need some expert help here.
It is a 95 sc auto. The problem is a rough idle mostly in gear. I have no codes. I have replaced motor mounts, egr valve, oxygen sensors, cam sensor, cleaned the maf sensor. My fuel pressure is approx. 36lbs at idle with regulator connected. I have replaced the fuel filter, spark plugs, wires, and even swapped out the coil. Fuel pressure increases accordingly with acceleration. I have gone over all the vaccuum leak possibilities with carb cleaner. Meaning all vaccuum lines and intercooler conections. I have even gone so far as to try seafoam 2-3 times. I thought it might have been carbon build up on one of the valves. I have run cylinder balance test and passed. I have tried fuel system cleaners. The only thing I notice that is out of the ordinary is that my temp gauge will read a little cool at times. It gets to th N in Normal. The car seems to be running rich. I drive approx. 50 miles a day, and have to fill up every 3 days. When I pulled the plugs I noticed the 3 on the drivers side seemed to be black(rich). That led me to replace the oxygen sensors. The odd part is that it was only the 3 on the drivers side. The others had normal color. The car runs well and has good performance while driving and seems to have plenty of power. The vac gauge shows approx. 18 at idle in park, goes to approx. 12-15 in gear.
I am desperate PLEASE HELP!!!!
engine may not be reaching correct operating temp. due to a faulty thermostat. i say this because of what you noticed about temp. gauge, therefore attempting to correct itself from running in closed loop mode;cold eng. temp. reaching correct temp. will allow it to go to open mode & can then sense a/f ratio & change as needed on comp. demand.
 
Back
Top