1992 Ford Mustang LX

Home  \  Repairs & Maintenance  \  1992 Ford Mustang LX

I'm the owner of a 1992 Ford Mustang LX 2.3 liter motor and, unfortunately, an automatic. I changed the spark plugs and now the car is idling low and the rpms aren't up to where I'm used to them being. I didn't change the air filter, a friend has suggested doing that before totally panicking. I've changed plugs on cars before, but I've never had a problem like this. Is it an oddity or is this something that is normal for this particular car? Any help at this point would be greatly appreciated.

Thanks in advance.

posted by  jynx

What brand plugs did you use? Did you have to gap them or were they the DO NOT GAP type ? Single or 2 plug per cylinder ? Could you by any chance have crossed any plug wires? What was the rpm idle before and after the swap? How is acceleration? Do you have any miss ? I forgot what my question was :laughing:

posted by  lectroid

I used Champion spark plugs. Had to gap them myself. Gap required is 0.054, I made sure they were all gapped the same. 2 plugs per cylinder (which is rather annoying IMO). Couldn't have crossed plug wires as I did them one at a time to avoid that problem. RPM idle prior was right about 900 rpm after the swap idle rpm is at about 500 :) . Acceleration starts of slowly, but once I get up to about 25 mph if I back of the gas and then hit it again the car has pick up to it. And no, I didn't miss any. :) 8 were bought and 8 were replaced.

posted by  jynx

Some engines have not a specific gap, but a gap range. Example: .052 - .056. And anywhere within that range is fine. If I were you, I'd re-gap them to the exact size the old ones were.

What I'm saying is; the old plugs may have been gapped at the minimum of that range. (.052) and you gapped them to the max of that range (.056) and that's where the change is. That's one possiblity. The other is, there the wrong heat range, or depth reach. Last but not least, the old plugs could not have been resistorized and the new ones could have been. weakening your spark. If your sure a plug wire didnt get disconnected, or crossed, then this is about all the possibilities for the spark plugs themselves being the problem.

posted by  DodgeRida67

You might want to verify the spark gap specs. I think it should be.044, not .054. I can't swear to it.

posted by  lectroid

You know what I think your right. I'm 95% certain it's .044 like you said.

posted by  DodgeRida67

Well, I did use one of those nifty little "computers" at wal-mart and that's how I knew which plugs to get and it also said what the gap was to be set at. I'll check again just in case though.

Thanks. :)

posted by  jynx

I must've been having a Barbie moment. I just called the local auto parts store and.....It is .044.


Thanks all. :thumbs:

posted by  jynx

Thanks for the reply. No one on this forum makes mistakes :laughing: :laughing: Just wish we had a spell checker :cussing: I can't spell or type for Sh*t, This still a pretty good/fun place to be :thumbs:

posted by  lectroid

There's always dictionary dot com... :thumbs:
.
.

posted by  BavarianWheels

I have that, just HATE bouncing back and forth. :mrgreen:

posted by  lectroid

Unfortunately the car now sounds like a badly tuned lawn mower. :( I can't win for losing with this one. It was suggested that I change the plug wires if they're rather old. As I've only had the car for 2 years and I've never changed the plug wires maybe that will be the next step in trying to solve the problem. And it's idling at about 400 rpm's now. :cry:

posted by  jynx

:banghead: :banghead: :banghead: :banghead:

Sucks. Just sucks. I know how it feels. However, I might know where your trouble now lies. Since you over gapped them by 1/4 there untire gap, it's certain they were missfiring like crazy. They could be fouled up. Hopefully you cleaned them before you put them back in after you re-gapped them to .044? Check, double check, tripple check your firing order. You have a Ford, I've seen firing order's in manuals be wrong before. I have one that's incorrect and stumped the hell out of me once after replacing ignition module and pulling distributor. Clean, clean, clean your throttle body. Dirty throttle body can cause your situation. After this, if nothing works, change plug wires. That don't work, get drunk....or maybe your coil is weak.

posted by  DodgeRida67

If you bought the plugs @ "wally world" (Walmart) you will probably have Autolite 764 or Autolite AP764 Platinums which should be gapped @ 0.044 inches

Anything else done besides changing plugs?

If not, lets make sure the plug wires are connected to the right terminal on the coil packs for both sets of plugs. If the cylinder which is firing is not paired with the correct cylinder which is not firing, the voltage to the cylinder which is supposed to be firing will be low and you will get a weak spark (this system is a true waste spark distribution system. The link below should link you to a diagram to show the plug and coil pack connections.

http://www.autozone.com/images/cds/jpg/small/0900823d80194130.jpg

Next, I would check the condition of my plug wires (4K ohms/ft - 15000 - 20000 ohms max resistance as well as any cracks in the insulation, etc) Replace them if necessary

If this doesn't help and nothing else was done to the car, its time to check for trouble codes and go from there

posted by  tbaxleyjr

Actually I did get Autolites (not platinums). When I gapped them improperly the car wasn't misfiring. And I do the plugs one at a time to avoid the possibility of crossed wires. Only changed the plugs. The car had been missing a bit the past week. Bothered me to the point that I started driving the mini van to and from work. Oh another new development as well....The check engine light comes on and STAYS on as soon as I start the car. I try to fix one problem and end up with new ones. I did notice that one of the old spark plugs looked a little rusty. 3rd plug in on the right side of the motor as you are looking into the engine compartment. I'm hoping that's not part of the problem. Thanks for all the advice and input GREATLY appreciated. :)

posted by  jynx

I want my Toyota back. :( Simple to maintain and wasn't fuel injected. I didn't totally remove the plug wires so whatever order they have been firing in for the past 2 years is the order they're in now. Maybe that's been the problem all along. :banghead: Ok, just a quick question here....How do I clean the throttle body? I think I know where it's at. I had to remove the tube/hose connection to it and the air filter to get to half of the plugs. One of Ford's better ideas I suppose. Yes, I replaced it and made sure that the hose clamps were tight. :) I figure by the time I get this all sorted out I will be able to take the spark plugs out and put them back in in my sleep. And what would you recommend using to clean the throttle body and the spark plugs? It's time's like this when I wish I had a garage. And getting drunk would probably just make me go sit in a corner and cry. ;)

posted by  jynx

Remove the plastic tube in front of it and use air intake cleaner. Don't use regular carb cleaner as it will destroy the tefelon coatings Ford used on their throttle bodies in early 1990s. Clean the MAF sensor while working in this area.

if the plugs are OK, the plug wires OK, and the MAF sensor and throttle body are OK, get the trouble codes pulled and we'll do more figuring.

posted by  tbaxleyjr

Ok...two part question....What's an MAF sensor and where is it located?

:confused:

posted by  jynx

manifiold air flow sensor - it will be either a vane or a hot wire grid located close to the air cleaner. It tells the ECM how much air is flowing to the engine so the ECM can regulate the fuel injection system and maintain (with input from the O2 sensors) the proper fuel aix ratio. It is cleaned by using the same type cleaner (NO carb cleaner) as used for the throttle body

Since the check engine light is on, we need to pull the trouble codes. The haynes book should tell you in Chapter 6 or I can link you to a site with specific instructions for pulling these codes with a jumper wire and counting flashes of the check engine light. You can also buy a device for about $30 which will make the connections for you and you count the lights on the device or if it is one like I bought @ O'Reilleys, will give you a digital read. With the codes, any of the regulars, including myself, can help point you into what we think are likely paths.

posted by  tbaxleyjr

Prolly should have asked this earlier....What would you recommend using to clean the plugs with? I seem to remember seeing plugs cleaned with gasoline when I was younger. Asked the young man at the auto parts store and he led me over to emery cloth. Then again he did talk to me as though I was a small child. *shrug* And the getting drunk part is beginning to look like a better idea each and every day.

posted by  jynx

The carbon will come off with no problem using gasoline and a rag to wipe it with. Don't soak the whole plug in gas, just stick the electrods in about 1/4 in of gas or so and slosh the plug around and wipe it clean immediatly. If it doesn't come clean then the car just hates you. :laughing:

posted by  DodgeRida67

Well it seems at least part of my memory is still in tact. :wink2: If it doesn't come clean the car is going to the scrap yard and I'll find an old toyota with a carb to own. :laughing:

posted by  jynx

By the way, make sure you put anti-sieze on the plug threads before you put them in after cleaning.

posted by  DodgeRida67

Permatex 133K is a good high temp anti sieze. Be sure and don't overtorque the plugs either - fixing stripped threads is a pain in the butt at best with a helicoil, a new head at worst.

posted by  tbaxleyjr

Hand tighten the plugs, right? And I've owned a car where the person who last put the plugs in stripped threads on one of them. :banghead: :banghead: And I have to agree with your description of fixing them with a helicoil. And if it would come down to getting a new head, I'd find a different car, chalk it up to experience and start paying someone to do all my mechanical work. :wink2:

posted by  jynx

hand tight + 1/16 to 1/8 turn if the car has aluminum heads, if the car had iron heads, hand tight + 1/8 turn to 1/4 turn.

I am an enthusiast myself and not trying to beat a flat rate manual labor estimate. Many people posting here do not have the assortment of tools some of the others have but I personally use a torque wrench and tighten to about 15 ft-lb on a 12 mm plug in an aluminum head, 20 ft-lb if it is an 18 mm The haynes book will have specific values for your car.

Once you get the plugs and wires checked out, the check engine light still needs to be addressed by pulling trouble codes or having them pulled

posted by  tbaxleyjr

Also, this would help in further diagnoses greatly, what is the manifold vacuum reading?

posted by  DodgeRida67

Ummm....What was the question? :confused: No idea. But my loving spouse went out and bought me a whole new set of plugs.....Bosch platinum....apparently pre gapped, but I'm checking to make sure. :)

posted by  jynx

I don't think those are gappable anyway. :hi:

posted by  DodgeRida67

And the question was what is the vacuum reading at the manifold?

posted by  DodgeRida67

I'm hoping when you mention clogged cats you are talking about the catalytic converter. :) If I remember correctly the person we bought the car from removed the catalytic converter as it was clogged and causing all sorts of problems with the car.

posted by  jynx

Plugs and wires are changed. :) I also changed the air filter. And as I was checking for loose wires/hoses I found one. And I think it may make a difference and give an explanation for the check engine light being on. The O2 sensor was disconnected. :doh: I'm giving up til this weekend. Only 2 hours of daylight a day to work on this isn't getting it done. :(

posted by  jynx

That's illegal. :ohcrap:

posted by  DodgeRida67

The vacuum reading is very important. I will also need to know your position from sea level or else the vacuum reading will not do awhole lot of good unless its obviously way off. Just need to know how high or low you are from sea level. I hope you'll know...

posted by  DodgeRida67

It is?! :ohcrap: :banghead: :banghead: :banghead:
Great. :( Yet another problem to contend with. And the car is slightly missing and running rich all at once. :(
Off to the parts store to purchase a torque wrench.

posted by  jynx

Anywhere from 20' to 112' above sea level. Unfortunately that's as close as I can get to accurate. That's the unfortunate part about living in Florida. The sea level changes by the mile. :(

posted by  jynx

The car hates me. I've given up hope of ever getting this thing running properly again. :(

posted by  jynx

That's close enough. That close to sea level it should read near exact to specs.



Dont give up. You just need to check manifold vacuum.

posted by  DodgeRida67

All hoses are attached & intact. Still running badly. I think I have either a dead cylinder or a bad plug. I'm going to try checking the plug. If it's not the plug then I'm thinking it's the cylinder and in which case the car is going to the scrapyard as it's not worth replacing the motor in this car.

posted by  jynx

I haven't checked ecm codes as of yet. I haven't found any splits, cracks, holes, etc in any hoses. And the car starts off at an idle of about 550 rpm. I give it a little gas to listen to the motor, let off the gas and then it drops to 500 rpm and only fluctuates slightly. And today I think I'm going to take DodgeRida67's suggestion and get drunk.

posted by  jynx

Dude, before you do anything else to your car, check for trouble codes. That will end your woes. I'm suspecting your vacuum to be shot way up. So gimme that reading :mrgreen: If your vacuum is high, there's something you can do to fix the vacuum and your slow idle. All at once, with a screw driver. So get the trouble codes and vacuum reading!

posted by  DodgeRida67

Color me stupid....I found the egr valve position sensor and the clips that hold the electrical connector are broken, due to my carelessness while trying to replace the final spark plug. Too little brain and too much brawn was used at that point. :(

posted by  jynx

One problem....It's not broken wires. It's broken plastic clips. If it were broken wires I'm sure that'd be easier to fix. So what you're saying is at this point if I remove the negative battery cable for a few minutes it will clear the codes and then the car will relearn how I drive? :confused:

posted by  jynx

What he was saying is, Once you fix the problems associated with the trouble codes disconnect your battery for awhile so the computer will be reset so the codes will then go away and it will gather all new various information over the next couple miles and adapt to your driving tendencies when you run your car again.

posted by  DodgeRida67

Your Message