Still Misfiring

[MidNiteBlu 5.0]

Well after buying a new coil and making sure the spark plug wires are good my car is still misfiring. It is driveable but anything above 2000 rpm it misfires alot.

i have run out of solutions and am about to take it to a mechanic. Anything else i can check?

Take those platinum plugs out,throw them across the street,then install some autolite or NGK spark plugs.

[HotRoddin]

Have you put a vacumme guage on it ? Could be a sticky valve ?

[PKRWUD]

Could be a restricted exhaust, too. Definitely put a vacuum gauge on it! That should really help you ID it. Let me know if you need me to re-post my vacuum tips post.

Take care,
~Chris

[MidNiteBlu 5.0]

I could try the vacuum gauge. I just wish i actually had the time to do it this weekend because i really dont. i have a 8-12 page term paper to write due tuesday

Well we have a vacuum gauge so we will try to fit that in the schedule between my paper and my dad wanting to work on his 66 hehe.

Chris that would be helpful if you posted that again

Thanks,
Nick

[PKRWUD]

The vacuum that is created in a normaly aspirated engine (one that is not blown or turboed) gives you a great tool for diagnosing engine problems. Just about any internal engine problem can be identified with a vacuum gauge !!! I'll teach you some of the basics:
1) A steady reading of between 17" and 22" is considered normal for a stock engine.
2) A low but steady reading between 10" and 15" would be caused by retarded ignition or valve timing, or low compression.
3) A very low reading between 4" and 9" means you have a vacuum leak.
4) If the needle fluctuates as you increase the engine speed, you have either an ignition miss, a blown head gasket, a leaking valve or a weak valve spring.
5) A gradual drop in reading at idle means you have excessive back pressure or partial blockage in the exhaust system.
6) An intermittent fluctuation at idle means you have either an ignition miss or a sticking valve.
7) A reading where the gauge needle drifts anywhere between 12" and 22" indicates that your idle mixture is unstable. This is more common on carbureted motors.
8) A high and steady reading indicates that the ignition timing is too far advanced.
9) If, when you quickly close the throttle after running at 2000 rpm for ten seconds or more, the gauge needle DOES NOT jump two or more inches above what it is at idle, your piston rings are shot.
10) If the reading at idle is lower than normal, but the gauge needle fluctuates three inches on both sides of normal, your valve guides are excessively worn.
These are but only a few of the things you can learn about the condition of your engine with a vacuum gauge. Keep in mind that a blower or a turbo will create a false reading because the boost they create offsets the vacuum reading.

The following is the way to find out if you have an internal vacuum leak from a defective intake gasket:
1) Hook up a vacuum gauge to the intake manifold.
2) Fully close the throttle plate by backing out the idle screw all the way.
3) Plug up the PCV valve opening.
4) Disconnect and plug any vacuum hoses attached directly to the intake manifold.
5) Disconnect the wire to the positive side of the coil.
6) Crank the engine and observe the vacuum gauge. From 3" to 7" of vacuum (at a minimum of 250 cranking rpm) is normal. A defective intake manifold gasket will give, in most cases, a zero reading.

With a vacuum gauge, there are two easy tests you can run to determine if your exhaust is restricted (cats clogged).

First test:
1) Attach vacuum gauge to manifold vacuum source.
2) Observe vacuum at idle.
3) Snap throttle to WOT and release, while watching the gauge.

The vacuum gauge should drop to almost zero when you hit WOT. When the throttle snaps closed immediately after, the vacuum should read 4" to 6" higher than what it did at idle. It should then settle back at the same reading it was at idle before the WOT snap. This whole exchange should go from idle reading to idle reading in 2-3 seconds, tops. If it takes longer for the gauge to return to the same idle reading, your exhaust is restricted. The longer it takes, the worse the restriction.

Second test:
1) Attach vacuum gauge to manifold vacuum source.
2) Warm up engine.
3) Observe vacuum at idle.
4) Leave engine idling for 10 minutes. Do not touch anything on the car during this time. In fact, go inside and fix some coffee.
5) After 10 minutes, observe the vacuum.

If the vacuum is the same or higher, you don't have any resctrictions. If the vacuum gauge has dropped, you do have a restriction. The more it drops, the greater the restriction. If it drops 1" or more, you have a serious restriction. 2" or more and you might as well have the exhaust welded shut. Keep in mind that a rich exhaust will clog up cats in a hurry.

Hope this helps a little.

have you checked the distributor cap to see if it has any cracks?This will cause mis-firing problems.

How is the rotor inside? check the simple stuff

[MidNiteBlu 5.0]

The cap and Rotor are like brand new and i did check them they are fine. Could it be the TFI module? i know I got a recall sheet in the mail soon after i bought the car I just need to find it. i have no idea how old the TFI is and knowing the rest of this car it most likely ir original

Oh and the Coil does buzz kinda an interesting sound but i cant hear it after turning the stereo on. I will try the vacuum test later today after I get some more work done on my paper

[MidNiteBlu 5.0]

Could this be a bad MAF too? Im just throwing out ideas. Im sure its stock 13 year old one too.

[PKRWUD]

Absolutely.

[MidNiteBlu 5.0]

How would I check it? Or do I just have to buy a new one?

[PKRWUD]

Borrow one that you know is good. Don't throw money at hoping. Prove it, and then spend the money. Unless you're rich, in which case drive it up here and I'll fix it for you.



Take care,
~Chris

[MidNiteBlu 5.0]

Damn i have no idea. The vacuum test turned out just fine. Im just gonna be drivin it to school and back for awhile, maybe take it to a mechanic.

I just looked at the TFI moduel recall i have and the damn thing expired in October Could that be the problem too? How expensive are they?

i wish i had acces to a good MAF but I really dont.

Dammit this sucks

I just looked at the TFI moduel recall i have and the damn thing expired in October Could that be the problem too? How expensive are they?

A bad TFI module wont be showing these kinds of conditions that your talking about.What a bad TFI module does is they usually get hot and cause the engine to stop at any time and at any speed.

This is one reason why Ford went through a recall for this.Pretty dangerous thing to have happen on the ol' highway.

I'm sayin again,change those platinum plugs out and run copper-tipped plugs

[MidNiteBlu 5.0]

You think the Platinum plugs are the problem? Theyve been in thier for 6 months or so with no problem. Plus usually last longer than that dont they?

i have another question. I have 9mm Ford racing wires and the 5th nd 6th wire are very close together and sometimes touch. Is this a problem with large wires like mine? But then again they always have been really close for close to a year...

You think the Platinum plugs are the problem?

platinum is an inferior conductor compared to copper plugs.

the copper tip plugs have a better thermal conductor and would perform better under hard acceleration.

The only advantage is you will be getting longer life out of the platinum plugs.

I have 9mm Ford racing wires

These wires have a history of spark jumping between the wires.Take and open up your hood at night and look to see if you can see spark jumping around the sparkplug wires.It will look like a light show.If you see this,it's a bad thing.

Also they are the highest resistance wires on the market.the lower the resistance,the better the spark travel.

[MidNiteBlu 5.0]

Well i guess I wont be buying platinum plugs again. hehe.

So are you saying the Ford Racing wires are crap? I mean my car is basically stock so i dont think I have alot of power going through them anyways. (compared to a race style ignition) I dont know this is really stuping me and i think im gonna take it to a shop even though I dont really want to hehe

[MidNiteBlu 5.0]

help!