Bad miss at 30-35mph

[PushnFords]

Well, I bypassed some leaking vacuum hoses. and the car is running a little better. I think my problem is a sensor or electrical though. Today on my lunch break it was running fine when I stopped at a red light and suddenly it was missing really bad. Stumbled when I took off but eventually cleared up. I'm going to pull the plenum tomorrow and make sure I've got the vacuum issues taken care of (hopefully) and then I'll start looking at the sensors and see if I have any codes.

[91waggin]

To read codes, (if you have a yellow CEL on your dashboard):
1. Start the car and get it up to operating temperature. Shut the engine off.

2. Hook together the self-test plug and the self-test input as shown in the above picture. A bare metal paperclip or other piece of scrap wire works fine. They are located on the driver's-side fender under the hood.
3. Get a pad of paper and a pen.
4. Sit your ass in the driver's seat.
5. Turn the key on, but don't start the engine
6. You'll hear the fuel pump come on and a bunch of relays click.
7. You'll see the CEL flicker a whole bunch of times really fast. Ignore this--it's for the fancy readers that most of us are rightly too cheap to buy.
8. The CEL will start to flash slowly. It will spit out codes like this:

9. I find the easiest way to mark down flashes is to make hash marks on the paper and figure them out later. Like this:
||| |||| |||| ||||||
3 4 4 6
This is a code 34 followed by a code 46. There's a 2 second pause between digits and a four second pause between codes. Once you start to see codes repeating themselves, you're done with the first part of the test.

10. Turn the key off.
11. Without disconnecting your self test connectors, start the engine.
12. You'll see four flashes indicating that the computer for a v8 is hooked up.
13. Wait.
14. Wait some more. Your engine will probably do a number of funny things including revving up and down and maybe almost stalling. Keep waiting.
15. It will eventually start flashing codes, the same way as above. Once it starts repeating codes, shut the engine off, figure out what codes you have, and look them up. There's a sticky around here somewhere explaining the meanings of all the 2-digit codes.

[91waggin]

Possible causes of this problem that I've heard of:
**Most likely** This problem doesn't usually throw any codes.
Bad plugs and wires. Even if they're fairly new, shitty wires go bad fast. This is something you should do regardless of when you think it was done last. I usually do this every two to three years. Replace plugs with Motorcraft SP409 copper plugs. Anything else is a waste of money. Seriously, these plugs are $1.48 apiece on Rockauto.
Replace wires with Ford Racing Performance Parts wireset. Available at http://www.summitracing.com/parts/FMS-M-12259-C301/
Replace cap with something from your local parts store with brass terminals, not aluminum.
Replace rotor with something from your local parts store that has brass terminals.

If this hasn't fixed your problem, it wasn't a waste of money. You'll still probably run better and get better mileage than you did before, once you figure out the problem.
Doing an ignition parts tuneup should absolutely be step one in figuring out this problem. There's a 95% or better chance this will fix it altogether.

**Next most likely** This problem may throw a code.
There is something wrong with either the EGR position sensor or the EGR valve. In some cases, the position sensor is telling the computer the wrong things, and the computer is opening the EGR valve the wrong amount, or when it shouldn't. Also, there could be a chunk of something holding the EGR valve pintle open.
Easiest way to diagnose this problem is to remove and cap the vacuum line going to the EGR valve. It's a single vacuum line (OEM hard vacuum hose color is green, but that info is useless if the hose has been replaced) that goes to the hockey-puck shaped plastic thing next to the throttle, facing the front of the car. If the problem goes away, it's EGR related. Time to take the EGR apart (.5 hours work) and see what's going on. Maybe you have to replace the EGR valve or position sensor. Both parts are under $30.

Other possible causes:
Bad TFI module. This is the timing module that sits in the side of the distributor. They get very hot, and sometimes will fail due to that heat. The distributor acts as a heatsink to carry away that heat, and between the module and the distributor there should be a layer of thermal transfer paste, like is used between a computer CPU and heatsink. Overtime, this stuff gets dry and crumbles, and leads to TFI failure. When you purchase a new TFI, they will often give you di-electric grease rather than thermal transfer paste. This will cook the new TFI pretty quickly, and you'll be back at square one. Instead, go to Radio Shack or another computer store and get some high-quality thermal transfer paste for a computer. My recommended brand is Arctic Silver. Apply to the TFI module, and scrape to a thin even layer with the edge of a credit card; the layer should be paper thin. Reinstall TFI module. You may have to rotate the distributor to get the TFI module out. Make a scribe mark on the distributor base so you don't have to reset the timing afterward. If you don't like the idea of putting the TFI back on the distributor, there are relocation kits available that mount the module on a huge heatsink elsewhere int he engine bay. This is how Thunderbirds and other assorted Fords came from the factory.

Bad distributor pickup. This will probably be indicated in codes. These cars use an in-distributor pickup (PIP) instead of a crank or cam position sensor. Without this sensor, the computer has no idea where the engine is rotationally, and is just guessing when to fire the fuel injectors. It's generally easier to replace the entire distributor rather than fish the damn pickup out of it.

Bad ignition coil. Not usually indicated in codes. Check the resistance between the two small wires on the coil (BATT and TACH. TACH is green, I think). If the resistance is less than .8 ohms or greater than 1.6 ohms, replace the coil. If the first test checks out, test the resistance between BATT and the coil tower. Resistance should be between 7700 and 10500 ohms. If it's outside spec, replace it.

Bad MAP sensor. Not usually indicated in codes. There's also no easy way to test one of these, since you need an oscilloscope to do so. Just grab a few from the junkyard and take them home. They don't go bad very often, but it's happened to me.

[91waggin]

Well, I bypassed some leaking vacuum hoses. and the car is running a little better. I think my problem is a sensor or electrical though. Today on my lunch break it was running fine when I stopped at a red light and suddenly it was missing really bad. Stumbled when I took off but eventually cleared up. I'm going to pull the plenum tomorrow and make sure I've got the vacuum issues taken care of (hopefully) and then I'll start looking at the sensors and see if I have any codes.

Generally, vacuum leaks don't make speed density fuel injection systems run that crappy, because they can pretty much take the vacuum leaks into account, since they rely on the amount of engine vacuum for their calculations of how much air is entering the engine. Often the only symptom you get will be a higher idle.

[91waggin]

Jesus. Sorry about the novels.

[PushnFords]

Well I dug out my code scanner tonight and figured out how to use it. I'd used the small scanners like AZ has but it has been a few years...the one i have is a little more complex. Anyway I have KOEO codes of 85 (canister purge solenoid) and 34 (EVAP sensor) which makes sense because the solenoid has been removed and the vacuum lines rerouted. The KOER test brought up a 92 (HO2S System Rich Bank 2). Because of that code it won't let me do a cylinder balance test. I didn't have my timing light handy but the distributor doesn't look like it has moved in a LONG time. I'm still planning on pulling the intake to check the vacuum hoses...need to do that anyway...and will see about testing the O2 sensor.

[gadget73]

34 is egr related, not evap related.

PFE or EVP circuit above the closed limit of 0.67 volts.

usually thats either a chunk of crap under the pintle on the egr valve thats not letting it close, or the sensor is whacked.

[PushnFords]

Ah...I must be too tired to read! What is the bolt torque for the upper intake? So far my Haynes manual is 100% worthless. If it says the torque I can't find it.

[PushnFords]

I dug that little screen out from under the PCV valve and have it soaking in carb dip. Going by the parts store today over lunch to pick up some vacuum line...most of the lines under the intake were badly cracked and the MAP hose was about to collapse. Hopefully tonight I can snag an O2 sensor socket and get mine tested. While I have the plenum off I'll check out the EGR valve and see if it has something stuck in it or if I need to order one. So...here's the question I have I guess:

Plenum bolt torque? Can't find it in the manual.
IAC the same between Mustang & Crown Vic? I have an almost new one off of an HO intake I bought.
What is the "T" series of parts through Rock Auto? They are cheaper...but are they junk? Looking at the EGR stuff....
Which side is Bank 1 & Bank 2?

Thanks for the help!

[86VickyLX]

Will these systems store codes without illuminating the CEL?

you do not have a check engine light.
You have a holy shit, the engines messed up light. Which will only come on with very little to no oil pressure, or if it's been overheated badly.

No info on plenum bolt torque. Note that you're bolting into aluminum, so just make them snug, the about another turn after that.

Replace that PCV screen!!! DON'T REUSE IT!!!!
The IAC is the same with a difference only being a 90 degree bend for the electrical connection. To make this work, unscrew the motor from the valve, and rotate it 180 degrees. Otherwise you'll have to plug in the IAC before you bolt it up.

Bank 1 is drivers side, and obviously bank 2 is passengers side. Fix your vacuum lines and stuff first.

[91waggin]

Oh shit. He doesn't have a CEL? Fuck I thought he said he had one, so I didn't look at what year car he had. All my code pulling instructions are no good then. Balls.

[86VickyLX]

Can make that light a check engine light. But you'd need other means of monitoring coolant temp and oil pressure.

You could use your skills, but all you'd need would be a 12 volt test light. Hooked to battery positive, and to the Self test output wire.

[PushnFords]

I tore the upper intake off and ordered parts...picked them up today. I've got a new PCV valve installed in a new grommet and all of the vacuum lines under the plenum either capped off or replaced. The PCV hose was fun...four elbows. While I had the intake off I figured I might was well check the EGR passages. Took two hours to get the throttle body and EGR spacer off. They were completely corroded together and around the bolts. Took a hammer, a chisel, and a few pieces of 2x4 but I got everything loose without destroying anything. Everything is cleaned up now and the intake is bolted back down. I don't have an EGR gasket (guy at Carquest forgot I guess) and I forgot to tell him I needed the plenum to EGR spacer gasket. Hopefully I can pick those up tomorrow and get it back together. I'm betting I'll end up replacing the EGR valve though...lots of carbon and gunk in it.

[PushnFords]

Ok, the car is back together. I pulled the upper intake and replaced the vacuum lines under it, the PCV valve and grommet, and replaced the dist. cap with one I had with brass terminals. The EGR spacer and throttle body were both cleaned. I bought an HO intake a while back that had a pretty new IAC valve so I installed that as well. Fired it up and checked for codes...yep...got some. And the miss is still there. So I started swapping parts between the HO intake and the LOPO to try and narrow it down. After each change I redid the KOER test. Here's what I have:

With EGR valve & position sensor from HO intake:
13 - Unable to control idle, low speed
34 - EVP
92 - System running rich, Bank 2

With EGR valve off of HO intake and my original position sensor:
31 - EVP (I think my scanner said no EGR flow detected)
92 - System running rich, Bank 2

With original CV EGR valve and position sensor:
33 - No EGR flow detected
92 - System running rich, Bank 2

With CV EGR valve and HO position sensor
34 - EVP sensor out of range
92 - System running rich, Bank 2

Before I tore the car apart I was getting the 34/92 codes with the CV EGR valve and position sensor. So...do I assume both of my used EGR valves are bad? The one off of the HO intake didn't look the best and the pintle was stuck when I started cleaning it up. Or...is there something else that can give me the code 34? I'd like to test the O2 sensor but I have a feeling I'll destroy it trying to remove it so I might just replace both sensors (my understanding is the Mustang sensors had longer wires?) when I get a little cash saved up again.

[PushnFords]

Hmmmm...the website I was looking up the codes on doesn't say it but when I look at the code definitions on this forum it says #34 is Insufficient EGR flow/Excessive exhaust back pressure; or EVP voltage above closed limit(SONIC)/PFE sensor voltage high or out of range. (O)(R)(C)

I've noticed my car has a rotten eggs smell sometimes. Is is possible my EGR valve and position sensor is fine and I have a bad or plugged catalytic converter?