'02 GT Intermittent problem (Reward for help)

[stangsdado]

OK. I’m going to sweeten the deal for anyone who helps me. I’ve got an ongoing problem with my stang and I’m so desperate that I’m willing to send anyone who helps me resolve this problem $50 either by Paypal or by check.

Let me start by specifying everything done to my car and then the symptoms.

I’ve got an ’02 5-Speed SOHC 4.6L. It has the following mods:

MAC Long-Tube headers
MAC Off-Road Pro-Chamber
Flowmaster 40-Series mufflers
Typhoon Intake Manifold
Steeda Dragon Plenum and Throttle Body
MAC Cold-Air Intake with 90mm MAF housing
Steeda Underdrive pulleys
Ford Motorsport 3.73 gears
Walbro 255 LPH fuel pump

Alrighty, onto the problem. I’m going to describe what the car feels like as best as I can. When you begin driving in first gear, immediately, you feel a subtle vibration in the engine, almost exactly the same as you feel when traction control kicks in. If you keep the gas at the same pressure, you feel this vibration throughout all the gears. If you get to a certain point in the RPM range in any gear and you ease off the gas to a minimum, the car feels like it jerks very little and the vibration disappears and it feels normal. It stays normal until you press the gas any harder than you were holding it before. Sometimes, the car will have the same vibration when you’re idling, and other times it won’t. There is no difference in response from the car whether the A/C is on or off. Obviously, this vibration is impacting acceleration a lot and it will take twice the time to get through the RPM range with this problem than it took when the car was driving normally. Sometimes, it will throw a code, but the codes vary so much that there is no rhyme or reason. I’ve gotten a code for lean in either bank and then the next time rich in either bank. Then I’ve gotten a code for a cam sensor but no matter what the code is, once I reset it, it never comes back. The latest was for incorrect reading in the upstream O2 sensors. I played with the EGR recently through my hand-held programmer and I thought it may have been stuck in the open position, but the problem persisted even when I turned the EGR system off and installed a small piece of aluminum between the EGR and plenum to block any possible leaks. Currently, there are no codes. One thing worth mentioning is that I’ve never once gotten a code for a misfire, which is the first thing I thought this could be when it originally started.

The following things were done/installed in effort to fix the problem:
Ford Motorcraft 255 LPH fuel pump and assembly
Ford Motorcraft fuel filter
Ford Motorcraft 19lb injectors
Cleaned/oiled MAC filter and let stand for 24 hours before re-installing
Cleaned the MAF sensor with carb-cleaner followed by electrical contact cleaner
I’ve pulled the wires off each injector and coil one by one but every single one produced the same result, the engine would idle even rougher.
In one final play of desperation, I played with the timing and A/F mixture through my programmer all to no avail.

One more problem I’m having is with the ABS system. A year ago, it started intermittently turning on and off until a few months back it turned off completely and never came back. I should point out that the main problem started happening before the whole ABS problem and the ABS has been off even when the other problem went into remission a few times.

Any input will be greatly appreciated.

 

[Winters98GT]

I'd bet it's your cold air/MAF or typhoon intake, none of which helps, but more likely hurts your performance. The Mac cold air hurts performance and gets heat soaked, and your stock meter isn't anywhere pegged with your setup. Put the stock stuff back on.

It's probably causing you to throw some of the codes you are seeing. The ABS could be related as well, or not.

I'm not sure how the 2v computers hold codes. My car holds them for in 2 modes, "history" and "current". The history are codes that have been thrown in the last 50 cranks. Are your codes current? Good luck.

Mark

 

[VEE EIGHT]

Damn I could use $50......but I can't help you. Good luck.

 

[nyuk98gt]

stangsdado:

Motor mount(s) or transmission mount starting to fail. Have you checked them recently? If you have done a few WOT runs, the mounts will get tired. Torque is good for speed but hell on motor mounts.

Chris

 

[tag4car]

What have you done to the IAC ?

 

[Kilgore Trout]

You probably ruined the MAF sensor with carb cleaner and now you need a new one. Also a custom dyno tune would probably be very beneficial.

You have a crappy CAI, a crappy intake manifold, and a crappy TB. Restore all those parts to stock and get a custom dyno tune after you replace the MAF sensor and it is installed in the stock position.

If you still have rumbling noise then it is the rear diff or possible some kind of ABS issue such as intermittent module or sensor failure.

If you really want to get to the root of it give that $50 to the stealership for diagnosis fee in their shop.

 

[stangsdado]

I'd bet it's your cold air/MAF or typhoon intake, none of which helps, but more likely hurts your performance. The Mac cold air hurts performance and gets heat soaked, and your stock meter isn't anywhere pegged with your setup. Put the stock stuff back on.

It's probably causing you to throw some of the codes you are seeing. The ABS could be related as well, or not.

I'm not sure how the 2v computers hold codes. My car holds them for in 2 modes, "history" and "current". The history are codes that have been thrown in the last 50 cranks. Are your codes current? Good luck.

Mark

As for the CAI, I've had this thing for 5+ years and never once had a problem with it so I got rid of the stock parts. The typhoon was an amazing add IMO. I immediately felt the engine rev up quicker. In any case, the stop plastic crap was cracked hence the need for an upgrade. I believe the codes on this car work on the "pending/current" basis. It takes one crank to generate pending and then another to display it as current.

 

[stangsdado]

stangsdado:

Motor mount(s) or transmission mount starting to fail. Have you checked them recently? If you have done a few WOT runs, the mounts will get tired. Torque is good for speed but hell on motor mounts.

Chris

I think I've already ruled out the driveline as well as mounts. They were done less than 2 years ago plus I'm 100% positive this has something to do with the air/fuel/exhaust because of the way the engine behaves.

 

[stangsdado]

What have you done to the IAC ?

Never touched except to reinstall after the intake install. Should this be checked? Is there a way to clean it?

 

[stangsdado]

You probably ruined the MAF sensor with carb cleaner and now you need a new one. Also a custom dyno tune would probably be very beneficial.

You have a crappy CAI, a crappy intake manifold, and a crappy TB. Restore all those parts to stock and get a custom dyno tune after you replace the MAF sensor and it is installed in the stock position.

If you still have rumbling noise then it is the rear diff or possible some kind of ABS issue such as intermittent module or sensor failure.

If you really want to get to the root of it give that $50 to the stealership for diagnosis fee in their shop.

I cleaned the MAF way after this problem started happening. Also, the car was running perfectly without any problems or codes for 3+ years with this setup.

I took the car to my mechanic and he pretty much told me, we're going to replace this, this, this and that and there is no guarantee that its going to be fixed. I don't want to spend thousands of dollars before I've exhausted all other options.

 

[Kilgore Trout]

Take it to Ford they will use the scan tool and their expertise to easily diagnose. My stealership only charges $35 for this.

 

[stangsdado]

Take it to Ford they will use the scan tool and their expertise to easily diagnose. My stealership only charges $35 for this.

I just called my dealership and they said that if its not throwing any codes, the only other thing they can do is a compression test which would cost me an hour of labor ($100). I'm gonna see one last time if my friend can bring me the tool from his shop and if not, I'm going to go buy one which is still gonna be less that the $100 the dealership wants. I'll post the results.

 

[Kilgore Trout]

Good luck man I know how annoying those difficult to diagnose and ongoing problems can be

 

[stangsdado]

Good luck man I know how annoying those difficult to diagnose and ongoing problems can be

Just a quick question. If it turns out my compression is lower on one or more cylinders, does this automatically mean rings? What else could it be?

 

[Mizark347]

There is no difference in response from the car whether the A/C is on or off

I'm sorry. I was going to start a new thread until I saw this one. I'm having a similar problem to yours. However, mine smooths out when I turn on the A/C. What does this mean?

As for your problem. The 90mm housing that your mass air meter is in can cause the MAF to act completely different. I say start by putting the stock housing back in.

 

[stangsdado]

As for your problem. The 90mm housing that your mass air meter is in can cause the MAF to act completely different. I say start by putting the stock housing back in.

I've had that MAF housing for years and with the SCT tuner, I set it to 90mm. Plus, I got rid of the original a long time ago.

 

[trombonedemon]

From experience, once you rings go bad you start to burn oil. What does your tuner do. For some reason it sounds like a sensor problem. If you know what your doing it might worth given your engine a complete overhaul. You know gaskets, seals, and see if you can scope your sensors, make sure they are reading the analog readings. If it is a digital the sensor is either off or on, if it is analog it looks kind of like a seismagraph reading or lie detector test. See if autozone or advanced auto would let you rent one. It can be a PITA if your no throwing a code. Diaganosing is a big buisness. Replacing the right part is the easy part. Sounds like Throttle Positions sensor, get your speed sensors working again if you can, that can make your engine read false signals. Try to get that scope if you can, would be a descent investment before any more power upgrades. Then get the correct readings from all data or ford if its not already programmed in the scope. If the engine does a drive cycle one time and the sensor is working its not going to throw a code or if its working after the car detects it then goes out again its not going to throw a code. Thats why a scope is handy. Sounds electrical not mechanical.

 

[Kilgore Trout]

Just a quick question. If it turns out my compression is lower on one or more cylinders, does this automatically mean rings? What else could it be?

Well, I would defer to one of the more knowledgable techs for the answer to that. I am just a hobbyist mechanic...

I will say that "rumbling" is usually attributed to the rear diff. Is it possible that there is a problem with your diff?

 

[stangsdado]

From experience, once you rings go bad you start to burn oil. What does your tuner do. For some reason it sounds like a sensor problem. If you know what your doing it might worth given your engine a complete overhaul. You know gaskets, seals, and see if you can scope your sensors, make sure they are reading the analog readings. If it is a digital the sensor is either off or on, if it is analog it looks kind of like a seismagraph reading or lie detector test. See if autozone or advanced auto would let you rent one. It can be a PITA if your no throwing a code. Diaganosing is a big buisness. Replacing the right part is the easy part. Sounds like Throttle Positions sensor, get your speed sensors working again if you can, that can make your engine read false signals. Try to get that scope if you can, would be a descent investment before any more power upgrades. Then get the correct readings from all data or ford if its not already programmed in the scope. If the engine does a drive cycle on time and the sensor is working its not going to throw a code or if its working after the car detects it then goes out again its not going to throw a code. Thats why a scope is handy. Sounds electrical not mechanical.

I'm inclined to agree with you that its electrical, not mechanical. My SCT tuner does data logging but the problem is once I get the log back to my computer, I would have no idea what I'm looking for.

I'm trying to get this car up and running properly so I can sell it to a guy that's already waiting with a check in hand so investing money into part by part that might or might not resolve it is not cost effective for me.

 

[GDawg]

My first instinct is motor mounts... Have you looked at them?