My age old problem...SOLVED Please Read!

I am having a very similar problem, so I pulled off the TFI module, wiped off the old grease, and put new dielectric grease on it and it has been taking it a lot longer to start showing the symptoms again, so Im thinking the TFI is going bad and only shows up when it gets hot. My car will miss and sometimes backfire under 3000rpms under load, anything above that and it runs fine. Before I played with the TFI, as soon as the engine hit 180 degrees it would start crapping out, now it takes it 20-25 minutes of driving before it starts crapping out. I plan on getting a new TFI module next week. I'll post my results if a solution isn't reached here.
 
How much does a TFI module cost?
From all I've heard, when the TFI craps out, its hard to start the car when its warm, and you lose spark.

My car is perfect starting warm, you can barely hear it crank.
 
I'd note that the 94-95's have a remote mounted TFI, which is to help reduce the heat failure rate that was an issue for foxes (III's).
 
HISSIN50 said:
I'd note that the 94-95's have a remote mounted TFI, which is to help reduce the heat failure rate that was an issue for foxes (III's).

Yeah, thats true.

I don't even think a mechanic would be able to solve this problem, would they?
 
Joe, this issue has plagued so many 5N95 owners - I've seen well-into double-digit threads since the heat rolled in - that I am not sold it isnt simply a stock tune issue. You dont see 94-95 Cobra owners complaining about this stuff.............
I'm wondering in my case if timing is being pulled because of a given IAT temp. My IAT and ECT DL'd alright while I was at 190* (ECT), but I need to check again and after letting the car heat soak or idle in traffic.


I also have the sinking suspicion that if I removed my hood, the car would run much better. The underhood ventillation sucks, and everything gets heat soaked bad (CAI, ergo the IAT, etc).

Random thoughts.
 
I am leaning toward the stock tune being the culprit. My brother has a SN and he has similar problems with low rpm bogging, pinging and poor throttle response when it is hot. I would think that it is a built in safety precaution where the computer dumps a little more fuel either with increased inj. duration or pulsewidth...as-well as backing off on the timing. Hissin you mentioned you checked your timing @ 1500 rpms...but im guessing there was no load on the car at that point. Without a load the computer will advance timing considerably for efficiency. I think thats why you saw 30-40 degrees. With a base setting of 6* its not making your low end power issue any better. A tweecer and wide band would let you know for sure. MAF's on the Sn's have also been known to cause serious issues?! good luck guys.
 
HISSIN50 said:
Joe, this issue has plagued so many 5N95 owners - I've seen well-into double-digit threads since the heat rolled in - that I am not sold it isnt simply a stock tune issue. You dont see 94-95 Cobra owners complaining about this stuff.............
I'm wondering in my case if timing is being pulled because of a given IAT temp. My IAT and ECT DL'd alright while I was at 190* (ECT), but I need to check again and after letting the car heat soak or idle in traffic.

Thats what I was thinking with my car, but the resistors didn't make a difference.
You can try it, 3.3K OHM resistors from pep boys.

Maybe it is the stock tune, that really sucks though.
I dunno though, it really feels like a problem. Hesitation and huge power loss, something I wouldn't expect thats supposed to happen.

Its weird, this problem doesn't happen at all in the winter. I can beat the **** out of my car for like an hour and the car still runs close to perfect.
Its only with high temps and even when its cooler, when its humid it runs like balls.
It gets me so aggrevated, I can't go to the track during the summer time :(.
 
Ninety15.0, I'm able to see PID's in real time and capture streams. You're preaching to the choir about this tune stuff. :) The puter doesnt just advance timing with no load for efficiency, the system is load-based period

If I had the cash, an RT would be on the 94. :banana:
Grady likes to bug me ever so often about it............ Maybe one day............Or not. :(
 
795.0pacecar said:
Around $30. Sometimes they crap out and are completely gone and give no spark, and sometimes they start acting up as they get hot.

Mine crapped out and would cause a miss at 3-4 or 4-5krpm only after the car was warm. Took a while to figure that one out...
 
ninety15.0 said:
I am leaning toward the stock tune being the culprit. My brother has a SN and he has similar problems with low rpm bogging, pinging and poor throttle response when it is hot. I would think that it is a built in safety precaution where the computer dumps a little more fuel either with increased inj. duration or pulsewidth...as-well as backing off on the timing. Hissin you mentioned you checked your timing @ 1500 rpms...but im guessing there was no load on the car at that point. Without a load the computer will advance timing considerably for efficiency. I think thats why you saw 30-40 degrees. With a base setting of 6* its not making your low end power issue any better. A tweecer and wide band would let you know for sure. MAF's on the Sn's have also been known to cause serious issues?! good luck guys.

Yes, but how does the computer know when its hot?
Is it when the motor is hot? Like it reads from the ECT or IAT?
Because I have tricked the computer with both of these sensors.
I think the tables for the ECT and IAT are the same so I just used a 3300k resistor which should tell the computer its around 50*, but I get the same symptoms.
 
Ok, I seriously think I might be on to something.

Last night it was a little cooler out, and the car was still running ****ty. I was getting pissed... I pulled over and pulled the resistor out of the IAT
 
I really think I might be on to something.
Last night as I was driving it was cool out, around 65* maybe. THe car was still acting like **** though.
I pulled over and pulled that 3.3k resistor out of my IAT and plugged the IAT back in.
What do you know, my car was acting 100% better in the cold air.
I come home and look up jrichter's table...uhhh
3.3k is right around 190*, lol. I was stupid and used ebay's advice in which resistor I should get instead of just looking for jrickter's. :bang:

Well anyway, I'm thinking since that resistor for sure intensified the problem, I'm wondering if the right 30k resistor would diminish the problem.
I have my fingers crossed.
 
I Fixed my PROBLEM!

Well I wanted to start a new thread since the old one isnt going to get as much attention.

Basically I would lose all power when the car warmed up. It was a dog, hesitating and no throttle response.

I used two resistors a 33k and a 10k and put them in place of the IAT sensor.

I can now peel out in 95* and it has never felt better!!!!! I haven't been able to do a burn out during the summer day, EVER.!!!!

I am positive this alleviated the problem.
 
Synned said:
Well I wanted to start a new thread since the old one isnt going to get as much attention.

Basically I would lose all power when the car warmed up. It was a dog, hesitating and no throttle response.

I used two resistors a 33k and a 10k and put them in place of the IAT sensor.

I can now peel out in 95* and it has never felt better!!!!! I haven't been able to do a burn out during the summer day, EVER.!!!!

I am positive this alleviated the problem.

Shouldn't the computer know the actual air temp going into the engine? This seems like something that wouldn't work well in all conditions, or else ford would have done this from the beginning. BTW what does a 33k and 10k translate to temp wise for the ACT?
 
This is where the differences in 94-95's and Aero foxes comes into play.

The 94-95 processor is load based, and to try to make the car run cleaner, there's too much timing and too little fuel.

A quick and dirty way to try to enrichen things is to do the IAT tricking. Sure it aint correct to do, but it can help. A 180* t-stat isn't factory correct, but it can make for a nice compromise..... this is the same kinda thing in my mind (When temps cool off, Joe will hook his IAT harness back up to the IAT I bet).

Joe, I'm glad to see you checked the resistance values for the thermistor - my recollection had been that there was a ton of resistance in some of the readings (the curve is parabolic as I recall).

Anyhow......... Enjoy!
 
795.0pacecar said:
Shouldn't the computer know the actual air temp going into the engine? This seems like something that wouldn't work well in all conditions, or else ford would have done this from the beginning. BTW what does a 33k and 10k translate to temp wise for the ACT?

I guess it should, I don't care I'd rather be running like this than before.

I just dont understand WHY I have this problem. I'm pretty sure the IAT is good, its the 2nd one.
Why does the stock computer want to do this?