Issues after intake swap (MPG & Stalling)

mhespenh · Nov 17, 2008

Hey all,

So I finally found a free weekend to install my TFS StreetBurner upper/lower -which turned into a four day event after bad weather, a failing water pump, gas leak from a cut injector o-ring, replacing what felt like every d*** vacuum line under the hood, not having a lot of experience under the mustang hood, and helping my friend reassemble his new 383 stroker monte carlo SS -

So long story short- everything went back together fine rlaugh, but I seem to have lost a significant amount of fuel economy (like 30%), and it seems to stall out quite a bit before it warms up- just randomly at idle, sometimes it seems to happen when I turn the wheel all the way one way or the other.

After searching around the most common problem seems to be vacuum leaks, but I'm sure there are none of those, since I replaced every line that even remotely involves the intake along the way (including those stupid hard plastic ones that break REALLY easily ). So what should I be looking for now?

Thanks! :SNSign:

greenlantern · Nov 17, 2008

Ok somebody needs to make a sticky on this so folks know whats up with these cars.

The problem you have is that you have changed the load. With a 94-95 anytime you make any changes that increase the amount of air moving through the engine you change the load. The T4M0 computer in these cars rely on load to provide a smooth running engine. When you mod the car you change the load and you throw the computer off. And the more you mod the worse it gets. What you need to do is to get the car tuned to eliminate this problem. Foxes (A9L computers) don't have this problem there RPM based and use look up tables. Totally different stratagy than the computer you have. You need to either invest in a tweecer RT. (And god help you when it comes to getting support for it.) Or you need to take it some place and get it tuned. Any future changes to the motor will require you to get it retuned.

They don't call these cars the redheaded stepchild of the heard for nothing.

mhespenh · Nov 17, 2008

greenlantern said:
Ok somebody needs to make a sticky on this so folks know whats up with these cars.

The problem you have is that you have changed the load. With a 94-95 anytime you make any changes that increase the amount of air moving through the engine you change the load. The T4M0 computer in these cars rely on load to provide a smooth running engine. When you mod the car you change the load and you throw the computer off. And the more you mod the worse it gets. What you need to do is to get the car tuned to eliminate this problem. Foxes (A9L computers) don't have this problem there RPM based and use look up tables. Totally different stratagy than the computer you have. You need to either invest in a tweecer RT and god help you when it comes to getting support for it. Or you need to take it some place and get it tuned. Any future changes to the motor will require you to get it retuned.

They don't call these cars the redheaded stepchild of the heard for nothing. Welcome

It was my understanding from reading around the formus that a new tune wasn't needed for just an intake swap, and would only serve to squeak out an extra pony or two, not correct problems. I thought you really only need to get into the tuning game when you dig deeper (heads, and cam, specifically). Am I mistaken?

revhead347 · Nov 17, 2008

Don't rule out a gasket leak. Not that I'm disagreeing with what has already been said.

Kurt

Danman765432 · Nov 18, 2008

Vacuum Leak could be very possible...I would check all the lines you replaced to make sure they are not leaking.

Zero Signal · Nov 18, 2008

Yeah the easy answer is to do the vacuum test. A new intake I shouldn't change your vacuum much over stock unlike a cam.

Also, make sure your sensors are all in working order including the IAC and especially the EGR. If the EGR isn't opening, you may be running more fuel than you need in closed loop.

Check the timing.

An intake swap shouldn't hurt the tune enough to warrant a fix via tweecer or tune. The T4MO should be able to adapt to a change like that.

divit250r · Nov 18, 2008

Zero Signal said:
An intake swap shouldn't hurt the tune enough to warrant a fix via tweecer or tune. The T4MO should be able to adapt to a change like that.

I agree with this. There is likely a mechanical (vac. leak, etc...) or electrical (sensor) problem causing this. Remember that the wiring on these cars has been through a ton of heat cycles since '94 or '95 when it was new, so any time you unhook sensors, injectors, etc.. and wiggle the wires, you risk breaking one. This is the joy of having a 14 year old toy. lol

Good luck!
Scott

final5-0 · Nov 18, 2008

As others have said ... you most likely got a V leak

2 things about the lower bolts

1) It can take 3 to 4 or even 5 rounds to get them to EVENLY tighten
when you do the install

You should not ... just tighten to x amount one time
and
Call it good

2) You gotta check those bolts after a couple of heat cycles cause
the gasket compresses

Yes ... You did change the load factors a bit

BUT

A tune should not be needed for that little project
however
I would reset the pcm

Good Luck

Grady

mhespenh · Nov 19, 2008

final5-0 said:
As others have said ... you most likely got a V leak

2 things about the lower bolts

1) It can take 3 to 4 or even 5 rounds to get them to EVENLY tighten
when you do the install

You should not ... just tighten to x amount one time
and
Call it good

2) You gotta check those bolts after a couple of heat cycles cause
the gasket compresses

Yes ... You did change the load factors a bit

BUT

A tune should not be needed for that little project
however
I would reset the pcm

Good Luck

Grady

I went through and double, and triple checked all my vacuum connections and hose, and there are definitely no leaks. Car also seemed to be running a little hotter than normal (between r and a in "normal").

So I followed the crazy procedure to reset the computer and force a relearn of the fuel tables (or whatever its called)- battery off for 30min, battery on, turn on all accessories, wheel all the way left and right, then drive (normal stop and go city-style, constant highway speed, WOT run). So I did it at my house, about 10 miles later it went nuts. The battery gauge started ticking (quickly going from normal to low then back), then the anti-lock and air bag dummy lights flashed a few times.

Then all accessory power went out for a second or two (felt like a lot longer while driving ).

Then everything was normal. In all it lasted maybe 10 seconds.

Now all the sudden it drives like a banchee. I mean, significant improvements, especially between 3 and 5k RPM. Stalling problem seems to be gone, as far as I can tell. Can't comment on fuel consumption yet, not sure how long it takes to relearn all the fuel consumption tables (if it even does?). Car is now running a little cooler (between o and m in "normal").

I'm assuming the crazy power flicker was the computer resetting in some way? Either that, or I've really pissed of a ghost...

Comments? Ideas?

revhead347 · Nov 19, 2008

WTF Mate??

Kurt

mhespenh · Nov 19, 2008

revhead347 said:
WTF Mate??

Kurt

I know, right!?

I thought my alternator was taking a crap on me. I'm not entirely convinced it isn't, though.

Also, is it normal to be able to hear the fuel pump whining while the car is running if you're standing behind it?

revhead347 · Nov 19, 2008

mhespenh said:
I know, right!?

Also, is it normal to be able to hear the fuel pump whining while the car is running if you're standing behind it?

Depends on how loud your exhaust is. As for the other stuff, if it isn't broke right now, don't fix it.

Kurt

final5-0 · Nov 19, 2008

None of that stuff you described
should be seen with a simple pcm reset

btw ... simple and quick pcm reset

disco neg battery cable
turn on headlights for 15 seconds
turn off headlights
reinstall cable

From all that you said above ..........

Sounds like you got some wires pinched, connections loose, or some
kind of wire issue due to the recent work

Also ... the V leak I was focusing in on would be an issue of a gasket
not sealing ... not a hose or hose connection

Grady

mhespenh · Nov 19, 2008

revhead347 said:
Depends on how loud your exhaust is.

Kurt

Loudish- magna flow + magnapacks. It's a distinct whine, def from the tank area. I don't suppose there is an easy test, eh? Naw, that'd be too easy Eh, if it gets loud enough to hear it IN the car I'll get worried.

final5-0 said:
None of that stuff you described
should be seen with a simple pcm reset

btw ... simple and quick pcm reset

disco neg battery cable
turn on headlights for 15 seconds
turn off headlights
reinstall cable

From all that you said above ..........

Sounds like you got some wires pinched, connections loose, or some
kind of wire issue due to the recent work

Also ... the V leak I was focusing in on would be an issue of a gasket
not sealing ... not a hose or hose connection

Grady

Grady- I'm gonna take the upper off this weekend and check (or as your describe, retorque ) the lower bolts. I think, actually, after spending some quality time under the hood with the car on, I may actually have a leak and/or restriction in the vacuum line going from the fuel pressure regulator (I think that's what it is- on the rear of the fuel rail, pass side) to the elbow- the line is just a LITTLE too short it seems. I'll swap that out tomorrow and see what happens.

As for my insanity with the power, I'm gonna recreate it exactly tomorrow and see if it does it again. My inclination is to think alternator and it was just a coincidence that it happened after the pcm reset- since the batt gauge is unusually sensitive to small things (like rolling up a window drops it by 1/4). I'll check the voltage its putting out tomorrow, it should be around 13V, right?

Thanks for all the help so far, fellas! :SNSign:

revhead347 · Nov 19, 2008

Remember 24 ft.lbs for the intake bolts is too much. They need to be wrist calibrated. As far as the pump goes, you should be able to hear it. As for how loud it is, that's kind of subjective.

Kurt

mhespenh · Nov 22, 2008

Alright- good news, and a lesson learned! Really REALLY check for vacuum leaks. They are the devil. The spawn of satan, I say!

The TFS intake moved everything over to the driver's side by about 1/2 inch, the vacuum line going from the elbow to the FPR was getting pulled/stretch slightly causing a leak @ the elbow. After replacing the line with one 1" longer my fuel economy seems to have returned to normal (I got 90 miles on the first half tank, and 60 so far on the third 1/4 since the fix). D'oh!

The PCM reset seems to have solved the idle/lack of power issues, and the ghost hasn't reappeared (although I'm still fairly sure I'll be replacing an alternator before too long...).

Thanks for bearing with the n00b, guys! :SNSign:

final5-0 · Nov 22, 2008

revhead347 said:
Remember 24 ft.lbs for the intake bolts is too much. They need to be wrist calibrated. As far as the pump goes, you should be able to hear it. As for how loud it is, that's kind of subjective.

Kurt

I do think Kurt has a good point to make here

The thing to keep in mind is

How much experience one has with a project such as this

One with little experience has no perspective of how tight things need to be

Simple Example

Say you were to tighten a bolt to 25lbs with a 1/2" torque wrench

Then you took a 3/8" ratchet which will be much shorter and pulled
down on that same bolt until it moved just sightly

Its gonna seem pretty tight with the smaller ratchet :Word:

All this is said to point out ... one with little experience
Well ... their wrist calibrator
It just ain't as accurate as
One who has done a good bit of work with motor projects

That is the key benefit about using a torque wrench
The amount of tightness is the same for all regardless of experience

Like Kurt ... I don't see the need for 24lbs on those lower bolts

IMHO ... 18lbs would do the job

When installing an intake on a SBF ... I do such things

Replace any bolt that is suspect ... Rusty looking ... that kind of thing
Make sure the bolt and hole threads are clean
Lube the threads ... I like to use antiseize
Run all bolts down to about 6lbs over and over until they all tighten evenly
Again at 12 and once more at 18
After two heat cycles ... pull all of em down to 18 for one final time

To keep the gaskets from shifting during installation

I use four sections of all-thread or 4 long bolts with the head cut off

I put them in the next to last hole on each corner to guide the lower
down nice and straight

I do use the end cork gaskets

I use 3M weather adhesive (YELLOW DEATH)
Man O Man ... that stuff can be hard to scrape off

Anyway ... I glue down those gaskets to the china wall
and
A pea sized dab of RTV in each corner

I've N E V E R had a leak with that method

OK ... I'm done ramblin now

Grady

revhead347 · Nov 22, 2008

Totally agree with what was said above. Only once did I not use the end gaskets, and it leaked that one time. I don't know why people think using a bead of RTV is so much better. However, I don't use the cork ones that come in the 1262 Felpro kit, I always buy a stock replacement gasket kit from Felpro just for the OEM style form fitting rubber end pieces. The whole gasket kit is pretty cheap, and I find that the form fitting gaskets seal much better. A small drop of silicone in each corner does the trick. I use a small 1/4" ratchet to tighten the bolts down (wrist calibration). Never had an issue. My old motor builder taught me that tightening the intake bolts to 24ft.lbs. will actually lift the heads causing head gasket failure.

Kurt

mhespenh · Nov 22, 2008

Thanks for all the great advice, I'll be sure to go easy on the wrench tomorrow. I did use the felpro gasket set with the OEM rubber ends + dab of RTV, so far no leaks

I ended up getting over 80 miles on that last 1/4 tank- a new personal best, and I've been doggin' it pretty hard (enjoying my new power ).

Woot!

2002BLGT · Nov 22, 2008

mhespenh said:
Thanks for all the great advice, I'll be sure to go easy on the wrench tomorrow. I did use the felpro gasket set with the OEM rubber ends + dab of RTV, so far no leaks

I ended up getting over 80 miles on that last 1/4 tank- a new personal best, and I've been doggin' it pretty hard (enjoying my new power ).

Woot!

I am down in Bedford , if you need someone to put the cam and heads on let me know ......

Issues after intake swap (MPG & Stalling)

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