EFI problem/ stuttering stalling

**bigmuddy** · 06/25/07, 04:29 PM

Well my stuttering stalling problem has reared it's ugly head again. Couple of weeks ago, I would be driving the bronco when it would decide to stutter like it wasn't getting enough spark or gas? I figure it was the TFI and swapped it out for a used TFI I had and it has worked fine with maybe a minor stutter every once in a while (hardly perceptable) anyway, last night it decides it's really going to start acting up and so I bought a new TFI and installed it and hell it stutters right out of the driveway

Kinda interesting is that it never dies and if you leave it in second (manual tranny) and keep the revs up it wants to do it quite a bit and as soon as you shift into third it quits but starts up again when the RPMs start going up. I have a fuel pressure gauge and it reads normal 32psi when idling and if you blip the throttle it will jump up to 39-40psi. If I slowly rev the motor up the gauge stays down around 32psi which doesn't seem right?

I am kinda thinking that it's an electrical issue like maybe the Hall effect sensor in the dizzy? also is there a possibility that maybe the Accel E-coil is blowing up the TFI?

Heres the skinny on my rig:

newer 88 5.0HO MAF motor with explorer upper and lower
mustang fuel rail with stock mustang fuel regulator
stock mustang MAF
explorer 65mm TB
recently cleaned stock mustang injectors
explorer serpentine system with 4G alt
BCB intank EFI pump and tank
Ryans EFI harness
The dizzy has around 12K on it with a new (elcheapo) TFI
Accel E-coil

any and all suggestion appreciated.

Ben

**bigmuddy** · 06/25/07, 05:16 PM

By the way, I am sans all smog crap and I pulled codes without anything strange coming up.

Ben

**bigmuddy** · 06/26/07, 09:41 AM

Hellooooooooo! Can I get a little help here please.............

Ben

**justinoshea** · 06/26/07, 11:28 AM

Quote:

I have a fuel pressure gauge and it reads normal 32psi when idling and if you blip the throttle it will jump up to 39-40psi. If I slowly rev the motor up the gauge stays down around 32psi which doesn't seem right?

Yes, that is normal. fuel pressure is regulated by vacuum. opening the throttle quickly will drop vacuum to 0psi (max fuel pressure), slowly will hold enough vacuum to keep pressure at 32psi.

Have you checked all 8 spark plugs? What is the timing set to with the SPOUT removed? Is the MAF clean and have reasonable output voltage at idle and a few thousand RPM?

Good luck

AZMike · 06/26/07, 12:32 PM

Have you been able to get a fuel pressure reading while it's sputtering? It could be fuel related. Other things I'd check:
- MAF
- TPS
- Ignition system
- Vacuum hoses

Mine ran like crap for a while and it was just a dirty MAF. Some electrical cleaner fixed it right up.

Ryan · 06/26/07, 10:04 PM

The Hall Effect sensor should always be replaced with the TFI.
They are kissing cousins, when one gets sick, both are infected.

The original TFI problem that Ford lost a law suite over was technically caused buy the Hall Effect sensor. An intermittent connection problem inside the distributor where the TFI plugs into the Hall Effect sensor.

**bigmuddy** · 06/26/07, 11:07 PM

Guys I am not at home but will check them when I get back home from Fargo on Thursday. Anybody know what the cost of a hall effect sensor is?

Thanks Ben

**bigmuddy** · 06/26/07, 11:15 PM

I got to thinking, the problem may have gotten worse since moving the air filter up by shortening the MAF tube. Anybody see any problem with the placement of the filter and length of the MAF tube?

Ben

byson1 · 06/27/07, 06:11 AM

Big Muddy I am no expert on this but I am reading C Probst Fuel Injection book right now as a reference for future installation of an EFI motor. This is in reference to the MAF sensor.
"The air flowing through the Ford bypass (inside the MAF sensor), past the measuring wires must be closely proportional to the total intake air, othersise the measurements will be false, distorting the air-fuel mixture. In the design of the sensor and its ducting, Ford considers the delivery of the air into the sensor to be even-flow. If you plan any rework of the sensor mounting or is duct work, consider the importance of the even flow of intake air"
You have a prety short bending intake so it may be affecting the airflow. Just an idea. Good luck.

**bigmuddy** · 06/27/07, 07:39 AM

I need to go back and read the Probst book myself but yeah that is why I posted the picture. The only reason I am thinking that it may not be the short tube is that it ran fine for several days with the short tube and then bam really starts acting bad. I will check it out eventually though.

Thanks Ben

pblackb592 · 06/27/07, 10:04 AM

I dont know what the problem is, but it looks like that filter in that location would be getting alot of header heat. Not that that would cause a driveability issue

**justinoshea** · 06/27/07, 10:31 AM

You may want to put a piece of straight pipe in between the filter and the MAF anyway. This will smooth out the turbulence (and electrical noise) caused by the filter before it reaches the MAF. you real problem is probally elsewere.

AZMike · 06/27/07, 12:14 PM

Quote:

Originally Posted by bigmuddy

I got to thinking, the problem may have gotten worse since moving the air filter up by shortening the MAF tube. Anybody see any problem with the placement of the filter and length of the MAF tube?

Ben

I've heard that you don't want turbulent air going thru the MAF. That could be contributing to the cause. Stick the tube back in and see if it gets any better.

**bigmuddy** · 06/27/07, 04:09 PM

Going to have to build or buy a tube to do that as I cut down the old meter tube and hook it up the way it is now. I beleive I am going to try and clean the MAF and then a new hall effect sensor and it that doesn't work I will try a new meter tube but like I said it ran fine after going to the short tube. I really like it like that as it saves a ton of room and is really easy to remove but I do have some concern about header heat but my fender wells are cutout. My real concern is the new explorer fan as it throws ten times the amount of air to the back of the engine compartment as the old flex fan did and I am thinking maybe there is turbulent air being blown through the K/N filter?

Anybody got a source for building new tubes?

thanks Ben

**justinoshea** · 06/27/07, 06:09 PM

3" ABS pipe, Home depot or Lowes

I got fancy and sanded & painted the pipes and elbows. finished it off with SS hose repair clamps. cheap, easy, money left over for beer. I run a 76mm (2.99") MAF, so it works out well.

Yes, the fan wash will screw up the idle, but should be ok under load/at speed.