90 5.0 Bad Stutter When Downshifting To Pass

Tbart77 · Aug 24, 2016

Hi. Im new here so idk if Im even doing this right. I have a mildly modded 90 5.0 tfs1 cam with explorer intake and gt40p heads. Crane hifire ignition a few bolt ons. Under normal driving you can run the rpms up to over 6000 and no problem. Its only when I downshift and nail on it, It revs and shuts off revs and shuts off if I hold the pedal down. I guess its not really shutting all the way off cause its still running but it sounds like im just revving and stopping when I have the pedal down. Any suggestions otber than pulling codes. Ive tried 3 different ways and nothing. My cel is not on either.

mikestang63 · Aug 25, 2016

you are probably hitting the rev limiter and shutting off the fuel. The factory tach isnt that accurate and can be off a few hundred rpm.

Tbart77 · Aug 25, 2016

That was actually my first thought but I can run it up to higher rpms than it cuts out at and hold it and its fine. Its only when I downshift or try to rev it up a lil and drop the clutch and launch hard. It will pull and cut off, pull and cut off, pull and cut off and if I hold the pedal down is like nothing is happening and im just coasting

jrichker · Aug 25, 2016

Dump codes sticky.
Look at the top of the 5.0 Tech forum where the sticky threads are posted. One of them is how to dump the computer codes. http://www.stangnet.com/mustang-for...codes-from-eec4-in-86-95-5-0-mustangs.889006/ I highly suggest that you read it and follow the instructions to dump the codes.

Tbart77 · Aug 25, 2016

I CANT GET THE CODES ON MY CAR! LIKE I SAID IN MY POST! I HAVE TRIED THE PAPERCLIP WAY AND THE VOLTMETER WAY!!!! NO CODES. NO FLASHES. NO SWEEPS OF THE NEEDLE.

mikestang63 · Aug 25, 2016

Dude, no need to shout at anyone. You'll get more responses that way. Jrichker is one of the most knowledgable members here- take it down a notch. If you can't run the codes check your grounds and your EEC.

Tbart77 · Aug 25, 2016

Omg. Screw this. Ive read soooooooo many of these threads and had so much stupid stuff asked aand said Im wondering if anyone on here actually has a mustang and works on it themselves. Im trying to draw some info from someone who may have had this problem. Im beginning to think all these forums are a waste of my time. I WOULDNT HAVE TO SHOUT IF PEOPLE WOULD READ MY FIRST POST BEFORE SAYING SOMETHING STUPID. I SAID IN MY VERY FIRST POST I CANT PULL CODES!!!!!

mikestang63 · Aug 25, 2016

@madmike1157 @Gearbanger 101 .Can you help this chap out?

CarMichael Angelo · Aug 25, 2016

mikestang63 said:
@madmike1157 @Gearbanger 101 .Can you help this chap out?

I've not been in admin for months now Mike.

mikestang63 · Aug 25, 2016

madmike1157 said:
I've not been in admin for months now Mike.

Damn.. thught I had the big hammer guy

CarMichael Angelo · Aug 25, 2016

mikestang63 said:
Damn.. thught I had the big hammer guy

Noobz is your one stop shop for that service, but I still have a few "privileges" left over from days back.

He considers himself warned.

mikestang63 · Aug 25, 2016

madmike1157 said:
Noobz is your one stop shop for that service, but I still have a few "privileges" left over from days back.

He considers himself warned.

Is that because they saw you with a box on your head,drinking with Dave? Haven't we all done that once or 100 times in our life @Noobz347

General karthief · Aug 25, 2016

wow, I'm new to join in posting but not new to the site. just joined in because of this post and I'm also semi-retired so I have more time on my hands to beat on my '89 GT. That said, tbart77 needs to back it down and find another gear to operate in, I have been come'n here to get incite on a few issues that pop up on by vehicle for years and these guys (and gals if any) are the bomb (if that's the right term) when it comes to advice and tech on the finicky eec4 stuff.
As for my advice, if you cannot get any codes from your computer 'probing' that you likely need a computer replacement/repair. That's thinking you are getting nothing including an 11.
As for a rev limiter, I did not know there was one on this type system, eec4, as I have winged mine to 6500 with no issues. If there is one where does it cut off fun?
Also what is 'bump'? like fist bumping? Sorry, I'm kinda outta wack with modern terminology.

Gearbanger 101 · Aug 25, 2016

Tbart77 said:
Omg. Screw this. Ive read soooooooo many of these threads and had so much stupid stuff asked aand said Im wondering if anyone on here actually has a mustang and works on it themselves. Im trying to draw some info from someone who may have had this problem. Im beginning to think all these forums are a waste of my time. I WOULDNT HAVE TO SHOUT IF PEOPLE WOULD READ MY FIRST POST BEFORE SAYING SOMETHING STUPID. I SAID IN MY VERY FIRST POST I CANT PULL CODES!!!!!

Etiquette isn't your strong suit, is it sparky? If we're all such blundering idiots here, and the FREE technical advice offered to you isn't to your satisfaction, why don't you occupy your valuable time elseware? Better still, why waste your time at all asking questions on a Forum and just hustle your car on down to the nearest garage and pony up the $100+/hr diagnostic rate to have it checked locally?

....or, sit down, shut your mouth, get rid of that chip on your shoulder and pay attention to some of the invaluable advice being offered "FREE OF CHARGE" to you by members here and don't get your panties in a twist when your every whim isn't immediately catered to!

jrichker · Aug 25, 2016

Tbart77 said:
I CANT GET THE CODES ON MY CAR! LIKE I SAID IN MY POST! I HAVE TRIED THE PAPERCLIP WAY AND THE VOLTMETER WAY!!!! NO CODES. NO FLASHES. NO SWEEPS OF THE NEEDLE.

Then you need to turn down the volume and learn something new...

Computer will not go into diagnostic mode on 86-90 model 5.0 Mustangs

Disconnect the battery positive terminal before making any resistance checks.
The voltage drop in the ground cable will cause incorrect resistance readings.

How it is supposed to work:
The black/white wire (pin 46) is signal ground for the computer. It provides a dedicated ground for the EGR, Baro, ACT, ECT, & TPS sensors as well as the ground to put the computer into self test mode. If this ground is bad, none of the sensors mentioned will work properly. That will severely affect the car's performance. You will have hard starting, low power and drivability problems. Since it is a dedicated ground, it passes through the computer on its way to the computer main power ground that terminates at the battery pigtail ground. It should read less than 1.5 ohms when measured from anyplace on the engine harness with the battery pigtail ground as the other reference point for the ohmmeter probe.

What sometimes happens is that the test connector black/white wire gets jumpered to power which either burns up the wiring or burns the trace off the pc board inside the computer. That trace connects pins 46 to pins 40 & 60.

The STI (Self Test Input ) is jumpered to ground to put the computer into test mode. Jumpering it to power can produce unknown results, including damage to the computer. The ohm test simply verifies that there are no breaks in the wiring between the test connector and the computer input.

How to test the wiring :
With the power off, measure the resistance between the computer test ground (black/white wire) on the self test connector and battery ground. You should see less than 1.5 ohms.

If that check fails, remove the passenger side kick panel and disconnect the computer connector. There is a 10 MM bolt that holds it in place. Measure the resistance between the black/white wire and pin 46 on the computer wiring connector: it should be less than 1.5 ohms. More that 1.5 ohms is a wiring problem. If it reads 1.5 ohms or less, then the computer is suspect. On the computer, measure the resistance between pin 46 and pins 40 & 60: it should be less than 1.5 ohms. More that that and the computer’s internal ground has failed, and the computer needs to be repaired or replaced.

See http://www.stangnet.com/mustang-forums/749974-computer-issue.html#post7490537 for Joel5.0’s fix for the computer internal signal ground.

If the first ground check was good, there are other wires to check. Measure the resistance between the STI computer self test connector (red/white wire) and pin 48 on the computer main connector: it should be less than 1.5 ohms. More that 1.5 ohms is a wiring problem

The following is a view from the computer side of the computer wiring connector: it is for an A9L, A9P computer.

Diagram courtesy of Tmoss & Stang&2birds

Check out the diagram and notice all the places the black/white wire goes. Almost every sensor on the engine except the MAF is connected to it.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds
(website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine

See the graphic for the 10 pin connector circuit layout.

90 5.0 Bad Stutter When Downshifting To Pass

Tbart77

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Tbart77

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CarMichael Angelo

my rearend will smell so minty fresh,

mikestang63

CarMichael Angelo

my rearend will smell so minty fresh,

mikestang63

General karthief

wonder how much it would cost to ship you a pair

Gearbanger 101

Straight Outta Locash

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90 5.0 Bad Stutter When Downshifting To Pass

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my rearend will smell so minty fresh,

my rearend will smell so minty fresh,

wonder how much it would cost to ship you a pair

Straight Outta Locash

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