Car Idles Fine, Give It Gas And Wants To Die

Sep 1, 2008
73
0
7
Denver, Co
So my car has been down for the past year after 3rd gear blew apart. Got a new transmission in it now. But all of the sudden, it wants to die if you give it any throttle. Idles perfectly, no codes in computer. All the sensors were replaced when I rebuilt the motor just before the trans went. If you quickly and lightly tap the throttle, it will eventually get up in the rpms. Any ideas? Already checked tps sensor, ect sensor, iat sensor, and for vacuum leaks, all ok.
 
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Onefine88

Previously 89SSC18
10 Year Member
Aug 3, 2006
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Sounds fuel related. Probably bad gas from sitting. The pump could be bad or as simple as a clogged up filter. Sitting for long periods can be tough on the fuel system.
 
Last edited:
Sep 1, 2008
73
0
7
Denver, Co
Thanks for the reply, I would've thought the same but I did pump out the fuel a while back and added 5 gal of new fuel a week ago. The whole fuel system is new as well, rails, injectors, regulator, pump, filter and lines have only about 1500 miles on them.
 

jrichker

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There are 3 steps: do them in order, do all of them, not skip around. If you do you will find and fix your problem.

Step 1.) No code 11 (two flashes when the computer dumps the codes)? A perfectly functioning system will always get a code 11, it is the everything is OK code. The 11 code is computer passed its internal self test.
If you don't get an 11, you have computer or wiring problems.
Please check and repost.

Step 2.) Make sure you have the Neutral Safety Switch connector plugged into the transmission. On a T5 it is a pigtail on the front of the transmission on the driver's side.


3.) You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix. :D

It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 134,000 hits, which indicates it does help fix idle problems quickly and inexpensively.
 
Sep 1, 2008
73
0
7
Denver, Co
Here is all the details of the car. There are 3 codes for the tad/tab, but those have been taken off the car for several years now, and a code 15, which I guess seems be normal since I keep disconnecting the battery. But that's all the codes.

The nss is not on the transmission. When I bought it, it did not come with one. The car doesn't start without it, so I just jumped the 2 weeks in the harness, as I'd the switch was closed.

I'll have to look into that check list, I did spend time looking on the internet for this problem, so thanks for the link.
 

jrichker

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All T5's have an NSS. Yours may be missing or damaged.

What the NSS (Neutral Safety Switch) does:
5 speed transmission: It has no connection with the starter, and the engine can be cranked without it being connected.
Auto transmission: It is the safety interlock that prevents the starter from cranking the engine with the transmission in gear.
What it does for both 5 speed and auto transmission cars:
The computer wants to make sure the A/C is off due to the added load on the engine for the engine running computer diagnostic tests. It also checks to see that the transmission is in Neutral (5 speed and auto transmission) and the clutch depressed (T5, T56, Tremec 3550 & TKO)). This prevents the diagnostics from being run when the car is driven. Key On Engine Running test mode takes the throttle control away from the driver for several tests. This could prove hazardous if the computer was jumpered into test mode and then driven.

Cars with a defective or bypassed NSS may have idle/stall problems.
 
Sep 1, 2008
73
0
7
Denver, Co
The nss just isn't there. And for some reason, mine didn't crank at all before I jumped it. That's when I looked at a schematic. As soon as I jumped it, it cranked and started right away, weird.

"Cars with a defective or bypassed NSS may have idle/stall problems", do you know why?
 

jrichker

StangNet's favorite TOOL
SN Certified Technician
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The nss just isn't there. And for some reason, mine didn't crank at all before I jumped it. That's when I looked at a schematic. As soon as I jumped it, it cranked and started right away, weird.

"Cars with a defective or bypassed NSS may have idle/stall problems", do you know why?
The computer is looking for the proper state of switches closed and open to set its' internal program correctly.

You may have a automatic transmission O2 senor harness. That would account for the no crank condition. See the drawing below and check the part numbers on it against the part number on the O2 sensor harness you currently have.

Diagram courtesy of Tmoss & Stang&2birds

O2 sensor wiring harness
mustangO2Harness.gif


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/ Everyone should bookmark this site.

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

O2 sensor wiring harness
http://www.veryuseful.com/mustang/tech/engine/images/mustangO2Harness.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pin out
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

87-92 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang87-92 PowerWindowWiring.gif

93 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang93PowerWindows.gif

.
 
Sep 1, 2008
73
0
7
Denver, Co
Wanted tip give an update, car is fixed. I started looking into the maf and found all 4 writes have voltage on them. 1 had 13v, and the others had 11.8v. I unplugged the maf sensor and checked the quits again. This time 1 had 13v, 1 had 5.8v, and the other 2 had nothing. So I thought the sensor had to be shorted internally.

I replaced the sensor the next dayand what do you know, still the same, no change. All 4 writes show voltage. So I started digging into the harness.

Come to find out, the guy before me did a maf conversion, and I found the ground wrote he had made that attaches to the body through a bolt next to the ecm had come apart. So I redid the connection, and the car revs happy now. Thanks for everyone's help. Hopefully this might help someone in the future.