1990 mustang gt running like crap when hot,but good when first start up.

1990GT331

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Nov 17, 2019
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Hi guys/gals, new to this website and needing help. I have a 1990 mustang gt just built a decent 331 stroker: eagle 331 stroker kit, b303 cam, world windsor jr heads, trick flow street heat, 24lb injectors and matching MAF, all new all new jegs brand hiflow water pump, etc etc...... just a little rundown of engine. all new sensors when i reinstalled engine. But the car runs great when cold but starts running like crap when it gets up to operating temperature. timing is perfect, not overheating. I know i had a MSD streetfire distributor and wires. first start up the car would run till it warmed up them shut down, figured out it was a manufacturers defect dist, so got a new one and this one will actually run when hot and not shut off but runs like crap when at operating temperature. Also dies when coming to a stop at redlights. Any ideas what it could be...?
 
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08GT500

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Jul 12, 2018
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Hi, sounds like a nice build.
1) I’d first extract any codes from the EEC, may be there w/o a CEL. (?)
2) Did you get this car tuned once you completed the build?
Sounds like the closed loop sets it off, open loop is mostly the default program, should be a code or codes I’d think.
Still have your old Dizzy? Stab it in & see what occurs.
I’ll reply when you convey the outcome.
Good luck!
-John
 

jrichker

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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. Codes may be present even if the CEL (Check Engine Light) isn’t on. You don’t need a code reader or scanner – all you need is a paper clip, or if your lady friend has a hair pin, that will do the job.
I highly suggest that you read it and follow the instructions to dump the codes. http://www.stangnet.com/mustang-forums/threads/how-to-pull-codes-from-eec4.889006/
 
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1990GT331

Member
Nov 17, 2019
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Arkansas
Hi, sounds like a nice build.
1) I’d first extract any codes from the EEC, may be there w/o a CEL. (?)
2) Did you get this car tuned once you completed the build?
Sounds like the closed loop sets it off, open loop is mostly the default program, should be a code or codes I’d think.
Still have your old Dizzy? Stab it in & see what occurs.
I’ll reply when you convey the outcome.
Good luck!
-John
Thanks so much for the help.
1)That is one this I have not done yet was get codes read yet. I may get that done today.
2) Sad but true not yet. I have dialed everything in such as set throttle position sensor, etc. just not actaully tuned yet.
3)And what does closed loop mean? No i sold it. I may end up trying another dist. and again thanks ofr the help
 

1990GT331

Member
Nov 17, 2019
8
1
13
32
Arkansas
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. Codes may be present even if the CEL (Check Engine Light) isn’t on. You don’t need a code reader or scanner – all you need is a paper clip, or if your lady friend has a hair pin, that will do the job.
I highly suggest that you read it and follow the instructions to dump the codes. http://www.stangnet.com/mustang-forums/threads/how-to-pull-codes-from-eec4.889006/
will do. I really need to check codes. I will post more when i check it out more as i go and hopefully figure stuff out. Thanks for the help for sure.
 
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1990GT331

Member
Nov 17, 2019
8
1
13
32
Arkansas
Hi, sounds like a nice build.
1) I’d first extract any codes from the EEC, may be there w/o a CEL. (?)
2) Did you get this car tuned once you completed the build?
Sounds like the closed loop sets it off, open loop is mostly the default program, should be a code or codes I’d think.
Still have your old Dizzy? Stab it in & see what occurs.
I’ll reply when you convey the outcome.
Good luck!
-John
Also could you explain the open and closed loop a little more? Thanks.
 

08GT500

Active Member
Jul 12, 2018
463
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Massachusetts
Also could you explain the open and closed loop a little more? Thanks.
Hi, I apologize. Certainly!
In a nutshell, when an engine engine is first started it runs in “open loop”, simply meaning the onboard Computer (coined Electric Engine Control ‘EEC’ by Ford) bases fuel and certain engine timing decisions on a default set of pre-programmed values (or tables) and limited engine sensors are utilized.
When the temperature of the engine increases (as measured by the Engine’s Coolant Temperature Sensor) and a certain threshold reached, the EEC begins to operate in “Closed loop”, simply meaning it utilizes all of the available onboard sensor’s input in it’s operation & decision making for proper operation, optimal performance & lower emission levels.
The Oxygen sensors are one example. They are utilized in closed loop operation as input to the EEC which continuously monitors & adaptively corrects (increases/decreases) the amount of fuel delivered by the fuel injectors by electrically modifying Fuel Injector pulses to adhere to a specifically programmed value air/fuel ratio (14.7:1 air to fuel ratio is considered optimal in a Gasoline engine).
Although the EEC and sensors can compensate well for intended purpose/design, when modification(s) are made to the engine, the EEC’s target parameters also must be modified, or poor performance, idle quality, emissions may result. The EEC fights back by throwing trouble codes, and may cease Closed loop operation.
That’s where a custom “tune” needs to be created, in the (Onboard Diagnostics 1) OBD-1 vehicle (95’ & earlier Ford vehicles & most others) that’s a Chip added to the EEC that interrupts the Factory data, and incorporates new programming values (or tables) in which the EEC operates within to compensate for these modifications.
Any further explanation or questions, please don’t hesitate! We’ll be here!
Good luck!
-John
 

1990GT331

Member
Nov 17, 2019
8
1
13
32
Arkansas
Hi, I apologize. Certainly!
In a nutshell, when an engine engine is first started it runs in “open loop”, simply meaning the onboard Computer (coined Electric Engine Control ‘EEC’ by Ford) bases fuel and certain engine timing decisions on a default set of pre-programmed values (or tables) and limited engine sensors are utilized.
When the temperature of the engine increases (as measured by the Engine’s Coolant Temperature Sensor) and a certain threshold reached, the EEC begins to operate in “Closed loop”, simply meaning it utilizes all of the available onboard sensor’s input in it’s operation & decision making for proper operation, optimal performance & lower emission levels.
The Oxygen sensors are one example. They are utilized in closed loop operation as input to the EEC which continuously monitors & adaptively corrects (increases/decreases) the amount of fuel delivered by the fuel injectors by electrically modifying Fuel Injector pulses to adhere to a specifically programmed value air/fuel ratio (14.7:1 air to fuel ratio is considered optimal in a Gasoline engine).
Although the EEC and sensors can compensate well for intended purpose/design, when modification(s) are made to the engine, the EEC’s target parameters also must be modified, or poor performance, idle quality, emissions may result. The EEC fights back by throwing trouble codes, and may cease Closed loop operation.
That’s where a custom “tune” needs to be created, in the (Onboard Diagnostics 1) OBD-1 vehicle (95’ & earlier Ford vehicles & most others) that’s a Chip added to the EEC that interrupts the Factory data, and incorporates new programming values (or tables) in which the EEC operates within to compensate for these modifications.
Any further explanation or questions, please don’t hesitate! We’ll be here!
Good luck!
-John
I guess another question is. Is there a way to check that?
 

1990GT331

Member
Nov 17, 2019
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Arkansas
Found some of my problem. I found number 4 and 3 sparkplug wires melted on headers. got some header wrap and spark plug socks I guess you would call them. Changed wires. Idling a little better. But still kinda erratic but not as bad. Idles up and down and a lot of times idles high. but don't stall on me is a good thing. finally hooked up some gauges to see if i was over heating or something. It runs at a perfect 170-180. And 55-60 psi on Oil pressure. Finally getting somewhere. Do you recommend me getting it tuned?
 

08GT500

Active Member
Jul 12, 2018
463
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Massachusetts
Hi,
Glad to hear that you got that far, see the post up above with the link that JRichker posted, highly useful, just need to jumper the connectors under hood with a paper clip or other small piece of wire. Also sent that in a PM. I’d sent you Tuning options in the PM as well. I’d have posted them here, for some reason it was not allowing... I’ll copy/paste & try again...
-John
 

08GT500

Active Member
Jul 12, 2018
463
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Massachusetts
PM’d you this 2 days ago:

Hi,
Verifying whether your EEC is running in open or closed loop? Tweeter Data-logging would be my choice. Measuring 02 sensor voltage would be the other, indirectly. Should see 0.5-0.7 DC Volts alternating back & forth when the motor is at operating temperature.
You’ve got a strong build in a great year Fox, sure it wasn’t cheap, know you want it running right, suggestions in your best interest are Codes & getting it tuned properly.
From the build details & the issues you’re experiencing, a custom tune will cure it. My concern is if the motor’s not running Rich, it may be running lean.
Pulling a plug & reading it for mixture is a suggestion. A wideband 02 sensor(Air/Fuel mixture) is a highly useful gauge to run, along with Water temp & grab an oil galley for a mechanical Oil Pressure gauge (Stock gauges are not quite adequate for the build). Pillar mount keeps them in view, very slick.
When the motor didn’t run warm with the first distributor, TFI sounds like the culprit. ‘Thin Film Ignition’. Grey, rectangular component mounted left side of Dizzy. The ignition harness plugs into it.
Sometimes they work in cooler Temp’s, fail when warm. Advanced tests for free, tests ok once, retest it & apply a bit of heat to it (bring a heat gun) if you run into that issue again.
Aftermarket ignition components cause issues, often. Not implying they’re all bad, but nothing is as reliable as OE ignition, sensors in Foxes, revert to OE if In doubt.
Retrieving the DTC’s (Diagnostic Trouble Codes) extracted via the link JRichkter posted should be done, that will point out
what’s going on, from the EEC’s viewpoint.
When you have a chance to pull codes, post them. Other helpful information would be posting Bolt-on’s, such as:
1) Running Headers (“long-tubes” or “shorty’s”.)?
Still running Cat’s?
2) Still Running EGR?
3) Any smog hooked up, or removed?
4) Does the EEC have a chip in it from previous mod’s?
5) Running an adjustable fuel pressure regulator? Fuel pressure Gauge on the fuel rail?
Pictures worth 1,000 words, if you want to post 1, or a few, also helpful.

Tuning:.
- Quick, effective, inexpensive way to get a good tune for your Pony, American Muscle, buy a Bama 4 bank eliminator chip, “tunes for life” is free, unlimited amount of tunes as long as it’s yours. Build more, update Tune. Fill in an online form with all the components you’re running. 300$ & you’d have it in 4-5 days.
https://www.americanmuscle.com/sct-4-bank-computer-chip.html
They do a good job, use Lethal Performance, SCT Derive III software in my own shop. It’ll run right, potential it has- you’ll get out of it, the chipset is simple to install to your EEC.
-Then there’s a Dynotune, if there’s one local to you with a strong, positive reputation. it’ll cost significantly more, but another very good option.
-There’s also a great Tuning forum here, on Stangnet. Dedicated specifically for tuning methods using various software/hardware.
Even if you use one of the other methods, you’ll learn about the in’s & out’s of Tuning, other valuable resources.

Good luck!
-John
 

1990GT331

Member
Nov 17, 2019
8
1
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32
Arkansas
Okay so finally got codes pulled(bought my own scannner) codes 21,22,24,31,67,81,82,85,95 are showing up.
 
Last edited:

08GT500

Active Member
Jul 12, 2018
463
52
38
Massachusetts
Hi,
Youextracted the codes,not sure why you didn’t just follow the advice & pull the codes- your own personal choice to buy a scantool. You should also consider the KOER test, and since the Motors been possibly running on the rich side, a cylinder balance test to see how it’s rings are seating.
Did you run the KOEO test with the car in gear? Code 67 below indicates you didn’t run the KOER test. KOER test shows up Codes which KOEO will not.
Here’s a good link for the above including key definitions to common abbreviations:
.

The Air Mgmt codes have to do with the operation of the TAB/TAD solenoids that control the routing of the air supplied by the smog pump to the heads and the exhaust system...if the system was removed, you need to do some hardware changes to "fool" the ECM in thinking it's still connected..same thing w/EGR sensor (EVP).31,81,82,85 DTC’s.

LEGEND FOR ABBREVIATIONS:
O: KOEO codes
CM: Continuous monitor Mode
R: Engine KOER codes

Code(s)......Brief definition(s) listed w/some
| cause & effect (CAPITALS)
|
21 - Engine Coolant Temperature (ECT) Sensor Out Of Self Test Range. 0.3 to 3.7 DC volts(O,R). -SENSOR ITSELF, CONNECTOR OR WIRING-VOLTAGE & GROUND.
22 - Barometric Pressure Sensor Out Of Self Test Range (O,CM,R)- ALTITUDE SENSOR, ‘BAP’ SENSOR OR ASSOC. WIRING, SENSOR (ITSELF) TEST REQUIRES OSCILLOSCOPE OR FREQUENCY COUNTER, ONE EFFECT:IS IDLE FLUCTUATION-“HUNTING”.
24 - Intake Air Temperature/Air Charge Temperature Sensor Out Of Self Test Range. V.REF. 0.3 to 3.7 volts(O,R)-IAT INFLUENCES/MEASURES TEMP. FOR AIR/FUEL MIXTURE-
31 - EGR Valve Position/Pressure Feedback EGR Circuit Below Minimum Voltage. 0.24 DCvolts (O,CM,R) -RUNNING AN EGR?, (NO?HAVE EGR DELETE?). Y? VACUUM SOURCE(CHK..), EGR PLUG VOLTAGE, POSITION SENSOR, EVR.-
67 - Park/Neutral Position Safety Switch Circuit Open; A/C On -Manual (O), Manual Lever Position Sensor Out Of Range/A/C On(CM,O), Clutch Switch Circuit Failure (CM)- A/C SYSTEM ISSUE, CLUTCH PDL SAFETY SWITCH (2) PURPOSE, 1-START 2-CPU.(#2 FAIL), KOER TEST MODE INOP. W/CODE 67, IDLE ISSUES -YOU RUN TEST WHILE IN GEAR(?)-TEST WORK WITHOUT CLUTCH IN?
81* - Secondary Air Diverter Circuit Failure (O)
82* - Secondary Air Bypass Circuit Failure (O) RE:81,82, 85, CHECK VACUUM LINE *ROUTING AND CONDITION COMING OFF THE DIVERTER VALVE ASSEMBLY, EMINATING OFF THE CHARCOAL CANISTER. # 85 IS ALSO ANOTHER CHARCOAL CANISTER SYSTEM ISSUE WHERE FUMES MAY/MAY NOT ESCAPE PER DESIGN, INOP SOLENOIDS, VACUUM LEAK IN ANY OF THIS SYSTEM MAY CAUSE IDLE & OTHER ISSUES, AND IMPORTANTLY; EXCESS POLLUTANTS. TANK LACKING VENT, CAUSING FREQUENT PUMP INTERRUPTION DURING FUEL FILL
85* - CANP Circuit Failure (O)
95 - Fuel Pump Circuit Open-PCM To Motor Ground (CM,O).

Now that you have pulled the codes, as you done the next step is . Please post the following, with some additional info.:
1) Running long tube headers?
2) What SMOG equipment did you remove, precisely, I.E.; Smog Pump, Evaporate. system, Cat’s, etc..
3) A picture or 2 would help immensely, full left, Right side.
4) Have an adjustable fuel pressure regulator? Gauge on the Rail?
It’s obvious that the codes that have been popped will affect Idle, drivability, HP/TQ Numbers, mileage. May also be placing an expensive build in danger.
Some mild builds will run on OE CPU programs, FPR’s & properly Curved distributors, clocked MAF sensors in addition to keeping certain components operational in getting some builds to run decent, but you’re best bet is getting it tuned to get the power, drivability, while protecting your investment. Contrary to beliefs running Cat’s have very little effect on performance.

Your next step is to record, jot down (Or copy/paste/print) out these codes, and dump them.
Start, warm up the car and take it for a 20 minute drive & the codes that reappear will be the focal point. Some will reappear, some won’t & then will we know the codes that are actually affecting things.presently.
Do the KOER, KOEO, Balance testing.

Take for instance, code 95. This indicates at one time the CPU attempted.to energize the fuel pump & it didn’t correctly respond, or was INTERMITTENT.
Simply stated, this may have been a product of active troubleshooting & is NOT INDICATIVE of a valid issue unless you have a repeat as active troubleshooting may have either CAUSED it’s occurrence, or CURED it.
Ok, Good Luck!
-John