1990 Mustang Breaking Up No Power Any Ideas?

Kabuki_notch · Jul 6, 2015

I posted this over at corral, but everything I tried was unsuccessful,

so this spring when I pulled my mustang out everything was fine, then one day driving it to work it had zero power when I hit the gas the car just felt weak, so I replaced the Fuel filter, Checked and set the TPS voltage and reset the base idle then the car ran great for about a week. Then my AOD TV cable bushing broke (that's a seperate issue) I replaced that drove the car a bit then it went back to the way it was before I replaced the fuel filter. I installed new plugs, wires cap and rotor a couple days ago, and I cleaned the MAF,. I took the car around the block it smells like it's running a bit rich and it felt like it did before no power, trouble shifting bogged down, constantly breaking up I barely made it back to my house.

I just pulled the codes, KOEO

31 - EGR Valve Position/Pressure Feedback EGR Circuit Below Minimum Voltage
67 - Park Neutral Position Switch Circuit Open
81 - Secondary Air Diverter Circuit Failure (O)
82 - Secondary Air Bypass Circuit Failure (O)
84 - EGR Vacuum Regulator (EVR) Control Circuit Failure (O)
85 - CANP Circuit Failure (O)

Before I continue to throw more parts at this thing any ideas? My EGR is deleted and my smog system is not hooked up. I read online somewhere that it could be the o2 sensors? or maybe the fuel pump?

nothing special stock 5.0 it's run great for the last 3 years.

Thanks in advance

Rastamonchant · Jul 6, 2015

I'm not sure if the problem arose before or after the smog pump and egr were disconnected but doing both of these things will make the 5.0 run like crap. Been there done that and got the headache. If your gonna stay EFI don't remove emissions, you'll save yourself so much time and headache.

jrichker · Jul 6, 2015

Defective O2 sensors usually set code 41/91

Does this problem occur only on a warm engine or both cold and warm?

Check fuel pressure:
The local auto parts store may rent or loan a fuel pressure test gauge if you don't have one.
Disconnect the vacuum line from the fuel pressure regulator. Check it for evidence of fuel present in the line by removing it and blowing air through it. If you find fuel, the fuel pressure regulator has failed. Reinstall the line; leave the fuel pressure regulator end of the vacuum line disconnected. Then cap or plug the open end of the vacuum line and stow it out of the way.
Connect the fuel pressure test gauge to the Schrader port located just behind the alternator.
Turn the ignition switch on & start the engine. Observe the pressure: you should see 38-41 PSI at idle.
Turn the ignition off; reconnect the vacuum line to the fuel pressure regulator. Then disconnect the fuel pressure test gauge. Watch out for squirting gas when you do this.

Fuel pump pressure test
Disconnect the larger of the two fuel lines up by the Schrader valve. It is the return line and does not have the Schrader valve on it. Find a piece of rubber fuel hose and clamp it on the return line coming from the regulator. Stick a bolt in the other end of the hose and make sure that all your connections are tight and leak proof as possible. When this powers up, you don't want fuel squirting everywhere. Hook up the fuel pressure test gauge. Turn the ignition switch on and watch for leaks. You may want to use a helper inside the car to cut the switch off quickly if you have a leak. To trick the fuel pump into running, find the ECC test connector and jump the connector in the Upper RH corner to ground.

Caution!!! You have blocked the return line for the fuel pump! Pressure will rise very quickly past safe levels with a good pump
If the pressure goes up past 55 PSI, the pump is good and the fuel pressure regulator is bad. If the fuel pressure does not hit 55 PSI or more in a few seconds, the pump is bad or you have electrical problems.

Kabuki_notch · Jul 6, 2015

Thanks for the response, this happens when the cars both cold and warm, I'm seeing 38#s I have an inline regulator the fuel pressure regulator doesn't show any evidence of fuel just a slight odor, I'll check the pump pressure next, I had friend mention it could be the ignition control module thoughts on that?

Kabuki_notch · Jul 6, 2015

Also I did notice this all after filling up the tank you think possibly a whole tank if bad gas?

jrichker · Jul 6, 2015

Kabuki_notch said:
Thanks for the response, this happens when the cars both cold and warm, I'm seeing 38#s I have an inline regulator the fuel pressure regulator doesn't show any evidence of fuel just a slight odor, I'll check the pump pressure next, I had friend mention it could be the ignition control module thoughts on that?

The TFI ignition control module usually shows up as a high speed miss on a warm engine. The PIP sensor inside the distributor going bad has the same symptoms as a TFI problem.

89oem · Jul 7, 2015

Kabuki_notch said:
Also I did notice this all after filling up the tank you think possibly a whole tank if bad gas?

It ran fine after replacing filter? Then slowly started acting up?

Could be, is there water in the tank from sitting over the winter? Did you happen to check the old filter for contaminates? I believe you can have pressure and not volume if a clog is happening. What do the plugs show is it lean?

Kabuki_notch · Jul 7, 2015

89oem said:
It ran fine after replacing filter? Then slowly started acting up?

Could be, is there water in the tank from sitting over the winter? Did you happen to check the old filter for contaminates? I believe you can have pressure and not volume if a clog is happening. What do the plugs show is it lean?

Thanks for the reply, yes I first noticed the issue about a month after I took out of storage, I replaced the fuel filter, unfortunately I didn't check it for contaminates. then it was good for about a week, made a trip to the gas station filled it full then i noticed it slowly coming back to where I am today, the car idles fine, runs fine but as soon as I give it gas it just chokes out sputters and wants to die. I havent pulled the plugs since replacing them last week

Kabuki_notch · Jul 12, 2015

Update on this, I unplugged the mass air meter and the car runs great no hesitation, I've already tried cleaning it, just be bad

jrichker · Jul 12, 2015

Disconnecting the MAF puts the computer into Limp Mode. Limp Mode computer operation disregards sensor input, disables the emissions controls and runs on a set of fixed parameters in the computer. This Limp Mode operation results in the engine using a "safe set of engine parameters" so that you don't damage anything. However, it also results in reduced power and economy.

If you have the stock 19 lb. orange or tan injectors and no custom dyno tune, a 94-95 Mustang MAF is a good replacement for an 89-93 5.0 Mustang MAF.

94-95 Mustang GT MAF - $40-$100. It is 70 MM instead of the stock 55 MM on regular stangs built prior to 94. It uses a slip on duct on the side that goes to the throttle body and a 4 bolt flange on the other. You need a flange adapter to fit the stock slip on air ducting that goes to the air box. Wiring plugs right in with no changes.
*1.) Metal flange adapter Ford MAF Adapters - Air Filters - Kurtz Kustomz Motorsports, Inc. KKM Buy the TR70 for $40. Or spend some time on eBay looking for one that may fit.

*2.) MAF & sensor interchange
The 94-95 Mustang 5.0 MAF & sensor is also found on:
1995-94 Mustang 3.8L F2VF-12B579-A2A,
1994-92 Crown Victoria 4.6L F2VF-12B579-A2A,
1995-94 Mustang, Mustang Cobra 5.0L F2VF-12B579-A2A,
1994-92 Town Car 4.6L F2VF-12B579-A2A,
1994-92 Grand Marquis 4.6L F2VF-12B579-A2A,
Evidently the –A1A, -A2A, AA, etc. on the end of the part number is a minor variant that did not change the operating specs. You should be able to ignore it and have everything work good.

Kabuki_notch · Jul 16, 2015

**update...so I purchased a new mass air sensor, car started right up idles great drove it about 8 miles to my parents house no skips, right before I got there it skipped once mildly, about an hour went by, got in the car to head home broke up bad I'm not sure how I even made it home the car was skipping whole motor felt like it was shaking, I managed to get it home barely, any other ideas feel pretty defeated car just doesn't want to run right I'm about to ship this thing

jrichker · Jul 17, 2015

For you remember that I previously asked you if the problem occurred on only a warm engine or on a warm and cold engine?
From your last post, It seems to be most prevalent once the engine is warm. Is this the case or am I jumping to conclusions?

Kabuki_notch · Jul 17, 2015

It's happened both on warm/cold engine yesterday it was when the car was warm driven for about 15mins or so. then it sat an hour and it was horrible driving it home. but on previous occasions like after I replaced the distributor, cap/rotor and plugs it was instant just from backing out of the driveway I felt it but not shaking as violently then yesterday. would that be the TFI Module if it happens when warm? I really feel like it's not a fuel pump issue unless the pump is getting warm and failing?

Boosted Saint · Jul 17, 2015

Look into tfi module symptoms when it goes bad.

jrichker · Jul 17, 2015

You did replace the distributor?

Kabuki_notch · Jul 17, 2015

I did not, just the cap/rotor plugs and wires that was an error in my last post

jrichker · Jul 17, 2015

jrichker said:
You did replace the distributor?

Do any other things quit working or work oddly then the engine act up? Things like the turn signals, A/C blower, radio? If so, check the ignition switch for signs of over heating or damage

No problems found there, then you probably have either a TFI or PIP sensor or ignition coil problem. The ignition coil is less than $20 and easy to change, so try it first.

Kabuki_notch · Sep 14, 2015

**Update** think I fixed the issue, 3rd injector on pass side was bad, replaced it and haven't had an issue since

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