WOT bogs down, running very rich... any help?

93GtMustang50 · Oct 26, 2009

Okay, so my 5.0 has been running very very well since I got it running again. Just some background: All she really needed was a very good tune up (cap, wires, plugs, rotor, cleaned throttle body, new IACV, new TPS, oil/fuel filter, oil change, radiator flush, new pcv valve and screen, checked timing, seafoamed the engine). It sat for about 3 years prior to my purchase so I had my doubts. But since, I've got it running very very nicely, until today. I've put about 2000 miles on it since i got it running so it ran very well for a decent amount of time. Heres what happened:

On my way home today, I opened it up to WOT and it bogged down and backfired and didnt really go anywhere. It also smelled of unburnt fuel. Then when I got to my driveway, I put it in reverse and it stalled out (my 5.0 is an AOD) then attempted to start it twice and it would not start. On the second attempt I listened and it seemed as though it was priming, but very faintly and weakly. I let it sit for about 30 seconds and then tried again and it primed properly and started right up. What do you guys suggest it could be?

JC

jrichker · Oct 26, 2009

Dumping The computer diagnostic codes on 86-95 Mustangs

Revised 19-May-2009 to update drawing for dumping the codes on 86-88 Mustangs with no check engine light.

Dump the codes and see what the computer says is wrong…Codes may be present in the computer even if the Check Engine light isn’t on.

Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.

Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

See Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical

If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see Digital Ford Code Reader (3145) – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

93GtMustang50 · Nov 27, 2009

This is a problem which comes and goes, Ive checked for any codes both when the problem is present and when the car runs fine (KOEO and KOER), and both times no codes are being thrown (except code 11), also I ran a cylinder breakdown test and all cylinders and injectors are functioning normal. Anyone have any suggestions at all?

liljoe07 · Nov 27, 2009

Nothing in the memory codes either?

seedeezy · Nov 28, 2009

I would take the hood off, put a fuel gauge in the test port and zip tie it up so i could see it work while i was driving. Then get back out to the highway and see what fuel pressure is doing on wide open. The noteable change you mentioned when you hit the key on key off and the music comming from the pump was faint twice and then heard, and then it started seems to indicate the pump is at fault. I would like to see what it shows on the pressure gauge under load.

93GtMustang50 · Nov 29, 2009

liljoe07 said:
Nothing in the memory codes either?

nope nothing in the memory codes either....seedeezy: ill give it a shot and see what I come up with but the problem is that this is sporatic, the problem comes and goes at its own will.

93GtMustang50 · Dec 1, 2009

okay, so new symptom. as it was driving it home tonight, i once again got on it at WOT and instead of backfiring and smelling like it was running rich, it just didnt pull nearly as hard as it should have. between 4000-5800 it just seemed very sluggish like I was pulling an extra load. dont know if this helps, my guess is the fuel pump may be on its way out...

Lawbreaker5.0 · Dec 1, 2009

93GtMustang50 said:
okay, so new symptom. as it was driving it home tonight, i once again got on it at WOT and instead of backfiring and smelling like it was running rich, it just didnt pull nearly as hard as it should have. between 4000-5800 it just seemed very sluggish like I was pulling an extra load. dont know if this helps, my guess is the fuel pump may be on its way out...

+1...

93GtMustang50 · Dec 2, 2009

new symptom: at WOT the engine will not rev above 3500rpms where as at partial throttle it will. I re-ran the KOEO and KOER tests and I am still not showing any codes. I calculated my mpg's from before this issue arose to now and its about a 6 mpg decrease. I dropped from about 18 in the city to about 12. I think it might be a bad TFI module now. The problem isnt as bad as when the engine temperature is low, but when its warmed up its very prominent, always. I wish to banish this demon from my car so anything please....

93GtMustang50 · Dec 2, 2009

okay, so i replaced the fuel filter today and what do you know, the car runs better. This fuel filter had about 1000 miles on it and it was horribly clogged. So now she runs better but its throwing some codes, KOEO memory code 95 and KOER code 12. The code 12 is for Idle Speed Control motor or Air Bypass not controlling idle properly (generally idle too low) - ISC and the code 95 is for Fuel pump: open, bad ground or always on - Power / Fuel Pump Circuits. Any suggestion on how to remedy these codes?

95 5.0 'Stang · Feb 4, 2010

93 I've got a 95 5.0 and was having the exact same problems. Replaced fuel filter after reading your post and it runs great now. Thanks for the helpeven when you weren't trying

WOT bogs down, running very rich... any help?

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