Running rich, loss of power, idle bounces

[fatboy0186]

I have a '91 XLT with 112,000 miles on it, 12,000 on the new engine. I decided to sell the truck to get something better on gas while in college, and then it started running like crap.

First, the fuel system has a low groan and grunt, as opposed to the whine it used to have on ignition.

It starts very rough when cold, the rpms only get up to 1000. When I touch the gas to up the RPM's, it stumbles.

When it warms up, the idle usually drops to around 400-500 and jumps right up to 900 and then back down. Sometimes it idles just fine, but usually bounces all over. It runs very rich, as the exhaust smells terrible.

When driving, it seems to have a loss of power. If I try to accelerate quickly or heavily, the engine stumbles around 2500 rpms. And when I go to shift, it kicks and stumbles.

I get a check engine light intermittently, but there is no noticible change while driving to trigger the light.

I took it in to get the computer checked for codes (not knowing I could do this myself) and they said TPS. Fixed that and still runs just as bad.

Checked the codes myself today and here is what I get:

KOEO of 67 and KOEC of 41. Not sure about the 67 (Clutch switch or circuit failure), but I figure I got the 41 because the engine is running very rich. I cleaned the MAS, IAC, and ATC and not much help. The manifold and sensors were covered in oil and gunk, and this bothers me because I just had the thing rebuilt a year ago. It used to ping like crazy after I had it rebuilt, so I've been running 93 octane to keep it down. I don't know if all of these things are related, but I'm putting them out there so hopefully someone can help.

Thanks for any input,
John

 

[MrShorty]

67 is almost always operator error during the KOEO test. Computer expects transmission to be in neutral. If the test is performed with the transmission in gear, you get a 67. If the test was performed with the transmission in neutral, then you need to check the neutral position switch.
Any KOER codes? How does the fuel pressure look? Any gas in the vacuum line to the fuel pressure regulator (gas = bad FPR)?

 

[fatboy0186]

Went out and checked my codes.

KOEO is fine, put trans. in neutral.

KEOC is still 41.

KEOR had a 21, 42, and 73. 21 is coolant temp. out of specified range, 42 is Oxygen sensor detects rich condition, and 73 is throttle position sensor/circuit. I just replaced that sensor with a Napa/Echlin part. Do I need to get one from Ford that is calibrated to my motor? I haven't been driving it, but it is still very choppy and runs terrible on startup.

 

[fatboy0186]

I pulled the fuel pressure regulator vacuum line off and couldn't really smell gas, but this was at the end that connects to the manifold. The port where a bunch of vacuum lines meet at the manifold was full of oil (like the rest of my manifold), so I started the engine, pulled off the fuel reg. line and sprayed some carb cleaner in there. I noticed that the idle jumped up when I disconnected the press. reg. line. Not sure if this means anything though. Im just trying to get this thing fixed.

 

[karl_burns]

SeaFoam

I think I've suggested this to almost everyone with engine hesitation / idle problems, but man it worked for me. $10. Ten minutes, and my truck drives like a dream now. Search on this forum for iot and you'll see tons of reviews for this product.
Got Aldive over the 30 mpg mark too! (along with a few other mods and maintenance)
Karl

 

[MrShorty]

Probably wasted your money on that TPS. KOER code 73 is almost always operator error during the KOER test. Near the end of the test, just before the codes are output, you get a pulse that is your cue to perform the dynamic response test (aka "goose" test). At this point you briefly (but strongly) "goose" the throttle. If the computer doesn't see enough change in the TPS output for the goose test, it sets this code.
KEOR 21 is also frequently operator error during the KOER test. Computer expects test to be performed on a fully warmed up engine. If the engine wasn't fully warmed up, then a code 21 can be set.
KOER O2 sensor codes can sometimes be set by performing the test on a cold engine as well, though it would usually be a 41 (lean). I suspect that KOER 42 is a key to your rough running.
Trouble with O2 sensor codes: they can be the hardest to diagnose. I would start with some basic checks:
1) Repeat KOER test and confirm the presence/resolution of code(s).
2) Inspect wiring. In particular: O2 sensor wires, PCM ground.
3) Check fuel pressure with a gauge. High fuel pressure can also cause a rich condition.
4) Clean MAF, Check MAF wiring.
That should get you started. Good luck, and let us know how we can futher help.

 

[fatboy0186]

Ok, retested codes, 41 KEOC and for KEOR is only 42 this time. Cleaned MAS and checked O2 sensor wires. Im going to change the fuel filter tomorrow, its got 112,000 miles on it, and pick up a guage to test pressure. I have a regulator off an old manifold I have sitting around, but I don't know how to test if it is good or not. Thanks for all of the input, I'm learning a lot about how to fix this thing myself. I wish I had known about the self test instead proir to spending $90 for some mechanic to do it.

 

[fatboy0186]

After searching some sites about explorers, I am fairly certain my problem is my fuel pressure regulator. I am going to replace it tomorrow along with a new filter. Hopefully this will solve my problems. But I noticed another problem today. On the gound by my tailpipe where I park at my house, I noticed a few good size patches of what I assume to be oil splatter on the gravel. Its a bunch of little black dots, pointing directly from the tailpipe. It doesn't smoke on startup or when the throttle is opened, but I wondering what this is caused by. Thanks again for all the help,

John

 

[fatboy0186]

Well, got a new fuel filter and the Napa tool to remove the lines. Tool didn't quite fit, so I couldn't the lines off, even after an hour of struggling. Tried to replace the pressure regulator, but mine is a 90tf, and the replacement is a 91TF. Has a different return line type. Not sure how to get the stock line off, as there is no bolt, only some rubber piece (I did remove the snap clip). This type is not detailed in my manual, only the spring type. Any help here?

 

[liqhx2]

black splatter

The Black splatter you see is carbon from your X running rich your should see my drive way i need to find out why mine is running rich

 

[hawgx2]

did you ever find out what your running rich problem was. I have the same problem

 

[fatboy0186]

It was the fuel pressure regulator. I'm in the process of fixing it now, but my fuel return line broke, so I need to fix that now.

 

[dirksurf]

fatboy,
my 91 x with 198,000 miles is doing the same thing. I have replaced the iac, tps, o2,
and still nothing. let me know if replacing that fuel pressure regulator really works.

 

[liqhx2]

dirk it is real easy to test your FPR all you have to do is take the vacum line off the FPR and if gas is pushing out of where the vacum is supposed to be then you have a bad FPR

 

[fatboy0186]

With mine, the FPR would not leak gas out of that vac. line until it was warmed up. If your engine is running really rich, let it warm up, then pull off that line, either at the regulator, or at the manifold, and if it smells like gas then your regulator is bad. My truck runs perfect now. Hope this helps.