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Unread 01-08-2012, 09:16 PM   #46
leftlanetruckin
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and all this can be checked in minutes with a decent code reader that can read live data.
The temperature can be seen, as well as open and closed loop status, the o2 sensor readings, and so on. The temperature sensor was the first $$ that could have gone to a decent reader that you would have had the rest of your life....
They aren't just for reading codes any more. With the advent of OBDII and cheaper electronics, a decent code reader is too cheap to not have IMHO.
Just sayin', after reading 2 or 3 pages of stuff that could have been checked in @3 minutes with a reader.
Flogging a dead horse I know, but sometimes it's cheaper to read the data than swap parts, it's certainly faster.

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Unread 01-09-2012, 04:35 AM   #47
oldtime_ironman
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Normally I would agree, except the YJ's are all OBD1. Most of them don't even have a diag connector. At this point all I can think is MAP sensor since that and TPS are the things that control fuel during open loop.
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Unread 01-09-2012, 05:51 AM   #48
Que89YJ
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Humor me here for a minute. You are reading rich in the exhaust not lean which means you are getting too much fuel into the system. The problem is fuel related because the sensor is reading correctly. Get yourself a fuel guage and read the fuel pressure. You might have a bad regulator, pinched fuel line, or a bad injector. Fuel pressure test is my .02
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Unread 01-09-2012, 06:18 AM   #49
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Quote:
Originally Posted by Bad_Dog View Post
I replaced my O2 sensor a couple of weeks ago. At the time, it was throwing code 21 (Oxygen Sensor Circuit) and 51 (Oxygen Sensor, Lean condition). Before I changed it, I cleared the codes a few times and would alternate between 51 (lean) and 52 (rich), but always got 21.

Replaced the O2 sensor and now I'm getting 52, running rich. I've cleared the code twice and still it only gives me 12, 52, and 55.

Back story... Before all of this, the Jeep was running fine. I started to replace the O2 sensor as a precautionary tune-up in November, because I've had the Jeep for six years and never replaced it and wasn't sure if/when it was last changed by the PO's. It was seized and I couldn't get it out, even after a LOT of PB blaster and elbow grease. After all of that, and disconnecting it a few times, it eventually led to error codes 21 and 51, which I figured is from the overuse of PB blaster that eventually put the nail in the coffin for the sensor. Ended up taking it to a shop and had them remove it and install the new sensor that I had already bought.

Is there something I should check with the O2 sensor to ensure it's working? Put a meter on it? Is there something else I should check? I'm at a loss.
Quote:
Originally Posted by Bad_Dog View Post
It does start. After I reset the codes, the first start-up, it's fine (I'm in NY and it's been very cold the last few mornings). After the first or second startup, it would run like it's hesitating. A lot of smelly exhaust. But after it warms up, it seems to idle fine. If I start it up and try to step on the accelerator before it warms up, it sounds like it's wanting to stall - I'm guessing that it's getting way too much gas and choking.
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Originally Posted by Que89YJ View Post
Humor me here for a minute. You are reading rich in the exhaust not lean which means you are getting too much fuel into the system. The problem is fuel related because the sensor is reading correctly. Get yourself a fuel guage and read the fuel pressure. You might have a bad regulator, pinched fuel line, or a bad injector. Fuel pressure test is my .02
Hi Que89YJ!
The OP says that he was running fine but getting a few codes before his attempt to remove the O2 sensor. He could not get the O2 sensor out so he had a local mechanic replace it for him.

Why does he get one good cold start up after dumping the learned memory?

Would high fuel pressure cause this run rich condition? Would a pinched return fuel line do so?

What makes me think that either the brain is sending too much fuel to this engine for the air it is getting.

Could it be retarded timing? Bad IAC?

What I get stuck on is why does he get one good cold start after dumping the memory?
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Unread 01-09-2012, 06:26 AM   #50
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Once a code is set it is going into a default calibration so clearing the memory with a battery reset a getting a good start makes sense. The code is telling you that you are getting too much fuel, the question is if you are. Check the rail pressure and the bleed down for a bad injector.
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Unread 01-09-2012, 06:28 AM   #51
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Quote:
Originally Posted by Que89YJ View Post
Once a code is set it is going into a default calibration so clearing the memory with a battery reset a getting a good start makes sense. The code is telling you that you are getting too much fuel, the question is if you are. Check the rail pressure and the bleed down for a bad injector.
Hi Que, I was hoping you would come along here. The thing that mystifies me is that his plugs in the pic on page 2, do not look like a rich engine at all - its totally contrary. But yes, fuel pressure test does make sense.
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Unread 01-09-2012, 06:33 AM   #52
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Quote:
Originally Posted by Que89YJ View Post
Once a code is set it is going into a default calibration so clearing the memory with a battery reset a getting a good start makes sense. The code is telling you that you are getting too much fuel, the question is if you are. Check the rail pressure and the bleed down for a bad injector.
He pulled some of his plugs and they were clean. He does have rich exhaust smells. How could that be?

Running rich usually fouls the plugs. Maybe he should pull all of his plugs to see if he has one or two cylinders that are not firing.

Why does this happen after one, cold start, memory dumped cycle?

That would rule out a bad rotor or a bad distributor cap or bad plug wires I would think.
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Unread 01-09-2012, 07:44 AM   #53
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He isn't running it long enough to foul the plugs. You might be right but If you have spark and you are blowing a rich fault then the next logical step is pressure.
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Unread 01-09-2012, 10:41 AM   #54
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Originally Posted by Que89YJ View Post
He isn't running it long enough to foul the plugs. You might be right but If you have spark and you are blowing a rich fault then the next logical step is pressure.
I like your logic which is based on knowledge! That is unbeatable.

So, if his pressure if too high because of a faulty fuel modulator that could be the problem?

I thought it would run OK, and then the excess fuel would return back to the fuel tank.
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Unread 01-09-2012, 11:09 AM   #55
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Nope, the pump is putting out 70psi and if the return line or the pressure regulator are bad the rail and the injectors will see all 70 psi and it will dump too much fuel.
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Unread 01-09-2012, 11:16 AM   #56
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Nope, the pump is putting out 70psi and if the return line or the pressure regulator are bad the rail and the injectors will see all 70 psi and it will dump too much fuel.
That would not be good. Thanks for the clarification.
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Unread 01-09-2012, 12:10 PM   #57
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Quote:
Originally Posted by Que89YJ View Post
Humor me here for a minute. You are reading rich in the exhaust not lean which means you are getting too much fuel into the system. The problem is fuel related because the sensor is reading correctly. Get yourself a fuel guage and read the fuel pressure. You might have a bad regulator, pinched fuel line, or a bad injector. Fuel pressure test is my .02
Ok, full disclosure...

At the original time that I first attempted to remove my O2 sensor (and failed, which is why I took it to a garage because I couldn't get it out), I also replaced my fuel filter and the fuel hose coupling that attaches the filter to the steel fuel lines. It was slowly leaking fuel and had an awful fuel smell after you got out. I found that the rubber fuel hoses (about two inches worth, on either side of the filter), were deteriorating. I bought a piece of fuel hose, cut it to size and installed it. Ran it and confirmed that there were no leaks. The original fuel hose/coupling that came from the tank to the fuel filter-in, was L shaped. Since I couldn't get a replacement "L" shaped hose, I just took straight hose and gave it enough slack so that it wouldn't be crimped.

Again, what originally prompted me to replace the O2 sensor was because I would get intermittent 51 (lean) readings. I'd reset the computer and drive for a few weeks with no problems and then it'd come back again, sometimes with the code for O2 sensor (21 or 22? I forget). Figuring that the O2 sensor was going out, that's what prompted me to replace it. Since I had to crawl under it to fix the gas leak, I tackled both at the same time... It would alternate between 51 and 52, but often got the code for O2 sensor. Again, I was thinking that this was all related to the failing O2 sensor.

Fuel filter was replaced and then a couple of months later, I replaced the O2 sensor. .....and we're back.

How do I test the fuel pressure? And how would a crimped fuel line generate too much pressure? Wouldn't it be the opposite?
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Unread 01-09-2012, 12:39 PM   #58
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To test fuel pressure you need a FP tester (gaugewith a hose and fitting), you can borrow/rent one from most parts stores from what I hear, hook it up to the schreader valve on your fuel rail. I'll let someone else give you the numbers you need, I don't want to give you the wrong ones. As for the pinched line, if it's a return line your pressure will go the hell up since the pump gives out around 70 PSI and the system needs only about 30 something.
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Unread 01-09-2012, 12:56 PM   #59
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The regulator brings down the pressure by bypassing the 60-70 psi of pressure from the fuel pump to 31 psi and dumps what it doesn't need to the return line. So if the diaphram in the pressure regulator rips or the return line gets pinched you will see the full pressure at the fuel rail. The only way to get too much fuel is a bad O2 sensor,fuel pressure being too high, or a bad injector dumping fuel. You have done the O2 sensor so a fuel issue seems to make sense. Check the fuel pressure running 31psi, disconnect the vacuum line to the pressure regulator 39 psi, and then turn the key off and pressure drop should be less then 10 psi for 20 minutes.
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Unread 01-09-2012, 01:58 PM   #60
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Here's the tool you need:
http://www.harborfreight.com/fuel-in...ter-92699.html
$17.99 at Harbor Freight.

It screws onto the test port on your fuel rail. As Que said, 31 PSI running (idle) and then take the vacuum hose off the regulator, it should jump to 39 PSI. Then shut off the engine - the pressure shouldn't drop more than 10 lbs after 20 minutes.
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