I have a 93 Ford Explorer, manual transmision. About a month ago it intermittently started running very rough. I does this wether the weather is rainy or not. The engine has done this when it just started up, cold, and when it's been fully warmed up. I have been able to drive it, but it has been quite a challenge. When running, there is a very noticable noxious exhaust smell. The check engine light has come on some of the time. When the eec codes were checked it only revealed 522, the car wasn't in park or neutral when running the test. I have tried clearing and rerunning this test several times, yet 522 still shows up. No other fault codes. Don't know how this would cause engine to perform so bad. The fuel tank has been near full when it happened so I believe the gas to be good/ no water. The engine has a lot of milage on it, over 200K, so I'm not sure if something inside could be malfunctioning, but don't know how to check. The car will run for days very smoothly before this happens again. Any help to isolate would be appreciated. I have changed plugs, wires and the pcv valve and it still occurs. It's like the engine is hitting on one cylinder when it happens. thanks

 

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Noxious exhaust smells are often associated with a failing CAT converter. CAT converters usually fail because something isn't right in the engine, usually running rich for a long time. Suggest check for fuel in vacuum line to FPR and fuel pressure.

 

Mrshorty has a good point. I would suspect more codes though too like HEGO's not switching, too rich. # 17X something.

Do some more investigation. Check you plugs, even though they are new, to see how the engine is running on the inside. Are they rich or lean?

Hard mechanical issue may be present too. Do a compression test and look for any significant inbalances. I guy a few weeks ago had a rough idle problem and found a couple cylinders wore the valves and seats down soo much he had lost all compression. that was on one head. The other head had cracks in it.

So you never know what you may find.

 

Did you check to make sure you have consistant spark on all cylinders? Do you have white smoke coming out of the tailpipe when you first start it up? I have a '91 and a '92 and both needed new intake manifold gaskets. On the '91 it was obvious because it was leaking to the outside but on the '92 it was leaking into some of the ports and coolant was getting into the engine and it was running rough. Some folks have had good results simply retorquing their intake manifold without changing the gasket. Unfortunately cracked heads and leaking head gaskets are also rather common on the 4.0 V6. How does your oil look? Does it have water/coolant in it? I'm still trying to find out if you can have a cracked head or blown head gasket and NOT have water in the oil. I was having a bit of trouble with the '92 but it seemed to go away when I put in a new radiator. I think the radiator was clogged and was somehow creating enough back-pressure to force coolant into the engine and causing white smoke out the tailpipe. I put in a can of stop leak along with the new radiator and it runs great again. I suspect this may only be a temporary fix though.

 

With 294K miles on the engine, I'm sorta afraid to check compression. Seems like, though, if crack, low compression, valves worn out, it would be consistant, except for maybe a sticking valve, and I'm not sure it would take engine performance down to barely able to drive. Found no fuel in vacuum line. I'll have to get a gage to check fuel pressure and compression. Noxious smells are only when engine is acting up. When it runs normally there is nothing out of ordinary.
Today, it has malfunctioned consistantly. Engine codes are all normal except the persistant 522, not in park/neutral.
I pulled three of the easy plugs to pull and all are covered in black carbon, I suspect the others are too. I let the engine warm up twice to see if egr would effect and it does not.???

 

With the milage I quoted above, I'm sure there is plenty of wear inside the engine, but it has performed remarkablely well over the years. Oil is normal, that is, no evidence of water intrusion. I'm also sure, when the engine is operating normally, there has to be some oil going out the tailpipe, however, it isn't very noticable and I only add a quart at most between 5K oil changes....most of that leaks out I would say that the spark is consistant across the cylinders, but haven't checked with any type test equipment. I say that because of the carbon on the three new plugs I pulled a little while ago would indicate to me that the plugs are firing, but ignition output may be weak or messed up??

 

Ah ha! Now you have a sign. The black plugs means you'e running too rich. Did you pull plugs from just one side or was it from the 2 different banks? I assume you have a Fed car, no CA. Fed cars in 93 were MFI - multiport fuel injection - where all 3 injectors on a side fire at the same time. CA cars fire one at a time.

Check the other plugs too. We need the whole picture. I can help narrow it down but without the total picture there are too many variables right now - like bad O2 sensor sending a lean condition to PCM so PCM richens up a side, or the bad fuel regulator you're still checking on...

 

Even had one guy change the 2 O2 sensors but inadvertantly swapped the connectors right/left. That really messed up the motor signals.

 

OK, I pulled two of the three plugs on the right (hard) side and they, too, were carboned up. I have a Fed car. Where do I go from here?

 

Not sure which I would do first, but, as I noted above, one thing to do is check for fuel in the vacuum line to the FPR and the fuel pressure. I might also pull codes from the computer to see if the computer can see the problem.

 

Looks like he already checked and vac lines are dry. Still does not eliminate the P regulator. When the diaphram fails, you get fuel in vac line. But if it is stuck wide open and does not regulate at all, you will get too much fuel each time the injectors fire. If this is the case, the PCM can correct only so far (based on 02 sensor readings.

Key here though is that we are looking for something that affects both banks. Fuel P reg does that. If both 02 sensors are bad, that could be it too - but not just one of them. Make sense?

Side note - let me guess. The plug not pulled yet is the passenger side rear. Wonder why?

What would I do? 1) check fuel pressure. Should be about 35 PSI engine running. 2) Swap out both O2 sensors. Not sure how old they are but new ones can't hurt and the Bosch ones at Autozone work great and are only $0 each.

Next - we might be looking at something more evasive. Any other control component - MAF, throttle position sensor, even the coolant temp sensor all affect the A/F mixture.

If all that checks out OK, do you have a coolant loss? Maybe coolant getting into engine and O2's sensing lean and PCM dumping extra fuel. Lots of ways to go but start eliminating the low hanging fruit first.

 

Thanks. I'll work these items and advise. I'm all for low hanging fruit. Will tackle the fpr/ fuel pressure, and go from there. I would have thought that other possiblities like, MAF, throttle po.... would have given me a code, but I'm far from knowedlable on this. I may have a complete failure now as engine hasn't worked right for a few days. I haven't driven auto over the last few days so I could isolate. My Os sensors are original like everything else on the engine, except the alt. It's really been a good engine.

 

Holly cow a 1993 car with original O2 sensors? Are you the original owner to know this to be true? I bought my 93 new and even the dealers changes out the O2's 3 or 4 times in the 6 year warranty (extended). I have since changed them at least twice and one of them 3 times.

I would ditch those bad boys right now. Don't even think of keeping 12 year old O2's and try to solve your problem. Get the Bosche brand - best luck fo me so far - just $40 each at Autozone.

I have yet to see you comment on the codes except they were checked and you got nothing - OK who did the check - are they competent? Something is going on and we need a reliable read off you computer. You will never get a CEL for the tranny not being in nuetral. This is a KOER (key on engine running) code. The CEL goes on when you are driving because it detects a problem when you are driving and it will store that trouble code. You get that coed with a KOEO (key on engine off) test. Did you go to Autozone for the test?

Get your own code tester and do the analysis yourself. I use an Autoxray unit - awesome. autoxray.com or search the web for one of their distributors. If you plan on keeping the vehicle, you need to be able to read the computer to be able to fix it.

So I'm at a loss without more data form your car. Get a good computer read and it will tell you, or the rest of us, what you need to do.

 

I am the original owner and the sensors are too. I have been reading the codes with a tester I got from Walmart, so not sure how competent I am, however, when I originally experienced the problem I was in TN. I went to a local garage, where a mechanic put their tester, a much more sophisticated looking one, on and got the same 522 code and no other error codes. I started the car after that and it ran ok, so I headed home. Drove to FL without any further recurrance, until a few days later. It's been like that for a few weeks.
I've been waiting to update forum, cause car is running ok, for now. A couple of days ago, I performed fuel pressure and vacuum tests. Fuel pressure was about 40 static and came down and stabilized at 32 when engine was started. I pulled off vacuum hose and it went up to about 42, then reconnected and it again stabilized at 32. There was no sign of fuel in vacuum hose when I checked. Vacuum was at 21 at idle and stable. With those readings, it looked like everything was within normal range, so I decided to remove test equipment and drive the car. Well, it worked normally, so I'm waiting for it to malfunction again and will try to get new fuel and vacuum readings.
Can O2 sensors malfunction intermittently to cause a problem like this? I don't have a problem changing them out but wanted to try to catch the problem first.?

My code tester is probably a cheap one, but it got the same results a pro shop tester did. I could not get it to go in to a KOER test after trying several sequences of buttons, etc. so didn't get much further than the KOEO. I'll look at getting a read from a shop around here.