97 explorer sport OHV with a stick...only bank 1 lean. Looking for advice.

[dgr6853]

For starters I wanted to make sure which bank was which.--which side is bank 1--drivers or Passengers. However, about six months ago, both banks were running lean and I was able to replace the gaskets between the lower intake and the upper intake, and that took care of the problem.

Before I replace the gaskets six months ago I replaced the Mass Air flow and the TPS.

About a month ago I replaced the spark plug wires and the spark plugs--not with Motorcraft---will be redone with Motorcraft.

The car basically runs like poop. It has a pretty bad miss or stumble. The problem is worse when the car is cold an when it warms up its not as bad but still there. Ive drenched with starter fluid the whole upper part of the area the engine looking for a vacuum leak but haven't found any.

With the forscan software Ive been able to see that all of the O2's are reading in at 0 volts and that the computer is pulling all the fuel trims in at -100%. Now, neither of those two things can be normal.

After I did the intake gaskets the car passed CA smog six months ago...with a tail sniffer and everything....I think.

Any advice would be appreciated.

 

[96eb96]

Did you replace the gasket under the fuel rail? 97s had a big issue with that.
-100 seems like an extremely RICH condition. Is that for both banks?
That means the pcm is subtracting almost all fuel because there is so much.
Could be leaking fuel injectors, bad pcm keeping an injector open, damaged regulator, or maybe exhaust leak? How is fuel pressure?

 

[dgr6853]

no, I didn't replace the gasket under the fuel rail. I figured that it was pulling all the fuel because it was rich. However, if the oxygen sensors aren't cycling how does it know that its rich. Actually it just occurred to me that if its super rich then it would never cycle lean out or enriched and thus the O2's would never detect a change in condition.

Not sure what the fuel pressure is. But it does have it. I have thought maybe that there was a bad fuel injector and or a bad PCM. I know that the Forscan software couldn't reset all learned behavior...maybe the PCM?

I also don't want to spend money on stuff I don't have to. but it almost seems as though I am going to have to start throwing parts in a round about fashion. i.e.. replace one downstream O2 and see if its cycles...then I know that that the PCM would have been getting bad info and possibly caused the problems as a result. Also, new O2's would also accurately tell me what the engine is doing and if the engine is actually running rich or lean.

But also, the code is saying that bank 1 is lean...but the PCM is pulling fuel?...something isn't adding up. Sorry, I think out loud. or in this case as I'm typing.

 

[96eb96]

If both 02s are saying the same thing I wouldn't replace them yet. I also don't know the exact code.

Another thing that causes issues like this is a dirty MAF sensor. Tell me the BARO parameter from forscan. Set Units to hz, i actually requested him to make that unit available.

Lets get this straight

Bank 1 on Ford is always passenger.
1) you have a lean code? what is the code exactly
2) You have very negative fuel trims on both banks. that is bizzare.

There is one last thing - 97 and 98 explorers have problems with obd datastreams. I'm on this forum too long. Are you getting readings from the FORSCAN PCM menu? or the OBD MENU?

 

[96eb96]

bay area is like sea level, you should read 159ish hz for Baro. If that is off we have a big clue.
unless you drive in the high mountains....

 

[dgr6853]

96eb96---thanks for your help. Ill take a look at that in forscan in a few minutes. I went ahead and replaced bank 1 upstream sensor. It is now cycling. However, now the bank 2 upstream sensor is cycling as well. Bank 1 and Bank 2 Upstream sensors are cycling almost identically. Bank 1 downstream sensor is also showing activity while the Bank 2 downstream sensor is not showing any voltage or amperage--(whatever the unit of measurement is). with this one change the car is almost running like it should.

I did a PCM reset by unplugging the battery and shorting the cables to the battery for 15 minutes.

I would have done more diagnostics thus far except that I told the wife to drive the car after the PCM reset and while she went to the store the serpentine belt jumped and came off....I think I have a bad tensioner. When I drove to her I noticed that the return coolant hose had collapsed. I drove it home by accelerating and then cutting the engine. Luckily she was only about a mile away from me.

so I managed to put the serpentine belt back on--for now--and filled it with water to keep her cool and continue with diagnostics. I will do a flush on the coolant tomorrow. For some reason the radiator was only half full when I opened it and the overflow tank had no coolant in it.

I will look at the barometric sensor---MAP sensor?

 

[dgr6853]

Barometric pressure was at 29.8 mm of HG. and the local barometric pressure according to a weather website was 30. so, I don't think that is off.

 

[96eb96]

glad to hear things are working.
there are issues with the idler and tensioner pulleys, good idea to replace both. They tend to self destruct after 100K.

BARO is a computed value that tests the MAF sensor and overall breathing of the engine. There is no MAP sensor. It also informally checks for blocked exhaust. Your number is very good.

What are your fuel trims at idle now?

 

[dgr6853]

The fuel trims are at about 5% to 7% in the positive direction. I don't recall if those numbers are for long or short and I don't know if that is a good or a bad number.

 

[96eb96]

The fuel trims are at about 5% to 7% in the positive direction. I don't recall if those numbers are for long or short and I don't know if that is a good or a bad number.

If they are long term trims at idle that is acceptable for our engines. You may have a very tiny leak somewhere,but I wouldn't worry.
I'm also working on my plenum gaskets now and I found a bit of air leak around the throttle body gasket, it was all flat. was a few bucks at autozone. Takes like 3 minutes to replace.

 

[dgr6853]

Guess I was wrong. Those were Long trims in the negative direction. the a look and tell me what you think?

 

[96eb96]

I am also dealing with these issues, after replacing the gaskets still I believe I have a vacuum leak somewhere, idle could be a tad better. I suspect something on the 3 way line that comes off the intake, because if I hold my finger over it trims approach zero.

remember total trim is ltft+stft, so you have to consider that.
so bank 2 is + 7
bank 1 is about -10

interesting..
try creating a small vacuum leak and see if it there is a fast response on stft
if you have propane or brake cleaner spray a bit in and see what happens.

That will just verify the oxygen sensors.

Again, positive trims at idle mean air enters the system, so fuel is added to compensate.
neg trims could be a bit of a leaky injector,but technically those numbers are ok, unless there is some other symptom.
The service manual says 20 either way is acceptable, but around 10 should be fine.

Also, what are the numbers at 1500 rpm

 

[dgr6853]

well, over the last few days the car seems to be running amazingly well. I haven't run anymore datalogs but its running pretty smooth. Just replacing the 1 oxygen sensor seems to have made all the difference. I think that moving wire harness around caused the other upstream oxygen sensor connect to the ECU. In any case the rig is running smooth.