P38 running rich

[wilsby]

My 4.6 is running rich.

We cleared all codes and reset running parameters with testbook, and everything appeared fine. Old codes indicated left bank was doing funny things and was close to limp home status. We assumed most of it related to recent battery problems. No exhaust anlyzer available at the time.

Two hours later it fails smog with huge margin.

CO ~5%, limit .5 idling and .3 at 2000rpm
HC 200, limit 100
Lambda unstable, but mostly just above .8

Where to look? Newly serviced with plugs, oil, oil filter, air filter. New battery (largest yellow top), charged overnight, but still old alt charging 13.7 V. New alt due this week. Outside temp just above freezing. TPS less than 6 months, stepper cleaned at same time. New manifold gaskets.

[Pugsly]

MAF?

prolly need to put it on autologix and see whats up. rich = ecu trying to preserve the engine / limp home?

[LR Max]

Kinda sounds like O2 sensors. They regulate all that good stuff. I'd check to see if they got messed with during the manifold gasket repair. It might be as simple as they got unplugged and never plugged back in. Also check around in there to see if everything looks ok in the exhaust system before the cats just to make sure. Scrutinize the left side since that is where the problem appears.

After you fix the problem, you probably should run the truck hard to remove all of the unburnt carbon from you're combustion chambers. That'll clear it up so you won't get sticky valves.

[wilsby]

Keep it coming!

MAF should give symmetrical problems, but what do I know?

Lambdas are fairly recent, about 50k miles, but I have had oil on the contacts from a leaking pan gasket. I fixed the gasket and cleaned the contacts with contact cleaner, but I may need to do it again. Left side was particularly soiled, so it adds up. And yes, they were both reattached.

[LR Max]

You getting any misfires? You didn't say anything about that, and that would definately cause richness. I remember once on a RR 4.0 one of the factory spark plugs (yes, straight out of the box, at the dealership) was improperly gapped and would not fire.

Check you're air injection. If that is inoperable then it'll mess up you're emissions. I'd look at the air injector on the left bank closely. Are any of the pipes leading to the injector cracked/dead?

Is the engine making any wierd, loud *ticking* noises? The exhaust manifold gaskets could have been improperly installed (while doubtful, still check).

I am sorry but I am still looking at the lambda sensors as the problem. It just sounds like their area of operation which is being messed up. Look at the wiring too, just in case. I'd say pull them and have a look.

Have a go at that, and come back with the results.

[wilsby]

No misfires, engine runs strong.

Air injection? New to me, will have a look. Unless you mean the stepper motor thing, which was thoroughly cleaned a while ago.

Not loud but weird ticking present, but that is on the right side. According to my mech noting to worry about. All he does i LR, and he says it's neither manifold gasket, lifter nor bad cam lobe. Could be a pinhole in a manifold weld.

As you say, left lambda is the main suspect. I hope it's just a bad connection.

[AlanB]

Coolant Temp Sensor?

[pendy]

Well a reneck would remove the oxygen sensors and swap them to the other side. Then drive and recheck the symptoms. Heat em up with a propane torch when they are out to clean em.

I can't believe you doubt my pselling ability.

JP
If you got someone running testbook on it why couldn't they diagnose it for you?

[wilsby]

Well a reneck would remove the oxygen sensors and swap them to the other side. Then drive and recheck the symptoms. Heat em up with a propane torch when they are out to clean em.

I can't believe you doubt my pselling ability.

JP
If you got someone running testbook on it why couldn't they diagnose it for you?

We'll get it on testbook again, and hopefully with an exhaust analyzer at hand. I'm not paying standard rates exactly, so there is a limit to how much I can pester him. We were pretty sure we had fixed it last time. Everything looked good on testbook after the reset, but deteriorated fast.

So I guess I'm looking for a second opinion. The reneck method seems useful. :D

[LR Max]

Air injection? New to me, will have a look.

Well, the US RR 4.0/4.6 engines have them, might not have them for everywhere else. It is the stupid looking thing that has two connections into the cylinder head, and prevents you from getting to the spark plugs easily.

But it sounds like that stupid little option never made it onto you're truck. Truly lucky.

On a random note, one of my buddies old-ass Ford Thunderbird used to have a lot of trouble trying to pass emissions test. He had all of the vacuum hoses replaced and it greatly decreased the amount of toxic fumes the car was spewing.

If you're vacuum lines look anything like the ones on my sisters 95 discovery, that might be a good maintenance thing to do in the future.

[PTSchram]

[QUOTE=LR Max]Well, the US RR 4.0/4.6 engines have them, might not have them for everywhere else. It is the stupid looking thing that has two connections into the cylinder head, and prevents you from getting to the spark plugs easily.


QUOTE]

If this were the case, he'd have a code for something along the lines of drive cycle A out of spec.

It is almost certainly not the MAF as this would affect both banks correctly.

While a redneck might remove the sensors and swap them side to side, an engineer would make a cable that allowed them to remain in situ (have somebody explain that word to you Pendy :flipoff2: ) for testing-easier to hook up a coupla cables than to remove and swap.

I'm surprised it isn't throwing a code for the oxygen sensor stating that it is "running on open loop due to sensor failure".

I can only suggest ideas as I have no idea what the Testbook has for a readout. The Rovacom family of machines yield the above responses in such situations.

[wilsby]

New lambdas fixed it. Runs clean as ever and passed inspection.

The common cure for most problems on a P38 seems to be to get fresh sensors. New height sensors fixed the EAS, and the new TPS didn't hurt either. A new heater temp sensor is going in and hopefully fixing the climate's "book" message.

[NEVROVR]

A new heater temp sensor fixed the climate control problem on my P38A. Use a heatsink compound on the mating surface to ensure good heat transference.

I'm curious Christer, what were your symptoms with the EAS that led to replacing your position sensors? I'm getting erratic behaviour from my '96 4.6 HSE as well. Overnight it will sometimes drop and take a long time to come back up and other nights it will still be where I left it.

Lonn

[wilsby]

I'm curious Christer, what were your symptoms with the EAS that led to replacing your position sensors? I'm getting erratic behaviour from my '96 4.6 HSE as well. Overnight it will sometimes drop and take a long time to come back up and other nights it will still be where I left it.

Lonn

My height sensors had bad spots, and the EAS would default to high position unpredictably due to humidity and going out of their normal range when driving the Zuk onto the trailer, among other things. I could reset it by pulling the fuse and replacing it, but I got fed up with the unpredicatability. I may replace my slightly frayed airbags with time, but no reliability issues right now.

Is your dropping down correlated to cold nigths? It's air we're dealing with, and pressure will drop with temp...

[NEVROVR]

It is very cold at night, but it was happening during the warmer months as well. Some days it will completely lose all pressure overnight and other days it will be normal. I'm kind of waiting for something to fail before tearing into it. I've already replaced the air springs and tested all the fitting for leakage. No leaks were apparent, but other than a leak, only an errant self-leveling system would cause all the pressure to escape, I think. When I put the system into lock mode I don't lose pressure. Of course, it could be that the gremlins didn't attack on the few nights that it was in lock mode.

[evilfij]

"Well a reneck would remove the oxygen sensors and swap them to the other side"

Is this a reference to the testbook challenged among us?

[wilsby]

Don't need no stinkin testbook. Just shell out GBP 95 per sensor and climb under there with your 17mm wrench.

Don't know if it matters, but I drove around for a while to allow the adaptive stuff to settle before I took it to the test station. Good as new.

[PTSchram]

A new heater temp sensor is going in and hopefully fixing the climate's "book" message.

I would strongly suggest revisiting the testbook before replacing sensors on the HeVAC system.

The P38's HeVAC system is known for many problems that appear to be sensors but in many cases are either firmware glitches or fusebox related. Occasionally, the fan motors will fail.

Pendy's had many fans fail, I seem to be plagued with less obvious issues requiring somewhat inspired parts replacement.

Peace,
PT

[wilsby]

Testbook said temp readings oscillate between 5000 and 8000 C. I don't think you need to tranfer that to F to see that it is out of whack. :flipoff2: That was last summer, I just haven't gotten around to change the thing.

Heating and AC works, but may be confused and not give 100%.

There may be other issues, like sticking flaps, but the sensor is the first step. It has been on my shelf for a few months now, just need to find the inspiration to tear into the dash. Plan to wire extra lights at the same time.

[PTSchram]

Don't be surprised if the sensor doesn't fix it.

While the first step is to replace the sensor, it does often lead one to the realization that the controller has suffered a meltdown.

Alssso, keep in mind that the controller will revert back to the last temperature sensedd until the vehicle speed exceedds something like 25 MPH. Someday, I'll wire up a circuit to fool the BeCM into thinking the vehicle is moving so I can test HeVC controllers andd cruise controls.

[wilsby]

While the first step is to replace the sensor, it does often lead one to the realization that the controller has suffered a meltdown.


Optimist!

I have been told that if the display shows realistic outside temps, the controller is usually OK. It does, and the system is working remarkably well to be molten down.

I like to think that this sensor will fix ALL electric issues on the truck. :flipoff2:

[PTSchram]

Optimist!

I have been told that if the display shows realistic outside temps, the controller is usually OK. It does, and the system is working remarkably well to be molten down.

I like to think that this sensor will fix ALL electric issues on the truck. :flipoff2:

LOL. After having done the third BeCM swap and replacing several fuse boxes and the odd HeVAC controller I've come to be very pessimistic with the P38. In many cases, one does not have definitive proof of a particular piece having failed and it takes the preponderance of evidence to convince one to replace frightfully expensive parts and hope they work!

Oops, forgot to add that you're right, if it shows realistic ambient temps, you should be OK.

[wilsby]

Thank's for the support.

The fusebox has also been swapped recently, so rule that out.

I know what the factory authorized shops charge, and I guess that is why most P38's around here are in a sorry state. Buying the odd parts from the UK and installing them myself is not too expensive, though.