Fuel trim/open loop question.
 

I recently installed an Ultra-Gauge Blue and was hoping to find a reason for some "odd" engine behavior. The odd behavior is very subtle, but I drive the car daily and I can tell "something" is up. Strange noises at certain RPM, times when the engine doesn't feel it's pulling smoothly...just little things.

The fuel trims are crazy negative. LTFT averages between -14 and -25 depending on engine load. STFT averages between -3 and -41 depending on engine load. I think these readings may be largely meaningless because the Ultra-Gauge also indicates that the engine never leaves open loop mode.

The MAF shows between 1 lb/min and 5 lb/min which also seems to be load dependent.

The volumetric efficiency gauge stays at 0%; never moves. I don't really even know what that gauge is measuring.

Timing advance shows between -32 and -64

oxygen sensor bank one and two each blink back and forth between 0 and 1 volt.

oxygen sensor "wide?" bank one and two are steady at 1 volt.

MAP pressure is steady at 21 psi

Boost pressure is steady at 6 psi

I don't really know how to interpret this data. Could someone help to direct me in the right direction? I am actually afraid to drive the car now for fear i am doing damage somehow.

There are NO engine codes. No pending codes either. Just the lovely p1111

Thanks all

If you're sure it's staying OL (open loop) it may well be unable to figure which codes to flag but is unhappy.

In OL some OBD values are junk (er, not required to be reported meaningfully) so be cautious what you trust.

- trims should mean subtracting fuel (whereas OL you expect richer) but they may be junk?

In OL it's not watching the O2s. It relies on MAF and sticks in (plenty of) fuel.

You might unplug the MAF and see if it's better or worse. Better would mean a faulty MAF. No change might mean it's already disconnected. Expect OBD code(s).

I would start with a good cleaning of the MAF, since your trims indicate a rich condition. Only wrong fuel pressure, leaky injectors or a bad sensor could cause that. I am surprised both banks lambdas are switching, but they seem to be, meaning they might not be the root causue. That leaves the MAF.

Initially the engine doesn't like having the MAF disconnected (it tries to stall), but gets used to it. You will get Restricted Performance and that limits the engine to 3000rpm - but it will tell you if it's the MAF.

If you've got a P1111 set, and no ck engine light, I would find someone with another brand handheld scanner to see if it is really in open loop mode.

If it is, you need to get that resolved asap.

Awesome responses, thanks!

I just got home from work and am heading out to troubleshoot (drove the old BMW to work just to be safe).

So I am going to get the car up to temperature, unplug the MAF and watch to see what the fuel trims do? Is that correct? The car idles good now, even in open loop, so unplugging for an "improvement" is I presume an improvement in fuel trims?

I cleaned the MAF just a week or two ago so I'm wondering if I over-cleaned the thing! Perhaps I sprayed it so vigorously with the MAF cleaner that I damaged it in some way. I will completely remove it from the housing and inspect/clean it thoroughly anyway, since it's so easy to access.

Results: I cleaned the MAF again and started the car. I let it warm up until the thermostat opened. The Ultra-Gauge still showed closed loop all of the time with LTFT around -12 steady and STFT between -20 and -32. I unplugged the MAF. The idle stumbled and fluctuated for a few seconds and then re-stabilized. I got four codes related to MAF and Powertrain. The LTFT did not change, of course, but the STFT jumped up to the -40s. I plugged the MAF back in and the STFT went back to the low 30s/upper 20s. I cleared the codes and turned off the car.

Any interpretations?

Just a little more info. I decided to check the fuel pressure (can't believe I have not done it before). At idle the reading is 33 psi which seems to drop slightly when I give it gas. That seems low to me, but it is a basic $35 fuel pressure gauge from Oreilly's Auto Parts, it may not be perfectly accurate. The fuel filter is new and I was told the fuel pump was changed last December, before I bought the car. Could low fuel pressure cause an open loop? This person who said the fuel pump was new however is also the person who said he was almost positive the car had the new metal timing gear.....FALSE. I replaced it myself last month.

Any opinions?

The fact that no codes appear when the system gets stuck in open loop is disconcerting. I first started noticing mild driveability (sp?) issues almost 1,000 miles ago, so if it's causing harm then I wish there was some way I could have known sooner.

Your codes would come from HIGH fuel pressure. Your ECU is reducing fuel!

I thought from some various reading that if the system stays in open loop, for whatever reason, that the other readings may be suspect. If there was any condition that could cause the system to be stuck in open loop, perhaps I could remedy that...and then get more accurate readings. At least that was my line of thinking.

Ross, are you saying that the fuel trim readings are accurate despite the loop status? Please forgive me if I don't have the vocabulary yet in this area. Like so many other aspects of car repair over the years though, I WILL learn.

Also: What can be surmised from the results I listed above regarding the unplugging of the MAF?

It runs rich till it can go CL (closed loop), when it can figure a lower but safe amount of fuel.

If it's not going CL then I think the trim etc figures are suspect.

It's worth checking temp sensors (ECT, IAT) have plausible values as it needs to see them do sane things e.g. ECT start to get warmer and reach a fairly hot value.

Question is why it's not going CL. It wants to see O2 sensors doing sane things, for example.

If it goes CL it can then tweak fuel and if it gets this far and has trims as mentioned something weird and bad would be happening with fuel - bad MAF being one possibility, bad fuel pump another, etc.

But if it is not going CL I would be very dubious about trusting reported trims (unless a knowledgeable tech on these cars says they are valid).

Another cause of weird trims (but in CL) is a blocked cat conv but usually only one side is weird as they don't both block at once.

Does the Ultragauge say the engine comes up to normal temperature ? What JagV8 says makes sense. If it never thinks the temp is warmed up it won't go into closed loop. That or the O2 sensors aren't reporting reasonable numbers.

I am confused! In the Results paragraph from Post #6 gives trims reported to be from "Closed Loop" operation. Now we are talking "Open Loop" . Which is it?

I misspoke, that was open loop in post 6. Still getting comfortable with the terms. Sorry.

Temperature shows steady between 194 F and 204 F once the car is warmed up.

How about for grins and giggles, start with a hard reset so that way the STFT & LTFT will reset back to zero. Chances are it won't fix the problem, but I have seen much weirder things happen.

make sure you are getting signal from all 4 o2 sensors. Datalog and see if anything is out of ordinary.

I did a hard reset a couple of days ago. I did another one this morning and drove the car to work. I am leaving work now and will monitor for any changes on the way home.

Home now:
The LTFT stabilizes around -8 at highway speeds and the STFT still runs as high as low -30s but it's all over the place. I understood that the LTFT should adapt slowly, like every 6 or 8 minutes, but mine fluctuates based on RPM. All of that may be a moot point if the system really is in open loop and the readings are unreliable.

The O2 sensor gauges on Ultra-Gauge give voltage, and they all four give varying readings. I don't know if that means they are working properly. I will learn how to data log and see what that tells me. The fuel trims fluctuate evenly on each bank. There is no anomaly that occurs on one side that does not occur on the other. If this is because open loop is not using O2 sensors then this tells me nothing about them I guess.

Usually after a hard reset my OBD II readiness goes from p1000 to p1111 rather quickly. After 60 miles of various driving today I still have p1000. I think this may be an indication that the UG is accurate in telling me closed loop is not being achieved.

I just got home from one of the most difficult days at work I can remember. I was solving unsolvable problems all day with little or no resources. My brain is mush! But, I am going to try to concentrate enough now to work on this issue. I truly appreciate all of your efforts to help me.

Theory
 

My leading theory is that the MAF sensor is failing. The lb/min readings range between 1 and 5, with actual and calculated being exactly the same...according to the UG. I can't determine from researching if this is normal. I guess even if that is normal, if it's wrong then it's a problem

I can order a new MAF for as low as $29.99 with free shipping on Ebay, but obviously I don't want to buy something that may be inferior (at least not TOO inferior). I wish I had some local "Jag buddies" who could let me swap one out and see if that's the problem. I will probably just order one and be done with it. If that's not the problem then at least I'll have a back-up on the shelf.

My budget right now is only about $50, so does anyone have a recommendation as to which one to order? The part number stamped on mine is LNE1620CA.

I'd replace the MAF and all the 02 sensors. Luckily Jaguar dopes the threads on the factory sensors so it's a 30min job tops including driving the car up on ramps. Amazon has Bosch OE replacement cheap.

I'm going to agree with post #5. I looked at the ultra gauge website. Don't get me wrong, it looks like a nice scanner for the money. I'm just not convinced that it's able to properly connect and accurately give you information. I would trust it more on a Chevy, ford or some Chrysler pos. Jaguars are not easily connected to. -32* and -64* of timing cannot in my mind be right. I don't even know if that's possible to pull that much timing, (referencing -64*), -30* maybe. An engine ECU goes into CL based on ECT (I believe at or around 120*F) and 02 sensor input. (Must be fluctuating between .000 mv lean and .100 mv Rich). I don't doubt that there's something wrong with your MAF or your car, but I'd have to say at this point I'd like to see a quality scanner on there first before purchasing parts. Autologic, Snap-On or obviously some Jag dealer scanner. Going back to the beginning, what kind of noises are you hearing? Knocking or rattling from the engine area?? What year is your car? Just how much worse is your car running as opposed to before? Has your mpg gotten worse?

I both agree and disagree with the addict. The sensor and the communication do not care what brand of car is on the other end, but the numbers you post are not reasonable, so something is amiss.

If you are in open loop the trims are not necessarily valid, but the raw lambda sensor voltage numbers are still valid. in one case, I believe you posted 1 volt readings from the wide band sensors (S1), which is indicative of a very rich condition,but then you read a varying voltage on the S1 log.

I agree with the advice to get a scanner system to chart your lambdas and then post the actual parameter number, not just the name, and lets see if we can sort it. There are several programs that will run on your laptop using the same ELM hardware that will do the job. It is entirely possible to believe you have EITHER bad lambdas OR actual rich running condition from the data so far. Does the exhaust smell really rich?

I wish someone would explain this "disconnect the MAF" troubleshooting technique to me. Obviously it is to put the ECU in a backup strategy that does not use the MAF, but what is that supposed to show?