Clean the injectors! You are spitting, not spraying

 

Based on what? Wouldn't clogged injectors show problems all the time rather than intermittently?

 

It's only twelve bucks. You are over thinking it. It will be intermittent based on load, altitude, barometric pressure, dirt, humidity, temperature, gas quality. Trying to help here, not start a ^^^^ing argument. Nothing else has worked!!

Take a look at these injectors from a Range Rover V8:


HomeForumRange Rover Model Specific Technical ForumsRange Rover Sport / L320 MY2010+ Engine Misfire - TSB

 

I'm not trying to start an argument, I'm trying to understand your thought process. I'm not a fan of throwing money or time at a problem and hope it goes away. I prefer to solve problems by understanding what caused them and then addressing that issue.

In my experience, injectors become clogged when debris makes its way to the injector filter or pintle or gas (byproducts) congeal around the same area. Those obstructions in my experience tend to be permanent... A clogged injector hooked up to a flow tester will produce about the same results as many times as its tested until it's cleaned. It won't be better one minute than the next. I don't understand how foreign matter like that could come and go based on atmospheric conditions since the injectors exists inside a sealed system under consistent pressure and I'm trying to. I don't understand how the injector cares about barometric pressure or humidity, etc.

To date, I haven't done anything other than a MAF cleaning and "resetting" five wire terminals, so I'm not getting your comment about "nothing has worked." I've done visual inspections and taken measurements, but I haven't replaced anything or spent any money yet. Maybe this thread seems long to you, but understand the car has done maybe 300 miles since it started. It doesn't represent a huge slice of the car's life.

If you can help me understand your thought process on injectors being sometimes clogged, I would appreciate it. That concept doesn't mesh with my experience, so I'm eager to hear someone else's.

 

Sorry: not interested in this any further.

 

With an issue like this, you do need to "throw time" at attempting to solve it. Otherwise, it's just guess work. To understand what caused your problem, you need to know what is the problem--that's the second step of problem-solving.

Sometimes you do just need to try and replace things to figure out what is causing your problem. Have you been able to get your hands on a MAF?

Since this is an intermittent problem, I would be inclined to believe it is something related to sensors or an electrical issue as I've said before.

Furthermore, I noticed members suggesting possible issues but you refute it based on YOUR experiences. Well, your experiences are unique, and others might share a different perspective to the same idea. I may be wrong but this is just my opinion.

 

To clarify, I meant "spent time replacing parts without a reasonable belief those parts are the problem." It definitely costs time to diagnose a problem, but that's very different in my opinion than just taking things apart and putting them back together, hoping something changes in the middle. Eventually, sure, maybe you get there, but knowing and guessing is what separates experts from amateurs.

I haven't refuted anything - when someone suggests a concept that doesn't mesh with my experience, I want to understand the nature of their suggestion. That's how people learn. I think - I certainly hope - that in an instance when I've asked for more information, I've also indicated my thought process as well so that maybe we can both walk away knowing something more. I don't think it's unreasonable to ask a random person on the internet to support their opinion with a little logic. Maybe that's not true, but if someone asked me "Why does my 335i stall?" I wouldn't just say "Replace the fuel pump," I would offer that the 335i has a Bosch fuel pump which has proven unreliable, and for random stalls it's a likely culprit, here's a link to the TSB." This is the internet, anyone can say anything they like - asking someone to support their recommendation just doesn't seem that unreasonable. I dunno, I guess it's a judgment call.

 

Have you got the trims back to sane values yet?

 

Open the distributor cap and look to see if there is fusing or black on the rotor arm. In my experience, the car would randomly cut out in the same speed range as you. I changed the distributor cap and arm, and spark plugs and the problem never came back.

 

Hello pjmc378,

Welcome to the Jaguar Forums! It's great to have you with us.

We're grateful that you've taken the time to offer your experience, but you have posted in the forum for the X308, the Jaguar saloons offered from 1997 to 2003, with V8 engines and coil-on-plug (COP) ignition controlled by the Engine Control Module (ECM). These engines have no distributor, distributor cap or rotor arm.

Please visit the New Member Area - Intro a MUST and post a required introduction so we can learn something about you and your Jaguar (year, model and engine) and give you a proper welcome.

Cheers,

Don

 

Tough question to answer, but the short one is yes - generally. 95% of the time fuel trims are exactly where I would expect them to be, +/- 5% on both sides, with maybe a little more variance in short term but that's not unexpected. When first started cold they tend to be a little more extreme, but I'd expect as much. *Occasionally* in the past couple weeks I have watched them climb into the double digits, but only briefly under specific circumstances, like major throttle changes. However, on my last drive - after adjusting the MAF connector terminals - the values remained completely sane all night. I've not had the opportunity to drive the car since, but should get more miles on it this week.

 

It's not much, but I've put about 100 miles on the car in the past two weeks. I have not had the issue reoccur since "tightening" the terminals on the MAF.

Some other observations since the adjustment:

Idle MAF readings are lower - 5-6g/s at all times, vs. the previous 6-9g/s range

The range of fuel trim readings post adjustment is wildly different - before I had consistently negative fuel trims, now fuel trims are generally positive. But, the fuel trims in general seem more dynamic, with more activity between +/-10% rather than always being negative. So, instead of always being rich (and the O2 sensor pulling fuel) the trims are more varied with some give and some take.

MAF readings while moving are more consistent - no/light throttle on the freeway yielding 26g/s, etc. There appears to be a closer relationship between speed/throttle and MAF readings. Somewhat anecdotally, I have not been able to reproduce that crazy sudden 120+g/s reading I got before. Major throttle adjustment from cruising yields more gradual air flow increases, with the range largely staying under 100g/s at safe (but not necessarily legal) speeds.

No CEL has returned, but even when I was having The Issue the CEL was a one-time apparently random upset.

I'm not saying the problem is solved - 100 miles isn't much - but there is a demonstrable change - and apparently improvement - in behavior.

 

When the LTFTs are hardly changing look at them with hot engine at idle.

 

That essentially never happens - at least not that I have observed. At idle with a hot engine I typically see LTFT floating between +/-3%. On the road, at speeds varying between 40mph and 70mph, the variation is a bit wider, +/-10%. But as I mentioned in my last post, since the adjustment there is a lot more action on the fuel trims - they virtually never hold still for more than a second or two.


Edit: * More than a second or two with a warm engine - with a cold engine they're a bit more sluggish

 

Forget road speeds.

They ought not to be moving much if at all at idle but 3% is small enough to ignore.

Not much point reading them with anything but a hot engine.

 

It's been a while, but I thought I would follow up on this:

Over the summer (maybe July or August) the local Pick & Pull had a half off sale, and while scavenging some Saab parts I found an '02 XJ8 that offered its throttle body up to me for $40. I couldn't say no. I'd gotten nowhere with watching live data and blankly staring at the engine bay, and ultimately the thing that precipitated this entire odd problem was the total failure of the car's original throttle body and replacement with a used one. I thought it would be interesting to see if the problem was the fault of the used throttle body.

I ran this second used TB in August and into September. The second used throttle body made things both worse and better - more frequent and more dramatic loss of power BUT a far more responsive throttle when it worked. The first used one was a bit lethargic off the line, but would stumble at 70mph and *rarely* trigger a restricted performance mode. This second one drove like a 400hp car should drive, but stumbled over a wider range of speeds, and virtually always trigger restricted performance when it did. With no other symptoms than a stumble and restricted performance with both parts, along with no CEL or other useful diagnostic data, I felt strongly the problem was indeed the throttle body in some way. Still, I endured the new issues until they made me VERY LATE for an important meeting the first week of September. Nothing like leaving the Q Ship at home so you can drive the ultra reliable 300,000 mile 1986 XR4Ti. Grrr.

At that point things get a little fuzzy - I think I:

1. Took apart the TB the car came to me with, which was a rebuild. Since its core issue was the TPS literally falling off (the quality of the rebuild was AWFUL) I took measurements from the two used TBs and rebuilt the rebuilt, placing the TPS accordingly. Interestingly (I think, anyway) this did not fix the issue with that original TB... Starting the car yielded either instant restricted performance, or a wildly revving engine - 500-2000-500-2000-500-2000... I flagged this crap rebuild as a crap rebuild.

2. I next yanked the TPS off the first used TB since it offered the generally best results and installed it on the second used TB which offered the best response, and adjusted the TPS to spec. The car started right up, but seemed to have a tendency to die. After a few restarts it would stay running, but obviously that wasn't right. I made an assumption and rotated the TPS a mm or two counter clockwise and that sorted out the starting issue.

(I will mention that each TB replacement was done with the battery disconnected, hoping the car would relearn the 'new" TB)

It's now been five months and about 500 or 600 miles. The car has not repeated its 70mph stumble or entered restricted performance once. A couple weeks ago I did observe what I think was a random loss of power pulling out of a parking lot, but it was freezing cold, the car had just started, and there was a massive downpour. It definitely could have been a too-fast throttle transition or TCS - it happened so quickly I can't be sure. But, just that once. It is demonstrably more responsive off the line than it has been ever in my ownership, and while the only 400hp cars I have to compare it against are big displacement engines (primarily GM LS motors) it feels genuinely good. I'm feeling generally positive about it. Also, it seems that the car is not running as rich when cold and the idle is smoother when hot - which I also think was a too-rich mixture. This is *genuine* hypersensitivity, but when you're fighting this sort of random issue you start paying attention to every little detail.

The only caveat to all this is that I changed jobs back in October, so it's not being driven in the same way it was, or the same places. But I have tried to recreate the common failure scenarios to the best of my ability and had zero issues. That plus what I feel is generally better running makes me feel like maybe this issue is licked, and the problem was likely the TPS. I'm thinking that likely the TPS has a bad spot on it, and removing & rotating the TPS just moved that bad spot into a place that's "less important," but maybe the interaction of ECM and the two TPS tracks is working "more right" now. Hard to say.

I'll follow up if anything further weird happens, but here's to hoping I don't have to.