Injector question

I've been dealing with an electrical gremlin for some time now; radio going dead and dashboard gauges racing and dropping flat and a "fluttering" of my engine when I press it hard. It seems to stall for a few moments before gaining speed, then lags. It's constant and is most noticeable above 3000 rpms in low gears. My Indy seems to have resolved the dashboard issue by replacing a frayed wire in a harness, but wants to replace an injector that, he says, is failing to inject fuel sporadically at high rpms.

I have a video of the gauge malfunction on my IPhone but I don't know how to upload it.

I trust my Indy, but I'm reluctant to change one injector and not all of them at the same time.

Thoughts of the collective body are much appreciated.

05 987S 6spd

BTW, BRBS in a few short days!

KtS

There are shops that can remove all 6 injectors, install them on an injector testing unit and determine fwhich one if ailing, unde which conditions and by how much
The can then calibrate them all to delved the same flow each.
Generally shops that wor on and prepare racecars will have this test equipment.
Happy Boxstering
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

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Kevin the Slow in NYC
I've been dealing with an electrical gremlin for some time now; radio going dead and dashboard gauges racing and dropping flat and a "fluttering" of my engine when I press it hard. It seems to stall for a few moments before gaining speed, then lags. It's constant and is most noticeable above 3000 rpms in low gears. My Indy seems to have resolved the dashboard issue by replacing a frayed wire in a harness, but wants to replace an injector that, he says, is failing to inject fuel sporadically at high rpms.

I have a video of the gauge malfunction on my IPhone but I don't know how to upload it.

I trust my Indy, but I'm reluctant to change one injector and not all of them at the same time.

Thoughts of the collective body are much appreciated.

05 987S 6spd

BTW, BRBS in a few short days!

KtS

the problem.

With no CEL thus no hint of which injector how does the indy propose to id the bad injector or injectors?

If the injector (or plug or coil) is misbehaving at idle with proper equipment (PIWIS2 for instance) the tech can disable each cylinder's injector, and spark, in turn. The one that has the least affect on the engine's idle speed when disabled points to the weak cylinder. More investigation is necessary to determine if the injector, plug or coil is bad.

At higher engine speeds, I'm not sure if the same disabling test has any validity.

Pedro is right in that some shops have the equipment by which injector performance (flow rate and pattern) can be viewed and either the weak injectors cleaned or if cleaning doesn't help the flow/pattern the injectors replaced so they all flow the same right amount and all have the same and correct pattern.

I do not know what is more expensive though... removing all 6, testing them, possibly replacing one or more that can't be resurrected, or just replacing all 6. If plugs are due having this work done at the same time might save you some money.

If one or more injectors is highly suspect. They're not cheap to replace.

Talk this over with your indy, but you might want to see if disconnecting the MAF and then clearing the error codes to reset all the fuel trims/etc to their defaults then driving the car around has the same symptoms appearing. The check engine light might come on after a while but you're after the symptoms. Be sure when the MAF is connected again the codes are cleared again to reset the fuel trims/etc. They'll be off some due to the MAF being disconnected.

Sincerely,

MarcW.

The CEL comes on, but it turns off after a few seconds. My Indy is a Porsche mechanic, but I don't know the technical stuff about what tool he used or what codes he collected.

I do trust him, I was just concerned about changing one injector verses changing them all out. I'm going to ask questions tomorrow, but I'm inclined to take his advice.

Thanks for your help,
KtS

and AFAIK the injectors last indefinitely. So unless the problem is caused by particles/dirty gas/residue I don't think there is any value in replacing all of them. And if it is caused by one of those, using Techron and/or getting them cleaned should solve the problem.

The injectors are kind of expensive and the labor cost shouldn't be too bad -- "you" have to remove the side of the intake and disconnect the fuel rail but that's not all that much work.

On the other hand, you can get a fuel injector repair kit ($9 from AutoHausAz, for example). Compare that to > $200 for a replacement injector.

For all of the above reasons, I recommend changing/fixing just the failing one(s). I would personally try the repair kit. We could do the job at TSBL or BRBS. If you haven't already done it, I would first run a couple of consecutive tanks of Techron.

I'd think something stuck in there by virtue of its own size and shape, and not because a sticky residue is holding it would remain lodged.
Also wouldn't a couple tankfuls (32 gallons!) of Techron be problematic? Maybe a 50/50 Techron/gas mix would be better.

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Laz
I'd think something stuck in there by virtue of its own size and shape, and not because a sticky residue is holding it would remain lodged.
Also wouldn't a couple tankfuls (32 gallons!) of Techron be problematic? Maybe a 50/50 Techron/gas mix would be better.

Techron will dissolve these particles and what results will pass through the injector holes.

Non-fuel derived deposit particles in the fuel injectors are rare, unless the filter got compromised.

I might add here that my 02 had its fuel pump fail and I finally got to see the fuel pump and its 'in tank' filter.

The 02 Boxster has no serviceable fuel filter. The filter is actually a part of the fuel pump housing. A portion of the pump's housing (made up of some kind of plastic) consists of some fine mesh, sort of what you might find on a water pump used in a fish tank or aquarium. This fine mesh though as fine as it is is not as fine a filter element as is say a paper or ceramic fuel filter element.

Based on the amount of debris in the mesh -- not a lot but there was some -- I have to believe quite a few smaller particles were pumped through the fuel rails to the injectors.

My WAG is the filter filters out particles that are of the size that can do 'damage' to the injector pintle or even block/plug up the holes of the injector tip. Smaller particles are passed through and based on the fact my 02 is on its original injectors where they apparently do no harm.

Where the fuel injectors really 'suffer' is at the tip. The engine gets hot then is shut off. This heat soaks the fuel injectors and over time any gasoline that lingers at the tip will dry and leave some deposits. Over time these deposits can build up to the point the spray pattern, even the amount of fuel the injector can deliver, is affected.

Techron is designed to dissolve these deposits.

Techron that one adds via a bottle to say 10 or 16 or 20 gallons of gas is way stronger than the Techron that is blended in some fuels. At best the regular use of one of these Techron treated fuels will help keep a clean fuel system clean. It won't resurrect one that has been fouled by running crappy gasoline.

Which reminds me... A week or so back I was speaking to a tech about his Porsche training and part of it covers fuels. He said during one class the instructor demo'd fuel quality in a interesting way. He brought in two one gallon containers of gasoline. While only a small amount of gasoline from each container is necessary for this demo the instructor wanted enough gasoline to demo this to the several classes he was teaching over the week.

Anyhow the instructor poured a small beaker full of one gasoline sample into a clean beaker filled with distilled water. He did the same with the other gasoline sample, using a different small beaker and a separate larger beaker filled with distilled water. Both beakers had the same amount of water and the same amount of gasoline per larger beaker. All fluids were of the same (room) temperature too.

The instructor stirred both large beakers with a glass or quartz rod and let the gasoline stand. In not too long a time one sample exhibited quite a bit of stuff at the bottom of the beaker, while the other sample remained clear.

I won't name the brands but the gasoline of the sample that produced quite a bit of stuff at the bottom of the beaker was not a top tier gasoline though it is a popular brand based on the number of stations around that sell it. The other brand of gasoline, the sample that remained clear, is a top tier gasoline.

Sincerely,

MarcW.

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Kevin the Slow in NYC
The CEL comes on, but it turns off after a few seconds. My Indy is a Porsche mechanic, but I don't know the technical stuff about what tool he used or what codes he collected.

I do trust him, I was just concerned about changing one injector verses changing them all out. I'm going to ask questions tomorrow, but I'm inclined to take his advice.

Thanks for your help,
KtS

But unless there's something else that behavior points to a coil more than anything.

By something else, say if the two banks' short or long term fuel trims differ some (more than say a few precent, this can be an injector problem.

If an injector is leaking this causes the DME to lean that bank's injectors out. If an injector is partially blocked or for some reason not injecting the expected amount of fuel, the DME will enrichen that bank's injectors.

However, I'm not the expert and if you trust the indy and I'm not saying you shouldn't, do what he advises.

Sincerely,

MarcW.

I just had my injectors cleaned, checked, and overhauled for @ $22 each. Very happy with the results. You get a sheet showing the before/after. No affiliation just happy customer as of last week. I sent them in on Monday got them back Thursday.

[www.rceng.com]

Steve

It does not take much, debris wise to foul an injector(had this issue with an Audi awhile back). New factory seals will also probably make a huge difference. It made a noticeable difference on our 01(base). You might consider having them cleaned and matched.
regards

No, there is an internal filter in the injector itself. Even the smallest amount of debris will foul the pattern. This is why I change out our fuel filter every 20-30k. By the look of the debris in the old filters, one might think petrol stations pump dirt along with petrol in your tank(ie don't ever change pump/tank filters). You should be able to find a shop who can properly clean them out(needs removal) and match the pattern(or correct it, new head). I can tell you, if you've never replaced both o-rings seals, you'll notice a difference afterwards. Go with factory o-rings, the china made units do not fit properly(too loose). It's a real SOB pulling the injectors out, but worth the results(no leaks, quicker starts, improved performance, idles smoother).
regards

My injectors that got cleaned were on my other car... and it took about 5 minutes to remove them and replace them. Commercially available injector (Techron and alike) cleaners are almost worthless at cleaning injectors, they do nothing for actual material/debris that might be clogging them. At some point in the near future I'll have the ones in my Boxster cleaned too, probably at my 90K service just for peace of mind.

hmmm, just can't put my finger on it!




Steve
Guards Red 1999
I'm not a race car driver, but I play one in 2nd and 3rd gear

Just stay away from Kevin......



Edited 1 time(s). Last edit at 05/16/2012 11:54PM by JMstamford,ct. (view changes)

Ed from Long Island (Tampa)
05S Cobalt/Blue/Blue