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I have what I have heard called a "fish-bite miss" in my '88 S4.
Car runs fine otherwise, but at steady state cruising, there is a barely noticeable intermittent stumble.
Prime suspects are the usual: intermittent fault in injection or ignition.
Plugs, caps, and rotors are new. Leads are Beru but not original, but I have no idea when they were replaced. Coils and ignition amps are originals.
I want to start with the injectors, but being here in Oz, and thus so far away from all the usually recommended injector services like Witchhunter, I was wondering if this device might be worth trying in the home workshop.
I have what I have heard called a "fish-bite miss" in my '88 S4.
Car runs fine otherwise, but at steady state cruising, there is a barely noticeable intermittent stumble.
Prime suspects are the usual: intermittent fault in injection or ignition.
Plugs, caps, and rotors are new. Leads are Beru but not original, but I have no idea when they were replaced. Coils and ignition amps are originals.
I want to start with the injectors, but being here in Oz, and thus so far away from all the usually recommended injector services like Witchhunter, I was wondering if this device might be worth trying in the home workshop.
Anyone with experience with it, or any alternative suggestions?
What is that in US Dollars? And does it really say $1,000 for shipping? Geez!
Witch Doctor has an excellent reputation, but their service is not rocket surgery and I’m sure that Australian fuel injected vehicles need that service too. So just Google to find a shop with good reviews in Australia and send them off. If they have never been serviced they almost definitely need to be. You’ll get a report of what percentage of flow was available prior to them being cleaned. I just did a Google Search for >. injector cleaning Melbourne Australia < and I can see that you have MANY companies to choose from.
Bad plug wires are a very typical cause of a misfire. If you don’t know how old they are you should probably replace them with new. And that would complete the area of services you already did regarding new spark plugs, caps and rotors. An old-school way to just get an eye on them being bad is to put the car in a pitch black garage at night, open the hood, start the engine and observe if you see arching from the wires.
I’ve read tons about injector cleaners, and they do work, although it may take several applications for an older car - especially if it was run with cheap gasolines. I think in your country the laws require all gasolines to meet the “newish” EU standards and they all have cleaners added. Here in America that is not the case and many people seek out the cheapest gasoline they can buy, and those fuels really contribute to injector clogging. To get the best quality gasolines with detergents added we have to use major national brands like Chevron, Shell, etc… But running an additive every 3000 miles is recommended. Liqui Moly has a great one it seems, I’ve known of the brand for many years but have never tried their products; but I’ve been reading Amazon reviews recently about it and I’m going to give it a try soon. Techron is probably the most commonly known / accepted product here in the US, I always run it before each oil change.
The ignition amps are almost never the culprits. Coils either really. Save those for another day.
Cleaning the injectors would be an option. That tool you linked to is very similar to the one that a lot of shops use, and it may make sense if you own 3 928's as indicated in your signature. The injector cleaner works by running injectors cleaner through and running the injectors at various duty cycles. It's pretty slick and works great. I have a buddy that has a shop and we used his cleaner tester and saw improved results. Here are links to the process https://youtube.com/playlist?list=PL...ou3eT4hY9E_eF4.
Assuming you can get the cleaner locally and avoid shipping, it may be worthwhile to consider other options.
you could likely find a local shop with a cleaner that would do it for you for about an hour's worth of service for about a quarter of the cost
you could replace your original fuel injectors with more modern 4 hole injectors for improved fuel atomization and flow. IIRC you can get these replacement injectors with new seals for about $50-60 each ($200-$250). That is what I did in this post.
you could go one step further and upgrade your injectors to a higher flow rate but upgrades are a slightly different story.
Best of luck and let us know which direction you go.
What is that in US Dollars? And does it really say $1,000 for shipping? Geez!
AUD$370 is currently about USD$250, and the vendor offers free postage within Australia.
From surveying the local market, it will cost me almost that much to have eight injectors cleaned.
If I need to send them to Melbourne (from Perth), buying the cleaner/tester is cheaper.
... and transport to Melbourne and back is currently running about 10 days each way.
Every injector cleaning after that first eight is essentially free.
Be mindful that as I am aware those machines require a special cleansing fluid that is far from cheap so suggest you check out cost/consumption before committing to avoid surprise. I rate the injectors as needing a clean every 10 years or so depending on usage. With that relatively small capacity machine you would need to clean in two batches of 4 injectors [no big deal]. At that price point a nice piece of kit to have in reserve and you mght even consider a cottage industry approach to pay for it..
That being said I doubt your perceived problem will have anything to do with the injectors. The Bosch injectors do seem a bit prone to building up deposits and that tends to reduce the flow and/or degrade the spray pattern thus atomisation degrades some and that causes a loss of power rather than hesitation in my experience. Hesitancy I tend to put down to ignition issues like spark leakage mentioned above.
Be mindful that as I am aware those machines require a special cleansing fluid that is far from cheap so suggest you check out cost/consumption before committing to avoid surprise. I rate the injectors as needing a clean every 10 years or so depending on usage. With that relatively small capacity machine you would need to clean in two batches of 4 injectors [no big deal]. At that price point a nice piece of kit to have in reserve and you mght even consider a cottage industry approach to pay for it..
That being said I doubt your perceived problem will have anything to do with the injectors. The Bosch injectors do seem a bit prone to building up deposits and that tends to reduce the flow and/or degrade the spray pattern thus atomisation degrades some and that causes a loss of power rather than hesitation in my experience. Hesitancy I tend to put down to ignition issues like spark leakage mentioned above.
Good point about the fluid. I need to look into that.
I agree that the injectors themselves are probably not the cause of the problem. Harness & ignition seem more likely, but I have to start somewhere.
Good point about the fluid. I need to look into that.
I agree that the injectors themselves are probably not the cause of the problem. Harness & ignition seem more likely, but I have to start somewhere.
Best way to find electrical problems is to pee on the HT cables- you will surely know if there is a problem!! If that does not float your boat then just run the car in a dark place and look for "dancing fairies".
AUD$370 is currently about USD$250, and the vendor offers free postage within Australia.
From surveying the local market, it will cost me almost that much to have eight injectors cleaned.
If I need to send them to Melbourne (from Perth), buying the cleaner/tester is cheaper.
... and transport to Melbourne and back is currently running about 10 days each way.
Every injector cleaning after that first eight is essentially free.
LOL, I just used Melbourne because it’s the first Australian city to come to mind! Insert Perth in your query instead.
If you aren't so interested in the "flow balancing" capabilities of the fancy machines, you can duplicate a lot of the cleaning function with a good ultrasonic cleaner, one of those on-car air-over-cleaner cannister devices, and a few 9V batteries or a similar power supply. The cleaning process starts with basic exterior cleaning of the injectors, followed by some time in the ultrasonic. There are numerous fancy barely-caustic cleaning solutions to use in the ultrasonic, but in the US anyway you can use Simple Green detergent to get external varnish and coking off the ends of the nozzles. Again a US product, Berrymans B12 cleaner is a good choice to push through the injectors after the filters have been removed, cleaned in the same ultrasonic, and put back in. Then cycle the injectors with about 60PSI of air on the cannister, the injector in the top of a glass jar so you can see the pattern, and do that until you see a good pattern and good shut-off.
I have all the pieces to do this project, and consider adding a microcontroller to precisely manage the pulsed power to the injector. With that, each injector could be tested for flow and flow consistency among the set. It would be handy to have a fuel rail instead of trying to get a piece of hose to seal around the top of the injector, and enough safer that I may need to go find a used rail for the task.
What the DIY is missing is spares of the pintle caps and filters should the existing ones be gone/damaged/etc.
It's been ten-plus years since I replaced the injectors. I could clean the old ones, add new o-rings, and just swap. I may try an "on-car" cleaning first to see if it helps any. In the meanwhile, the B12 in 15oz cans is maybe US$3.50 at WalMart, cheap enough to buy by the dozen and use to both treat the fuel and in the cleaning cannister. It has a decent dose of Toluene is in it, so use extreme care to not get it on skin (it's fat-soluble and a serious known carcinogenic and nervous-system destroyer), breath the spray fumes or get them near skin or eyes, or get it on paint.
If you aren't so interested in the "flow balancing" capabilities of the fancy machines, you can duplicate a lot of the cleaning function with a good ultrasonic cleaner, one of those on-car air-over-cleaner cannister devices, and a few 9V batteries or a similar power supply. The cleaning process starts with basic exterior cleaning of the injectors, followed by some time in the ultrasonic. There are numerous fancy barely-caustic cleaning solutions to use in the ultrasonic, but in the US anyway you can use Simple Green detergent to get external varnish and coking off the ends of the nozzles. Again a US product, Berrymans B12 cleaner is a good choice to push through the injectors after the filters have been removed, cleaned in the same ultrasonic, and put back in. Then cycle the injectors with about 60PSI of air on the cannister, the injector in the top of a glass jar so you can see the pattern, and do that until you see a good pattern and good shut-off.
I have all the pieces to do this project, and consider adding a microcontroller to precisely manage the pulsed power to the injector. With that, each injector could be tested for flow and flow consistency among the set. It would be handy to have a fuel rail instead of trying to get a piece of hose to seal around the top of the injector, and enough safer that I may need to go find a used rail for the task.
What the DIY is missing is spares of the pintle caps and filters should the existing ones be gone/damaged/etc.
It's been ten-plus years since I replaced the injectors. I could clean the old ones, add new o-rings, and just swap. I may try an "on-car" cleaning first to see if it helps any. In the meanwhile, the B12 in 15oz cans is maybe US$3.50 at WalMart, cheap enough to buy by the dozen and use to both treat the fuel and in the cleaning cannister. It has a decent dose of Toluene is in it, so use extreme care to not get it on skin (it's fat-soluble and a serious known carcinogenic and nervous-system destroyer), breath the spray fumes or get them near skin or eyes, or get it on paint.
Hi dr bob,
To be honest, I have no idea how "flow balancing" works beyond measuring the flow of each injector, and rejecting those that are outside some assigned specification. Can individual injectors be adjusted in some fashion to change flow rate?
The device that I linked has cute little measuring tubes to check individual flow rates, and apparently also has enough additional (useful?) functions to make building my own rig something I would do only once I get further down my "honey do" list.
As to cleaners and solvents, I have previously searched for an Australian supplier of products mentioned here like Simple Green, Kroil, PB Blaster, and Berrymans B12 without success. Maybe that's a business opportunity I should investigate, since freight on small quantities from the US to Oz is so expensive.
“Flow balancing” was nothing more than finding the poorer flowing injectors and repeatedly running hem through the cleaner to see improvements. If you can’t get them within a very close margin then consider replacing.
You can use this flow test of new and original injectors as a couple of data points for you to target
Last edited by Michael Benno; 06-14-2021 at 02:04 PM.
Might as well add that removing injectors and going through all of the trouble seems to be antiquated now. I’ve just learned that the dealership, or those at home with a compressor, run the cleaning solution directly in to the fuel line these days. They pull the fuel pump relay and the car runs directly off of the solution and it achieves the same effective cleaning. I like it! 😀 If you are curious there are YouTube videos, I saw one that seemed made in Russia, a low budget at home version of the service; I only mention it because he has before and after showing that it worked - one injector was almost completely clogged in the before.
I've got a few pieces for on-car cleaning, including a modified fuel rail end cap and a cannister made for the duty to hold the cleaner. Getting the plumbing to work well with no leaks is key. After that, cleaner goes into the cannister. FP is disabled, vacuum hose at the fuel pressure regulator is lifted and plugged. I pinch the fuel return line that goes to the fuel cooler, but that's not really necessary unless you want to push fluid through the injectors at greater than about 55PSIG. It does an OK job especially if there's not much in the way of deposits on the injector tips. Passing a lot of oil-laden vapor into the intake from crankcase ventilation? That results in a lot of the coking we find on injector tips, and there's no good way for an on-car cleaning to get those off.
I started seeing a symptom of pinging under medium load, like accelerating briskly up hills at 70-80 MPH maybe faster but not much your honor. Figured that I'm doomed to another injector cleaning. But I dumped a couple bottles of B12 in half a tank of gas, which works out to about twice the dose that they recommends for "maintenance" cleaning. A hundred miles of driving later, no pinging. Hardly a universal solution, but an easy first step that's well under $10 to try. It works in the cleaner cannister too for a full-strength assault on injector deposits without the removal steps. If that doesn't work, out they come for cleaning or replacement.
06-12-2021, 02:09 PM
Injector Cleaner/Tester Recommendation?
If that does not float your boat then just run the car in a dark place and look for "dancing fairies".
