I know at least one of us that has had this done. Is there really any reason? If one or more injectors was not working correctly I would assume you would know you have an issue and the OBD2 system would alert you? It is only about $150.00 to have a set done but I don't really know if it's needed?
JJ
I've done it a number of times in the past, worth it if you have some doubts and never had your injectors cleaned before. Not only can a dirty injector be low on flow, but it can also leak fuel when closed. I've had cases of both in the past when I had recurring fuel line contamination issues until I replumbed.
Typically on OBD2 cars you typically only get a warning if you lost connection to an injector, or if the computer is having to add positive fuel trim over a certain threshold. For LT1s I believe that number was 25% more fuel than normal before it throws a CEL, which is a lot. Have only seen that once when a vacuum port was left disconnected. Not yet sure what the % cutoff is on LS1s but hope to never find out.
One quick way to check is run the car, let it warmup, then compare the short/long term fuel trims between bank 1 and bank 2. My 5.3 with cleaned injectors idles with 4-7ish percent positive fuel trim and is never more than 3% off bank to bank, My 125k mile Tundra is a few % less, etc
Think of it this way, if you have 4 injectors on a bank with only 3 of them are pushing out 100% of the fuel they're expected to spray, and the 4th one is clogged and only puts out 50%, perfect/ideal math would say the computer would richen up the bank 12% to make that bank run 14.7 AFR again at idle, so you'd still have a "safe" +12% TRIM over normal, which usually wouldn't trip a CEL and you wouldn't know unless you watched fuel trims or felt the car was running "rough"
To take another example, during R4 at MSRH I had an injector connector work loose because it wasn't clipped in. It was running rough, had an injector harness code, and the + fuel trim on that bank was "only" 15-17% from from I recall, which would've never tripped a lean code. That's an extreme example with complete loss of one injector though.
Last edited by Pranav; 02-08-2017 at 07:36 PM.
I'm sure all of this is true and correct I just wonder how real an issue this is? How many have had to have then ch=ecked?
JJ
I'm sure Sean would happily tell you about the injector that failed openOriginally Posted by ShadowBolt
and grenaded a new engine. Although doing an injector clean and test
might not have found the offender prior to its failure.
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Laissez les bons temps rouler
I agree I doubt this service would have prevented Sean's issue.
JJ
My three times I've had them tested/cleaned
1. First ever start of my first LT1 when building the car, would only run on starting fluid because most of the injectors were completely plugged with varnish
2. Blew a motor and wanted to check, glad I did because they were starting to clog again with varnish and one was leaking slightly when closed; this prompted me to re-plumb, but was not why I blew the motor
3. New LS swap, immediately sent used ls injectors from ebay off for cleaning; didn't do initial test because the tech smelled bad fuel when taking them off the rail, so they went straight to cleaning. No clue if they were clogged or not but they definitely sat for a while and didn't feel like repeating #1 again nor cheaping out and putting a new motor at risk.
Ultimately if you suspect you have a fueling issue then it would be worthwhile to spend the $150 to find out rather than risk another motor swap. If everything is fine, you're not running lean at WOT, fuel trims are not way off, then maybe not...
As far as what causes injectors to clog and leak, in my case it was definitely varnish from old fuel line and definitely fixed by cleaning, but at the time it was a very small leak. There's no telling what caused Sean's injector to stick open, was it more and more varnish build up or did it break? Sean if you have that injector you should donate it to Injector RX here in town so we can find out lol.
Even despite all of this, we haven't taken into account if a perfectly clean injector works fine when cold but has trouble firing when hot; a lab test wouldn't figure that one out I think...
Last edited by Pranav; 02-08-2017 at 07:38 PM.
New injectors, cheap insurance.....
Jerry did you clean the MAF? Check the cylinders with your scope? You obviously have something going on with either the fuel or electrical/spark or both. Still running weird?
Bryan Leinart
CMC #24
I typically have the injectors cleaned every 4-5 seasons as cheap insurance. It's good peace of mind to get a flow sheet showing they are all within a few percent of each other since the computer can't tell exactly what is going on with each cylinder independently..
At least you guys can check each bank thru the ECU. Even with my "fancy" EFI, I only get to monitor one bank... Now, I've selected the bank that has historically been on the lean side, so hopefully that will equate to a longer life span for the engine..
I used a place in San Antonio last time (Mike Montgomery's recommendation) for cleaning.. I can dig up that info if you need it.
Marshall Mosty
AI/SI Texas Regional Director
2011 NASA-TX American Iron Champ
AI #67 "Mosty Brothers' Racing" (RIP)
ST6 #21 Toyota Corolla (being revived)...
I've had 2 sets cleaned, both entered within a few percent and left within 1-2cc/min of each other. Stock LT1 injectors generally get turned away. Apparently the colied wire that forms the electromagnet to open the pintle has insulation that gets washed away not only by fuel over time, but also more aggressively by the compounds they use to clean the injectors. One of the reasons stock LT1 injectors blow. There are certain LS injectors that play nice, but you really need to do your homework.
RM CMC Director
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