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Hi everyone, I have a 2005 6 port (S1). I installed a reman engine about 4,000 miles ago (bought the car with a bad motor). Ever since the first start, I have been having a vacuum leak-like symptom. Idles high until it's warm, then it starts to choke and die. Fuel trims show that it leans out, goes rich, and then stalls. Is drivable but fuel trims go lean briefly and then shoot to -25 anytime I hit the gas.
I pulled off the vacuum hose that goes from the intake duct to the OMP injectors and gave it a good suck... The vacuum completely disapates after about 2-3 seconds. Does this sound unusual to anyone? I would imagine that system should be holding vacuum.
Notes:
New oil injectors
New vacuum lines from the little vacuum "manifold" to the injectors
new vacuum manifold thing (I forget what it is actually called)
Have NOT replaced the hose from the intake duct to the vacuum "manifold"
New everything else pretty much
New Upgraded ignition system
New intake gaskets (everywhere)
New vacuum solenoids on intake manifold
Shutter valves were cleaned and vacuum tested before re-instillation
There's a lot more I did to the car when I put in the reman engine but this seems like the most relevant info.
The test procedure for oil injectors is if they hold some vacuum for more than a minute (you can google the exact procedure). May want to test them individually to see which one is passing air or if they all are.
But, that isn't your vacuum leak, since any air passing from engine back in the intake is already metered and won't affect fuel trims. I think your fuel injectors are miswired, a common issue when reinstalling engines and will cause negative fuel trims (vacuum leaks/unmetered air cause positive trims). I'm not sure what you mean by "trim goes lean", trims aren't rich or lean.
You can also check the plastic vacuum distributor for the 4 oil injectors.... I had mine leaking air from that piece and it was a nightmare trying to chase the problem down.
The test procedure for oil injectors is if they hold some vacuum for more than a minute (you can google the exact procedure). May want to test them individually to see which one is passing air or if they all are.
But, that isn't your vacuum leak, since any air passing from engine back in the intake is already metered and won't affect fuel trims. I think your fuel injectors are miswired, a common issue when reinstalling engines and will cause negative fuel trims (vacuum leaks/unmetered air cause positive trims). I'm not sure what you mean by "trim goes lean", trims aren't rich or lean.
I found an oil injector that doesn't hold vacuum. Everything else seems to hold vacuum well. However, I will need to confirm this with a vacuum gauge.
I will double check the routing on my fuel injectors.
This vacuum hose routes to the intake duct AFTER the MAF sensor, but BEFORE the throttle body. It's my understanding that air entering the intake after the MAF can still create a lean condition.
When I say lean I am referring to a positive fuel trim.
Originally Posted by Ricky SE3P
You can also check the plastic vacuum distributor for the 4 oil injectors.... I had mine leaking air from that piece and it was a nightmare trying to chase the problem down.
Good suggestion, I did an improvised vacuum test and it did hold for quite a while. Again, something I'll have to confirm with a vacuum gauge.
The test procedure for oil injectors is if they hold some vacuum for more than a minute (you can google the exact procedure). May want to test them individually to see which one is passing air or if they all are.
But, that isn't your vacuum leak, since any air passing from engine back in the intake is already metered and won't affect fuel trims. I think your fuel injectors are miswired, a common issue when reinstalling engines and will cause negative fuel trims (vacuum leaks/unmetered air cause positive trims). I'm not sure what you mean by "trim goes lean", trims aren't rich or lean.
It appears to me that each connector only reaches their designated injector, (if connected from shortest to longest) seeing as the wires are different lengths.
Being the skeptic, and the novice that I am, I snapped some pics of my current routing. If you have a moment to critique them, it would be greatly appreciated.
Junction 1:
3 connectors, wired to the first 3 primary fuel injectors
Junction 2:
2 connectors, wired to both secondary fuel injectors
Junction 3:
4 connectors, one is wired to primary injector 4, the other 3 are for the vacuum solenoids on the back of the upper intake manifold.
Note: I did loosen the bolts that go through the primary fuel rail and the vacuum distributor so see if I could slip out the vacuum distributor. They were tight when I got in there. I also removed the vacuum line to my front oil injector, which does not hold vacuum. I did this in order to vacuum test the oil injector and the rest of the oil injection system. I have not confirmed my vacuum tests with a gauge.
08-21-2023, 04:04 PM
