Every time I fix one problem, another one pops up.

I just put 4 hole injectors on my 2.5 MPI. Exact same design, exact same flow rate, just 4 holes instead of 1.

Now, I keep getting code 27. Now from my understanding, code 27 shows that an injector isn’t reaching it’s highest voltage, or it’s just not working. But this is what confuses me. It’s only happening at idle.

Allow me to elaborate. If I crank my Jeep up in the morning, it idles low. Really low sometimes. It doesn’t miss or sputter, but once I go and give it gas, go though a few gears and then put it in neutral, it then starts to idle really low, misses a few times, sets a CEL, (same code, 27), then it stops missing, increases the idle to just about 1.1k, and it runs like a dream. I’ve tried to reset the PCM, made sure all the connectors are tight and secured on the injectors and any other sensors, but nothing works. I don’t get a miss at any other time, only the one time when it sets the CEL and increases the idle again. I can let it idle after that for however long and it won’t miss again, until I cycle the key and do that process all over again.

Should I start testing the resistance of each injector? And is there any way to tell which injector is causing code 27?

I should also state I don’t have OBDII. Nothing to plug in and diagnose anything with.

 

Seems like a logical place to start, and a careful inspection of the wiring and connectors. Are the replacement injectors the same impedance/resistance as the originals?

 

While it is having the problem, if it will run long enough, you can disconnect an injector. If the problem gets worse then that injector was working correctly, connect it again and try the next one until you find the one that makes the smallest change. Perhaps that injector has a sticky pintle or something. You could try putting one of your old ones in place of it since they are supposed to flow the same. If it runs much better that way then you will know that injector is in some way defective. Lots of labor, but you don't have to buy anything...

 

Whats confusing to me is that she runs better with these new injectors after the issue “corrects” itself. Even at idle, she runs really smooth and my throttle response is a hell of a lot better, even more so after resetting my PCM. I just messaged the seller to see what the resistance of these injectors are, as it wasn’t stated in the listing.

And when I re-sealed the intake again, as soon as I fired it up it was missing, and it seemed like #1 injector wasn’t plugged in all the way, but I couldn’t tell all that well because it wasn’t a complete misfire, more like a “soft” misfire, if that makes any sense at all.

Once I get a response from the seller, i’ll test each injector for the proper resistance. If that checks out, then i’ll move to the ASD relay and make sure it’s always providing power to the injectors, and then from there check all the wiring again

 

The ASD relay provides power to alot of things under the hood, if it was malfunctioning you'd have a bunch more problems.
You can check the resistance on the injectors now, if they're all close to each other then ones not likely the issue at least electrically.

 

Okay. The seller said that the resistance should be 12.5 ohms, and each injector is as follows:cylinder 1-14.4

cylinder 2-14.6

cylinder 3-14.3

cylinder 4-14.2

So it’s not 12.5, but the resistance is within .4 of eachother. So it seems that I might have some more wiring issues to take care of

 

Found the issue. It appears the connector pins for #3 injector were bent/corroded, so a junkyard connector and some heat shrink worked wonders. CEL hasn’t come back on, and it seems to run even better than it has before

 

A little late to the party, but I was going to suggest looking at the connectors. I recently replaced injectors on my V10 Ford E450 and after firing it up I had the same issue. I figured it was a connector issue so went back and checked the #7 cylinder connector. Although it looked connected it was only 90% connected. Removed it, repositioned it, and all was well. FYI, replacing injectors, coil packs, and spark plugs on a V10 E450 is a job that require patience, and it helps if your contortionist.

 

Could be your connection was ok until you disturbed it to put in the new ones. One of the pitfalls of working on an old vehicle. Or it could have been part of the problem all along.

I'm ready to hear in a couple days that it has been solid for a while.