Code 27: injector circuit malfunction (what would you do?)

[miwoodar]

Greetings,

What would you do?
A) get an ODB1 scanner and continue down the rabbit hole? or
B) throw in the towel and take it to a mechanic?

I've owned my garaged 95 YJ for 16 years and have loved it since day one. I've done almost all of the work on it and it's in excellent shape (my dad is a mechanic). The problem? It must have heard whispers that I was considering selling it and now it's pulling a Herbie on me. Clearly, it does not want to be sold.

A few times recently, it gave me a check engine light (super surprising). The flashing light sequence indicates code 27 for an Injector Circuit malfunction. It's intermittent.

* The injector plugs are receiving both positive and ground (used a test light). Removing an injector plug will cause a rough idle and an immediate CEL.
* I put seafoam through the intake, independent of this concern, a couple of months ago (four-hole mustang 5.0 injectors have ~50k on them).
* I popped in a new relay into the Auto Shut Down relay slot (no change).
* If I disconnect the battery, it will usually show code 27 prior to starting. The CEL stays off after restart.

Poking around the engine bay while running, I can occasionally hear it drop a cylinder while pushing/pulling on the wires on/adjacent to the injector rail. It is not consistent though. No single push/pull anywhere will cause a reproduceable response. I really do not want to rip into the wiring harness as I'm concerned I could end up with a litany of other issues.

I have spent a ton of time with the vehicle this year and have finally finished all of the projects I had been dreaming of over the last decade. I'm just not sure what to do next. I have no interest in playing guess-and-check with a pile of parts swaps (definitely not if I go mechanic route). The engine bay is CLEAN. It's never been mudded or abused in any way.

Thoughts?

 

[miwoodar]

Forgot to mention that I cleaned the male/female sides of the injector plugs with electrical cleaner.

 

[Chris]

If I was a betting man, I'd almost bet you've got a break somewhere in the wiring harness. I can't tell you how often this is the case and how often it gets overlooked because in many cases it requires doing some serious investigative work and tearing apart the wiring harness.

I don't trust mechanics anymore (it's so hard to find a good one) so if it were me I would figure it out myself.

 

[miwoodar]

Thanks Chris! How is this usually done? Would an experienced mechanic take the harness off and inspect it off of the vehicle? Or would they leave it in place and probe and probe and probe?

A period correct OBD1 would tell me which injector, 1-4, is not firing, correct? I'm having a hard time figuring out which one to get without going to an MT2500. Google just wants to convince me to buy OBDIIs until the cows come home.

 

[dieselearl]

that a GOOD looking machine. you can be commented for the good work that you have done. why are you even thinking about selling. the cyl that it seems to drop, change out the injector to another place and see if it still happens. maybe just a bad one. keeping driving till it get worse? run you gas tank low, put in more sea foam may just need a real good cleaning? with the experts on this forum i bet it can be fix without a heavy bill. checking the wiring take time, but you already got a lot of time spent. keep us posted. good luck

 

[JKP]

Nobody ever wants to test/inspect the wiring... You're gonna have to inspect the injector wiring for chaffing.

 

[Plastic Fury]

I had a similar issue with my 95. I went through the whole Jeep when I bough it, pulled the engine, etc. I swapped out the OEM injectors that were nasty with rotted o-rings for a new set of K-suspension 4 hole injectors during the rebuild. It ran great for a month or so and then I began to have an intermittent problem similar to yours. I would lose a cylinder or two and then it would be back. Sometimes I could turn it off and restart and it was normal again. Other times, that didn't work and I'd be limping it back home. I played with the harness while idling and sometimes it would do it and sometimes not.

I had considered one of the new injectors could be faulty and during the rebuild I was very thorough and like you mentioned, I cleaned all the injector connections with good electronic cleaner. I had intended to then hit all the injector connections with some dielectric grease but just forgot to do so. When trouble shooting, I remembered this and went ahead and applied some to all of the injector plugs. In my case, that did the trick and for over a year now, it's been running like new.

Just a suggestion before tearing into the harness as it's a simple task and in my case, fixed the issue. I was at the point that I was ready to open up the injector harness and begin inspecting all the wiring but thus far, glad I have not had to.

 

[miwoodar]

Thanks friends. I think I'll put some miles on it and see what happens. This seems better than tearing into wiring for an intermittent problem.

I haven't checked the ohms on the injectors (could it be this?). I did apply dielectric grease to the clips when reinstalling. Your Sahara is beautiful!!

Would any of the ODBI readers be able to pinpoint where the fault could be happening if it becomes persistent?

My friends were shocked. The only reason I was considering selling was that I knew I would never own a miata unless I opened the spot in the garage (we no longer need four seats or 2nd 4x4). I bought the project miata (2002) to force the sale, then baulked. Then this happened.

The first time I got the CEL was immediately after dropping the fuel tank to finish POR15'ing the last bit of the frame/replacing the tank skid plate. Nothing I've read would point me to return to the fuel pump wires/plug as the culprit. Agreed? The CEL came on as soon as I restarted though. If a bit of something got mobilized and made its way to an injector maybe? Is this remotely possible?

As part of my prep work, I swapped RC 2.5" for OME 2" (RC bushings were shot at less than 20k miles). This is the lift I always wanted - the ride is better than ever. And I love it more than ever.

 

[miwoodar]

Nobody ever wants to test/inspect the wiring... You're gonna have to inspect the injector wiring for chaffing.

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I've learned how to do a lot of stuff over the years - way more than I ever could have imagined. I really think the only way these things stay on the road is through enthusiasts. If I had to pay for all of that labor, it would have never happened. Maybe this is just my next avenue for growth.

My dad had a Spitfire around the time I was born. The wiring problems never ended. In spite of being at ease with circuitry and being a career mechanic, he says the best thing that ever happened to that car was it being totaled by an errant pickup truck. Fortunately, nobody was in it at the time.