Hey guys,

My CEL came on the other day, so I read the codes. I'm getting 25 and 27, something about the injection system. Anyways, my idle has been running really rough and sometimes taking right turns (most noticeable) I'm getting a bucking hesitation type thing. I'm pointed toward the fuel system, but I don't know how complex the 91's system is. I changed out the fuel filter last year. Fuel pump? (my experience is that they are usually good or not)

As always, any insight is greatly appreciated!

 

I'd start by connecting a fuel pressure gauge and see what you're working with. Fuel pumps can die a slow death, providing enough pressure to run the engine, but not enough to run it properly.

 

Code 25: Automatic Idle SPeed motor driver circuit. Short or open detected in one or more of the AIS control circuits.

*This is often related to the idle air control, mounted on the throttle body. You could try cleaning it, but for this code, I'd consider replacing it. Don't buy a cheap one from ebay; they're junk. Clean the throttle body while you're at it.

Code 27: Injector control circuit. Bank output driver stage does not respond properly to the control signal.

*Code 27 can be tricky. It means the computer isn't seeing the injectors pulse. This can be anything from a fuel injector connector, a fuel injector, or possibly even the computer (be sure you rule out everything else before swapping the computer).

I'd start with chasing that idle air control, clear the codes and see where you're at.

 

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Is this the part that I should try to throw at it?

 

Just try cleaning that and the throttle body out first before throwing money at it, carbon usually just gums it up. Look for an unplugged injector, broken connector or broken wires for the injectors. Then test the injectors and computer

 

I took off the throttle body, took the IACV out and scrubbed it up (was pretty nasty), jiggled the injectors around and voila (for now at least). She's running better than ever.

Thanks guys

 

Well it didn't last too long. Back to the square one. I'm thinking that something with the injector code must be causing the fouling in the throttle body. Anybody know of a guide or something that I can test the signal to the injectors or how to pull the injectors and clean all of them?

Thanks again!

 

Maybe I should try to find some 703 injectors and upgrade them while I'm trying to sort this out.

 

When I pulled the throttle body off, it really wasn't dirty at all.

 

I ohm tested and all of the injectors read 14.6. All of the connectors look good. I rechecked codes and I have 15 (speed sensor, does this have to do with why my speedo is intermittent?) and 27 still (fuel injector control circuit).

 

I swapped to the neon injectors (thanks Programbo!) and reset the PCM, and right now all seems good. No codes yet after a quick spin.

Do you guys know if there should be a bit of a gap under the injectors? I couldn't really force the bottom of the injectors into the cylinder head, so I just lined them up and bolted the fuel rail back on. I ran the engine and took a flashlight looking for leaks and I think I'm all set, but that gap just made me nervous.

So now the front pipe / cat junction split open and I'm wondering if that's why my idle is total ****?

Thanks!

 

Just kidding, code 27 is back. How can I test my injector wires before buying a computer?

 

So I took out the computer to see if a component was burned up or something. Unfortunately the board has a rubber coating over it. I cleaned up the plug contacts with a cleaning spray and re-installed. I cleared the pcm again after installing and I haven't yet seen any codes after a few quick trips. The jeep's also running wayyyy better.

I checked each injector plug one at a time with the DVM.
With the key on (priming) one pin on the plug would read 5v to ground. Running, the other pin would read between 0 and 1v. They all tested this way, so I'm thinking that the wiring is good.

You guys think I may be out of the woods that easy?

Thanks,

 

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