Z24i 1986.5 - Stumped with the TBI system.

[MikeOnaBike]

 

Good day all.  Been having hell with my dad's old D21.  It had a motor replacement several years ago and ran okay afterward.  Fast forward a few years - he hasn't driven it in a few years because it doesn't run right, so I've taken it on as a project for him.  It wont idle right unless it's idling fast.  After reading a lot on this forum (thanks btw - especially to datzenmike!) I have learned a lot about this truck.  Here are a few things that don't add up to me:

It's an 86.5 z24i, but it has two injectors instead of one. Is that normal on the 2.4? The manual I have says that it should have one - but the manual is from 88 not 86 (I was unable to find a 1986 service manual anywhere.)

It has no Idle-up solenoid.  There's not even a threaded spot for one in TB, but there is a FICD . The harness is 6 pin rather than 8 pin.  4 wires for injectors and 2 wires for FICD.

After replacing the A/C dash switch, I now get a little power to the FICD, (not 12v, but it actuates as it should with the A/C on.)

 

Is this not the correct TB for this motor?  It has the old toggle type ECM, so I can't get it into "modes" but the code it throws is 23 and occasionally an 11.  The timing is set to 10 BTDC when warm.

 

Thanks!

 

[datzenmike]

The Z24i has two fuel injectors.

 

Timing for the Z24 (so I assume the same for the Z24i) is 3 degrees. Ten would be much to high. Check that both intake and exhaust side plugs are firing. It won't run well on single plugs.

 

11 code is crank angle sensor

23 isn't listed as a code for anything

[Icehouse]

I got the same rig.  86.5 D21 with the Z engine.  When I got it the truck ran funny.  Exhaust plugs were in the wrong order.  It only showed up at low rpms, well I mean noticeably.  My dad's rule was always do a full tune up before trouble shooting, you might save your self a headache.  My buddy sold a car once he bought because he couldn't figure out an issue.  His buddy bought it.  The dizzy cap was broken and for a couple bucks it ran perfectly.  

[datzenmike]

Just in case...

 

[MikeOnaBike]

On 11/7/2023 at 12:34 PM, datzenmike said:

The Z24i has two fuel injectors.

Thanks.  The service manual clearly states that the z24i should have one and the 30 should have 2.  Not sure what that's all about - but it is a service manual from 88 and not from 86.

 

Timing for the Z24 (so I assume the same for the Z24i) is 3 degrees. Ten would be much to high. Check that both intake and exhaust side plugs are firing. It won't run well on single plugs.

Again, service manual says 10 degrees but I'll try 5 and see if that helps.

 

11 code is crank angle sensor

Got the 11 code fixed, it was a bad ground to the distributor.  It also helped with the rough idle.  However, it still shows code 23 and doesn't idle right until it warms up.  If I put 12v power to the FICD, it will idle up and the A\C compressor will kick in, otherwise neither works.  I checked power out to the FICD and ground.  Ground is good, but the power is mVolts and not 12V. Unsure if that's correct or if the FICD is not receiving power from the ECU.

 

23 isn't listed as a code for anything

It's flashing code 23.  It the only code I have left. I have found some reference to it online as a idle switch code.  The 88 service manual I have doesn't reference it, but I believe there was a different ECU between 1986.5 and 88.

 

Thanks for your help Mike.

 

[MikeOnaBike]

17 hours ago, Icehouse said:

I got the same rig.  86.5 D21 with the Z engine.  When I got it the truck ran funny.  Exhaust plugs were in the wrong order.  It only showed up at low rpms, well I mean noticeably.  My dad's rule was always do a full tune up before trouble shooting, you might save your self a headache.  My buddy sold a car once he bought because he couldn't figure out an issue.  His buddy bought it.  The dizzy cap was broken and for a couple bucks it ran perfectly.  

 

Thanks!  I have done a pretty thorough tune up.  New plugs, wires, cap, rotor, fuel filter, fuel pressure check, verified good spark to all cylinders, compression good, quadruple checked the wire placement and the ignition and exhaust coil wires.  That's all good. 

[datzenmike]

I checked and the Z241 after '88 did only have ONE injector. Learn something every day.

 

10 degrees seems like a lot but might only apply to the '89. Try to find out what the '86 is set at. These are CAS (crank angle sensors) and maybe how they are set compared to the regular distributors they replace.

[MikeOnaBike]

34 minutes ago, datzenmike said:

I checked and the Z241 after '88 did only have ONE injector. Learn something every day.

 

10 degrees seems like a lot but might only apply to the '89. Try to find out what the '86 is set at. These are CAS (crank angle sensors) and maybe how they are set compared to the regular distributors they replace.

Thanks again.  I found that the 86 is supposed to be 5 degrees +\- 2, so you were right on! 

[datzenmike]

Yeah that's much better.

[MikeOnaBike]

Found the issue(s).  Intermittent ground to the crank angle sensor and vacuum leak between the throttle body and the intake at the gasket.  Reset the timing to 5 degrees.  Runs smooth as a sewing machine now.  FIDC issue was empty coolant in the A/C system - I assumed that it'd send and idle up signal on start-up even without the A/C system charged (because it does so when the A/C is turned off) but no.  Thanks for all the help. Hopefully this will help someone else along the way.