eaglescout526

Huh. Interesting. Ok. Well only one way to find out. Is every sensor getting 5V from the ECU?

Not as far down as I thought it was gonna be. If you remove the air bonnet, how open is the throttle?

Sounds good and no problem!

Give it a shot. Worst that can happen is it chokes on too much air. Not very. I’ll give ya an example. On chunk my 84 XJ, I swapped to TBI. The screw was too far in and wouldn’t idle for me. I unscrewed it enough(one or two full turns)just to get him to run and idle after two key cranks. I can’t do the adjustment since I’m still missing the down pipe for the exhaust. But there’s a real world situation of how sensitive it is.

This makes me think the ISA screw is too far down and the throttle is all the way closed.

Can you start it with the vac line plugged in and your foot down on the pedal? If you can, adjust the ISA until it will start. Can I get a pic of your ISA? I want to see what we are working with here.

Sounds good. Id test the IAT. Both with the engine cold and at operating temp. It’s based on resistance if I remember correctly. So you’ll be looking for low value while hot and high while cold. I could have that backwards. Cruiser always had a picture of the how the values should be in relation to the temp. I’ll have to find either said pic or take a pic from a manual.

Yes. The ECU can see that the MAP is not getting vac and just defaults to start up values. Which is why it runs rich. If you unplug the map entirely, the ECU will kill the engine. It basically goes back into closed loop with the vac line unplugged. The ISA isn’t that finicky at all actually. It sounds like it but if you follow my ISA adjustment write up that’s straight from the AMC TBI book, it’s less daunting and scary than it seems. I dont know if you have an REM or a tach but you need one of those for the adjustment process. You can test the IAT but that’s just related to air temp.

You can get a new connector for the ISA. I’d recommend getting a weather pack pin removal tool and just swapping the new connector in place of the old one. If it has been messed with, I’d suspect the screw on it is too low and the engine isn’t getting enough air. Hence you unplugging the map. That’s my logical thinking

I feel ya haha. Has the ISA been adjusted or played with? If unplugging the map helps it run better, I’d suspect it’s not getting enough air into the engine which makes me think the ISA has been messed with.

The MJ in your post contradicts the transmission you have in your signature. I digress. Any year 2.5L ECU will work. As far for it not running with the MAP vac plugged it, you could be having an issue elsewhere related to vacuum. Anything else you know about the MJ? Did the previous owner do their own work on it? Did they do any modifications to make it “run”?

Its worth it and a conversation piece too. The only sensors you can not do is the axle....unless you want to drill into the diff cover or swap axles. Thats the problem I have run into. Course I do not know where you would put the trans sensor on the AW4 or AX15. But nothing a drill and tap cant solve. I do have the thread size and measurement. Course the idea of it being a wall hanger is cool too.

No problem. You dont have to unplug the CPS to test it, you can backprobe it so the voltmeter leads stay in contact or have someone help you if you unplug it and test it. The VAC can only be found during cranking. I think 31psi at idle is normal. With the regulator vac line unplugged you should get 39psi.

Its a crap shoot honestly. When I worked at a dodge dealer, there was still some floating around. They could be gone, they could still be there. But you want to make sure that any aftermarket sensor outputs .03 VAC or higher.

It wasnt that bad actually. The challenging part was separating it from the old harness and getting the harness in with the same rubber gromet as the ECU harness. Rest was just lining up where wires went. Honestly, if anyone found one, a sentry set up, it can be installed on an MJ too, youd have to do some drilling and tapping for the old sensors.

Late night experimenting with YouTube. First clip of the sentry in action.

Speedo is good. Took a night spin and that was fun. I can not wait to actually be able to drive this Jeep. Oh and the power is much much better vs the carb. Sure still got 3.55 ratio but it was still fun and still had power to go vs the carb would fight with me a little to just go.

Thickness from starter gear ring to top is 1 1/8” From bottom to top is 1 3/4”.

Ok so I learned the speedo is just dead. It bounces all over the place, balance wheel was out of whack. I did a quick swap around and it should be good. I gotta do another quick zip up and down the street to test it.

It’s funny you bring this up cause I am having a mildly different issue. I can drive the XJ just fine but putting the CPS on and all the way brings it too close to the flywheel yet I’m using the right era bell house. But it needs one bolt and to be close enough to run haha.

Crankshaft position sensor is heat soaked or the coil is. A common problem that seems to pop up when the parts are old. But don’t trust those aftermarket CPS’s though. They can be crap out of the box.

I can bust out my carbed flywheel this evening and measure for ya. It’s the same as Renix just without the gaps for the ECU to read

Ok not much new here in this pic. Added some chrome vents to help give some class to this classless XJ. Also took my original dash mat that was with little red and threw it on Chunks dash. I think it looks pretty good actually. Also got the trans sensor wired in, it works and shows full now. Still need to add the engine but that requires draining the oil to add... I am gonna wait on that. Speedo cable is in. I have no idea if it registers as I was not paying attention when I pulled him back in the garage. Whoops. Still dont know what I am gonna do about the axle sensors. I can only guess where they go and well the D30 does not look like a fun one to add if my guess on where it goes is correct. Still have lots to do.

When I tore apart a 4.0L engine bay harness I found that exact diode. If I remember, it’s tied into the AC circuit.

Could be the relay that does the clicking you are after is newer and quieter. As for the synchro blink, well I have noticed my lights do the same but its barely noticeable except on the emissions light and low washer light. I can see them blinking with the blinkers and watch the voltmeter bounce slightly as I have the blinker on. So your issue sounds normal.