RENIX 2.5L Choke

I have a problem with my 1986 2.5L XJ. It is throttle body injected and has the remix computer system. I am pretty sure that it should have some sort or choke. The ISA motor works (recently replaced) and my cold idle is around 2700 rpm for like 5 sec. then drops to my normal hot idle. So there is basically not type of choke and I am wondering what would cause this problem. I have replaced the CTS and O2 recently and I am left wondering what would be causing this now choke condition?

tgoff said:

I have a problem with my 1986 2.5L XJ. It is throttle body injected and has the remix computer system. I am pretty sure that it should have some sort or choke. The ISA motor works (recently replaced) and my cold idle is around 2700 rpm for like 5 sec. then drops to my normal hot idle. So there is basically not type of choke and I am wondering what would cause this problem. I have replaced the CTS and O2 recently and I am left wondering what would be causing this now choke condition?

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There is no choke so check your temp sensors, intake air and coolent.

Check the throttle position sensor

I just received a FSM and I was able to find out what inputs the ECU gets for the warm up mode. It gets inputs from the CTS, MAT, MAP, speed, knock, throttle, and AC sensors. My coolant temp sensor was bad and has been replaced. I have tested both the MAT and MAP sensors and they both spec out so they are still good. This leaves me now with only the speed, knock, and throttle position sensor. I will test these later today and hopefully solve the problem. I have one more question how do you test the knock sensor without the diagnostic tool M.S. 1700? Under the 2.5L cec section of the FSM it mentions the knock sensor but when I try to find a part number or replacement part I can't find one. So does the TBI 2.5L even have a knock sensor and if so does anyone know the part number? Thanks.

You test the knock sensor, believe it or not, with a hammer.

Hook up a timing light, find your timing mark, and have a friend watch the mark while you crawl under the vehicle and whack the side of the block with the hammer. If the timing mark jumps, the knock sensor works. If the timing doesn't change, the knock sensor doesn't work.

Well I found out that my engine speed sensor (crank position sensor) was way out of spec so I will be replacing that tomorrow. I need a way to test the throttle position sensor the FSM (1988 and I have a 1986) says to test for voltage while the harness is still attached through the back terminals. However my terminals are insulated too well and I don't feel like cutting insulation off the wires to get to them. I am hoping that someone has a different way of testing it besides voltage, like resistance specs maybe.

voltage is the only way to go, use some t-pins to backprobe the connector