Renix idle issue

[stephenspann27]

Since I'm getting backfires through the intake when it's having a hard time starting.. my dad said its probably the CPS. He said if you are getting backfires through the intake it's and indication of the timing being off. And.... if it runs half way decent when it's warm the timing should be set pretty close.

 

[90Blue_XJ]

Since I'm getting backfires through the intake when it's having a hard time starting.. my dad said its probably the CPS. He said if you are getting backfires through the intake it's and indication of the timing being off. And.... if it runs half way decent when it's warm the timing should be set pretty close.

Generally speaking your dad is correct. But with MPI type engines the timing is controlled by the computers and the computer varies many things depending on the inputs and not so much the mechanical things like it was on carb equipped vehicles. So the info Dad has is more in keeping with a carb type vehicle.:rof:

 

[xjtrailrider]

If you are getting "backfire" through the intake on a RENIX you should take a look at the EGR valve first, it may be opening up at the wrong time or stuck open.

 

[stephenspann27]

If you are getting "backfire" through the intake on a RENIX you should take a look at the EGR valve first, it may be opening up at the wrong time or stuck open.

Good point, thanks guys!

 

[89xj]

Generally speaking your dad is correct. But with MPI type engines the timing is controlled by the computers and the computer varies many things depending on the inputs and not so much the mechanical things like it was on carb equipped vehicles. So the info Dad has is more in keeping with a carb type vehicle.:rof:

but, the cps does send an input signal to the computer. timing is variable(advance and retard), so a faulty signal from the cps would affect timing. this is why some people modify the cps to advance the timing or get a high altitude cps.

 

[stephenspann27]

I think I have a CPS on my parts jeep.. it's pretty pricey right?

 

[90Blue_XJ]

I think I have a CPS on my parts jeep.. it's pretty pricey right?

About $40-$60
CPS sends pulses to the ECU and the ECU needs to see three before it turns on power to the injectors to open them at the right time. So in a sense the ECU neds to see those pulses before it does anythinhg about timing for the ignition.:read: