High idele / relay Q/A

I know that every XJ is different and this is a hard question to answer, but..... Okay I have replaced tps sensor and Idle motor, checked vacuum lines, played with electrical relays, searched...but nothing. I have however come up with a "sort of fix".

Here are particulars: 88 4.0 manual stock basically

On some start-ups you get crazy high idle, sometimes will kick down on own.
If you kill it you are guarnteed crazy high idle, that won't kick down for anything.

Here is the fix...on the passenger side electrical panel under hood, there are four blue relays in a nice straight row. During high idle if you pull the third relay from the front out, the idle drops really low, put relay back in, idle runs perfect. I have replaced and swapped the relays to no avail.

Now the question, what does that relay run? Is it an essential need? Is there a way I could put a switch in line on the power end of the relay to cut power to it and end high idle....? I know that the switch thing is a little redneck, but would it work? (no need to bash me...lol)

Just some thoughts and questions...

Thanks for any advice

Maybe this will help.

It's called the B+ Latch in the picture it's called power latch.
What it's for is to reset the IAC when you turn the key off.
It powers the ECU for 3 seconds when the key is turned off to reset the IAC motor.
Some times you can hear it click after the key is first turned off.
You can even hear a buzz from the IAC as it's backing off.

Thanks guys, is there a way to "manually" shut this relay off. When engine is killed no amount of turning the key off or on will fix high idle. Do you have any idea of the proper way to fix it, or possibly a redneck fix?

jeepchkee said:

Thanks guys, is there a way to "manually" shut this relay off. When engine is killed no amount of turning the key off or on will fix high idle. Do you have any idea of the proper way to fix it, or possibly a redneck fix?

Click to expand...

No redneck fix fix it right but then rednecks are used to walking.

Good point, and I agree, any ideas on how to fix it?

What would be broken or wrong?

This helped mine for a while, now something else is causing the IAC to jump up and its not the latch relay, with the latch relay removed and the TPS properly set somethng causes the IAC to open anyone else got ideas on what else would make the old renix box open the IAC

wilcharl said:

This helped mine for a while, now something else is causing the IAC to jump up and its not the latch relay, with the latch relay removed and the TPS properly set somethng causes the IAC to open anyone else got ideas on what else would make the old renix box open the IAC

Click to expand...

Low temp detected by MAT or Coolent Temp or open connection, A/C compressor run, low voltage detected from ALT, knock detected, gear selected signal detected, high o2 detected.

How many miles on the O2 sensor in your rig? The Renix is a first gen type good for about 60-80k according to Bosch.

I suffer the same thing - reset the computer lasts one day, and the other causes appear to be less important than the O2 at this point, as I have 154k plus and no clue when the O2 was changed last by the previous owner.

So I'm giving it a shot - maybe it will help my 14 mpg.