Phydeaux33

1988 2dr Renix 4.0l 120,000 mi.Have done all of Crusier's tips except for the following: 10(its a manual),17,19,20,24,27,30,32,35,36,39,40,and 41. It has always idled at 850 after warm up, I did a seafoam clean through brake booster port and now idle is at 1000. I took it out this morning and when I pulled out the idle jumped to 2500 and stayed, I stopped and shut it down and a minute later started it and it was fine the rest of the trip to town.I have so far done the following:
- Verified TPS (still reading .83 of 4.89)
- Cleaned IAC and checked O-ring (its 6 months old Advance Auto)
- O2 sensor looks good (6 months old NTK)
- Verified for VAC leaks visual and parts cleaner
- Verified intake nuts (all new studs and gaskets 6 months)
- Verified power latch relay was functioning to reset sensors
- Cleaned IAT
I am running out of ideas at this point, I suppose the Chinesium IAC could be the problem just looking for some other input.

tech

I would see if the IAC is still under warranty and change it .

YeepinJeep

Did the same thing with my '89 and have the same issue except I haven't had a spike to 2,500. For me it starts and idles normally, but if I take a long drive for example 45 minutes to work when I park it will idle at or just under 1,000. I don't remember having a high idle prior to the seafoam, but I did just get the car so I am still learning it. Yesterday after a long drive I disconnected the plug at the IAT and the idle seemed to have dropped down into the normal range. Before or after the sea foam I cleaned the IAC and throttle body, but I am guessing that after sea foam either the IAT or IAC got fouled. I haven't taken the IAT out for cleaning yet so that will be my next step, and also checking the resistance on the coolant temp sensor to make sure it is in range. Also should note TPS was changed to fix another issue but did not affect RPM's.

Phydeaux33

So I got the IAC on warranty, no improvement. Its not that it runs bad no misses, no hesitation the idle has just gone up 150rpms. Could it be the TCS?

Phydeaux33

And I meant the CTS, the one on the block not by the head.I won't have the jeep back until Friday, it went in for it's alignment after full suspension and steering upgrade. Just thinking what I should plan on looking at when it gets back.

JGibson

Try adjusting the IAC? I had to change mine out because of high idle, the new one didnt change anything until I adjusted it.

YeepinJeep

How do you adjust the IAC?

Phydeaux33

The IAC is non adjustable did you mean the TPS?

dmoe69

In your original post you say the TPS is set at 83% of 4.89. Did you mean 17%?

Phydeaux33

I said it is reading .83 of 4.89 which is 17%, so yes it is 17%. I could have worded it better.

dmoe69

How long have you had the XJ, and what made you want to do the Seafoam cleaning?

Phydeaux33

I bought it last August and have been rebuilding since then. Was " barn kept" on the post. After having everything out of it minus the motor (110,000 when purchased) it is very much 1988 intact (much to my delight). I only seafoamed it just to "clean the top end" now that it has been on the road for a few months, wish I hadn't.

dmoe69

O.K. cool, that helps. You're already familiar with Cruiser54's tips. In tip 8 (TPS testing and adjustment), just after the 5 steps for adjusting, there is a paragraph for correcting high idle after adjustment. It might be a good idea to try that process. Also, it doesn't hurt to run the TPS at 16% or even 15% if that fixes the idle and there are no new drivability issues. Lastly, the last time I had a high idle I was able to correct it by cleaning the grounds at the dipstick. I had just cleaned the damn thing 18 months earlier and was really surprised to find growing resistance in the ground loop again. While you are adjusting the TPS (if you decide to do that) you might check that you still have a solid ground between the B terminal of the TPS connector and the negative post of the battery. Also curious, is the C101 connector intact?

Phydeaux33

Yes the C101 is intact, and cleaned, the elimination is the only Crusier tip I haven't completed. I have the big 7 cable upgrade and all connections are good. I have undone all of the looms and soldered the ground splices during total tear down. I have thought about cutting down on the TPS, but have been trying to see if something else is amiss.

Phydeaux33

As far as the TPS I did a full check on it yesterday and all specs checked out and the ground was solid, i.e. no Ohm variation through its loom.