Other than iac and tps, what could cause high idle?

 

Check all of your vacuum lines make sure there are no holes or disconnected hoses.

 

When you run seafoam through the brake booster, does that stuff go through all the vacuum lines? If so they are no leaks.

I'll have to triple check the vacuum lines. Remix system has a ridiculous amount of vacuum lines.

 

O2 senor. Clean it before you replace it. Pull it out and spray it with brake cleaner shake and repeat several times. There is a bb in side that gets gunked up with carbon. Dose not mean it is bad you just have to clean it.

 

Mine runs at a high idle sometimes. Usually only in park or neutral. Also when I crank it over and it almost starts but I let of the key to soon and then crank it again till it starts it will start at like 2000 rpms and then drop down to 1200

 

I got the 89 Laredo changed tps, cps, fuel pump and filter also all vacuum lines that are visible. I got a fuel pressure regulator just haven't put it on yet hopefully that is what will fix it.

 

What is your temp at high idle. Could be its in worm up mode. That would give high idle and pore gas mileage. Could just be a temp sensor.

 

I'll pull the O2 sensor. Im not sure how old it is. It may need to be replaced anyways. I was going to replace it with my injector upgrade, but $50 is hard to come by for me atm.

As far as the temps, it was already warmed up. 1200rpm was in park but it is still 1000~1100 in drive and neutral. Sometimes still 1200rpm as well. When it is cold it is actually in the 800rpm range.
I just replace the thermo. A 180 was in there and swapped it out for a 195.

 

LOL, thats nothin....
I just got mine down to 1500 idle....it used to be 2100...

Make sure both your manifolds bolts are tight.
Thats what "fixed" (or lowered) mine.

 

Im having the same problem did anyone ever figure out what it was??

Ive been haven a hesitation problem since ive own this jeep and ive tryed replacing just about everything to fix that problem iac tps vaccum lines was also getting alil hot so i put a new thermo.

I started it one day this winter and noticed something strange that my idle was low at 10F outside i said 600rpm thats kinda low or the temp so i waited 15 mins till it warmed up and the idle was at 1100-1200.

My dad had played with the idle screw on the tb and the tps so we figured it was just that.

I goto start it up a couple of weeks ago and drive it idle is kinda low about 800 i let it warm up couple mins and the idle is up to 1200 rpm.

Its doing that hesitation and high idle in park and neutral. So i say im gonna swap out the throttle body.

I pop the new one in and start it the idle seems high at first then drops down a minute later like normal so i think 10 mins later the idle is up to 1200 rpm.

So the problem was the same. Any ideas?

 

First off, the TPS is adjustable and needs to be adjusted properly. Also, as you indicate sometimes people "screw" with the butterfly stop. Never supposed to do that. There is a way to get it back to stock.

All Renix Jeeps are prone to sensor grounding issues which give false info to the ECU. This, and the procedure below if it applies to your model year, should be done prior to a TPS adjustment. A good ground refreshing/upgrading is super important as a maintenance procedure.

To those of you with 87 and 88 models having the C101 connector above the brake booster, there is another source of poor continuity which can mess up signals to the ECU and from the ECU. That connector needs to be refreshed also.

A simple multimeter that costs $10 will work for you to test things. I will post below the procedures in order of importance. They're simple, cost almost nothing, take little time, and are very worth the time and effort. Don't take any shortcuts or skip any tests. If you're not familiar with using a meter, it's time to learn. You're in the Renix world now.

Renix Ground Refreshing
The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, and wasted money replacing unnecessary components.
The components grounding at the dipstick tube stud are:
Distributor Sync Sensor, TCU main ground, TCU "Shift Point Logic", Ignition control Module, Injectors, ECU main ground which other engine sensors ground through, Oxygen sensor, Knock Sensor, Cruise Control, and Transmission Sync signal. All extremely important stuff.
The factory was aware of the issues with this ground point and addressed it by suggesting the following:
Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. Scrape any and all paint from the stud’s mounting surface where the wires will attach. Must be clean, shiny and free of any oil, grease, or paint.
Inspect the wire terminals. Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Reinstall all the wires to the stud and tighten the nut down securely.
While you’re in that general area, locate the battery negative cable which is fastened to the engine block just forward of the dipstick stud. Remove the bolt, scrape the block to bare metal, clean and polish the cable terminal, and reattach securely.
Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for it’s intended use and subject to corrosion and poor connections at each end.
First off, remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Reattach securely.
Remove the other end of the cable from the rear of the head using a 3’4" socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely.
A suggestion regarding the braided cable:
I prefer to add a #4 Gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18" long with a 3/8" lug on each end works great and you can get one at any parts store already made up. Napa has them as part number 781116.
A further improvement to the grounding system can be made using a #4 cable, about 10" long with 3/8" terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. Napa part number 781115.
　
　
If you want to upgrade your grounds and battery cables in general, contact Jon at www.kelleyswip.com. He makes an incredible cable upgrade for a very reasonable price.
　
Revised 11-28-2011

Renix Jeep C101 Connector Refreshing
　
The C101 connector on 1987 and 1988 Renix Jeeps was a source of electrical resistance when the vehicles were new. So much so that the factory eliminated this connector in the 1989 and 1990 models. The factory recommended cleaning this connector to insure the proper voltage and ground signals between the ECU and the fuel injection sensors. We can only imagine how this connector has become a larger source of voltage loss and increased resistance over a period of almost 25 years. The C101 connector needs to be cleaned at least once in the lifetime of your vehicle. Chances are it’s never been done before.

Almost every critical signal between the engine sensors, injectors, and the ECU travel the path through the C101.
The C101 is located on the driver’s side firewall above and behind the brake booster. It is held together with a single bolt in it’s center. To get the connectors apart, simply remove the bolt and pull the halves apart. You will find the connector is packed with a black tar like substance which has hardened over time.
Take a pocket screwdriver or the like and scrape out all the tar crap you can. Follow up by spraying out both connector halves with brake cleaner and then swabbing out the remainder of the tar. Repeat this procedure until the tar is totally removed. This may require 3 or more repetitions. Wipe out the connectors after spraying with a soft cloth.
If you have a small pick or dental tool tweak the female connectors on the one side so they grab the pins on the opposite side a bit tighter. Apply a true dielectric grease, not the stuff that came with your brake pads, to the connection and bolt it back together.
　
　
Revised 11-29-2011


RENIX TPS ADJUSTMENT
Before attempting to adjust your TPS be sure the throttle body has been recently cleaned. It's especially important that the edges of the throttle butterfly are free of any carbon build-up.
IMPORTANT NOTE: Using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS. The letters are embossed on the connector itself. Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it parallels the valve cover and also over near the MAP sensor on the firewall. If you see more than 1 ohm of resistance, or fluctuation in your ohms reading, some modifications to the sensor ground harness will be necessary. The harness repair must be performed before proceeding. I can provide an instruction sheet for that if needed.
MANUAL TRANSMISSION: RENIX manual transmission equipped XJs have a three-wire TPS mounted on the throttle body. This manual transmission vehicle TPS provides data input to the ECU. The manual transmission TPS has three wires in the connector and they're clearly embossed with the letters A, B, and C. Wire "A" is positive. Wire "B" is ground. Key ON, measure voltage from "A" positive to "B" ground by back-probing the connectors. Note the voltage reading--this is your REFERENCE voltage. Key ON, back-probe the connector at wires "B" and "C". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For example: 4.82 volts X .17=.82 volts. Adjust the TPS until you
have achieved this percentage. If you can't achieve the correct output voltage replace the TPS and start over.
AUTOMATIC TRANSMISSION: RENIX automatic transmission equipped XJs has a TPS with two connectors. There is a flat three-wire connector, same as the manual transmission vehicles have, and it is tested the same as the manual transmission equipped vehicles—
FOR ENGINE MANAGEMENT RELATED ISSUES. However, the automatic TPS also has a square four-wire connector clearly embossed with the letters A,B,C, and D. It only uses three wires and provides information to the Transmission Control Module. Key ON, measure voltage between "A" positive and "D" ground. Note the voltage. This is your REFERENCE voltage. Back-probe the connector at wires "B" and "D". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be eighty-three percent of your REFERENCE voltage. For example 4.8 volts X .83=3.98 volts. Adjust the TPS until you have achieved this percentage. If you can't, replace the TPS and start over. So, if you have an automatic equipped XJ your TPS has two sides--one side feeds the ECU, and the other side feeds the TCU.
FOR AUTOMATIC TRANSMISSION RELATED ISSUES. Check the four-wire connector side of the TPS.
If you have ENGINE issues check the three-wire connector side of the TPS. For those with a MANUAL TRANSMISSION--the TPS for the manual transmission XJs is stupid expensive. You can substitute the automatic transmission TPS which is reasonably priced.
Revised 04-30-2012

 

ill be sure to look into that.

however ive sanded and cleaned and added a new ground to battery cleaned other grounds and nothing seemed to happpen.


The braided wire has some oil around it on the block end but ive cleaned the firewall end and sanded. Put a brand new ground cable on the battery. to block even added an extra chassis ground to the battery.



Ive replaced the original throttle body with another that doesnt appear to have anything played with had its tps replaced once.

From the looks of it and hasnt be moved or touched since i installed it on my jeep no screws have been touched on this new one and my problems are the same.


Except now since winter ive been getting this wierd idle the car will start off at 750rpm then after warming up it will be at 1200rpm.

Ill assume this is a different problem then my original.

 

You don't mention the grounds at the dipstick tube stud. Extremel critical!!

 

Yes just to refresh this post ive refreshed all the grounds like ive stated the negative that comes off my battery runs to a spot right next to the dip stick and ive sanded and put it back on

Btw that cable was acutally a positive battery cable so im pretty sure its plent thick enough. ive cleaned the fire wall ground sanded the paint right off.

I have a high powered audio system so do know about grounding.

My headlights dont flicker my radio doesnt flicker i dont pop fuses

So the car is grounded as good as it could be for what it is.

However i will try to follow up on some of the other stuff you mentioned here like the connectors.

I will also readjust this tps so i know its at the right volts. But ive adjusted 3 different ones and they dident make the car run better the problem was the same.

Also should i mention i get poor mileage 15-14 highway and 12 intown