High idle with start!

Every time I start the engine run it up to 800-2000 rpm.I have tryed to replaced Trottle position sensor,TDC sensor,Idle air control valve (clean the house),oxigen sensor,air temperature sensor,ECU but no response,hwat more can I do?
Per Garvaag
Larvik
Norway

Which engine and model year do you have?

It is a 1988 4,0 engine.
Per

Did you adjust the Throttle Position Sensor when you replaced it?

There's the C101 connector near the brake booster that can contribute to this and has been a problem for me. Most of the electrical connections to the engine pass through this connector. It's usually full of stiff and sticky grease and it's difficult to restore good electrical contact without cleaning it out. In my experience, the adjustment of the TPS wont have an impact on idle speed.

I have an 89' 4.0L. What does the C101 connector look like? any pics of it? where exactly would it be? I have looked for it but cannot find it.
TIA

C101 is the big connector just above the brake booster on the firewall. It was a trouble maker on both my 87 and 88 XJ. The best remedy is to eleminate it which is easier than it looks if you are intimated by electrical problems like I am. It caused high idle and eratic misses for me.
Good Luck.
MikeU

c101 only on pre 89s. Adjust tps for automatic per attached link: www.members.tripod.com/BillyXJ/SENSORS1/page1.html.

For some reason the link is not working so I copied it below:

"TPS - 1987-1990

The 1987-90 sensor has two pigtail leads. One has an in-line 3 pin
connector, containing 3 wires. The other has a square four pin
connector with 3 wires. The square connector is the one that is used
for the transmission controller. These wires can be identified by the
letters which are stamped into the connector.

Adjustment is simple though backward by most TP standards. With the
harness connected, test the voltage on pins A, B & D. The voltage on
pin A (reference voltage) should be approx. 5v

Voltage on pin D (ground) should be less than 0.1v. If the voltage is
higher, an additional ground wire can be spliced into the circuit.

Pin B is the TPS signal to the controller. The voltage on pin B should
be 4.0 - 4.4v at closed throttle. At full throttle, the voltage should
be 0.2-0.5v. The TP sensor has elongated holes for the hold-down screws which allow it to be ajusted.

Adjustment is as follows: (comments in brackets are mine)

1. Turn the ignition switch to the "ON" position

2. There are 2 wire harness connectors attached to the TPS. Inout/output voltage is checked at the SQUARE, FOUR TERMINAL CONNECTOR (though it only actually has 3 pins). The terminals are identified by the letters A,B,C,D molded into the connector.

3. Do not unplug the connector. The voltmeter leads must be inserted through the back of the connector to make contact with the terminals. Connect the positive lead to terminal A and the negative lead to terminal D.

4. With the throttle plate in the closed position, note the "input" voltage. It should be approx 5.0 volts

5) Remove the voltmeter positive lead from terminal A and connect it to terminal B. The "output" voltage should be 4.2 volts - 82% of input voltage. (NOTE: on my XJ, the input voltage was only 4.6 volts so I had to adjust the closed throttle output voltage to 3.8 volts as this is 82% of 4.6)
If this is not the case, continue with this procedure

6. Adjust output voltage as follows: with the voltmeter leads still attached to, carefully loosen the sensor mounting screws and slowly rotate the sensor until the output reading is 4.2 volts with the throttle closed (or 82% of your input voltage). Then, toghten the sensor mounting screws securely. "

The above info is the workproduct of another jeeper and is pretty much out of the factory manual. Also clean c101 of old lube, clean off corrosion, relube w. dielectric grease to prevent future corrosion. Check ground on tps w. mutimeter and splice in a new one if bad. Spiking high idle at startup is usually tps related. Greg

what was that web site?
I clicked on the link and it said it could not find the page.

GZ32

I thank you all for good response.Well,I have to look to TPS adjust,and the connector C101 it can be some there.
I have not web site
Thanks.

So what you guys are saying is that my 89' does not have a C101 connector?
TIA

No it does not. They changed the design.

I've heard that some '89s have the C101 connector and that others don't. I only know for sure that my '87 has it and my daughter's '89 doesn't have it. If its there, its just above the brake booster and probably has 20 wires passing through it.

Mine does not have the C101 Connector but it still idles high upon start up.

Have you checked for any kind of vacuum leaks? I've been fighting mine for a while but mine would go up to 3000rpm sometimes and not come down. I don't know if I fixed it yet or not, but I greased the throttle return spring and the throttle cable and linkage and so far so good. Hasn't done it in 2 days so far. I'll keep my fingers crossed.

Sporadic spiking high idle is usually a sign your tps is going bad per my dealer tech and my own experience. If not the tps and its connector then check the c101 per above posts on pre 89s. Greg

My '94 revs high at startup (3000rpm or more) but drops to normal in about 3 sec's. Do I have a way to just lower that first high rev without changing anything else? It's a 4.0 HO stock.

On my '87 I had this problem and found that a splice for the TPS was not soldered. The splice was a common for the TPS and several other sensors and is in a bundle that runs across the firewall on the driver's side (assuming LHD).

An immediate high idle that drops soon afterwards is indicative of the IAC not getting set to the correct position as you turn off the motor. There is a latch relay that holds the power on the ECU for a second or two after you turn off the key and that gives the ECU time to "park" the IAC. On the Renix the latch relay is over by the battery in the row of relays. I don't remember which one it is, but you can shift the relays around because they are all the same. Maybe someone will post up a pix of which relay is which.