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Idle problems

Gasoline

NAXJA Forum User
Location
Italy
Hallo to everyone, first all, please excuse me about my bad english, second, l wanted wirte you, becasue in past time you helped me more than one time, so l hope that this time you can do it again :cheers:.

Well, l start with my problem, on my 89 XJ Limited l have idle problems. I already read many topics about it here, but unfortunately my bad english made me understand little. So, when l bought my XJ about 4 year ago, so the idle was close to 900rpm, and l think was a good idle, but since one year or maybe more, the idle is always close to the 300/400rpm. So, l though abuot some sensors and l changed the injectors, spurgs and wires, rotor and all electrics stuff. Map sensor and OS too. The water sensor seems good. Anyway sometime in past time when l started the engine, the idle came up of 2000 and after l turn off and on for a couple of time the idle never came in the 300/400rpm.

So, with all these thigns l told you, are you able to telling me, what's the problems are? I want also say that at the first the fuel comsumpion was about 6/8Km per litre (sorry l don't know in your system) and now is always between 4 and 5. I know that the different is low, but why?

I have the 31" tires but with the 2.5 diesel axels, so the ration should be like the original.

Thanks to had read everything and hope you understood.

Bye for now. Moreno.
 
Do you have the 4.0 with the automatic transmission AW4 or something elso? Normal fixes for this are adjusting the Throttle Position Sensor and cleaning the Idle Air Control. The ground connections from the motor to the body and the body to the battery should be cleaned. If you need more help on adjusting the TPS, ask for it and the RENIX experts might respond. Mine is different.
 
First all, thank you for your help Winter, and you're right l forgot to write that my XJ is a AW4. I had check that trottle position in past time, but l think l didn't do a good job, so l have to check it again. Do you mean to clean the step motor to clean it, right? I did, and l had try to move it, and l found that it was a bit hard to move. I mean to push it inside the motor, maybe becasue it was already closed, l don't know the normal position. I hear a friend that he told me that he had try to move it out and it brake it. Anyway he told me that the movment is about 8 10 millimeters, is it right?

Thanks again.

Moreno :)
 
Moreno; this may be helpful. I would start with cleaning both the idle air control and the throttle body. They get carboned up over time; very common and can affect idle quality. Don't worry about your mastery of the english language. We haven't mastered it ourselves! Good luck and keep us posted on how it goes...

Cleaning the IAC:
1. Remove the IAC with a torx 15 driver (2 bolts)
2. Gently wiggle out the IAC from the throttle body
3. Clean the IAC with throttle body cleaner (not carburetor cleaner ) Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle as it is fragile and you can damage it pretty easily
4. Also clean where the IAC seats in the throttle body with the same throttle body cleaner
5. Consider cleaning the entire throttle body itself as long as you’re at it
6. Reinstall IAC and check idle quality
 
Thank you very much BirchlakeXJ about your help and abuy my english heehehe, Well, I think that you mean the IAC is the Idle stepper motor right? If it is, l did what you wrote me, but l can also think that maybe that little motor be damage. Do you know if there's a test to do so see if it work fine or not? I mean with it in hand, not mounted on the trottle body.

Then, can happed that it be also some electric problems? I mean do you know if there been other cases that was some wire to check or brocken around there?. And last question, if the IAC (if l understood well what it is) is the problem, it can be cause of fuel comsumpion?

Thank again for every help :)

Moreno.
 
Moreno,

Yes, the IAC is the stepper motor. I'm not sure of how to test it; maybe somebody else will chime in with more knowledge of this component. Generally, it's just cleaned and if still suspect after that, replaced. All wiring and connector for the IAC should be inspected closely; connectors are best cleaned with spray electrical cleaner. Do you have any access to junkyard (salvage) parts over there? Yes, the IAC can be failing to a point where cleaning it is of no value and replacement is necessary.

Here is a good link to understanding your RENIX vintage XJ. You might have seen it already but it bears reposting. Good luck!

http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm
 
Thank you very much for your help birchlakeXJ, l checked that link and tomorrow (weather permitt) l'll do those checking.

Bye for now and l'l let you know aobut it, thank you again :)


Moreno.
 
Moreno,

Found this information on "testing" of the idle air control. Hope it helps.

1. Verify that there are no vacuum leaks or other mechanical problems that can affect the idle speed.

2. Start the engine, let it warm to a normal operating temperature and observe the idle speed.

3. Turn on various things such as the air conditioning system, high beams and observe the idle speed.

4. With the brake pedal firmly depressed, place the vehicle in gear. Observe the idle speed. Return transmission to park.

5. If the idle speed does not immediately return to specification, the IAC valve may be faulty.
 
Wow, thank you birchlakeXJ, today l'll do that, also becasue here today the weather is bad (rain rai and again rain), so l can't do other check, but the last one you told me it is easy to do. I let you know just l'll back from those tests. Bye and thanks again.

Moreno :laugh3:
 
Hi birchlakeXJ and everybody, today l did that test you told me birchlakeXJ, and l could see that there was not really differents if l turn on the light and all electric accessories and the AC too. Yeah a little bit of idle change, but l could see was around (l know that l can't be perfect to say) 50/100 rpm. So l think that the IAC is over. Well, l still have to re check the TPS to be sure that it is ok, but if l understood well fomr you, when you turn on the lights and other electric components, the idle should be change a bit more than just 50 or 100 rpm, right?

If l can, in next 2 dyas l'll try to check the TPS and then l'll let you know.

Thank for now:wave1:

Moreno.
 
but if l understood well fomr you, when you turn on the lights and other electric components, the idle should be change a bit more than just 50 or 100 rpm, right?

Moreno, the idle air control should keep your idle steady with very little variation. If you see much of a variation especially under load, then the idle air control is suspect. If idle stays about the same no matter what you do or if it adjusts quickly under load to hold the idle steady without much variation, then the idle air control is doing its job properly......
 
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