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90 xj I-6 reves too high help???

jeepler

NAXJA Forum User
Location
toronto
hey can anyone help me my jeep reves at 1100 hundred rpm when it gets to the normal operation temp i changed the tps and adjusted and gave it a tune up. but still reves i was woundering if the iac could be causing it but im just getting in to jeeps and the off road sceen so if anyone could help i would realy appreciate it thanx.
 
Try monitoring the TPS voltage from cold start idle up to hot idle with a multimeter. It should read between 0.80 volts and 0.82 volts between the C+ pin and B ground pin on the TPS. Do this test with the engine running this time if you have already check and calibrated it with the power on and engine off.

Also check the resistance from the battery ground post to the firewall and to the engine block with the power OFF.

Then test the voltage with the engine running from the engine block (make sure you have good contact with bare metal, the valve cover works well if you scrape a spot bare) to the battery ground post.

The grounds (engine and firewall) should all read less than 1 ohm to the battery ground post, and less than 0.10 Volts in the other ground test mode (engine running).

A poor ground can change the TPS voltage and raise or lower the idle speed by confusing the ECU.

There are several other sensors, and parts that can cause idle problems but you should verify the grounds first with a meter!
 
thank u very much for the information im going to definitely try that hopefully this will solve my problem. when i changed the plugs they were carbined up i just bought the jeep and am trying to put it on the road but it failed the e-test so i have to get all the carbon blown out but the idel is just to high but once again thank u very much for the info and i will test and re post to let people know what happens.
 
hey guys i checked all the grounds and everything is good. but it still idles high i also cleaned the iac and it still idles high but do u guys know anything about an emiss maint light on the dash cause mine is lit up now that there is a new bulb in there the person before me pulled it out.
 
I also have a '90 I-6 and it too idles high when its warm but I think its 1200RPM or so. I'm a little annoyed with it but haven't done anything about it because it still passes the Cali Smog Check so I figure it can't be that bad. I wouldn't be surprised if I have a vaccum leak or a failing snesor causing it but I don't know what it is.
 
I recently posted an analysis and discusion about the sensor ground sensitivity at:

http://www.naxja.org/forum/showthread.php?p=243397355#post243397355

Once you have ALL the ground wire connections clean and tight, I would move on to eliminating all intake vacuum and vacuum line leaks. Even a very small, quite vacuum leak will cause a high idle. All connections to the valve cover (CCV lines etc) must be vacuum tight as well!!!!! Vacuum leak high idles are usually always present and are not normally temperature (cold or hot) sensitive.

Next most likely suspect is the TPS sensor and connectors. They must be calibrated after fixing the grounds and any loose wiring harness connectors.

If the idle is still too high, check the throttle linkage for binding, the IAC and its connector, the throttle body and the air and coolant temperature sensors and their connectors.
 
ok i think i have fixed the problem i was fooling arround with the plastic tubes for the ccv valve and noticed they were off so i put them back on and the jeep seems to idle fine now it stays running at about 7-800 rpm im gussing thats good but i was just woundering where i could get a ccv valve from mine is missing. and i just want to say many thanx to the wounderful people on this web site that had taken there time to help me figgure it out thanx so much.
 
The ccv "valve" is just an orifice that is molded in to the end of the tube that goes in the grommet on the aft top of the valve cover.
 
ya the stock pice that was there is gone they stuffed a rubber hose in there so i have to get one ill try a scrap yard thnx
 
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