Tristanplaysguitar4Jesus
New member
I start the jeep, sometimes it goes straight up to 2000 rpm, sometimes it starts normal. I've heard vacuum leek, idle control error, egr valve?
1989 cherokee 2000 rpm
- Thread starter Tristanplaysguitar4Jesus
- Start date
greg92jeepxj
Official Supporter
You have the 4.0 ltr I6 engine.( non- H.O.) Is the check engine light on , intermittant or not at all ? If so , could you get any trouble codes from it ? Just turn the ignition key to on position (but do not start) and off three times and on the third time , leave it on . Count the flashes from the check engine light . Each set of flashes will is a numeral . I.E. , four flashes , pause , two flashes pause or long pause before another code . The four and two represent code 42. That is just an example.
try to get any codes if you can or you can also go to pep boys , r&s Strauss , auto zone , advanced auto or any auto store that will check codes for free if you would like.
this problem can be caused by several different things . First , dirty or faulty idle air control valve , yes , vacuum leaks (look for torn rubber duct from air cleaner) from any vacuum source such as PVC , crankcase breather , intake manifold , power booster vacuum, outlet to heater control and to dash control , just everywhere and anywhere vacuum is used. EGR usually causes rough idle but good to check regardless. How is the engine temperature sensor on the thermostat housing and wiring ? Does dash gauge read accurate ? A trouble code may or may not reveal a fault , but if the engine controller (ecm) does not get an accurate signal from the temp sensor , ecm will assume engine is cold and open IAC valve and rev to the sky as it constantly relearns engine conditions. If any codes come up , even o2 sensor, all should be checked before replacing . If an o2 reads lean , the o2 may not be faulty but just reacting to a vacuum leak. Even exhaust leaks can cause an o2 to read lean . Bad for catalytic converter $$$!!! All this may sound very daunting , but start with a visual inspection of the obvious ; loose , cracked , broken , torn , missing , vacuum lines or just anything that does not look right . If found , fix those items and check performance after each repair . Also , erase codes to see if they return. Pull ecm fuse or battery positive for 10 seconds or more to clear trouble codes. Take it one step at a time and soon , when all obvious leaks or anything broken that can be related , then proper readings such as temp sensors (check wiring harness ! ) and o2 readings can be more accurately read .
Best of luck and let us know what you find as you can. Our resident senior expert jeep techs will have questions for you , please look for posts that could hit the nail on the head other than just my check list items . Again , best of luck and enjoy the forum . Welcome ! Sit and share ! :welcome:
try to get any codes if you can or you can also go to pep boys , r&s Strauss , auto zone , advanced auto or any auto store that will check codes for free if you would like.
this problem can be caused by several different things . First , dirty or faulty idle air control valve , yes , vacuum leaks (look for torn rubber duct from air cleaner) from any vacuum source such as PVC , crankcase breather , intake manifold , power booster vacuum, outlet to heater control and to dash control , just everywhere and anywhere vacuum is used. EGR usually causes rough idle but good to check regardless. How is the engine temperature sensor on the thermostat housing and wiring ? Does dash gauge read accurate ? A trouble code may or may not reveal a fault , but if the engine controller (ecm) does not get an accurate signal from the temp sensor , ecm will assume engine is cold and open IAC valve and rev to the sky as it constantly relearns engine conditions. If any codes come up , even o2 sensor, all should be checked before replacing . If an o2 reads lean , the o2 may not be faulty but just reacting to a vacuum leak. Even exhaust leaks can cause an o2 to read lean . Bad for catalytic converter $$$!!! All this may sound very daunting , but start with a visual inspection of the obvious ; loose , cracked , broken , torn , missing , vacuum lines or just anything that does not look right . If found , fix those items and check performance after each repair . Also , erase codes to see if they return. Pull ecm fuse or battery positive for 10 seconds or more to clear trouble codes. Take it one step at a time and soon , when all obvious leaks or anything broken that can be related , then proper readings such as temp sensors (check wiring harness ! ) and o2 readings can be more accurately read .
Best of luck and let us know what you find as you can. Our resident senior expert jeep techs will have questions for you , please look for posts that could hit the nail on the head other than just my check list items . Again , best of luck and enjoy the forum . Welcome ! Sit and share ! :welcome:
Last edited:
PretorDepot
New member
Go to advance auto. They will run an OBD check for free and tell you what it means.
cowboywelder
New member
could not have said any better you hit every thing that came to my mind at first and then some but on a side note my brother had the same problem with his 89 4.0 and it was a vacuum line dont remember witch one is was this was two years back sorry i could not be more help but i would check every thing greg92jeep xj said also just to be safe many things can cause the same problem
greg92jeepxj
Official Supporter
Thanks cowboy . Your quote on the bottom of your post is pretty accurate . Problem , errors and faults make themselves know and stand out on a normal running engine . My dad had an'89 too and although he always liked that truck , we did have to keep after it . If it wasn't EGR , ignition or electrical throwing a code , it just had us staying on top of what kept it idling rough at times. We learned to keep the IAC motor clean , cleaned and eventually replaced EGR and I think solenoid , and staying on top of the spark plugs for fouling from over rich conditions due to EGR getting picky every so often . These things slowly contribute to poor running and performance . Throw in an inaccurate coolant temp sensor , lazy O2 sensor , MAP , etc. and before you know it poor idle , hard starting and just terrible performance and gas mileage ? Fugetaboutit !
Not to say my '92 does not need TLC either , but thank goodness for cam dynamics , the H.O. Engines with no EGR just are a whole lot more reliable . Higher torque too ! But like I said , my dad liked that truck and was happy for what it was . Wished he didn't sell it. Just got tired of the upkeep . And throwing money at it once in a while . But hey , it's a jeep . That's what they do .
while Tristan's got a problem that must be addressed and looked over thoroughly , it's just a reminder that maintenance cannot be taken lightly . Even when it's working , got to keep up .
Tune ups and cleaning EGR and injectors go a long way to save money and increase longevity .
the 4.0 will last longer than any engine ever the cherokee had . Just got to give it the maintenance recommended . The jeep is reliable and dependable , but only with regular care .
thanks again . Lets keep 'me Rollin. Greg92jeepxj
Not to say my '92 does not need TLC either , but thank goodness for cam dynamics , the H.O. Engines with no EGR just are a whole lot more reliable . Higher torque too ! But like I said , my dad liked that truck and was happy for what it was . Wished he didn't sell it. Just got tired of the upkeep . And throwing money at it once in a while . But hey , it's a jeep . That's what they do .
while Tristan's got a problem that must be addressed and looked over thoroughly , it's just a reminder that maintenance cannot be taken lightly . Even when it's working , got to keep up .
Tune ups and cleaning EGR and injectors go a long way to save money and increase longevity .
the 4.0 will last longer than any engine ever the cherokee had . Just got to give it the maintenance recommended . The jeep is reliable and dependable , but only with regular care .
thanks again . Lets keep 'me Rollin. Greg92jeepxj
cowboywelder
New member
the problem my brother had with his rough idol was they thought it was a good idea to put a rubber spacer on the back of the plate the throtle cable mounts to but it is just glued on and not bolted or scrwed so if you wheel a little to hard( funny story on that one) it would come off but it would start just fine but after you let off the throtle it back off too far and kill itself wonderful things the engineers come up with but all i did to fix it was bend the mounting plates top back to hit the stopping plate they had where it was suppose to and got a longer cable and cut it to the new length
greg92jeepxj
Official Supporter
It sounds like he was thinking too hard about how to fix it but not enough about what caused it . Happily , you found the solution to correct the improper mounting procedure and solve it by redesigning a new control all together . Rather than just get something going for the sake of wanting to just drive it , I personally would rather just do what's necessary as you did before actually calling it good and finding out the hard way it's no good . Well , I would say you saved him from possibly losing control , or worse , with the poor set up that it was . I may have done things in the past similar temporary , but I was never comfortable with " temporary " .
I , just as you , would rather it be done right first time out if at all possible . I'm not a big fan of "rigging" something "just for now". A funny story deserves a funny story . Two summers ago , I was getting my A/C back in shape . I took so long with every repair , weekend after weekend , that I got it done just before Labor Day ! Just in time for the fall ! There's actually more to this story , but that could be a whole thread and I am still embarrassed to this day about it .
But i did get everything assembled right as I wanted and was happy . I learned that if you do not do a job right , you will have to do it again eventually. But I know that when it comes to four wheeling , that is just standard procedure . Buy it , build it , drive it , break it , repeat.
Never starts out that way , but Mother Nature is tough on our rigs . That's payback for driving hard on Mother Earth , I guess . Right now , my 4x4 is my daily commuter , grocery getter , take the woman out with ride , and haul back parts from wrecking yard all in one. Hope to have a dedicated second rig for fun soon , but right now , it's just not in the cards . Keeping my eyes open for ideas though ! That's what I love about this forum , I learn from experienced wheelers and find out more about jeeps than just up keep and repair . That's what makes our world go round , and that's a beautiful thing !
I , just as you , would rather it be done right first time out if at all possible . I'm not a big fan of "rigging" something "just for now". A funny story deserves a funny story . Two summers ago , I was getting my A/C back in shape . I took so long with every repair , weekend after weekend , that I got it done just before Labor Day ! Just in time for the fall ! There's actually more to this story , but that could be a whole thread and I am still embarrassed to this day about it .
But i did get everything assembled right as I wanted and was happy . I learned that if you do not do a job right , you will have to do it again eventually. But I know that when it comes to four wheeling , that is just standard procedure . Buy it , build it , drive it , break it , repeat.
Never starts out that way , but Mother Nature is tough on our rigs . That's payback for driving hard on Mother Earth , I guess . Right now , my 4x4 is my daily commuter , grocery getter , take the woman out with ride , and haul back parts from wrecking yard all in one. Hope to have a dedicated second rig for fun soon , but right now , it's just not in the cards . Keeping my eyes open for ideas though ! That's what I love about this forum , I learn from experienced wheelers and find out more about jeeps than just up keep and repair . That's what makes our world go round , and that's a beautiful thing !
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