Injector Swap, Possible Problems? *Lost!*
CF Veteran
Joined: Aug 2011
Posts: 1,031
Likes: 4
From: Blue Springs, MO
Year: 1993
Model: Grand Cherokee
Engine: 4.0L Laredo
"While i was working i took out the intake air temp sensor and cleaned it with carb cleaner and a light brush (never noticed a blue diode in there, more like a silver disc)"
Really?
Really?
Thread Starter
Senior Member
Joined: Jan 2012
Posts: 635
Likes: 2
From: Indiana
Year: 1999
Model: Cherokee
Engine: 4.0
CF Veteran
Joined: Nov 2011
Posts: 2,322
Likes: 1
From: Edmonton
Year: 1990
Model: Cherokee
Engine: 4.0
it doesnt learn anything anyways. its pure input/output run on the fly. 90% sure there is no stored information. someone else correct me if im wrong.
after my injector swap it ran rough at first start up, but no decrease in mileage. i average an extra 50kms per tank.
after my injector swap it ran rough at first start up, but no decrease in mileage. i average an extra 50kms per tank.
Thread Starter
Senior Member
Joined: Jan 2012
Posts: 635
Likes: 2
From: Indiana
Year: 1999
Model: Cherokee
Engine: 4.0
thanks for the input hank! yeah I have learned now that the computer doesn't learn anything, so im thinking one of the injectors has got to not be firing correctly, or some other gremlin is taking over!
CF Veteran
Joined: Nov 2011
Posts: 2,322
Likes: 1
From: Edmonton
Year: 1990
Model: Cherokee
Engine: 4.0
find some noid lights then you can watch them fire. mine are the 19lb ford yellows btw
measure resistance between terminals on the injectors, should be around 16 ohms. if that works out, and you still have problems, i would take them out and put 12 volts to one terminal, ground the other and listen/watch the injector, you should hear it click every time you ground/un-ground. check the inlet at the same time (plugged?)
the crank sensor and sync generator directly affect the injection timing btw...
measure resistance between terminals on the injectors, should be around 16 ohms. if that works out, and you still have problems, i would take them out and put 12 volts to one terminal, ground the other and listen/watch the injector, you should hear it click every time you ground/un-ground. check the inlet at the same time (plugged?)
the crank sensor and sync generator directly affect the injection timing btw...
CF Veteran
Joined: Dec 2011
Posts: 1,777
Likes: 22
From: PA KOTUFU!
Year: 1998
Engine: 4.0L 162,000
Maybe you messed up the IAT sensor with the cleaner. I would replace that.
Were your injectors new or checked out for flow? Maybe one is working but dumping in too much fuel.
Were your injectors new or checked out for flow? Maybe one is working but dumping in too much fuel.
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,579
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Im pretty sure i did get the correct plugs on the connectors, any way to tell for sure just in case? Also i pulled the plugs one by one while it was idling and did notice a change in the sound of the engine so that tells me that they are all firing. So your saying that it will take something like 50 warm up cycles to get it to learn the new trim? BTW thanks cruiser on the advice on the grounding refreshing, all mine were "cruddy" and now the intermittent wipers work better than ever!
Thread Starter
Senior Member
Joined: Jan 2012
Posts: 635
Likes: 2
From: Indiana
Year: 1999
Model: Cherokee
Engine: 4.0
And the winner is...
To the person that suggested one of the injectors was not working correctly; you win the million dollar prize of the day! I took all the 703's back out and cleaned up and re-installed the stockers and fired right up, idles good, not as much pep, but i can deal with that for the sake of it running well. Thank you to everyone for your help in the matter!
Member
Joined: Jan 2012
Posts: 108
Likes: 0
From: Truckee Ca,
Year: 1991
Model: Cherokee
Engine: 4.0 H.O.
To the person that suggested one of the injectors was not working correctly; you win the million dollar prize of the day! I took all the 703's back out and cleaned up and re-installed the stockers and fired right up, idles good, not as much pep, but i can deal with that for the sake of it running well. Thank you to everyone for your help in the matter!
I'm waiting.... I know, I know, my check is in the mail......
....glad to hear you figured it out.....
Seasoned Member
Joined: Sep 2009
Posts: 299
Likes: 12
From: Whittier, Ca
Year: 1989
Model: Cherokee
Engine: 4.0L
I did the Liberty injector swop on my 89' cherokee I6 AW4. I ran through the first tank of gas and watched the fuel meter plunge, and I could smell the Catalytic Converter working overtime. I got 13 mpg on that first tank. I performed the computer reset and got 18 mpg on the next tank.
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