1987 4.0L XJ Wagoneer - upgraded to 4 hole fuel injectors. Air mixture all wrong.

[CoryGuy]

Hi all

Here's a video I put together today showcasing the problem!

So I "upgraded" my injectors to refab 4 hole sprayers on my 4.0L I6. Now the Jeep either idles poorly and dies, or revs up and down after warming up. I drove it to try to break everything in, get fuel circulating again, and the engine warmed up. That did help some. After parking it the engine revved up and down.

Here's what I've done prior to and after install:

• changed gaskets
• replaced idle air control
• checked MAP vacuum lines to throttle body
• checked remaining vacuum lines
• checked each fuel injector functionality
• checked proper battery connection
• replaced O2 sensor last autumn
• "reset computer" by disconnecting power and such

The Jeep was running fine prior to replacement, just some slight acceleration issues and shuddering which indicated a bad fuel injector to a wiser mechanic than me, hence the swap.

Any ideas? Thank you in advance!

 

[superj]

and the old injectors were high impedance, like i believe the ones form the 4.0 are? i cannot remember if the renix engine used low impedance injectors versus high?

 

[CoryGuy]

and the old injectors were high impedance, like i believe the ones form the 4.0 are? i cannot remember if the renix engine used low impedance injectors versus high?

I've no knowledge of this. Can you elaborate?

To add, the seller stated this morning:

Bosch Model 9566-4 hole upgrade fuel injectors
"yes these are upgraded fuel injectors that work on that model vehicle, however if they are not working for you please go ahead and open a return case through ebay to facilitate the returns process"

 

[superj]

some injectors are high impedance, or high resistance. some, rarer, i believe, are low impedance. but if you run the opposite of hwat you need, they will burn out the ecu.



and you are 100% sure there is no slight vacuum leak. i know you said you checked but nothing was missed? google what causes a hunting idle as that is what you are experiencing now.

 

[superj]

and, just a side note, check out this guy's page.

Leigh Performance Machine (strokedjeep.com)

i had an 87 cherokee, like yours. i put a 6" lift and 31s on lost performance. i got an oversized throttle body from him and the jeep was night and day different. it accelerated better than on stock tires with just that throttle body upgrade.

 

[CoryGuy]

Follow up!

Here's a video I put together today showcasing the problem!

 

[JPNinPA]

Does this have a throttle position sensor? If so, manually open and close the TB valve 20-30 times and see if your situation improves. You could remove it and spray with air to knock dirt out. or replace it. When you put it back do not coil the switch or twist it on. Coiling the spring changes the resistance snd will lead to this or other start issues.


Never look down on anyone unless you are helping them up - Jesse Jackson