My 2001 4.0L ECU doesn't like #784 injectors

[oldmanjeeping]

I really appreciate the collective wisdom and insight of this group of Jeep experts. Several months ago, I started researching the various threads on Jeep XJ fuel injector issues. At that time, I was chasing a P0302/303 misfire problem on my 2001 Cherokee Sport. This problem had been coming and going for a long time, but seemed to always go away on its own. I had written it off to the infamous cylinder head problem. Finally, I decided to check a few other things before replacing the head. To my surprise, all (6) cylinders had 155-165 psi of compression, but I had a couple of wet ones. These original injectors with only 248K miles on them were leaking. Based on the many positive references I found in these threads, I quickly ordered up (6) new Bosch 280-155-784s and installed them. Reset the ECU and took it out for a nice long ride. It stumbled for a while, but settled down and ran great after 10-15 miles. Before I got home the CEL came on with P0172/175 codes. No more misfires, but serious rich running, setting these same codes every time I backed out of the driveway. I reset the ECU again, and ran several full tanks of fuel thru it, but the codes were not going away. Checking the ECU a little more closely, I recorded a bunch of live data that told the story. The O2 sensors were working great, but the long-term fuel trims were to the negative rail, averaging -30. I gave up, purchased and installed (6) remanufactured OEM 04854181s and all is well.

I have to assume that all ECUs are not the same. Many have found the 784s to run great, giving improved performance and better gas mileage. But not everyone has had that experience. I do wonder how many Jeeps are running around with the 784s with large negative fuel trims, just not as close to the ragged edge as mine were.

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[lawsoncl]

Genuine Bosch? The market is flooded with fake Chinese knockoffs.

 

[oldmanjeeping]

Advertised and sold as new Bosch injectors, shipped in a Bosch box. Are there any distinguishing features on the real things? The vendor had +++ feedback on these parts.

 

[lawsoncl]

The usual signs are they were listed on eBay, 50/50 chance of running like crap when installed, and the set cost less than $150.

 

[oldmanjeeping]

I guess I was blinded by the Bosch box. I'm now thinking you're right. There's no Bosch markings on the actual injector. The vendor swears his supplier swears they are manufactured by Bosch but we all know what that's worth. At least he's offering me a refund. I plan to leave my suspicions in my feedback to his site. What's a good source for "real" Bosch #784 injectors (hoping I don't need them soon)?

 

[Bent]

K suspension. They also support a couple naxja chapters with fundraising.