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View Full Version : Fuel injector upgrade for the 4.0, and how to?


bradleyheathhays
October 13th, 2017, 11:24
What's this I've been reading on the fuel injector upgrade for the 4.0? I've had my 96 XJ since 2006 and had the same injectors all that time. It's always had a little misfire even after a tuneup so I figure I might as well try this upgrade, especially since I saw one report of it only costing like 30 something bucks from ebay. Maybe those are used injectors?

Is this worth it and what model injectors should I be looking for?

Also, in a vid I saw there was a lot of gunk around the hole the injector came out of. One guy said to clean it up with a q tip soaked in carb cleaner. Another said to scrape it out with a screwdriver. When I do my plugs I just blow everything out real good w/ compressed air before I take them out. Should I do this same step when doing the injectors? This would be the first time I've taken the fuel rail or injectors out btw.

RCP Phx
October 13th, 2017, 11:27
What year?
http://www.jeep4.0performance.4mg.com/tech_specs.html

Johnnie Walker
October 19th, 2017, 13:28
Clean the best you can first to help prevent stuff from falling in. You could use the air if you like.

LessThanJoe
October 19th, 2017, 20:04
If this is the first time you're taking the injectors out, I highly recommend the extra work of taking the intake manifold off to do the swap. It's more work, yes. Some extra bolts, and a new gasket for the intake/exhaust manifold. However while you may be able to get the loose stuff around the injector out with air, to really clean that port you're gonna need to brush it and theres really no good way to stop gunk from falling in. It would also be a great opportunity to clean out all the oil/gas residue that has built up in the manifold. I just put new injectors in my XJ and I took the manifold off. I'm glad I did.

asymptonic
October 20th, 2017, 10:09
While this thread is going, what's the recommended injector swap for a '98 4.0? That tech spec doc doesn't seem to have an injector with compatible PSI and flow rates, or I'm reading it wrong.

jhc7399
October 20th, 2017, 10:45
Year 4.0/Injector Model#:

87-91 - 0280155746
92-98 - 0280155703
99-01 - 0280155784

These are the what you want if you are doing the four hole upgrade injectors. If not you can replace them with the one hole stock injectors. Those can be found on most auto parts sites.

What ever you don't go on to ebay and buy the $50 "new" injectors. They are all Bosch knock offs from china. They say "Lifetime warranty" but it very hard to send back a warranty product to China in any considerable amount of time if they live up to the warranty at all.

You want genuine Bosch rebuilt injectors.

Aversnell
October 22nd, 2017, 10:49
Year 4.0/Injector Model#:

87-91 - 0280155746
92-98 - 0280155703
99-01 - 0280155784

These are the what you want if you are doing the four hole upgrade injectors. If not you can replace them with the one hole stock injectors. Those can be found on most auto parts sites.

What ever you don't go on to ebay and buy the $50 "new" injectors. They are all Bosch knock offs from china. They say "Lifetime warranty" but it very hard to send back a warranty product to China in any considerable amount of time if they live up to the warranty at all.

You want genuine Bosch rebuilt injectors.

I literally did this upgrade yesterday, so here’s another tip: I bought a set of remanufactured Bosch 4-hole injectors from eBay. The seller and multiple reviewers said they fit my 96 XJ. And they did, to the extent that they fit and my Jeep is running. However, the injectors did not have grooves for the retainer clips, so I had to ditch the clips. Looking around, I’ve read that the clips aren’t that important, and are there mostly to hold things in place during assembly, but omitting them has made me nervous, especially given that one reason I replaced the injectors was a fuel pressure leak down problem. I may get new injectors and start over, not sure yet. So my advice: make sure the injectors you choose have little grooves near the top, for the clips. Also right after installation, I threw a code 27, which means bad injector. On inspection I saw that one of the electrical connectors had a tiny crack at the bottom... apparently that’s enough to throw the code. I thought I might need to find and buy a new connector, but wrapping it tightly in electrical tape did the trick. Good luck.

asymptonic
October 23rd, 2017, 09:38
Does this image show that groove near the electrical connector?

https://cdn.shopify.com/s/files/1/0240/6573/products/0280155703_1024x1024.jpg?v=1380032626

Aversnell
October 23rd, 2017, 09:43
That looks like the right groove.

asymptonic
October 28th, 2017, 16:11
Just a follow up. Wife assisted in this yesterday and it went pretty smoothly. We did find that there was quite a bit of carbon-gunk around the injector holes which we cleaned out with a pick and a vacuum cleaner to keep it from falling into the engine. Should I check the cylinders or is this just an injector-hole thing?

Benefits are pretty clear so far, and in line with what others have said. Sharp, quicker start time, and more pep in the 1500-2000 RPM range accelerating in low gear. Won't know a difference in MPG until I can get on a road trip this year. I was getting 20-21mpg highway so we'll see.

All in all, a pretty easy procedure and I snagged the injectors for ~$150 so not to bad on cost either.

asymptonic
October 29th, 2017, 12:17
Spoke too soon. After three day of great driving, leaving the store today I had some rough idling and shimmy in the engine. After shutting down to inspect and starting back up, a really rough start and the engine threw code P0301 (misfire in cylinder 1). Could that injector be suspect? What should I check?

asymptonic
October 29th, 2017, 13:06
Additional info: There was also a strong fuel smell from the exhaust while it was misbehaving. After shutting down and restarting once more, it was back to normal.

jhc7399
October 30th, 2017, 13:29
What model injector and where did you get them?

asymptonic
October 30th, 2017, 15:18
Bosch remanufactured 0280155703. Here's the ebay link:

https://www.ebay.com/itm/Set-of-6-FACTORY-REMAN-Bosch-Upgrade-Injectors-1991-98-Jeeps-4-0L-0280155703/201436597666

Its running fine again right now. I measured 12.6-12.7 ohms on three of them, including the #1 cylinder indicated in the code. FSM calls for 12 ohms. It started rough the first time I tested this afternoon but subsequent starts were fine. Feels like a lemon injector, but not sure if I should try and replace just that one or go back to the originals for now.