In my experience, matching your axle gear ratio to the tires being run will is pretty much the best thing you can do for power. All of the throttle body mods, plugs, wires, programmers might get you a little. But it won’t even compare to having proper gearing. Unless you spend thousands and many hours swapping in a 4.6L Stroker or adding a supercharger.

To quote Stevie Wonder from over 50 years ago: " When you believe in things that you don't understand, then you suffer". A bigger throttle body will only make more noise. MAP will not be affected, partial throttle response will suffer. Bigger plug wires won't increase ignition secondary voltage or current. Your big-assed cat and turbo muffler get choked down by the stock sized exhaust pipe that now runs precariously close to the rear driveshaft. Your air filter now gets to suck in heated under hood air and is restricted by the primary filter, thus negating the bigger throttle body to begin with. Other than that, great job!

I got my injectors from Ksuspension. Noticeable difference. Ran smoother, more pickup. Eadier starting. The best benefit was gas mileage. I used to get 170 miles from a tank. With the new injectors, I got 250 miles from a tank of gas.!

As far as motor upgrades on my 98XJ; Banks Header, Hi-flow cat, Flowmaster 44, true cold air intake, 62mm throttle body w/1" spacer, 703 four hole injectors, MSD Blaster coil pack, MSD ignition wires, cap & rotor w/iridium plugs, Mechman HO alternator w/two XS batteries with all 1/0 wiring. Also, all sensors are new & are Mopar and I have an on board OBDII that streams live data to my phone!! Now I didn't do all this for power, I did it to let her breathe and be more efficient especially with 170k on the OD. 😉

Recommend replacing intake manifold with a post '97 intake. The updated intake allows more airflow to the ports, and will take advantage of your new throttlebody.

One of the greatest motors ever made. The only flaw. The fuel injectors are right next to the exhaust manifold. The fuel gets hot. After a while you go through catalytic converters, or mufflers. My suggestion. Buy fuel injector boots. They go around the fuel injectors. Solved my problem. ✌️

Yes! Good to use regular plugs, never Iridium. The 4.0 is an older designed engine, its happier with copper

there is a 4 part interview with Rick Mudge on youtube on the AMXJ channel i highly recommend every 4.0 owner take a listen. Rick Mudge was the engineer in charge of AMC- Jeep & Chrysler cylinder head, intake amd exhaust development from 1976-2001, hes the godfather of the 4.0 and knows more about them than anyone i suspect.

The greater plug wire diameter really only buys you more silicone for greater ability to resistance to loosing slight spark energy if routed near grounding items. I used to manufacture and test ignition systems back in the day. 8-)

I put a 62mm tb and a spacer on my 2.5... Lost low end torque, gained high end power, but I have a sweet intake whistle now

Great video, Happy to see you back to working on your TJ. Throttle body is my next planned upgrade. I have already done the ignition and fuel injectors on my 98. waiting on you guys to take a trip down to Cross Bar in Oklahoma.

Great video & picking up 15hp & 20 trq is actually really significant considering where you started.

One more setup you may want to try. a Holly Capacitive ignition system with tri-fire sparkplugs. Both create a tri-leg spark to ignite all fuel, and the capacitor (energy storing) ignition also creates, generates high/fast enough firepower to keep the juice flowing. I used a blaster coil and 10mm sparkplug wires, a Holly performance distributer cap and rotor; and Jeep oem style injectors with a four hole design.

Tune the EFI for even better results. Not jeep related but. I put a 75mm ported TB on my chevy s10 4.3 factory was 75mm necked down to 70mm with a restriction plate on the butterfly. After opening up the factory TB. It has instant throttle response and noticeable difference. But then took hp tuners and tuned it for the extra intake flow and got even more noticeable performance increases. Im sure if you tuned the pcm you'll definitely have a bigger performance gain then from just doing bolt on mods.

Great video. Next time you want to “machine” or “lathe” a fitting down, chuck it up in a drill and run it against some sand paper or a bench grinder. Keep on keepin on brother

good info, fix the exhaust leak, then recheck your performance!

I hate to say it for us with the older 4.0s with many miles but the best way to get more HP and torque is a head job recently did mine and it’s like a completely different animal now

Thanks for sharing that simple problem solving sorting out issue from adding new parts

I read a long time ago that some good power can be gained by swapping a TJ air intake manifold into a YJ. they basically redesigned it for better flow to make up for the power loss due to emissions regulation changes.

One other thing: if you change to an electric fan you can gain almost 30hp at the top end. This has been tested and proven. The only drawback as far as I'm concerned is that the mechanical fan moves more air, and sometimes that's what you need when you're moving slow out on the trail

i have the CRT kit in my 5.9 jeep, works good so far

Knowledge is power. Thank you.

I placced a Banks Header on my 4.0 with a K&N intake - Banks claims a 12 hp bost on his dino with that combo

Good honest video!

I have an 01 wrangler 60th anniversary will be doing a complete tune up soon this was a good video these 4.0 are real offroad warriors 💪 there's so many cool things you can do to these beauty's 👍

My 97 TJ 4.0 is the last model year with the single, primary coil setup. According to a couple of racecar builders I confer with regularly, my dreary throttle response, especially at the lower end was more about the explosion trigger and completeness, than the air and fuel content, which i had already addressed, similar to this video. They suggested that in order to prevent a "slow/low" firing condition, the ignition system needed a "middleman" to develop and maintain enough voltage for a sufficient amount of spark, firing consistently within the prescribed/preset timing intervals. I needed something between potential and execution that could/would manage the process. The primary reason that the (single) "coil over (spark) plug" is now the industry-standard is precisely for control and bottleneck elimination. The ECM can precisely control the voltage discharge level and timing consistency at each cylinder. This was less important in "the olden days" before the emergence of automobile standard and attachable, electrical gadgets and devices. Every time a device is turned on or off, there is a corresponding surge or drop in the direct-current loop. The residual effect is absorbed or lost within the succession of other devices powered at that time. There are only two ways to resolve the condition, "coil-over-plug" so the ECM can regulate it, or if that's not possible, then installing a regulator, one-step past the ECM, would be the next best thing. With that "regulator" you also get the additional benefit of an RPM "limiter" (in case you snap something within the drivetrain during high acceleration) The CDI prevents major damage to the engine from the ensuing spike in RPM's, while the uncontrollable bottleneck is also avoided, thereby eliminating the loss of performance from primary voltage-lag (slow) and/or a lowered, constant throughput (low). I used the Holly (MSD) Street-fire CDI. This essentially replaces the primary function of the ignition coil, while providing as much voltage as needed, when needed by the sparkplugs, to ignite the fuel, while also protecting the engine, (offroad) if say you bottom out and snap a u-joint during an up-hill climb.. Additionally, in order to fully and more effectively utilize the 3-legged spark, produced by the Street-fire CDI, I installed the E3 Tri-Fire sparkplugs (E3.58), which are made to split the spark into three legs. Then, in order to insure against any other bottlenecks, I installed the following: Taylor 36271, 409 Spiro-Pro Spiral Core 10.4mm Spark Plug Wire, a high-0performance Accel 120330 Distributor Cap, and a "Borg Warner D228" Rotor (better build). I also replaced the coil with an "MSD Blaster 8228". All other engine mods described in this video, are already installed and modified for optimum performance. The difference in performance is truly "night and day". One other thing I want to mention concerning "mods": I recently installed a "Spal 30102049 16" Curved Blade Performance Fan", but I am planning on switching back to mechanical. It's just way too, dang loud and the pitch is irritating and as obnoxious as heck. The Jeep is completely customized and that one aspect repels any would-be observer, coming within about a 20 ft radius.) I'll just keep a spare fan-clutch onboard; 'Cuz in the Jeep world. as we all know: "Two is one and one is none!"

I put the 4-hole Mustang injectors in my 97 XJ something like 22 years ago. Still in there. Honestly not sure they really made any difference, but I always figured better misting can't hurt things.

A banks header pipe and 3" free flow exhaust hot coil low resistance wires made a big difference for me

I already had the 62mm throttlebody on my 4.0 when I got the Jeep, decided to do some other mods too. Cause its an 01 WJ I have electronics so ended up with Ksuspensions Viper coil mod and love it, also did a 12 hole injector swap. Injectors were el cheapo used so I'm expected a CEL soon but my mileage and power difference is noticeable over stock. Cold air intake, KSuspension 12 hole injectors and battery wire kit are next followed by skid plates. As for your throttlebody missing the sensor nipple the ones from the stock TB come out easily with a torch and, at least on the ones I worked on, can be pressed into the new with a bit of sealer on.

Damn good video and knowledge. Thanks

Great video man! Nice Jeep.

I did a 4.0l swap into my 82 CJ. I connected my MAP sensor to an extra port on the intake.

The TB comes like that to allow drilling and tapping for the map sensor, before 1995 you can plug it, as those 4 liters used a different fuel injection system.

Your mpg will likely improve when you fix the exhaust leak.

Look on The Horsepower Monster channel. They have done a few vids on getting power out of the 4.0. Like 800+ HP levels. (Bore/stroke, turbo,....) I don't think you need that, but some of the mods would definitely help better then just a throttle body and some sparkplug wires.

Great video, Kelly. You get a new camera? Really clear video. Thanks 👍🏼💪🏼🇺🇸🇺🇸🇺🇸

So I’m running the 12 hole injectors from K Suspension and I’m super happy with them. When I swapped the new injectors in I also swapped in a billet fuel rail as well.

Picked up ksuspension 12 hole injectors and the ripper coil and plug wires also the 7 large wire upgrades. Most noticeable change was the idle smoothed out. Also a better throttle response and picked up about 4 miles per gallon. The starter spins must faster and lights no longer flicker. Best money ever spent. Looking at selling my suburban and getting a 4.o stroker.

Those inline filters are good for diagnosis. If you have "running" issues and have gone the mile. Go ahead and throw in a fuel filter. It could be dirty fuel. It usually is not the throttle body, kinda nice of em.

Thank you for the info

Great vid, man!

Hey Kelly love the content! I’d recommend reaching out to Keith at Newcomer Racing if you have any questions on the 4.0s. He’s “the guy” when it comes to building out these dinosaurs

I was honestly dissapointed at the end of the vid but then you posted the #s from the test and I actually enjoyed the vid knowing that putting all that $ and non factory stuff on is not worth the minimal hp gain. I do think that you need to get the right injectors because I have heard good things about those

It may sound weird but the best upgrade is a 258 american motors inline six( 4.2L) they can be built for off-road use and if you use the right parts can be made to belt out 250-85 hp before having to worry about breakage. The only downside is the engine is all cast iron so a 258 weighs about 275 pounds more than a typical 4 liter (from 1996-06,end production year)

Great video.

MyTJ has an actual tuner on it. I had a jump from 133 HP to 145 HP with everything else stock. This was done on a dyno. It is the biggest bang but its is expensive. With HPtuners now supporting the Jeep 4.0 it is fully tunable just like an LS. Now saying that I still want/need more power and I am looking into a turbo. it needs just a little more power to run down the highway.

Had a 258 that was built by Clifford and a ford 300. Both put out 300hp and around 485 foot pounds of tork at the rear wheels. Always liked to see a built straight 6 under the hood. Clifford research was the go to guys in the 80s for building straight 6 engines. Not sure who is today.

Wish I’d seen this and had your advice before I changed plugs and injectors and fuel pump and fuel tank. Can’t start and no idea why! Thanks for a great video.

7:48 Looks like a small blow-by filter I've seen on CAT engines in semi's. Some of the renix Jeeps had for crackcase vents that prevented oil in your air box at high rpms. Kinda like an air dryer in compressors. That was the upgrade fix for it I believe.

For the throttle body modification. I don’t know if this was mentioned. But why didn’t you use a threaded hose fitting? Tap the throttle body and get a brass fitting with thread on one side and barbed end on the other?

What about the edelbrock aluminum head? Could increase some efficiency. Maybe a mild cam swap too

Do a stroker kit on the channel man! High quality/modern videos for that subject aren't something that's really common. I'd be interested to see how you like it!!!

Can you do a little update when you get those injectors? They definitely helped my old renix xj, but those injectors were 35 years old.

4:58 Great Advice!! 🙌

Man your a STUD... Got these parts and the throttle body didn't have the right shit but you kept going and Jimmy rigged the MAP sensor and got'r done!

Raffy at K Suspension is outstanding. I put his Viper coil and plug wire conversion kit, his power wire kit and his rebuilt 4hole injectors in my 4.0 TJ and I was impressed. Let's face it, we're not in a race vehicle, so the wide open HP isn't important but the torque is and mine picked up more torque. You'll be pleased with His injectors. They are worth the money.

Whike the upgraded injectors are a good call there has been a lot of debate whether the majority of the increased performance is simply coming from new clean injectors & not as much the improved Squirt. I woukd love to see someone throw on just new OEM single hole run those for a month & dyno if possible to see the mpg, hp & torque they are getting & then throw in the Bosch & test again.

One way or the others, you need to change the spark plug sometimes. From what I heard the in-line 6 should be change every 50 000 km. So it's just regular maintenance.

I got an 01 cherokee and used 12 hole injectors off a chevy hhr from a junk yard and they swap right in

I think you will be able to get a better throttle body and get better results.

That is the throttle body I got from ebay as well.. looks like yours missing that tube sticking out mine didnt..but the hole on mine where one of the module goes in was slightly smaller and I could fit it in..i had to sand down that module..makes me wonder if these manufacturers ever tested or measuring anything before they machines them.

Never increase the gape on your plugs. I have played the that game for years with random misses then tried to lowering the gap by a couple of thousandths and all the engine I have done this run the better and over time the gap opens anyway. I’m 56 and and done this on Toyota Jeep Chevys

Iv learned over the years that a daily driver slightly modified does not benifit from expensive ignition but heavily modified non pump gas engines do just my opinion

Had a 99 cherokee put dodge neon injectors the 4 hole ones in it noticeable better mid range power o er the single holes.

Can you please explain how you make the computer learn

Do the throttle body spacers actually help even if there's no fuel introduced at that point? My 4.7l stroker is being built right now so I'm looking for all the best options

Fuel injectors are the best and most important upgrade you can make to a 98 and older Jeep. Chrysler put the oldest crappiest injectors they could on them from the factory. I pulled injectors at the scrap yard and they even had a lower flow rate then stock and the difference was night and day. The first thing I noticed was that I actually had engine braking in 4 low unlike before. The other thing was I got 5 more MPG. I did later pull higher flow injectors for it and they work great to. Funny story Chrysler invented the the fuel injector. Also funny story Dodges and Chrysler of the 90's years had ev6 injectors while Jeep had ev1's....

Hey. I'm rebuilding/restoring a 1987/1988 Jeep (AMC) Wagoneer Limited 4.0L S6. I don't have much experience with these kinds of things but am wondering if these addons would fit, particularly the throttle body as mine has the spot for the sensors, etc.

The throttle body bushings wear and cause wandering idle due to vacuum leaking by and noone sells a new or reman, at least not when I had my 95 4.0 jeep. The distros wear out good as well but are available still. Though they all say that warranty voids if you remove the cap....so how do you get it timed properly?

I wonder if the aftermarket throttle body would fix my low rpm intake whistle

on the throttle body instead of the epoxy why didn you just thread the hole for a screw in hose barb? just curious

I don't need a sragstrip engine. Just dependable low torque to sucessfully climb up to my cabin.Dandahermit

heads up- in our first race with the ebay 62mm throttle body like this, the throttle stuck in wide open twice. luckily our driver was able to get it to the pits and we had to lose a few hours coming up with a fix. the problem is it wasnt machined perfectly, and once it got hot the butterfly expanded more than the housing and caused it to hang up. beware.

How is the CRT kit going. Was thinking about getting it for my 99 xj. Did you gapped plugs to .060 No misfires???

I can't see the throttle body really helping airflow without an intake manifold and valve/cam upgrades. The 2000 TJ has distributer less ignition. Not sure when they started it though. Ngk makes platinum plugs also.

Ive had a 4.6 stroker kit and also a 4.0 with centrifical supercharger and they both gained alot of power over stock and i liked them both but if i was goimg to do it a gain id say id have to pick..... LS swap lol.... but really id take the stroker kit again it toom less tuning and both were reliable but the charger i had to do alot more to get it dialed like more heat protection under hood and i ended up doing i think 3 completely diffrent custom intake setup untill i got one that flowed right and kept intake air temps down ( was my first time ever doing something like that so i had a learning curve). But i liked the stroker more i ordered it threw it in i added a good clutch and a bigger radiator and hit the trails i think from when i got the motor till i was loading my cherokee on the trailer headed tof the rubicon to test it out (i live bout 3 hours from the rubicon) was 4 days only working at night after i got off work with just my cousin helping and 1 friend on the last day. But since then i drove my friends ls swaped cherokee with just a stock truck motor and it feels almost as powerfull as the 4.6 and was much chealer and if he adds a few parts l ike a cam and intake and a holley sniper kit instead of the carb set up he has it would kill my 4.6 . And i forgot to say both my motors were in a 99 cherokee 4 door, manual! 38s and tons, with a advanced adapters doubler, and a homebuilt 4link long arm front and rear.

so can you use these parts in a 2000 xj 2:42 i noticed the parts you used say for 99…?

If you want more usable power, you're FAR better off spending your money on lower gears, than on engine upgrades. My 99 with an automatic transmission is running 4.10s with 33" tires. It's a little revvy on the highway, but on 37"+ tires it's probably just right.

Nice video man! I have a 62mm TB sitting here for mine right now. That said don't bother with a stroker build. I did that to my last Jeep and it was the biggest waste of money! It makes very little extra power for the money. Do a 5.3 LS swap and the trans to go with it. Its not much more expensive than a well built stroker, and you have plenty of power. Don't mod the 5.3 or tune the crap out of it. just a box stock 5.3 is all you need. Plenty of power, much better MPG, sounds great, and way more reliable than the 4.0 is.

I got a 89 jeep Cherokee pioneer 2 door will that throttle body fit on mines?

You have just done some of the suportmods for the real power adders to work and breath. A stroker will add torque, a super charger will add more torque and help make up for poor flowing intake side of the head.. Is it worth it ? Vs a real v8? Depends on a few things smog being one . Personally if I'm going big power like I did with my sb 400. I started with 3/ ton axles than a atlas, nv 4500 , than the eng.

I have the Kenne Bell on a 4.6 “poor man” stroker….. that’s a really huge difference from stock🤷🏻‍♂️😂

It never hurts to have an extra in line fuel filter. Which the clear filter let's you see how dirty you fuel is.

My throttle body had a vac leak from the center shaft that caused a rich condition

Kelly can you go into more detail on the method to have the ecu to relearn? it looks like you have used a jumper cable to connect the positive and negative together at the battery!? that might go boom!!! [ i know what you did but it's unclear and others might actually do what it looks like.]

Would you be able to explain more of what you are doing at 11:49? It kind of confuses me

Bro, you need to check Newcomer Racing and his videos on The Horsepower Monster's channel. Your opinion that 'the straight six 4.0L isn't a very tunable engine' will be forever changed. The mods you did in this video are definitely worth the cost, considering if you replaced those items with OE equipment it would be about the same cost. The only thing you're missing in the equation is remapping the ECU, it's completely necessary when modifying for gains and is the reason you weren't very impressed with the HP/torque improvements, if it was even 10-15hp you would notice it immediately on WOT.

I got an aluminum radiator for my 99 tj 👍runs cooler 😂

I have a bored out stock throttle body and it whistles like crazy I need to go put the og one back on, curious how this ebay one does

Get some ford 4.2 injectors,already to flow more fuel and are plug and play to jeeps harness.

Could you ha e threaded the brass and the hole and used epoxy as a sealant? Or was that easier

You really need to check out newcomer racing. He tunes and builds these engines and he works winders with them.

Check out Flyin Ryan performance.

Cracked header tube will mess w the O2 Sensor, causing bad data back to ecu

I would imagine it would be amazing if you had a 5 speed trans in a Grand Cherokee it might help. You have more gears & better aerodynamics to get more out of the engine. Other than that I don't see much of a reason unless you are after torque

They have 12 hole injectors. Work better then the 4 hole.

Anybody recognize shifting hard when put into drive and reverse? Just installed mine and it hits hard when shifting into drive and reverse. I do know my tyranny mount is almost gone. Waiting on the new one. Does the ecm have to relearn after a larger theottle body is installed?

Kelly, I have an extra set of Bosch 4 hole injectors rebuilt by Precision Auto Injection I'll hook you up with if you're interested.

Is it ok to manually shift the auto , I wanted to know cause I have a 3speed auto 98 tj and would like to do so to rev it out more

That's why I'm going with a 4.7L stroker for my 2001 XJ...💪😁😁