Throttle Body Replacement?

[Hmr]

Need some advice:

Just bought a 1997 TJ! It ran great for about two weeks, then popped a code (P0302) ran fine for about a week after that then on my way back from the gym it started dying when under any load and producing a high idle. Took it to the shop the next morning and they told me no misfire but needed a new MAP sensor. Replaced that then they called back and said the code was still coming up. They did a smoke test and identified the throttle body was leaking. They were unable to find a new one and told me to order one and bring it back for install.

Does this sound correct? Suggestions on throttle replacement options?

 

[ItchyDong]

I’ll bet my sack that a MAP sensor will never cause a single cylinder misfire. Their computer invoice suggests replacing a valve spring, the hand written note seems like it’s for a whole other 97 Jeep Wrangler. Find you another shop bud.

You can bet it’s not the coil because it would have a companion cylinder misfire as well. You can swap spark plugs or just throw in a new one because you’re in there already and it’s cheap. If that doesn’t fix it, swap #2 fuel injector with another cylinder and see if the problem follows.

Edit: I’m an idiot and just realized they are in fact from two different places disregard

 

[ItchyDong]

Depending on where the leak is coming from, you may need a throttle body. Idk without seeing the smoke test in person.

 

[macleanflood]

Could be a leaking shaft. I don't think there are any viable aftermarket throttle bodies. I'd do everything to fix yours.

-Mac

 

[Moglocker]

Could be a leaking shaft. I don't think there are any viable aftermarket throttle bodies. I'd do everything to fix yours.

-Mac

They all leak,it’s not your problem of the misfire,no replacements are available,you can do the o ring fix.i would say the problem is valve related.

 

[B1Toad]

Could be a leaking shaft. I don't think there are any viable aftermarket throttle bodies. I'd do everything to fix yours.

-Mac

Is this one not any good? https://bbkperformance.com/products/jeep-4-0-62mm-throttle-body-91-03

 

[macleanflood]

Is this one not any good? https://bbkperformance.com/products/jeep-4-0-62mm-throttle-body-91-03

No first hand experience.

It's larger than stock...so...

-Mac

 

[Moglocker]

No first hand experience.

It's larger than stock...so...

-Mac

Yep I heard they make a large hissing noise

 

[Christian.mers]

I went with a 62mm and they do make a hissing noise for sure. It’s very obnoxious. I believe it’s because the opening for the Intake Manifold is machined at 60mm and you’re slapping a 62mm TB on so the air that’s coming in just hits that lip where the Manifold isn’t cut to the same diameter to match the TB. I’d imagine the air is hit that lip and cause all kinds of turbulence going into the manifold but I can’t really see air so I’m no expert.

You could port the intake manifold if you’re that down bad but I don’t see the point because the engine is programmed to take a certain amount of air in so you won’t see any benefits unless you tune it for the increase in air.

Again, I’m not a very knowledgeable guy when it comes to engines or vehicles as I’ve only been getting into them for about 2 years. Maybe someone else on here could correct me if I’m wrong.

 

[TJRick]

Yep I heard they make a large hissing noise

I have the 62mm BBK throttle body on my 1998 Jeep Grand Cherokee 4.0 and it doesn't make a hissing noise.

I only replaced mine because it had a large leak in the throttle body, and I couldn't find a stock replacement either.

 

[Christian.mers]

BBK is the only replacement TB that I’ve seen give better than crappy results (From guys on the forum giving advice). Ebay TB’s usually leak at the butterfly (from what I’ve experienced)

I have personally never had any encounters with this BBK TB but I’d most definitely steer clear of Ebay TB’s even though you may save a buck or one hundred

 

[TJRick]

BBK is the only replacement TB that I’ve seen give better than crappy results (From guys on the forum giving advice). Ebay TB’s usually leak at the butterfly (from what I’ve experienced)

I have personally never had any encounters with this BBK TB but I’d most definitely steer clear of Ebay TB’s even though you may save a buck or one hundred

I decided to go with the BBK precisely for the reasons stated above.

From my research, the Ebay replacement throttle bodies are all made overseas, whereas the BBK is an American company.

 

[MikeE024]

Is this one not any good? https://bbkperformance.com/products/jeep-4-0-62mm-throttle-body-91-03

I purchased a BBK a while back. I returned it the next day because it also badly leaked when I smoked tested it with compressed air.

Could be a leaking shaft. I don't think there are any viable aftermarket throttle bodies. I'd do everything to fix yours.

-Mac

I installed O-rings using this video about two years ago. I then bought a spare on eBay and did the same mod so I'd have a spare ready to install if it leaked again. I later purchased butterfly shaft bearings (with the little seals inside), but I never installed them.

 

[CharlesHS]

For several years I had a lean idle miss that I troubleshooted for some time with no results.
While cleaning the IAC I accidentally sprayed some cleaner near the throttle shaft and the idle smoothed out some.
Tested several more times and determined the problem was air leaking thru the shaft.
There were no OEM replacements available so I purchased a BBK TB.
The factory throttle body ID is 56mm and the BBK is 62mm and the intake manifold opening is approximately the same ID.
While replacing the TB; I disconnected the ground cable so that the ECU could relearn the A/F trim values.
Upon initial restart the engine was running rough; after driving the Jeep for 45 mins the engine was idling normal and there was a noticeable difference in throttle response. Can't speak for HP, but there is a noticeable difference in TQ.
You ask how I can make that determination....
There is a long elevated bridge at Blount Island Terminal on the way to JAX airport where with the A/C on I previously needed to down shift into 4th to maintain 60 mph. Now with the A/C on I can maintain 65 mph without down shifting.

 

[CharlesHS]

Could be a leaking shaft. I don't think there are any viable aftermarket throttle bodies. I'd do everything to fix yours.

-Mac

Thank you for this informative video....
I might give this a try with the TB that I removed and keep it as a spare.

 

[GoldenGorilla]

I highly doubt a throttle body or MAP sensor in any way would cause only a P0302 code. This is a misfire just on cylinder 2 and that diagnosis makes no sense.
I'd suspect a leaking fuel injector o-ring or clogged injector, coil pack or spark plug, a dying upper bank 1 O2 sensor or possibly an issue with a piston skirt/rings.

I installed the BBK 62mm throttle body at the same time I did my 1.7 roller rockers. I don't believe it on it's own would have a significant impact on power on a stock motor, but it wouldn't hurt it either. With more significant head/cam/stroker/forced induction work, the 58mm stock bore would eventually become a bottleneck. I plan to go down those roads eventually which is why I picked it up. Fit and finish is good.
I do get a small whistle sound at a specific partial throttle position near closed, say 10-20% open. I believe it is the crisp sharp edge on the throttle plate. It matches the machined opening on the horseshoe intake manifolds and that is not the source of whistling. Compared to other noises on the jeep, it's very small and infrequent.

Coincidentally, the tests Jezza is running today released throttle body also show no significant difference on a stock motor.

 

[Christian.mers]

I previously needed to down shift into 4th to maintain 60 mph. Now with the A/C on I can maintain 65 mph without down shifting.

I couldn’t imagine going 60mph with the A/C. It’s such a draw on the engine, I can feel a dramatic and noticeable Difference between settings. I’ve noticed that the Foot setting and the defrost setting tend to not place that draw on the engine but they usually don’t pump out cold air on hot days

 

[MikeE024]

My understanding is that the 62mm BBK gives a placebo effect by providing more air without needing to push the pedal as much, but the stock TB provides the same amount of power by simply pushing the pedal down a bit more.

 

[GoldenGorilla]

My understanding is that the 62mm BBK gives a placebo effect by providing more air without needing to push the pedal as much, but the stock TB provides the same amount of power by simply pushing the pedal down a bit more.

I'd agree with this. The stock throttle body from my 04 4.0L is 60mm above the throttle plate and then narrows to 55mm below it except the notch where the bottom side of the IAC outputs. I don't have the type of caliper to measure the deeper part at the throttle plate, but I'd say 58mm seems true. The BBK is 62mm straight through.

It's like sport mode on a modern manual with electronic throttle. Can't change the power the engine produces, just a placebo effect of "more response" with less gas pedal movement. I'm pretty sure I swapped the BBK in 1 or 2 days before tackling the roller rockers and I don't recall noticing any difference from stock at that time. But if you can't find a good stock throttle body anywhere, it's a USA made available replacement for stock that will cause no adverse effect. Just make sure to buy the correct one for your year's IAC setup.

I was expecting this when I bought the BBK. It was thinking to bigger mods down the road, not what you'd traditionally call bolt on. I don't have the time or inclination to test each mod one by one like Jezza is doing, but I really appreciate his series and I'm sure it will be a valuable resource to people thinking critically about what you can do to make power with the 4.0L platform.