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s3nt3nc3d 11-12-2009 10:04 PM

The Infamous Jeep Tap (and a question bout the TPS sensor?)
First off...I've heard references on here to the "infamous Jeep tap"...and my friend/owner of the dealership I bought my Jeep off of asked me if mine has it the other day. He said he doesn't know the cause but every 4.0 he's ever seen has developed it...usually around 70-80k miles.

I'm not worried that this is going to destroy my engine...from the reading I've done on here and him assuring me that this engine will run for many more years without any problems, I'm confident it's nothing major. However, I'm very anal about my vehicles and I at least want to know the source of this issue...and if there is an easy fix, it'd be nice to know too.

Basically...has anybody here figured out the cause of the infamous Jeep tap? It's usually only noticeable while the engine is cold and is just a rapid tapping noise...I've noticed mine is the most noticeable just under 2000 RPMs while cruising through town. I'm guessing it's a lifter issue...but thats the best I could come up with. As I said, I'm not too concerned, but I like to be educated and understand the noises I'm hearing.

Also, I've noticed that no matter how gently I press the gas down, I can not EASE it up in RPMs...but rather it immediately jumps up to around 1100 RPMs before I can ease it up.

ie. If I touch the gas, nothing happens...I'll slowly push the pedal down to open the throttle body up and it won't gentle increase the engine RPMs but rather will jump up straight to 1100 RPMs. From there I can ease it up in RPMs, but for the life of me I can't drop below 1100 and hold it there (aside from idle).

Is this programmed into the computer, or do I have a lazy TPS sensor that isn't registering the throttle opening as slowly as it should be? I just find that it causes me to buck and surge a lot when accelerating, cruising, and shifting. Not to say I'd be a pro driving a stick after only a month...but every little bit helps. :cool:

s3nt3nc3d 11-12-2009 10:08 PM

One other doesn't belong here really, but I figured I'd lump it in here instead of starting another thread...does anyone have a cheap source for Optima batteries? My battery is acting a little weak and I figure I'll go all out on a good one, especially if a winch and more lights are in my future. Those puppies ain't cheap though!

s3nt3nc3d 11-13-2009 05:42 PM


RedWrangler 11-13-2009 06:10 PM

I've heard al sorts of answers about the tap. mine does it at idle, and has done so since day one. I gave up trying to understand it, and since 112,000 mile later, all is well, I've learned to live with it, although, every gear head who hears it always gives me the "Hey, you've got a valve tap."

I found this site, it has free shipping and no tax, but they're not cheap.

Optima Battery Optima Batteries Free Shipping! Best Service! Deep Cycle Batteries Yellow Blue Red Top Optimum

Amazon sells them too. Just google Optima batteries and you'll find a large number of vendors, with different deals.

VARedLeg82 11-13-2009 07:05 PM

Before owning my current TJ, I had a '94 Grand Cherokee with the 4.0. It developed the "tap" around 110k, and still has it (with no issues) at almost 190k now (with dad as a farm truck these days). Never had any issues, and I drove it all the way up and down the east coast and out to Oklahoma a couple of times and back.

The best I could ever figure was that it's just noisy valves, but that won't hurt you. I've seen a few older Chevy's that reportedly sounded like that new. Yeah, it's annoying, and for a while it was troubling. But, take care of your engine and it'll take care of you. These things are champs.

Jerry Bransford 11-13-2009 07:12 PM

Not all develop that tap, my '97 4.0L has 182,000 miles on it and it's not making any noise that I can hear. I have heard of that issue though but I don't think it's anything serious.

On the battery issue, I have had three Optima batteries in my TJ and never again will I run another since they were bought out and cheapened on how they are made. All three of mine failed prematurely. The battery that has come out in the past couple years that has replaced the Optima as the #1 battery choice for Jeeps that are tough on batteries is the 3478DT Diehard Platinum made for Sears by Odyssey. It shares the shock/vibration resistant design of the Optima but it uses a purer lead and makes more efficient use of the space within the battery case so there's more battery per square inch. My TJ even spins faster while starting since converting to the Diehard Platinum several months ago.

Most of the hardcore wheelers I know switched to the Diehard Platinum, it has won over a lot of wheelers. Especially since it is made by Odyssey who makes mil-std batteries for the military.

Not to mention post-sales support on the Diehard Platinum is as close by as your nearest Sears store. Same pricing for a better battery. :)

jdub2k5 11-13-2009 07:25 PM

3 Attachment(s)
im still using the factory battery

s3nt3nc3d 11-13-2009 07:31 PM

I'm assuming my battery is factory...but it's definitely nearing the end of its life. It's very slow to crank on these colder morning...pretty sure it's gonna fail me the first time we get 0*F weather. Reminds me of trying to start our big diesel tractors on a 20*F start cranking and just pray the engine catches in that first couple cranks. haha

Jerry, thanks for the info on that Die Hard battery...I will definitely keep that info in mind when I get a little extra cash, and from all the reading I've been doing on these forums, you definitely know what you're talking if you say Optima batteries aren't what they once were, then Optima batteries must not be what they once were;)

Anyone care to comment on the acceleration (tps sensor?) issue...trying to figure out if that's normal or not.

Thanks for all the replies so far!

Jeepzcb09 11-14-2009 12:43 AM

my grand cherokke 4.0 had "the tap" at 175,000 and ran exclent(i sold it to get my wrangler) and my wrangler 4.0 with 128,000 has "the tap" and runs fine, the 4.0 is just a loud motor!!!

Jerry Bransford 11-14-2009 07:48 AM

Sorry, didn't see that part of your question S3nt... yes it seems to me too that that particular problem is most likely caused by a TPS with a bad spot. They get worn/dirty inside which can cause all kinds of problems like that. :)

s3nt3nc3d 11-14-2009 08:35 AM

Thanks Jerry, seemed a little matter how hard I tried, the lowest RPM I could hold it steady at was 1100. I'll have to pick up a TPS when I'm out at the dealership with some money...I'm out there all the time dropping off my boss' mail, but I never have cash on me. lol

Jeepsr4me 11-14-2009 09:05 AM

I can hear my injectors firing when I got the hood open, and that to me sounds like a tap.

But heard about a lot of different things others have found that make that noise. Some say bore rock, piston having a slight amount of movement in the bore.
Others say the lifters wear the bore where they are located and rock.

s3nt3nc3d 11-21-2009 12:41 AM

Hey guys...just wanted to post an update...

Today while on my lunch break I replaced my battery (ended up going the cheaper route and got a Duralast Gold from Autozone...1000 cranking amps/800 CCA if I remember correctly). Figured out that my old battery was still the OEM battery (almost 8 years old) wonder it seemed weak. Also learned that while my Jeep was supposedly driven by an older woman as her DD and never went off sure had a lot of dirt/gravel/mud underneath the battery and more mud up underneath the fuse/relay box. Ah's a Jeep so I'm not all THAT surprised.

Also replaced my TPS sensor...helped a tiny bit, but honestly didn't make that much of a difference at all. I'm just gonna assume it's pretty much normal...and if not, ah well...I'll adjust.

cntrybmpkn86 05-23-2010 11:35 PM

Check the cable that goes from the pedal to the butterfly on the throttle body to make sure its not sticking or has a little bit of rust on it. It has not done that to me on either one of my TJs but it happened on the tractor a few times.

jwalk214 05-23-2010 11:44 PM

i think its just chrysler. Had a minivan that made that same tap. My 08 wrangler does it when i first start her up, tap goes away within 40 seconds. only 13,000 on the wrangler, around 90,000 on the minivan before we sold it

619random 05-24-2010 11:18 AM

My jeep got the "Tap" around 80k miles. I can only hear it when I'm going down side streets at around 20-30mph. I have just learned to live with it.

Just think of it like a jeep STD. :P

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