Looking for distributor cap and button suggestions

[TJBob]

Hey guys/gals, I have a 99 4.0. Looking for suggestions on a distributor cap and button. Crown auto make a good one? Is there a specific aftermarket cap and button to stay away from? Jeep runs fine, except for some intermittent high RPMs at idol. just time for a tune up I believe. Going to clean the IAC today too.

 

[KCsTJ]

I would check wermopar.com get a genuine Mopar cap and rotor.
I recently accidentally "fixed" a nagging misfire problem I could not find for several weeks. Even went so far as to replacing valve springs

Stick with OE parts and you should be fine.

That intermittent rise in rpms is most likely a vacuum leak
.. I would check all vac hose connections

 

[Jerry Bransford]

Use only those with brass contacts inside the distributor cap and on the rotor. Cheap distributor cap & rotor sets come with aluminum contacts and they won't last nearly as long. I'd suspect any made with brass will be very good quality. This may require the counter guy to open several boxes for you but that's ok.

I looked at a couple online sources like Amazon and I only found one rotor (from Accel) that mentioned it used brass contacts, the rest don't say what the contacts are made from. I suggest buying locally so you can see what the contacts are made from.

 

[TJBob]

I would check wermopar.com get a genuine Mopar cap and rotor.
I recently accidentally "fixed" a nagging misfire problem I could not find for several weeks. Even went so far as to replacing valve springs

Stick with OE parts and you should be fine.

That intermittent rise in rpms is most likely a vacuum leak
.. I would check all vac hose connections

Thanks for the reply. I figured OEM was probably best. I’ll check out that site. I’ve looked over all my vacuum lines, and can’t find a leak. That was my first suspicion... not saying there isn’t one, just can’t find it. I’ve asked around at local parts stores to see if anyone rents smoke machines, to no avail. So I figured I’d try plugs, wires, distributor cap, button, and try cleaning the IAC. Couldn’t hurt. It’s due for a tune up anyway. The idol issue isn’t very consistent. Every once in awhile when I come to a stop, it idols at 1,000-1,200 rpm. I touch the gas pedal and it usually returns to normal.

 

[TJBob]

Thanks Jerry! I’ll definitely look for that!

 

[KCsTJ]

Thanks for the reply. I figured OEM was probably best. I’ll check out that site. I’ve looked over all my vacuum lines, and can’t find a leak. That was my first suspicion... not saying there isn’t one, just can’t find it. I’ve asked around at local parts stores to see if anyone rents smoke machines, to no avail. So I figured I’d try plugs, wires, distributor cap, button, and try cleaning the IAC. Couldn’t hurt. It’s due for a tune up anyway. The idol issue isn’t very consistent. Every once in awhile when I come to a stop, it idols at 1,000-1,200 rpm. I touch the gas pedal and it usually returns to normal.

Try.this cheap vac tester...

It's a simple fluid transfer pump, $10 at Harbor Freight and a cigar.
With this set up you can do your own simple vac test.
Plug the tail pipe with a rag and plug the throttle body also. Works like a charm!

 

[astjp2]

Napa premium cap and rotors are brass, the rotor tip is black but if you scratch it, it should just be plated brass. Otherwise you may also consider using a ford cap and rotor. The 300 straight 6 had an adapter that allows the use of a big HEI style cap and rotor. the larger separation between the posts has been known to improve idle.

 

[TJBob]

Try.this cheap vac tester...
View attachment 82794
It's a simple fluid transfer pump, $10 at Harbor Freight and a cigar.
With this set up you can do your own simple vac test.
Plug the tail pipe with a rag and plug the throttle body also. Works like a charm!

That’s awesome! I’m def gonna pick one of these up! I seen where a guy made one out of a paint can on YouTube. But it wasn’t Clint Eastwood approved haha! Thanks for the info!

 

[TJBob]

Napa premium cap and rotors are brass, the rotor tip is black but if you scratch it, it should just be plated brass. Otherwise you may also consider using a ford cap and rotor. The 300 straight 6 had an adapter that allows the use of a big HEI style cap and rotor. the larger separation between the posts has been known to improve idle.

Something to look into, thanks! Edit: do you know if the adapter is built into the cap for the for 300, or is it a separate piece?

 

[astjp2]

this is what they did with the 258, older 4.0's used the same cap from what I remember
CAP & ROTOR

The cap and rotor I used is listed for a 1984 Ford F-150 Pickup with the 300, I-6. Make sure that you use the premium cap with brass terminals. Otherwise, you can run into problems down the road. These came from Advance Auto as well. Below are pictures of the larger cap as well as the new Cap Base Adapter.
borrowed from: http://keith.cj8.tripod.com/tfi_upgrade.htm

​

CAP BASE ADAPTOR

The new large Motorcraft cap will not fit on the stock distributor. To make the match I needed a cap base adaptor. This will allow me to fit the larger cap on the stock unit. The adaptor I used came from a 1982 Ford F-150 Pickup with the 300, I-6. Make sure that you get the adaptor that SCREWS down to the stock distributor and CLIPS to the new cap. If your local parts house has the bottom clip type try the same adaptor for a 1981 P/U. This came from Advance Auto as well.

 

[Wildman]

I've had good luck with the FirePower ignition kits.

https://www.amazon.com/dp/B002Y336LQ/?tag=wranglerorg-20

https://performancedistributors.com/product/jeep/

 

[Igoo65]

Make sure that your intake and exhaust manifold bolts are torqued to the correct spec. I had all kinds of idle problems and as soon as I tightened those bolts, my Jeep ran great!

 

[Jerry Bransford]

I've had good luck with the FirePower ignition kits.

https://www.amazon.com/dp/B002Y336LQ/?tag=wranglerorg-20

https://performancedistributors.com/product/jeep/

I installed that Screamin Demon coil into my '97 TJ and it failed several months later, stranding me literally out in the middle of the desert. Fortunately someone came along who had a spare ignition coil and gave it to me for free, great guy. And zero change in performance after installing that old used ignition coil.

I'm real particular on replacement ignition systems. Especially where ignition wiring goes and ESPECIALLY where "low resistance" ignition wiring goes. Low resistance ignition wiring sounds great, right? Actually it's not and it just tends to add static and electrical noise to CBs, AM radios, and it can interfere with the computer. The big secret to "low resistance" wiring is that it's a scam. It actually costs LESS to manufacturer low-resistance wiring and there is ZERO performance benefit to it. True. OE ignition wiring has resistance ADDED to it at extra cost. The sole job of that added resistance is to eliminate spark/static ignition noise.

Does the added resistance decrease performance by reducing voltage to the spark plug? No, at least not in a significant way. First, the OE ignition coil produces far more voltage than is needed to reliably ignite the air-fuel mixture. Second, there's an electronic reason why the OE ignition wiring's added resistance does not significantly reduce the already higher than required voltage. That reason is described by Ohm's Law. There is so little current (microamperes) in ignition wiring that the added resistance does not appreciably drop the voltage. V=AxR (E=IR) or Volts dropped by the resistance equals the amperes times the resistance. Such a small current traveling through that resistance means you get an insignificant voltage drop across that additional resistance.

Low resistance wiring is really more of a scam for us Jeepers. It sounds great and it is intuitive that lower resistance would be a good idea but it doesn't help. Really.

Between that Screamin Demon ignition coil that failed on me and that expensive low-resistance ignition coil that does NOT improve performance over the OEM ignition set, I personally sure wouldn't install that expensive kit. The only way it could improve performance over the OE coil and OE ignition wiring set would be if the existing coil or ignition set had gone bad. Will it improve performance over a good set of OEM ignition wires and OE ignition coil? Nope.

 

[TJBob]

Thanks for the advise guys! I’m just gonna grab a mopar cap. That’s what’s on it now and budget friendly. Gotta order plugs too. 3 of my local shops don’t seem to carry the autolite xp985 on the shelf. So it was a bust for the tuneup today. Have to wait until next weekend. Did some frame and axle painting instead haha!

 

[ranger101]

Definitely check/clean the IAC. I had an occasional high idle from my IAC sticking after the engine was warmed up. It would like to hang up after driving 15-20 miles at freeway speeds. A quick cleaning straightened it right up and I haven’t had any issues since.

 

[TJBob]

Definitely check/clean the IAC. I had an occasional high idle from my IAC sticking after the engine was warmed up. It would like to hang up after driving 15-20 miles at freeway speeds. A quick cleaning straightened it right up and I haven’t had any issues since.

I did run some carb cleaner through it today, we shall see if it helped

 

[Daniel.Lee]

I have a cylinder 1 misfire that I am still trying to address so I ordered one of these guys from Quadratec. Just an option. Jerry told me about how brass contacts are much better so I listened to his advice. I haven't received it yet but once I do I can let you know!

https://www.quadratec.com/products/55101_60X_PG.htm

 

[KCsTJ]

Just a note of interest, I got my 97 distributor cap and rotor from Wermopar.
It did not come with brass contacts.
I used it anyway.
I would remove it and take a pic but it cured a several month search for cyl #3 misfire on my 2.5L.

So I'm not even going to look at that cap wrong.

 

[Wildman]

I installed that Screamin Demon coil into my '97 TJ and it failed several months later, stranding me literally out in the middle of the desert. Fortunately someone came along who had a spare ignition coil and gave it to me for free, great guy.

I'm real particular on replacement ignition systems. Especially where ignition wiring goes and ESPECIALLY where "low resistance" ignition wiring goes. Low resistance ignition wiring sounds great, right? Actually it's not and it just tends to add static and electrical noise to CBs, AM radios, and it can interfere with the computer. The big secret to "low resistance" wiring is a scam. It actually costs LESS to manufacturer low-resistance wiring and there is ZERO performance benefit to it. True. OE ignition wiring has resistance ADDED to it at extra cost, its sole job is to eliminate spark/static ignition noise.

Does the added resistance decrease performance by reducing voltage to the spark plug? No, at least not in a significant way. First, the OE ignition coil produces far more voltage than is needed to reliably ignition the air-fuel mixture. Second, there's an electronic reason why the OE ignition wiring's added resistance does not significantly reduce the already higher than required voltage. It's formulated by Ohm's Law. There is so little current (microamperes) in ignition wiring that the added resistance does not appreciably drop the voltage. V=AxR (E=IR) or Volts dropped by the resistance equals the amperes times the resistance. Such a small current traveling through that resistance means you get an insignificant voltage drop across that additional resistance.

Low resistance wiring is really more of a scam for us Jeepers. It sounds great and it is intuitive that lower resistance would be a good idea but it doesn't help. Really.

Between that Screamin Demon ignition coil that failed on me and that expensive low-resistance ignition coil that does NOT improve performance over the OEM ignition set, I personally sure wouldn't install that expensive kit. The only way it could improve performance over the OE coil and OE ignition wiring set would be if the existing coil or ignition set had gone bad. Will it improve performance over a good set of OEM ignition wires and OE ignition coil? Nope.

Well I've ran one of these kits on my 2.5 & 5.2 so far and never had any issues. I don't know if my CB or radio had more static after installing them. I can't remember.

As Jerry and anyone else will tell you the brass style distributor caps and rotors are going to be the best. The 2.5 & 4.0 are very picky about what plugs you run in them. Back when they made them I had the best luck with Champion Truck plug but they stopped making them. What works on my V-8 doesn't matter in this case.