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Unread 03-08-2009, 11:42 PM   #1
89cherokeeJP
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89 cherokee with renix ignition upgrade

i was just looking for an upgrade for my ignition system it's an 89 cherokee with 4.0 any advice would be great looked all over and all i found was a possible the ford I6 parts found on this website if this is good let me know


http://www.jeepz.com/forum/cj-yj-tj-...-0l-ignition-u pgrade.html

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Unread 03-09-2009, 02:00 AM   #2
5-90
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Why for? The RENIX (that's what you have) system is plenty powerful, and even supports strokers up to ~4.7-4.8L displacement. (Increased compression usually means you need to increase ignition spark energy.)

That's pretty good, for a system designed in the 1980's - some later systems have a hard time with that! And, you're probably not going to run the engine fast enough to need a system that works faster - there's a horrible harmonic issue 6000-7000rpm, and it's been strong enough to snap cranks.

What, specifically, are you trying to do? I'm certainly not averse to you spending the money - but maybe I can help you find a better way to spend it... The principal problem with RENIX has been found to be the grounds - the ECU's reference ground is that stupid little strap on the firewall, and it usually needs replacing by now. Replace that, add a secondary ground (min 8AWG) from the battery negative post directly to the chassis, and you'll improve things significantly.

Hit me backchannel for information on mains upgrades...
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Unread 03-09-2009, 07:56 AM   #3
89cherokeeJP
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I'm have trouble with it stumbling when i get about 1500 to 2200 rpm. I wanted to see if hotter cap and button setup would fix this since when it took the stock cap and button off and cleaned it it improved the stumble problem.
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Unread 03-09-2009, 02:06 PM   #4
89cherokeeJP
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bump to top need some more input
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Unread 03-09-2009, 02:13 PM   #5
88XJSport
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5-90 is pretty much the Renix expert of all the Internet. See NAXJA if you dont believe me.

Sounds like your stumbling issue could be a bad TPS, low fuel pressure, or some other sensor. Definately not a weak ignition system.
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Unread 03-09-2009, 03:12 PM   #6
89cherokeeJP
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i think i maybe getting to much fuel a friend of mine has an H.O 4.0 and was building a stroker and my fuel injectors went bad so he gave me his well long story short i looked on the net and found out that H.O injectors run about 21lbs and my stock injectors run about 18lbs
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Unread 03-09-2009, 07:48 PM   #7
88XJSport
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You found your problem. Renix injectors should not exceed 19# or you run too rich.
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Unread 03-09-2009, 09:19 PM   #8
89cherokeeJP
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but would running the hotter cap and coil setup from the ford equal that out
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Unread 03-09-2009, 09:27 PM   #9
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Quote:
Originally Posted by 89cherokeeJP View Post
but would running the hotter cap and coil setup from the ford equal that out
No.

However, if you're stumbling because you're running rich, that means your fuel metering and feedback are probably off. Check/replace MAP, IAT, and HEGO sensors. (The MAP and IAT are standard GM parts - if you can't find them anywhere else, Marren Fuel Injection has reasonable prices. Google them. The HEGO is an oddball, but it's still available at/through your local - Bosch has a part number that works, but I don't recall what it is. Bosch is OEM for most anyhow.)

If fuel trim is causing you to run silly, then fix your fuel trim. Hotter ignition is like treating a broken leg with aspirin - it will mask the symptom, but it doesn't fix the problem.

Also, use an analogue ohmmeter to check TPS sweep and function - they're known for developing flat spots in the track (due to the way they're built. It does take some time...) and the fix for that is replacement. Using a digital ohmmeter will not give an accurate test, you must use an analogue for the check to mean anything! The test takes about two minutes - you're just making sure that the sweep of the sensor will not "skip" or "stick" anywhere on the track. That usually happens at the part-throttle opening that corresponds to where you cruise the most.

Going from 18-19# to 21# (at the same pressure delivery - I think early HO is rated for the same pressure as RENIX...) should not cause signficant fuel trim problems - the system can adapt for that (I have 21#/hour in my 88, and no trouble there.) However, switching to the larger injector can bring a problem elsewhere to light - and that may be what happened for you.
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Unread 03-11-2009, 07:42 AM   #10
89cherokeeJP
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i adjusted the throttle postion sensor 5 volts in and .8volts out but it still runs like crap right after adjusting. it ran horrible but turned it off and cranked it up again now it runs about what it did before adjusting it. is there any perfect way or ways to test the map sensor and iat sensors if so LMK
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