Starting Rough, Running Rich?

Have a car? Is it broken? Want to make it faster? Got cool pictures?
5.9Limited
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Post by 5.9Limited »

hm...didn't know that about plugs. I'll check mine tomorrow to see what they look like. I've run these plugs in all my cars and always noticed an improvement...not as noticable with this jeep but I figured it was because the jeep was already a lot stronger and faster than any other vehicle I owned before it. so Im not against switching , and like you guys have said, I 've heard good stuff about the NGK's too.
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5.9Limited
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Post by 5.9Limited »

so i jsut went out to my ride to look at the info decal to pull the plug serial number and looked it up... standard champion plug is whta the # pulled, so I could probably find the NGK equivalent right?? is buying a platinum or irridium plug all their craked up to be.??? I used to think so...but if my bosch's end up being the source of my problems, I geuss I heard wrong!!
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mr tibbs
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Post by mr tibbs »

I would try the stock cheapies first. If the Jeep runs better you know where your problem lies, plus they are cheap! :wink:
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5.9Limited
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Post by 5.9Limited »

very true... Im guilty of being an upgrade junkie...sometimes its best to stck with what works eh??? I think I'll head to the auto parts store tomorrow...
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5.9Limited
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Post by 5.9Limited »

ok here's a question....with my upgraded wires and coils...Im supposed to be able to run a stronger gap. stock gap is .040... I guess Im supossed to be able to run a .060... recommended?? make a difference???
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mr tibbs
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Post by mr tibbs »

I might go up .005, maybe .010, but IMO .020 is a pretty big jump. Spark plug gap is a fine line between burning everything in the piston chamber. Finding that happy medium between to small of a spark and to much of a gap is pretty hard when you start adding upgrades in there. I always upgrade my intake and usually the exhaust as well and I never really touch my spark plug gap.
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5.9Limited
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Post by 5.9Limited »

ok so i never made it to the parts store for the plugs... but I decided to give a jeep forum one last shot... and what'd ya know I got an intelligent response :shock:

a guy chimed in who has the exact jeep as me, similar upgrades and similar problem..actually his is worse,, but he tried plugs and got no result...tried MAP sensor, IAC and no result... so he dealt with the issue for a long time then his fuel pump died. when they removed the bad pump they relized one of the connections to the sending unit's O-ring had deteriorated cause the system to lose a little pressure when the cars off.... now I don't know if IM dealing with the same issue, and will surely replace the plugs, IAC and MAP as im getting closer to 150k miles anyway... but ...its an Idea I guess...
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mr tibbs
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Post by mr tibbs »

I would start with the cheap stuff and work your way up. :wink:
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5.9Limited
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Post by 5.9Limited »

thats the plan... plugs are obviously cheapest... MAP runs about $100 , IAC is about the same too... next on my upgrade list is electric timed distributor. i've heard they give huge results in idle and throttle repsonse over standard point style distibutors... so I won't bother with a cap and rotor as I'll be replacing the whole unit.
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wash with gasoline
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Post by wash with gasoline »

before you pull the fuel tank i would put a pressure gauge inline and see if it drops while it sits. and if you ever do have to pull it make sure to do it when its low on fuel.
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Post by 5.9Limited »

finally bought plugs today...standard factory manual stock plug for this vehicle. talked to my mechanic and he very much agreed that even with ignition upgrades, stock plugs are the way to go, and tha alot of "performance plugs" aren't what they're cracked up to be. I'll be tossin' them in tomorrow afternoon ...I'll let ya know.
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seandiguer
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Post by seandiguer »

Is it only on starting that its a problem?? Does it idle properly or does the rpms seem low? Does it have a miss while running or under load? (ie:going up a hill) Is there blue/black smoke coming from the exhaust? What year is your jeep?

Most sensors will set the the check engine light. If the light is not on, i would suspect a bad iac valve. I have ran into this alot at work, where the iac valve is bad but does not set the check engine light. Usully the vehicle will have extended cranking and very low idle when first started..

another thing to check would be fuel pressure.. This shouldnt make your jeep run rich though, but lean.. But if the o2 sensors are working properly, they sense the vehile running lean, and try and compinsate for this by telling the computer to add more fuel.. vicious cycle i know..lol

Before starting, cycle the key on then off, 3 or 4 times to prime your fuel pump.. if it starts better then suspect the fuel pressure bleeding off, or a plugged fuel filter..

How did the plugs look? if completely worn out, they could be adding to the problem, but i would still suspect something else.. Also if they are worn out, replace the cap and rotor too cause there probably in the same shape.

A bad map sensor will cause hard starting and extemely rich running conditions.. If it is bad, you should be able to unplug it and see if your jeep starts normally. By unplugging it, it will put the computer in base setting mode for the map sensor. But this will set your check engine light on.

A complete tune up never hurts. Plugs, cap, rotor, injector flush, fuel filter and wires if needed.. Then you know what your working with, and make your vehicle a lot easier to diagnose, and never hurts in the fuel mileage catigory either

pz excuse speeling mistakes.lol.
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Post by 5.9Limited »

thanks sean for all the good input. my jeeps a '98 5.9 Limited with the 360 c.i mopar magnum engine...a rare jeep, but a not so rare engine seeing as it was what was used in all the dodge ram 1500's of that era. I'll try unplugging the map sensor and see what that does, as far plugs go I never got to changing them the other day (long story) but will be doing that soon...perhaps tomorrow.

btw, where's the IAC valve located?? is it also on the throttle body??

I've tried priming the pump and its still unpredictable...sometimes it works, other times it doesnt. the jeep will be going in for a list of tune up stuff within the next couple months.. (brakes, tires, a small lift possibly,) and whatever this starting issue is if I can't fix it. keep the suggestions coming, much appreciated.

and know wurys abowt thu speling... :)
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5.9Limited
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Post by 5.9Limited »

put the new plugs in this morning...my quickest time ever for a plug swap... 8 plugs, 35 minutes...Im no mechanic but I thought that was pretty good.

Here's what I found... The Bosch Plat. 4's that I had in there were def. due for a swap. I have a log w/ all my serviec reciepts taht I check before swapping out the plugs, and was reminded that I bought these plugs for my LAST jeep that was identical to this one....then put them in this one before selling the other... ( im confused just reading that.. ) :shock: .. anyway...they're a little over 3 years old...so they were due. and I found that my valve cover gaskets are seeping a little and some of the oil made its way down to the plugs...only one looked dirty past the threaded portion...still not good. that will be addressed soon...

first start up with the new champion stock style plug was good...no rumble and fired as normal...since than its been back and forth between 50% better, to completely normal so Im happy with that. it seems like its getting better the more I run it too... next will be the MAP and IAC... I found a seller who can get me both factory direct together for a reduced price...
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seandiguer
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Post by seandiguer »

I've been away for a while.
If oil is leaking onto the spark plug boots then it may cause a missfire. I recommend putting dielectric tune up grease in each spark plug boot before putting it on the plug.(or fix the leak and install new wires) Also, change your cap and rotor. If its been 3 yrs since you've changed that, it will be corroded inside.
The iac motor is in the throttle body.. you can easily remove it (2 torque bit screws) and clean it.. some intake cleaner and a toothbrush work real good. Also clean inside your throttle body as best as you can.. Do not just spray intake cleaner inside, cause when you go to start it, it will be flooded.. Use the toothbrush and a rag with some intake cleaner..
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thedeal7235
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Post by thedeal7235 »

when i worked on these back in college, they were also known for injectors going bad, and ecus, -just my 2 cents
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5.9Limited
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Post by 5.9Limited »

the ecu seems to be fine..everything else is working great, all the sensors and such... I've heard that if the ecu goes bad that a tell tale sign is when the info center in the jeep give you indicators that are wrong...like "driver door ajar" when the door is closed, or something like that...

I replaced the injectors about 6 months ago...I made the mistake of buying remanufactured ones...they have a warranty...but it is possible that one could be faulty....the jeep runs strong and smooth though...just this nagging starting issue.. mpg has improved some since the new plugs went in...starting is still up and down... :?
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