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93_Rarity 03-01-2015 08:00 AM

Rough Idle When Warm, Dies Sometimes
It's been awhile since I have posted, but since then I've gotten a new truck! My old 93 is dead, but I just bought a 4x4 automatic 97 with a 4.0 last week. A huge step up imo. I'll update my signature in a while.

Anyways, I haven't done anything to it yet (I.e. Spark plugs, oil) , but everything checks out good as far as fluids go. I found a problem though- it drives fine when it's cold, but when it warms up it likes to idle weird (like a MMMMmmmmMMMMmmmmMMMMmmmm) and sometimes dies. I don't have any problems with power loss or anything like that, but it's really bothering me and I'm not sure what it could be- maybe the fuel pump? Or one of the cats backed up? Like I said, I have not a clue about something like this, so any hope would be appreciated! ^.^

djfllmn 03-01-2015 08:14 AM

Re: Rough Idle When Warm, Dies Sometimes
clean the IAC to start

93_Rarity 03-01-2015 09:57 AM

Re: Rough Idle When Warm, Dies Sometimes

Originally Posted by djfllmn (Post 2403255)
clean the IAC to start

Thanks, I'll grab some cleaner at work tonight and try it. I'll update in the morning!

CharlieM 03-01-2015 05:01 PM

Plan on replacing the intake gaskets, they not hard to do and no special tools needed. The intake is plastic so when its cold they leak till motor warms up.

93_Rarity 03-03-2015 02:13 PM

Re: Rough Idle When Warm, Dies Sometimes
Cleaned the Iac yesterday, didn't seem dirty at all but went ahead. Didn't notice a change, so I had a friend run diagnostics on it and the only code that came up was too lean mixture. He said it was probably moisture built up in the gas tank and to run some Iso-heet through to get rid of it. Filled up, put a bottle in and by the time I q back home it was idling a heckuva lot better, been almost perfect since. Still stumbles every now and then, but I'm hoping if I run a few more tanks through with that stuff it will hopefully be perfect! Any thoughts?

mwillika 03-08-2015 07:48 AM

Re: Rough Idle When Warm, Dies Sometimes
Sounds like almost the exact same problem I've been having. I'll have to try out the iso heet and see how it works!

yellowrangerfx4 03-08-2015 08:38 AM

Re: Rough Idle When Warm, Dies Sometimes
System lean codes usually indicate a vacuum leak. a common problem with 4.0 liter engines is the intake plenum gaskets leaking (as stated earlier) Wouldn't be a bad idea to replace them. If you had a tank full of bad fuel, it would be good to replace the spark plugs, replace the fuel filter and clean the MAF. Once you have done that, try disconnecting the battery for ten minutes to clear the codes and then drive it for a while and see how it does. If the light comes back on, or if you continue to have problems, get it scanned again to see what codes are present after the reset

mwillika 03-08-2015 09:10 AM

Re: Rough Idle When Warm, Dies Sometimes
A few months back, around December, I had this issue, it got so bad that it had a very hard time starting. I replaced all the upper intake gaskets, and the biggest one at the bottom (cant remember the name) was clearly not sealing anything. After replacing these the problem went away, for the most part. It starts fine most of the time but if its particularly cold it will act as if it isn't getting enough fuel. Its been showing the lean code for almost the entire time I've had the truck, about 25k miles. MAF has been completely replaced, as has the fuel filter and plugs. I'm going to try the fuel cleaner next time I fuel up and see how it goes.

93_Rarity 03-11-2015 06:41 AM

Re: Rough Idle When Warm, Dies Sometimes
Sorry, my internet access is lacking nowadays lol. Well I tried running it through again almost empty and it had pretty much same result, but it seemed to take a little longer for it to start idling weird. While I was waiting on this week's check to come through to start troubleshooting, I tried running some some gumout fuel system cleaner through it. I only drove it about twenty miles home and nothing seemed different. Next day, my buddy and I took our trucks off-roading (mine more for if he got stuck, which he did). A lot of revving and pulling later, I noticed that it wasn't stumbling anymore just sitting there. Took it through a small pond a few times, no problems. Been driving it every day and haven't had any problems at all. I didn't replace any gaskets or lines or anything, so maybe the fuel filter was blocked up? Don't really know, but I'm not gonna complain ��

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