sinnaevd Posted December 21, 2006 Share Posted December 21, 2006 smells like i am burning an excess amount of gas, and its also idling i little rougher then i would like, although runs and revsup quite well. it was sitting befor i picked it up but i have no idea how long other then a basic tune up, what should i be looking at? its burning extra fuel i am almost sure of it, and it kinda a concern as i need it to pass etest so i can DD it any tips fellas EDIT: engine is a 4.0, sorry for not mentioning it cole it is the Renix system also, is there anything to use to clean otu the engine bay? does engine degreaser work well or will it mess up my electronics? Link to comment Share on other sites More sharing options...
JOMJ87 Posted December 21, 2006 Share Posted December 21, 2006 Motor????? Mine has always ran rich but I cleaned everything and did some vaccumm line work and it helped alot but not near completely. BTW mines a 2.5 Cole Link to comment Share on other sites More sharing options...
512tr Posted December 21, 2006 Share Posted December 21, 2006 My vote is the O2 sensor, it's the main controlling fuel sensor in a warm engine.. at idle and cruising. A non working O2 sensor will cause the engine to run rich, exept during acceleration/deceleration and at WOT. Link to comment Share on other sites More sharing options...
88MJay Posted December 21, 2006 Share Posted December 21, 2006 I remember reading somewhere that if you have a crack in the exhaust manifold or anywhere in the exhaust before the 02 sensor that it will fool the 02 sensor into thinking it's running too lean. I'm assuming that fresh outside air would be pulled into the system and thus lean out the exhaust so that the 02 sensor reads it as lean and tells the computer to richen up the mix. Does this sound like something that can actually happen? It seems logical but I wanted to run it past you guys. later, j Link to comment Share on other sites More sharing options...
Oizarod115 Posted December 21, 2006 Share Posted December 21, 2006 I remember reading somewhere that if you have a crack in the exhaust manifold or anywhere in the exhaust before the 02 sensor that it will fool the 02 sensor into thinking it's running too lean. I'm assuming that fresh outside air would be pulled into the system and thus lean out the exhaust so that the 02 sensor reads it as lean and tells the computer to richen up the mix. Does this sound like something that can actually happen? It seems logical but I wanted to run it past you guys. later, j i have heard of it online as well.. don't actually know though. Link to comment Share on other sites More sharing options...
512tr Posted December 21, 2006 Share Posted December 21, 2006 That correct, it could happen. If outside air is leaking (through a crack or leaking gasket) into the exhaust manifold, the O2 sensor will sense the oxygen in the air coming in, and send a increasing volt signal to the computer. The computer will “think” the level of oxygen in the exhaust is too high (lean mixture) and will increase the injectors bandwidth in order to richen the fuel mixture. As a result the engine will run too rich. Link to comment Share on other sites More sharing options...
sinnaevd Posted December 22, 2006 Author Share Posted December 22, 2006 so my only solution is to weld the manifold, or get a stainless steel borla header? lol i was thinking i might have to change the o2 sensor, but i never checked the manifold. any usualy spot where it will crack? Link to comment Share on other sites More sharing options...
88MJay Posted December 22, 2006 Share Posted December 22, 2006 Typically you can hear it ticking. Especially when it's first started up and cold. As it heats up the metal around the crack expands and will cause it to become quieter. Typically that is. Link to comment Share on other sites More sharing options...
512tr Posted December 22, 2006 Share Posted December 22, 2006 so my only solution is to weld the manifold, or get a stainless steel borla header? lol i was thinking i might have to change the o2 sensor, but i never checked the manifold. any usualy spot where it will crack? This is where I welded my old YJ(HO) manifold, will asume the renix cracks are similar. The welds held for 3 years.. It's now replaced by a Borla Stainless header. Typically you can hear it ticking. Especially when it's first started up and cold. As it heats up the metal around the crack expands and will cause it to become quieter. Typically that is. Don’t mix the ticking with the normal lifter ticking, on my 87 4.0 the lifters are noisy 3-5 seconds after cold start-up, until the lifters have sufficient oilpressure. Link to comment Share on other sites More sharing options...
sinnaevd Posted December 22, 2006 Author Share Posted December 22, 2006 thats the thingi was wondering about, cause i can hear the ticking, but i know that the 4.0's were kinda noisy. i guess I'm going to have to climb underneath of the jeep and try and see. the part that suck is its not like an exhaust piece, i can just stick my hand against it and feel for air....well i could it just wouldnt be the best idea i wouldnt think lol Link to comment Share on other sites More sharing options...
sinnaevd Posted December 22, 2006 Author Share Posted December 22, 2006 tried to get underneath to see, but i can't see a darn thing n e way to actually tell other then to pull it everything apart? Link to comment Share on other sites More sharing options...
Oizarod115 Posted December 23, 2006 Share Posted December 23, 2006 thats the thingi was wondering about, cause i can hear the ticking, but i know that the 4.0's were kinda noisy. i guess I'm going to have to climb underneath of the jeep and try and see. the part that suck is its not like an exhaust piece, i can just stick my hand against it and feel for air....well i could it just wouldnt be the best idea i wouldnt think lol i've got a killer ticking, so if anyone knows how to check for it without pulling it like he said... that'd be vital info. Link to comment Share on other sites More sharing options...
512tr Posted December 23, 2006 Share Posted December 23, 2006 thats the thingi was wondering about, cause i can hear the ticking, but i know that the 4.0's were kinda noisy. i guess I'm going to have to climb underneath of the jeep and try and see. the part that suck is its not like an exhaust piece, i can just stick my hand against it and feel for air....well i could it just wouldnt be the best idea i wouldnt think lol i've got a killer ticking, so if anyone knows how to check for it without pulling it like he said... that'd be vital info. I think you should easily be able to hear the difference in ticking from the lifters vs ticking from a exhaust leak. A very common engine noise on the 4.0, is the valve-lifter ticking. On my MJ Renix this was only at start-up, when the engine is cold, did change oil yesterday and now the start-up noise is gone :-) On my YJ I did have some serious ticking, it was not constant but randomly came and went away, I did try internal motor wash, different oil types, but the ticking didn’t stop. So I pulled the head and replaced the lifters and the ticking was gone. Here’s the reason for the noise: In 2 of the 12 lifters, the piston inside was “stuck”, it didn’t go all the way to the top, leaving a 1 mm gap between the lifter and the pushrod. Link to comment Share on other sites More sharing options...
BLHTAZ Posted January 5, 2007 Share Posted January 5, 2007 Mine has a rough idle and has been running rich as well. I put a new o2 sensor in it today as it appeared that it had never been replaced before. It is not running rich any more, but the rough idle is still there. I had a bad tapping noise, but that was found to be a broken valve spring. I can still hear a small exhaust leak, but can't find it and I am betting that it is going to soon be time for a header :D . I just wish I could figure out the rough idle issue... Link to comment Share on other sites More sharing options...
sinnaevd Posted January 5, 2007 Author Share Posted January 5, 2007 vaccuum leak was my idle issue its still not 100% but it passed the etest thanksfully check ur pollution bottle thingy underneat the front passenger bottle...or the houses going into ur air box. both of those were gone on mine and once i found the problem it cleaned up nicely also the small hose off of ur vavle cover, it will be the longer of the two. if its plugged it might make it run a little funny Link to comment Share on other sites More sharing options...
87MJJeep Posted September 28, 2007 Share Posted September 28, 2007 My '87 4.0 has a ticking only under load. I can't hear any trace of the tick when it's idling or revved in Park/Neutral. It doesn't seem any different hot vs. cold. I have another car with what I know is clearly an exhaust leak. It seems to behave the same way. I was curious if there is anything else I should look at before assuming it's just an exhaust leak, and I was curious if anyone can confirm valvetrain slack would tick/clack regardless of load or no load. The noise was no different after an oil change, too. Link to comment Share on other sites More sharing options...
sinnaevd Posted September 28, 2007 Author Share Posted September 28, 2007 that to me sounds like a lifter may be going....I'm sure someone else will chime in soon though Link to comment Share on other sites More sharing options...
Pete M Posted September 28, 2007 Share Posted September 28, 2007 Could be pinging? Maybe the knock sensor is bad or disconnected? :dunno: --Pete Link to comment Share on other sites More sharing options...
sinnaevd Posted September 28, 2007 Author Share Posted September 28, 2007 wouldn't a ping more show suspect of detonation? which you can only pray you don't have or you could have a serious issue i would imagin.... Link to comment Share on other sites More sharing options...
87MJJeep Posted September 28, 2007 Share Posted September 28, 2007 that to me sounds like a lifter may be going....I'm sure someone else will chime in soon though Hmmm. I have a LS1 Trans Am that has every freaking odd noise known (lovely tolerances there GM), and the valvetrain noise is present all the time in it regardless of load. In the Jeep, it's just hard to tell if it is a metal tick or a farting tick. LOL It's definitely not pinging. I have had enough dealings with that in other cars! Link to comment Share on other sites More sharing options...
87manche Posted September 28, 2007 Share Posted September 28, 2007 I'd bet cracked manifold, or a loose manifold. I thought for sure my manifold was cracked, turned out to be all the bolts were out of spec. retorqued that whole mess and no more ticking noise. have fun getting a wrench on some of those... :mad: Link to comment Share on other sites More sharing options...
sinnaevd Posted September 28, 2007 Author Share Posted September 28, 2007 yeah hopw for the manifold. mine was ticking a bit as well when I had it, i think it was the manifold, but i never could figure it out. the 4.0 certainly has its corks. the great news is you can beat the hell out of it til it blows if ya like. they are not an expensive engine to replace. there was one here in ontario that finally blew up after the fellow ohad 700,000 km's on the origional engine. other then tune ups and censors here and there, it was all origional Link to comment Share on other sites More sharing options...
87manche Posted September 28, 2007 Share Posted September 28, 2007 yeah hopw for the manifold. mine was ticking a bit as well when I had it, i think it was the manifold, but i never could figure it out. the 4.0 certainly has its corks. the great news is you can beat the hell out of it til it blows if ya like. they are not an expensive engine to replace. there was one here in ontario that finally blew up after the fellow ohad 700,000 km's on the origional engine. other then tune ups and censors here and there, it was all origional 700 KM is like what, 4 miles? seriously though, it's a great motor, it's been known to go well over 200K miles. Mine's at about 270, still runs great, good oil pressure, the occasional lifter tick when it's cold. it sure seems to love rotella T motor oil though. picked up about 5 pounds of oil pressure at hot idle. Link to comment Share on other sites More sharing options...
87MJJeep Posted September 28, 2007 Share Posted September 28, 2007 Off the top of your head, do you know the torque specs for the manifold bolts? I know they are tough motors. When I got my '04 WJ, I had a hard time choosing between the 4.7L HO getup and go over having the last Grand Cherokee year with the straight six. My dealer used a '88 or so Eliminator as their parts truck for years. Finally the driver door fell off. The drivetrain was still fine. I can't recall if the door fell off at 240K miles or if maybe the transmission was rebuilt at that mileage. Link to comment Share on other sites More sharing options...
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