I bought my jeep 95' 4.0L recently and have been going through changing oil all around, cleaning it up, etc...
It's had an odd smell from the exhaust since I got it. Smells like fuel. When I drive it for any length of time I come out smelling like... I don't know... gas or oil... I'm assuming from the exhaust. My thought it's running rich so I come away smelling like gas. Well, spark plugs were on my list of things to do so I get to changing those out. I pulled the first one and the wire connectors are pretty corroded as well as the maile connector on the spark plug. I decide to put it back in and just get a new set of wires and change them all out at once.
Well, I buy a new set of wires, distributer, rotor, and I already had the plugs so I get to changing them last night. Internaly the plugs looked good... as far as I could tell, on cylinders 1-4 and 6. When I did the 5th plug, it had a heavy odor of fuel and the plug was soaked, threads and all. I put everything back together, start it up, and it runs great, even more power than before... just enough to notice anyways which I was kind of hoping for since the plugs and wires and corrosion on them.
I was thinking that the jeep was running rich, hence the fuel smell in the exhaust. In my mind, finding the plug with fuel on it kind of proved my theory that all the fuel wasn't being burned in the cylinders so it made its way out through the exhaust.
That's where my question lies... If a spark plug smells of fuel, does that mean the spark wasn't hot enough to burn all the fuel or does it mean there's another problem? It wouldn't suprise me if that were the case b/c of all the corrosion on the plugs and wires... but I'm not sure.
I drove it to work this morning but I had my son with me to take him to daycare so I had my back window down. I'll see if I smell "grose," as my wife calls it, when I get home after I put the back window back up to see if the spark plugs helped.
I also bought a new O2 sensor to replace in case that was going bad. I don't have a check engine light so technicaly it should be ok but there are 145,xxx miles on it so I figure it wouldn't hurt anything. My first step was the spark plugs. If that didn't work then my second guess would be the O2 sensor. If those two things didn't work then what's next to fix the rich issue? The mass airflow sensor??? does it even have one of those? I need to check on that. Then I thought about the cat, which isn't making any noise... but I guess that doesn't mean anything...
You may have had an internally damaged plug wire on #5 that had a weak spark, causing the wet plug. If you still smell fuel; check the rollover valve in the rear passenger corner of the tub, above the plastic panel; the rubber on those deteriorates over time, and allows the fuel vapors to escape.
Alright, thanks for the idea. I'll look into that. I'll have to check my Chiltons Manual to see if I can find it in there. Would I be getting that much fuel vapor in the cab if there is a leak in one of the many rubber tubes coming out of the tank?
I did notice some wet metal on the tank skid plate on the rear under the body at one of the dohickeys sticking out (breather?) Smelled like fuel... on my todo list to check out. Just wasn't a large amount... not enough to fill the cab anyways, in my opinion.
The check engine light on the OBD1 only indicates when it knows it has a problem. Ther are many instances when a sensor will fail, but be in the operational range so the controller doesnt think there is a fault. The Check engine light will only help you when it thinks there is a issue. There is no mass airflow sensor. If you are getting that rotten egg stink from the exhaust you are probably running rich. Replace the O2 sensor, check your fuel pressure. Also make sure that you exhaust manifold is not cracked or missing any bolts/studs. This is a common problem in making the O2 sensor thing the Jeep is running much leaner than it is and cause the Jeep to start to dump gas. If you are smelling raw fuel inside the cab it is probably one of the vent hoses on the fuel tank, the rollover valve under behind the right rear corner, or the evap canister.
1) Replace the O2 sensor - I've already bought one so I'll put it in whether I need to or not.
2) Visually check for cracks on the manifold. I guess the best way to do that is from the underside? I can't really see to much from the top... unless the cracks on the top. I'll get a buddy to hold a rag over the exhaust pipe to see if that exagerates any leaks from the manifold
3) Check my fuel pressure - not really sure how to do that but I'll look into it.
4) I'll try to check the vent hoses on the tank, the roll-over valve, and the evap canister (I have to look into those as well) Any way to check some of those without dropping the tank?... other than the roll-over valve?
O2 sensor first. That is a big one. Te engine temp sensor on the thermostat housing regulates fuel and has a high fail rate. It is different from the guage sensor in the rear on the block.
Fuel pressure is easy. You put a deposit on a guage at the local auto parts store and hook it up to the valve on the fuel rail. Start up the Jeep and read the pressure.
The rollover valve is easily accessable under the rear corner and the 2 vent lines go to the rollover valve. You can check those without dropping the tank by disconnecting them from the rollover valve and blowing into the vent lines (High resistance) and drawing in air (Should have flow).
I am thinking that O2 and temp sensor are the likely canidates for it running rich.
Keep us posted.
The exhaust you need to check above and below. Check the manifold really good. Look for missing or broken bolt especially in the rear near the firewall. Its kind of a pain but a very common issue. Also check at the collector tubes from underneath.
I replaced the O2 sensor during lunch without any issues. I took it around the block and didn't notice anything so the real smell test will be after i get home from my wife.
I tried to look as best I could around the manifold and the collectors but couldn't find anything. I had a buddy block the exhaust pipe and couldn't hear or smell any exhaust either. I'll rule that out for now. I had a dakota that had an exhaust leak at the Y Pipe and there was no mistaking that. The jeep I had prior had an exhaust leak at the block as well... that's where I learned the "block the exhaust" method. Wouldn't pass inspection...
There was oil saturating the bottom rear most bolt on the manifold... couldn't guess where it came from or how it got there. I'll figure that out later
I'll also look into the temp sensor like you mentioned. I'll see how much it is and might just replace it anyways if it's not difficult. Let me see how my ride home is first... one thing at a time
Yeah, if I didn't have to take my son to daycare every morning then my wife wouldn't care... as much... I had to tell her the car seat would fit in the back of a Jeep several times before I bought it... luckily I was right Gives him a nice panaramic view!
I've wanted another Jeep for many years since I traded in my old one many many years ago. Family wasn't thrilled about the idea... whatever... gives my son and I something to do when he gets old enough to poop in a toliet.
Well, I drove home yesterday and although I didn't reek of unburnt fuel I did seem to still smell like exhaust... I drive home with the windows down, sides on and back up... guess the airflow is pushing all the exhaust in the cab with the back up and the sides on... which, I'm assuming, exagerated the rich exhaust. Don't remember that happening with my last jeep though... maybe I just need to stop doing that.
I'm still planning on checking everything out though. I haven't ruled out the exhaust manifold... but I don't really want to change that b/c I'm under the understanding that the intake manifold needs to be removed to get to the exhaust manifold... don't look forward to doing that.
I couldn't find anything regarding the engine temprature sensor in the Chiltons Manual but I haven't looked for it yet on the engine. I'll look into that then look into the fuel pressure and all the lines and breathers. Just need to find the time...
The temp sensor is on the the side of the thermostat housing and is real easy to do. Its only a 15 minute job. You just need to remember to burp the system when you change it. The manifold is a pita and if you dont hear or see it then I would put it on the back burner until you've checked everything else. That rollover valve is a common issue with cracking and letting a gas smell into the pass compartment because of where it is at.