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Engine Flooding after New Injectors/Spark Plugs

1264 Views 7 Replies 5 Participants Last post by  Fourspeedman
I've had my 2000 XJ for five years now. I've recently invested a lot into it to try and make sure it keeps running great for another five plus years. I hadn't changed the spark plugs since I got it, so I knew I was overdue for that. I was also pretty sure the injectors were stock, and I suspected one or more of them might have a crack in them.

I'm no gearhead, not by a long shot, but spark plugs are easy enough, and looking up the procedure for replacing fuel injectors showed it was pretty easy as well.

I first replaced all the spark plugs, ensuring the gaps of each were .035 inches. They're OEM Champions. One of the plugs had the tip bent in shipping so it was touching the ground electrode, but I bent it back to a .035 gap. All the others' gaps were perfect from the factory.

I took the XJ on a ~10 minute trip around the neighborhood after this just to ensure everything was going well. Everything went smooth. I should have taken it on the highway to be sure, though-- you'll see why in a moment.

Next I replaced the stock injectors (single hole) with remanufactured ones (four hole). I've read people warning against eBay sellers and some saying not to worry if reviews are good. I took the not to worry route, found a seller with excellent reviews and a fair price (~$70, I stayed away from the ~$30 stuff).

By the way, it does turn out one of the old injectors had a crack in it, so now's a great time for replacing them.

At this point I reset the PCM, or at least I thought I did. I realized later that I did the process wrong-- so I didn't actually reset the PCM at this point.

Started the Jeep up-- she started up without a problem, which surprised me as I was expecting it to take a few turns before gas filled up the fuel rail so she could actually have some fuel to start with. Took her around the neighborhood again for ~10 minutes without any problems. Afterward took her out to the highway just outside the neighborhood, accelerating up to 65 miles per hour. In about a mile the check engine light came on and was flashing. Turned around, went back home. Noticed the CEL remained steady when going below ~30 mph but would flash again when up to 50 - 60 mph. I noticed that idle was rough and the exhaust smelled like gas.

Checked the codes and found a misfire in cylinders 4 and 6 and a random misfire code. Tried turning the ignition to start back up again, but she wouldn't start. I took the hose off of the air intake and immediately could see gas fumes rising from the intake hole on the manifold-- looked like a mirage on a hot day. Pulling one of the throttle cables and looking inside, I could see it was completely wet, and I could hear it sizzling in there. It reeked of gas.

After probably an hour or so I tried turning the ignition again to no avail, and the exhaust when doing so still smelled like gas. Eventually I took out all six spark plugs-- the sixth one, which was the first one I removed, was wet with gas, but all the others were dry. I've decided to leave the plugs out with the hood open and battery disconnected all night-- I'm hoping that will at least give the engine a chance for the gas to completely vaporize so I can start over tomorrow.

Here are some of my suspicions, but I don't really know and am hoping for someone smarter than me to lend me some pointers:

* Perhaps because I didn't reset the PCM properly it was still programmed for the old injectors and was pumping too much gas into the cylinders, which didn't really cause any noticeable issue until I was accelerating a lot more on the highway to get up to 65. I'm not sure if that's a thing, though-- could a PCM adjusted for the old injectors result in this serious of an issue? And isn't the PCM supposed to adjust over time even without being reset-- resetting just forces it to relearn instantly? Like I said, I'm no gearhead, so please do correct any misconceptions. Anyway, if this one is true, I should be able to confirm by tomorrow since I've reset the PCM and am leaving the battery disconnected overnight while the flooded engine dries out, effectively resetting it again, but I have a bad feeling this isn't it.

* I think this one is unfounded, but I'll mention it anyway: I forgot to snap the intake throttle cables back into place over the engine-- you know, the little snaps on top of the engine block that keep the cables from wobbling around all over the place. Perhaps if the cables aren't snapped firmly back in place, they'll wobble as they're pulled and not allow the air intake to open as wide, causing the air/fuel mixture to be off kilter in favor of fuel. But I don't think that is true now that I've thought about it more-- seems like the cables should pull the throttle properly regardless of whether they're loose off the engine or not.

* Then I thought maybe that sixth spark plug was the one I had to bend back into a .035 gap-- maybe it was bad and wasn't burning fuel appropriately, allowing for accumulation of fuel in the cylinder over time when accelerating? But wouldn't only cylinder 6 misfire if that were the case? Not 6 and 4, unless spark plug 4 was also bad?

* Lastly but perhaps most likely is maybe I've just got crappy injectors and some of them are dumping fuel out like crazy. Like I said, the company had really good reviews, but it IS eBay after all. I'm hoping to exhaust (no pun intended) other possibilities before resorting to redoing the injectors again, though, and I'd like to be a bit more certain that it's really the injectors before I go shake my fist at the seller.

Oh, one more related thing-- now that the spark plugs have been burning a fuel-heavy mixture for ~20 minutes of drive time and at least one got visibly flooded, do you think they must be cleaned, or do you think they'll be fine since it's been just a short time? I've never bothered cleaning plugs before, but I don't want that to affect my future attempts at resolving this problem.

Thanks much in advance.
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the pcm should not even need a reset but sometimes there is a startup issue that it will fix by being at zero and it can start fast learn mode in some but it will learn the new injectors by itself, but yes a reset could not hurt.

re gapping the spark plug that that is normal and fine and as long as it does fire and not factory defect its fine.

the throttle cables though - if you mean the part of the cable that hold the casing rigid to the block then yes that can and will cause it to not fully pull the cable like it should not allowing the air it needs in. and since the injectors will take the tps and rpm and load and a bunch of other crap into account along with the old map it knows it could cause it to do some weirdness, probably not the big issue but a factor.

ya ebay and amazon are the worst on everything but everyone still uses them for i have no idea why but i tried some 4 hole injectors and even buying name brand stuff still had one ticking intermittent and one was stuck open and never ticked so it was dumping fuel in, now since you say number 6 is easily the wet one if you dont have a stethoscope change 6 and say 2 and see if the wetness follows, if so bad injector, if it stays in 6 bad control of injector. number 4 might be slightly bad but hard to confirm if one is very bad

the plugs should be fine unless they are super sooty black or other buildup / damage and then funny enough soak it in gas for a bit and use a soft tooth brush to try and clean em

yours is running where mine did not but thats cause mine had one bank super rich and one bank super lean, its sounds quite similar to what mine did and although i got new injectors, to put mine in is a very tedious and many hour job so i left the stock single hole ones in. after i went back to those and spent about 30 mins in the driveway to heat the cats up and clean them it finally started working again so you may have to baby it for a bit if the cats got too much fuel in them just so it doesnt die by itself

side note for anyone else a flashing check engine light means imminent damage so usually dont drive it home then or for even 30 seconds BUT it seems yours went back to a normal steady light and then yes go for drive it home if you feel its okay, just a thing i have never found people to know the difference between flashing and steady light.
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2000 is helpful as it is OBDII and the system shows lots of info.
do you have a scanner - sounds loke you do not SO we will try some workarounds.
The key on off trick only showed WHAT codes ?

Is engine reaching temp @220deg?

Fuel pressure and pressure leak down, you will need a pressure gauge often a loaner or rental a auto part stores.
Attach gauge - turn key to on not start - observe pressure it will peak in @ 3seconds then observe pressure drop over what is it in 5min? Let us knpw answers.

Driving the vehicle will have the system re calibrate fuel trims, BUT sounds like a leaking injector. Leys do the above test before worrying about Fuel trims and o2sensor readings.
Try to keep the running and driving to strict minimum if the CEL is flashing. The excess fuel can quickly burn out your cat converter and/or the O2 sensors. Because the ECM was reset, it is running preprogrammed data instead of using the sensor data to adjust the air/fuel mix. If the new injectors are flowing more the the stock ones this could be why there is excess fuel. I would suspect one or more faulty injectors are the cause of the problems.

As suggested, switch the suspect injectors to another cylinder and see if the problem follows the injector. The plugs should be fine.

I think 4 hole injectors are mostly a fad, my 98 has +284,000 miles and the original stock injectors. Two injectors did show cracks on outside so I brought home some genuine Jeep injectors from the junkyard and installed those.

This procedure will erase the 1996+ OBD-II "Adaptive Memory" stored inside the PCM and allow a new "Adaptive Memory" to be developed. After performing this procedure the PCM will re-learn and store into Adaptive Memory your engines performance characteristics. Perform these steps exactly as they are written, in the order they are written. This will cause the adaptive memory in the PCM to be erased and cause the PCM to go into Fast Learn adaptive mode.

Disconnect the POSITIVE battery Terminal clamp and firmly touch it to ground ( not the battery negative terminal ) for 30 seconds. The engine block or the A/C compressor pump will work as a ground. (This is to discharge the PCM capacitors, which maintain the Adaptive Memory).

Reconnect the Battery Cable
Turn Ignition Switch to the "ON" position but DO NOT start the engine
Turn Headlight "ON"
Turn Headlights "OFF"
Turn Ignition Key "OFF"
The PCM Adaptive memory has now been flashed, or erased from the PCM. When you start the engine it will be running off pre-programmed data tables that come with the PCM from the factory. When the engine gets up to operating temperature the PCM will start to collect and store new data for the Adaptive Memory.
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Thanks everyone for your input. Very helpful and insightful.

Welp, it wasn't the "easy" option, i.e. a matter of the PCM not having been reset and the throttle cables not secured on the engine block. I didn't think it would be, but I had to hold out hope.

Before attempting startup I had left the battery disconnected all night and all day but touched the contacts together for 30+ seconds just for good measure, and then I did the PCM clear procedure correctly this time (turn key to aux, turn lights on, then lights off, then turn key off). I was able to start the Jeep back up. There was some grayish smoke out the tailpipe at first with an obviously rough idle, but it evened out and the smoke went away in a minute or so. I let it run idle for 30+ minutes. The idle did seem just slightly more rough than usual, but it wasn't obvious, so sometimes I thought maybe I was just being too sensitive and I just never noticed it before. Exhaust didn't smell like gas. Took her out into the neighborhood, and almost instantly I could sense the acceleration was crap. After just a minute or two I could feel the engine really losing power and running rough, so I took her back to the garage promptly. No CEL light this time, so no misfires I guess. Exhaust smelled like gas again, and I took the air intake hose off the intake manifold again and took a peek inside; this time it wasn't wet at all, but I could hear it sizzling like before, and it did smell a bit like gas, and I could see fumes coming out. Maybe that's actually pretty normal, heh-- I've never taken the hose off the intake just after driving before. The fumes were definitely less pronounced than before, though. I did try starting the Jeep up again just to see, and like before it wouldn't start.

I also noticed the gas gauge went from over 1/8 full to nearly empty over the course of this ~40 minutes of running, especially when I was actually driving around (never got above ~25 miles per hour). Now, with mine I've always noticed the gauge get a little finicky once it drops below 1/8 of a tank and seeming to drop more quickly than when above 1/8, but this was obviously more exaggerated.

I took out and inspected each spark plug. All were dry except I'm pretty sure this time plug 4 was a little wet-- it dried really fast, and there wasn't much there to start-- just a thin coating. It did smell a lot like gas whereas the others didn't seem to. I found an anomaly on plug 1 this time: the tip was totally bent inwards, touching the ground electrode, and the insulator was all black/brown (see attached photo, bad one is clearly far right). That seems... really bad. Perhaps too much gas that exploded all at once and messed up the spark plug? I know for a fact it measured at .035 and was still clean on the insulator before installing it again yesterday, so this clearly happened sometime in the 30+ minutes of idling and probably no more than 5 minutes of driving.

And yes, the Jeep got up to temp yesterday and today just fine-- not 220, though-- mine has always hovered around 210 at speed, sometimes a hair under, sometimes a hair over.

I have a simple OBDII computer that I use to check codes (that's how I determined the misfires in cylinders 4 and 6), but it's not very advanced-- pretty much just trouble codes, clearing codes, and emissions readiness.

Anyway, it seems clear that it's got to be the injectors. The Jeep was running fine before and never flooded once-- a little hotter at idle than I wanted, and acceleration didn't seem quite as strong as it used to (these were the main two things that led me to try and replace the injectors), but it still ran really well with the old injectors, one of which was cracked. Maybe I'll go to a pick n' pull and just get some good-looking stock injectors from there, maybe replace just the one cracked one and keep the other originals.

Next thing I'm reaching out to the seller and see what I can do to return these or get some support at least. I'll share the seller's name and how it turns out when I finish the transaction, one way or another. Then posterity can learn from my experience.


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The plugs are probably fine but I second suspecting the injectors. Old mechanic hint: when a new part fails put the old part back and test. Put all the old injectors back in. Test. Start replacing with the new ones one at a time until you can reproduce the condition and rule out which ones are bad. FWIW I have replaced seven injectors on three Jeeps. Each time it showed as a cylinder misfire code. I always buy name brand new ones and they have always worked fine. No need to do anything to the computer each time. It is self-learning.
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Looks like I forgot to provide a conclusion here:

After swapping back to the old injectors, the XJ runs great. In fact, a couple weeks later I hauled a 4x6 trailer 600 miles, picked up 600 - 700 pounds of heavy metal comms equipment, and brought it 600 miles back home. Total altitude change about 38K feet up and down (according to Google Maps) across the Utah and Nevada mountains. She handled much better than I thought, and it seems simply replacing the extremely worn spark plugs and the air filter before taking the extended trip got my gas mileage back up to where it used to be (~16-17 mpg) and resolved the acceleration issue I had (slight but noticeable loss of power when accelerating at or over ~3000 rpm between 40 - 50 mph).

I will probably still try to replace the injectors at some point since one of them is cracked, but as things are running fine for now and I just don't have much time to tinker for a while, it's not happening right away.

The eBay seller refunded in full without question. Too bad they can't refund the few hours I wasted swapping these in and out. Seller's name is dimarmotorsportsllc. Like I said, they had good reviews, but this one just didn't work out.
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Thanks for posting the results. FWIW I would stick with new stock injectors. They are cheap enough to not justify re-builts.
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