Drove good when I parked it Friday....now it misfires!

[84FLH]

2000 Mounty. 413,000 miles. Orig 4.0 SOHC motor.

Parked at home last Friday (4/11) after work. Didn't drive until this afternoon (Sun 4/13). Vehicle now misfires under any sort of load.

Sprayed carb cleaner on hoses with motor running...no change. Put Heet water evaporation in tank, added 3 gallons gas, drove about 5 miles up to 60 mph to mix. Still misfired. Seemed to misfire less strongly at 55-60 mph.

Air filter is 2 months old. Wires, plugs, coil, replaced 3 years (36k miles) ago with Motorcraft parts. Coolant level good and no smell of coolant at exhaust. No bananas up tailpipe (Eddie Murphy).

8 months ago I got a Check Fuel Cap light. Replaced fuel cap with aftermarket cap but light stayed on. In January this year a local shop replaced the purge valve. They used a Motorcraft part (don't have the invoice at hand right now). The new purge valve made Fuel Cap light go off. But even when fuel cap light was on those 8 months, vehicle always drove good, even up to 80 mph (fastest I dare go)....except mileage went from 19.5 to 16.5.

Check Fuel Cap light came back last month. Same shop who installed purge valve pulled P0457 code two weeks ago. Said smoke test necessary. Even with light back on, vehicle still drove good up to 80 mph (fastest I dare go). Two hours ago O'Reilly's also pulled P0457 code but no misfire codes.

Could P0457 evap code be causing misfire?

What evap component(s) most likely causing misfire?

Thanks, everyone

PS: This shop is mostly a parts replacer operation. I never asked if they tested the original purge valve bad. And for all I know, the fuel cap light went away because they cleared the code. Then again, the light stayed off for four months, so maybe the original purge valve was bad?

 

[Josh P]

413,000 sounds like a record on a sohc. Has any of the timing components ever been touched?

 

[84FLH]

413,000 sounds like a record on a sohc. Has any of the timing components ever been touched?

Not during my 185,000 miles of ownership.

 

[410Fortune]

The plastic evap Lines and connections like to break at the canister purge valve under the battery tray

The canister vent valve is located at the charcoal canister above your spare tire.. I’ve seen that whole assembly rot away

You may have a gross evap Leak

The fuel filler neck can also have issues and should be closely inspected

You can watch your engine run in the dark see if any ignition wires are leaking around the spark plugs (blue arching)

Fix code first see if misfires persist

 

[amj441]

yes, this code is for the inability to pull a vacuum on the tank. it makes sense why your shop would try a purge valve as it controls whether or not engine vacuum is applied. but this code also means a large leak. This could mean any of the lones or hoses could be damaged or unplugged. like 410 said the charcoal canister is under the battery tray, as well as fragile lines ( i had to try 3 cars in the junkyard to replace mine). theres also a few vent hoses on top of the fuel tank. a smoke machine may help you narrow it down.

 

[410Fortune]

Charcoal canister is above spare tire

The canister purge valve is below battery tray and the canister vent valve is back at the charcoal canister

There are a bunch of plastics lines between the tank those two valves the canister and the intake it all needs a visual inspection

 

[84FLH]

Thank you, 410. After work today I will look where you said.

 

[84FLH]

Thanks, amj441. Will look at those items after work today.

 

[84FLH]

401Fortune, amj441;

Purge valve under batt tray still looks brand new (black, shiny plastic ... it was installed this January). Plastic elbows at purge valve in good condition (one yellow, other tan, IIRC). Rubber hoses from elbows to hard lines/manifold(?) under alternator are firm but not cracked and still have factory tags encircling each hose.

Tailgate latch broke inside. Must be those darn plastic clips that grap the threaded rod ends! Can't drop spare tire without opening tailgate for access to handle hole.

Charcoal cannister above spare tire looked good. Not cracked. Not even really dirty, considering 413,000 miles. Rubber hoses from top of cannister were mostly flexible. The solid metal lines that rubber hoses connect to were heavily rusted (scale). Couldn't bend either one by hand, though, reaching as far as possible lying on my back under vehicle.

Couldn't see/feel where these metal lines went to. So from the junction of rubber/metal cannister lines, to the purge valve up front, is unexplored territory.

Next I made rubber gaskets for my factory original gas cap from two pair of nitrile gloves. Lubed gaskets so they'd not bind up. Removed my locking gas cap and installed the rubber glove gas cap. Very tight fit. Started vehicle. Raced engine in park to 3000 rpm. Slight skip around 2900 but that's been there since I got vehicle with 245,000 on it. Thought I'd cured the misfire. Then I drove the *$*#! thing. Misfire still there.

Dropped off vehicle at shop that replaced purge valve in January.

Been watching this BAT auction this week. 2018 Wrangler Rubicon Unlimited with suspension mods. Once bids went over $25k I realized I was kidding myself! Just as well. It's dumb for a working man to spend $25k on a vehicle he can't test drive.

2018 Jeep Wrangler Unlimited Rubicon

Bid for the chance to own a 2018 Jeep Wrangler Unlimited Rubicon at auction with Bring a Trailer, the home of the best vintage and classic cars online. Lot #187,551.

bringatrailer.com

 

[donalds]

You can watch your engine run in the dark see if any ignition wires are leaking around the spark plugs (blue arching)

I've used this trick
If you mist the engine with a spray bottle with water it helps a lot

 

[Josh P]

How bad is this misfire? A little noise on a cylinder or like a timing chain jumped a tooth?

 

[C420sailor]

What’s live data telling you?

 

[84FLH]

Update. Monday. 4/21.

Local shop couldn't find (translation: didn't want to spend time troubleshooting) cause of misfiring under load. They said they could hear the front driver's side timing chain slapping, and maybe she'd jumped time. I had that cassette changed 130,000 miles ago. I have no chain rattle at startup. I think the noise is a valve lash adjuster (I hear it also).

This noise comes and goes, but I never hear chain rattle at startup. If I hear this lash adjuster (guessing) noise when I'm stopped in traffic, I turn ignition off, then restart. About half the time, maybe more, the lash adjuster (still guessing here) is gone. Truck also idles very steady at about 600 rpm, even if I hear the noise. So I don't think (ok, I hope) it's not a timing chain.

I recently read that a faulty EGR valve could cause misfiring. My EGR valve is, I believe, original to the vehicle, with 413,000 miles on it (or is it 416,000, I can't remember right now). I looked closer at the valve this past Saturday.

The tube threads at the EGR valve are hopelessly rusted and enlarged by the rust. They need Naval Jelly rust remover (works like paint remover) and wire dremel. Because I couldn't begin to loosen the nut (even after using PB blaster 3 days in a row) I tapped the EGR valve a dozen times with my aluminum flashlight, hoping to unstick it.

Then I started her up and reved it by foot to 3,000 R's in idle. No breaking up at 2700 as before. Got in. "Check Fuel Cap" light was off! Yay! Then I drove 10 miles 45-55 mph with no misfiring. Next day, Easter Sunday, I drove 45 miles without misfiring. Mileage was 19.5, which is what I've gotten for ages on highway. For last 6 months, though, I've got 16.5. I've read a malfunctioning EGR valve can cause loss of fuel economy.

This morning I drove 22 miles to work without misfiring. On way home this afternoon misfires started 2 miles from work. Pulled over, removed vacuum hose from top of EGR valve and (angrily) sprayed carb cleaner straight into nipple while holding throttle open by hand to about 1500-2000. Revs reduced slightly when spraying.

Next I sprayed car cleaner liberally around the two 10mm bolts that bolt the valve to intake manifold. Held throttle open by hand to about 1500-2000 rpm. Revs dropped a little but noticeably when I was spraying.

Then I used a tire iron to tap medium firmly, 360 degrees around the EGR valve perimeter. Three times. I admit I think each time was harder than last go around. I resisted, though, the urge to use large rock I noticed at the treeline. Got back in and drove off.

All misfiring symptoms gone.

Had phone message from dealer when I got home (called them this morning for quote to replace EGR valve and pipe from exhaust manifold). Almost fell off my chair when the message said "$979.31, if the input pipe doesn't break off at the manifold. Then you'll need a new manifold. That's about $1,000."

I was way too tired to call and tell them where to put the pipe and valve.

Going to work on those rusted threads this weekend. And keep my tire iron next to me in the vehicle.

PS: No lights on dash, and no codes pulled (shop cleared the only code there was, which was P0457, "Evap" system trouble). Rock Auto has correct Motorcraft EGR valve for $67. Aftermarket exhaust manifold tube for $60. With 413,000 (or 416) miles I don't really care if the tube's not Motorcraft. Could probably find the short tube into intake manifold on Epay.

Any Jeep guys here? Which of these JK Rubicon years is best, and why: 2014, 2015, 2016, 2017, 2018? The Monty is on borrowed time.

 

[Josh P]

Any Jeep guys here? Which of these JK Rubicon years is best, and why: 2014, 2015, 2016, 2017, 2018?

I'd say 2021 when you could get it with a 392