Totally stumped

[og]

OK for the diagnosticians on the board, here's a real stumper.

1998 Explorer XLT. 5.0 liter v8. Increasing driveability issues between 11/29 and 12/3 288,000 miles.

Took to dealer for diagnosis. Dealer claimed it was a clogged cats, claimed it improved when the O2 sensors were removed. Dealer wanted $3500 for new cats.

Took to local muffler shop I trust, who replaced the system, headpipes back. (for $1500)

No improvement in driveability. In fact, somewhat worse. Turning substantially worse by the time it got home. (two miles)

Pulled into the driveway and parked to discover the passenger side exhaust manifold glowing red.

Have had a small crack in the original EGR pipe. Thought that might be the source of the trouble, so I replaced. While I was at it, I removed the intake upper(you almost have to) and replaced gaskets, in case there were any vacuum leaks due to old or perished gaskets.

No improvement.

In October- for the very first time- I let it run out of gas. I thought, maybe I sucked up some gunk from the tank, and clogged the injectors.

I pulled the fuel rail and injectors, built a test stand, and flow tested the injectors. Used Techron and alcohol to clean, the fuel patternis nice and the injectors all seem to be clean. Reassembled (again!) and no change.

Used an old, properly gapped spark plug, clamped to the block, and confirmed i have spark. No idea of the spark is occurring at the proper time.

Injectors tick, so I assume they're injecting. Noid light test shows flash at all eight injectors

THe fuel pump did bleed down somewhat, so I replaced the pump. still will not start. Pressure stays up, apply vacuum to the regulator, and pressure drops.

Changed the Camshaft position sensor. No change.

THe ECU threw no codes. Still throws no codes.

TPS, MAF sensors all seem to be fine.

Any clues, folks? I'm utterly stumped. I LOVE my exploder, and want to keep driving her another 100,000 miles at least.

I have changed out damned near everything but the ECU, and that's probably next- but dang.

New plugs
New wires
New coil packs
New Camshaft position sensor
New EGR riser tube
New fuel pump
New fuel filter
New exhaust system

HELP!!!!!!!!!!!

 

[Mbrooks420]

With one side of the motor running hot I would suspect an incorrect air/fuel ratio. Did all of the plugs you removed look the same?

 

[Josh]

I wonder if that motor has an ignition control module? It almost sounds like your timing is off. If your truck has a standard cap and rotor, I would rotate the motor until the #1 cylinder is TDC on the compression stroke and see where the rotor is pointing. I'm pretty sure if your timing is way out, the motor will heat up. You sure nobody stuffed a potato in your tailpipe?

 

[og]

Plugs good, (less than 20,000 miles) and all had a light grey ash. (very small amount) Platinum plugs.

This is a 98, so no distributor- coil packs. I'm thinking that the fuel/spark arriving at the appropriate time is indeed a possible concern. Which would be, as you say, ECM. I will probably try to get one ouf of a yard, or from Auto Xone, and try this afternoon.

 

[Mbrooks420]

No distributor.

 

[Josh]

I still wonder if there is a way to check timing without taking the front of the motor off? It is still possible for the timing chain to jump however remote. My truck had an ICM problem that caused a no start condition, but did not cause a hot condition. Get one from the junkyrd if possible. Mine was a lot cheaper.

 

[MountaineerGreen]

I'd think jumped timing would cause a missfire code :scratch: You said they replaced everything from the headers back? Including catalytic converters?

 

[Provokr]

You sure nobody stuffed a potato in your tailpipe?

Clogged cats or something up your tailpipe sounds like my diagnosis, but you just replaced the cats... so did you check your tail pipe(s)?

 

[Mbrooks420]

For 1,500 the entire thing had better been replaced.

 

[og]

Whole system from manifolds back was replaced.

Additionally, I have done compression tests (early in the game, actually) and I have between 90 and 140 psi.

The variation (i'm sure) is because I have a crappy compression tester. The plugs in which I could get it tight, I got 140 psi. The holes where I couldn't tighten it up were about 90/95 psi, so I think the compression range is probably narrower than 90-140. In any event, I have compression, fuel, and spark. It just doesn't seem as if they're arriving at the party at the same time.

 

[og]

Oh: and in February I had to change the water pump. A bolt broke in the block necessitating removal of the timing chain cover to remove. The inside of the engine looks basically new- it has had a steady diet of synthetics since day one, and the result is the valve train and timing chain look as though they've just been installed- NO wear, No shiny spots, NO carbon buildup. The timing chain has slack wihtin spec, and the valve lash is in spec on all 16. (yes, I change the valve cover gaskets while I was at it)

 

[MountaineerGreen]

If one manifold was red like you described, I suspect a bad catalytic converter. Did they install 4 or 2 converters?

Do you have access to a scan tool to monitor engine sensors?

 

[og]

If one manifold was red like you described, I suspect a bad catalytic converter. Did they install 4 or 2 converters?

Do you have access to a scan tool to monitor engine sensors?

I have an Innova scantool+ computer interface and software. It won't monitor sensors on a non running engine, so far as I know.

Even when I had it running, it never ever once threw a code.


The entire exhaust system has been replaced. All cats. From the manifolds to the tailpipe. And even with new exhaust it made the pass side manifoild glow red.

The drivers side may have been glowing too, but it was too hard to see. (bright sunlight on that side of the truck)

 

[MountaineerGreen]

Maybe the converters aren't big enough for the 5.0? Not enough flow? The only time I have ever heard of glowing manifolds was a bad cat.

You should try this at night and see what it looks like.

When its running does it rev OK?

 

[og]

Maybe the converters aren't big enough for the 5.0? Not enough flow? The only time I have ever heard of glowing manifolds was a bad cat.

You should try this at night and see what it looks like.

When its running does it rev OK?

it does not run. It will not start. The cats are brand new, OEM spec cats.

 

[MountaineerGreen]

Well, how about unbolting the downpipes and seeing if it starts? If you have fuel, spark, no CEL, then it must be air. I had a 1990 Ranger with a catalytic converter that was clogged, it eventually got to the point it would barely run. We removed the converter, ran like a champ after that. Obviously, we only removed the converter for testing purposes, I replaced it later

It sounds like you went through everything throughly, probably more than most would have. Short of a small jump in timing, (not likely especially how you described the internals when you had the cover off) I can't think of what it could be. You can unbolt the flanges for no cost, see if it fires up.

We need jtsmith in on this.

 

[Turdle]

Did you replace the cranksaft sensor?

 

[og]

I have not replaced the crank sensor. I have had the front of the engine off, and i remeember what it was like just to get to the dang thing, so I'm not anxious to try to do so.

 

[DuncanOfEngland]

I think that the clue is the variation in compression readings and the glowing manifold. My money would be on recessed exhaust valve seats, caused by a clogged exhaust.

Duncan

 

[og]

No correlation between compression variation and the glowing exhaust.

I will be ordering a new ECM today. Hope that's it.