So... the truck is hosed again/still.

I heard "it" happen... Driving back from lunch one day, and "poof!" (as in an _audible_ "poof"), all of a sudden no WOT power and boggy acceleration. I've tried a number of things since. Here're the latest symptoms:

• Will generally idle, but kinda' rough
• NO power above 2500-2800rpm. You can hear the intake note change when the butterfly opens, but the engine just sputters
• Holding RPMs at 2500 or so produces a slew of misfire codes. The general P0300, plus P0301, P0302 and P0304. They're coming fast enough that the MIL is blinking to say "HEY! THIS IS SERIOUS!".
• Was running PIG rich (unburned fuel in the tailpipe). Swapped out the 370 injectors for the stock 240's and it's no longer pig rich, but that's a hack.
• _Right at_ 2800rpm OBD II shows Load = 97%, MAF = 10lb. Clearly bogus numbers, but explains why it's rich - the ECU is trying to feed fuel to match the "air flow".
• To be clear, the truck runs "pretty dern great" up to about 2700rpm. I can feather it right at 2800 and it'll fall apart.
• Everything is _fine_ when flooring it in the driveway while in neutral.

Knowns and "have dones":

• Replaced the exhaust from the headers to the tail. (thanks Randy!) New cat, new muffler, this isn't a clogged problem.
• There's a crack in the driver's side header, but it's been there long BEFORE this started happening.
• TPS sensor is fine, monitoring through ODB II shows 10-75% deflection
• I replaced my Supra MAF with the stock MAF. No change. (actually, Supra is "better")
• I pulled the 370cc injectors and went back to the stock 240's. No change.
• Compression test is fine. 120-150psi.
• Plugs are fine. Gapped to .032", they look good (though wet from being pig rich).
• No vacuum or boost leaks. Engine passes the "intake cleaner spray-down" test.
• I've disabled the SMT piggyback. No change.
• Replaced fuel filter. No change.
• Replaced ECU. No change.
• Replaced O2. No change.
• Physical timing (with a light) is spot on

I'm open to ideas...



update 10.09: Not the ECU, maybe FPR? Will have a new one this weekend.

 

Sorry to see her down again...

"audible poof" - Interesting.

"power loss" - as you mentioned... probably due to running too rich causing the truck to sputter.

I know you mentioned there are no boost leaks, but are you getting boost? Have you checked the supercharger bypass valve? Sometimes it can get stuck in the open position depriving your engine of boost.

Could be the O2 sensors as you said, but wouldn't that throw a specific code?

Good luck Mark!

 

Yeup, I'm generating boost, so the bypass isn't blowing and that piping is fine.

O2 will generate codes in basically catastrophic conditions. They can easily fail and/or spit garbage and the ECU thinks things are just ducky.


sigh... I can only hope that it's something STOOPID and we can all laugh. I'm "fairly convinced" that it's not internal.

 

PER ALLDATA

P0300= random cylinder misfire detected durring the particular 200 or 1000 revolutions.
P0301,P0302,P0303= for any particular 200 revolutions for the engine, misfiring is detected which can cause catalyst overheating (this causes MIL to blink)
P0304= for any 1000 revolutions for the engine, misfiring is detected which causes a deterioration in emission (2 trip detection logic)

the trouble areas for these codes

ignition system
injector
fuel line pressure
compression pressure
valve clearence not to spec.
valve timing
mass air flow meter
engine coolant temp sensor

hopefully this is helpfull. if you need any of the diagrams for the inspection process of these systems let me know i can email them.

i had a similar problem a few months ago when a vaccum line came off under boost. the poof and rough idle and loss of power were as you described. it also threw a P0300 & P0301. mine was straight forward to fix, the line on the check valve had come off.

 

Interesting... You're getting 10+ lbs of boost with that 2.0 pulley and you managed to run WAY rich. You removed the SMT, so I'm assuming in closed loop, you lose power after 1500 rpms as well - which is basically from the get go.

Something going on with the fuel pump perhaps? It is apparently not responding to what the stock or SMT ecu has to say.

 

How is fuel pressure controlled? Do you have an APR? Have you checked fuel pressure?

 

Oh nooooo, sorry to hear that Mark. Just looking down your list; how can you say the compression is good @ 120-150 psi? My FSM shows a minumum pressure to be 145 psi for the 5VZ

 

id double check on the ignition system.

 

Although mine wasn't s/c, my tensioner went bad and it skipped time. It ran like a 3cyl and you could hear the engine through the intake.

 

Sorry to here ya got problems. When I narrower my gap to .032, I heard a womp sound when I went sudden WOT like the flame was blow out so I increased my gap back wider. I have IK22 plugs.

It does not sound like it could be something that simple and I would think you would have experienced the problem as soon as you narrowed the gap but I think it is something you can try and won't cost you anything but time to try.

I'm curious what the problem is. Keep us informed.

koda4

 

The two things that I'd check are ignition timing and physical timing. My money is on a slipped timing belt. A lineup to TDC and visual should answer that easy enough. A shot with a timing light will answer the crank position sensor/spark time possibility. I assume that since you changed the MAF that you verified that you are getting air volume data to the OBD.

Watching with empathy.....

 

I'd definitely check this first. Then I'd go to the ignition system as mentioned by other folks.

I have a used (working) spare 02 sensor. Let me know if you need it. I'll send it right up.

 

Hey all... sorry for being slow to respond. Work is being killer and actually, _this_ process with my truck is draining the life outta me. anyway...

Thank you all for the ideas... I wanted to hear from humans about what they may think. I love Alldata (and the FSM) as much as any of you, but there's something different about hearing live words. (netwt12, don't get me wrong, I DO appreciate you posting that up, it's excellent data)

Random thoughts...

Fuel pressure; could be, but I know that when I cranked it over without the fuel rails tightened down there was fuel everywhere. I don't have a FP gauge, so it may be a choice between blindly swapping out the Walbro or installing a gauge. The Walbro's only 3 years old, so... Finelygotone: Control wise, it's via the SMT piggyback, which is pulled out of the picture now, so...


Compression; Hey Dale! The two 120 cylinders aren't optimum, but they're not bad enough to cause THIS much of an issue. Daryl's blessed off that it "should be okay". I'll deal with why they're only at 120psi after figuring out what's up.


Boost/Vacuum lines; I've had the top of the engine apart three times in the last week (pulling injectors, checking torque on the intake manifold, etc) and I'm fairly sure it's all back together. Remember, it passes the "intake cleaner test".


Ignition; I think this might be my next stop, but I might be jaded by seeing all the misfires and internalizing that it means "ignition!" when it could be so much more. One thing I forgot to share is that I had the ICM (ignition control module) go out on me a month ago. This is the small rectangular box (3x3x1/2) that sits on the passenger fender. What a thing to go! (btw, guess how much Schuck's wanted for a new one? THANK YOU DARYL!) But, when it freaked out, it ended up shorting out and pushing _constant current_ to the #2 coil pack. The pack was so hot that the plastic was _soft_. The pack continued to work after replacing the ICM, though obviously, it's life span is shortened. Maybe that's it.


Spark gap; Interesting! It's certainly easy enough to change and see what happens! Thanks Koda!


Timing; interesting idea. I'll have to dig up a timing light, I really hate pulling the front cover. The problem with this though is that I don't know if the symptoms really match. The "poof" and all... I dunno. I guess, maybe. (yeah, I know... I'm just trying to talk myself out of doing it!)


o2; I didn't get a chance to swap it last night and I won't be able to until the weekend now. Christian, thank you, but I have a couple laying around that I can toss in there.


MAF; yeup... I have airflow and air temp registering through OBD, but then I did with the Supra as well. sigh.



Again, thank you all. "more when I know more"

 

120psi is pretty low. what were the compression numbers?

this is the first thing id correct, the compression, b4 anything else. is 120psi w/ the SC or not? if so, its definitely too low.

 

I'd put my money on that being your problem. As long as your okay with the compression being so low. My .02

 

I'm betting on the timing belt too. Good luck!

 

check the O2 sensor after the cat. You are still running a cat, right?

 

low compression can be caused by cyl wash due to rich mixtures.

Any updates mark?

 

Hey Johnny; Not really... I swapped out the front O2 and gave the fuel filter a shake. The idle is now much smoother, but get to 20mph and put some load on the engine and it just bogs.

I hear you all rallying behind a timing issue, but if I jumped a tooth then it doesn't make sense (to me anyway) on how I could be running up to 1800/2000rpm 20mph at all, or being able to EASILY rev to ANY RPM when it's in neutral. hmmm...


@coil pack: This is something that I just got an opportunity to borrow off of a donor engine. So that's now easier to give a shot versus paying Shucks $157 for a 30 minute rental.


@Stormin: yeup, the cat's there (I found out it's blown again btw, that happened on the way home from the exhaust guy where it was brand new). The rear sensor in this engine doesn't have anything to do with fuel mixture or timing. It's there to support the ECU tossing lights for Cat failures. It's only sniffing the O2 content for comparison with the front sensor.


I think the mic on my digital camera is good enough to hear the symptoms. There's a lot on my plate right now and I'm still PO'd and not really wanting to work on this but I'll get a video up when I can. Saturday's my next open date with time to work on it.


Oh, and my new headers showed up... Interesting Catch-22 though. To get them to mate to the new exhaust work, they'll have to be put on first. He'll need to weld up the extension and the ball&socket joint on the new headers. So, technically I'd pull the old ones, put on the new ones, then try to survive the 20 mile drive to the exhaust guy (mostly freeway miles) with open headers.

Now, I could pull the old ones off, then run both sets up to him (off of the truck) and cross my fingers that the headers haven't changed design in 4 years (they're both Downey's, but who knows).

But then, to do any of THAT, the engine has to run... sigh.



Thanks all.

 

One step forward...

So, timing lights are cool 'cause not only can they confirm that your timing is okay (+9-11* at idle) but they can also show you that you have a dead coil pack.

The one that got roasty when the ICM went out was shot - $115 at Schucks (let's hear it for 25% coupons!) got me a new one.

Idle's now perfect, it'll run at 50mph as long as there's no load, but kick it a bit, or put some load on the engine (like an 11% grade hill by my house) and you have to beg it to keep running. There's a definite fuel smell as well, so I know it's still running WAY rich. A/FR's are around 12.5:1 at cruising RPMs around 40mph. EGT is about 1000*

I'm liking the sound of my new Flowmaster Super 44... Today was the first time I really got to hear it.


I just wish I knew why it was running so dern rich. I wonder if the lack of power under load is actually that it's flooding?