MonsterMaxx

It's bogging, no power (like can't hit 50mph), very high EGT (heads past 1500 all the wile it can't get out of it's own way.)

This is very new and sudden although I've been fighting high EGT's for a while (have to back off when it hits 1400?.) Though it's had good power it gets crappy MPG (14 hwy, worse in the city.)

Things changed suddenly when I downshifted, went for 3rd, hit 1st. Chattered the whole truck and redlined the engine.

Drive it now and it acts like it's getting no gas (if this were a carb engine.)

I've been letting it sit and riding the bike, but I need it next weekend so I worked on it today (was sure it was TPS and an easy fix.)

I don?t know what it?s problem is, but I know what it?s not.
? It's not the TPS, changed.
? It's not the AFM, checked with a known good one I have.
? It's not the computer, again checked with a known good.
? It's not fuel pressure related. Snap on remote gauge is still on there 38-42 psi.
? It's not O2, changed.
? I know the left cam has not jumped it's timing (distributor is driven from it and is still timed the same.)
? It's not timing related. While normally this engine likes a bit more timing than normal, I've tried it at various settings and it?s of no help.
? It's not plugs or wires, cap or rotor.
? It's not compression (within spec across the board.)

I'm pretty much stumped.

Suggestions?

ChickenLover

How old is the cat converter?

MonsterMaxx

It's not the cat, recently replaced (or should I say 'added' as it's predecessor had been gutted.)

rdharper

If these symptoms happened with your downshift... maybe timing is correct at idle, but not under load? Damage to the keyway so that you have slop under load? (just a thought)

I assume it idles well.

And no symptoms suggesting transmission problems.

hmmm...

MonsterMaxx

The symptoms were coming since I did the rebuild. High EGT's coupled with loss of power and poor MPG. The downshift (violent shaking) just caused it to fail completely - or so goes my theory.

I'm thinking maybe it's somehow in the distributor, but I have no easy way to scope it and find out.

Also when I had the Jacobs ign was hooked up it does the herky jerky (I'd run it for a while and it was fine, then one day it wacked itself out so I bypassed it.) I guess I need to plug it back in and see if it still does this. However, the high EGTs were there w/ Jacobs too.

How could a distrib cause high EGT? Maybe sending bad info the computer on RPM causing it to lean the engine too much?

rdharper

Although it sounds like you'd be well aware of this possibility... but any chance the distributor is off a tooth?

And sure, I think the high EGT (how high?) could be caused by wrong A/F mixture as well as timing.

MonsterMaxx

I can't see how it can be the distrib off a tooth and still be timed. I can set it to ten (stock) or 25 (what it liked on the dyno - this motor has a lot of 'work'.)
This also tells me that the cam didn't jump a tooth when I overreved it.

I just did a compression test. 155 at 5 beats, 165-170 max across the board.

Plugs are LEAN! Which is what I expected. Something is starving it for fuel. I'm mystified as to what it could be.
Seems like it could be what modern engines use for a crank position trigger - in the distributor. But short of buying another distributor I don't know what to test (I don't have a scope which would let me see the pulses.)

It idles fine. Smooth as can be and no 'funny' sounds.



I have a 6 channel EGT, when I say getting high previously this is highway running, under a load to coming off the load (like cresting a hill) EGT would climb, passing 1400, at 1425 I'd back off.

This recent failure (post downshift) I was just going up to UPS (a couple miles) it couldn't climb this tiny hill and EGT was heading for 1600, I backed off.

Jay351

Can I just ask why you shifted from 3rd to 1st?

MonsterMaxx

I was downshifting, slammed it and missed.

Numbchux

sounds like textbook clogged exhaust.....maybe a chunk from the old cat is stuck in the muffler, and got shifted around so it's clogging it now...

disconnect your exhaust after the header and see if it helps at all.

Jay351

That must have sounded ungodly!

mudbutt

Un bolt the exhaust at the front of the cat and drive it around. Change= problem found.

Inspect fuel pressure at the rail behind the pulsation dampener. Low pressure, check in front of/at the pulsation dampener. Isolate the pulsation dampener or the fuel pump. (I've seen a couple of pulsation dampeners tear causing a internal restriction just before the fuel rail.) Where is your gauge now?

Check the injector ground at the cam cap on the right bank, make sure it is tight.

That is the most "web" diagnosis I can do with out the vehicle here with me.

Also note, Toyota plugs like to run pink to brown stock (slightly lean)

dcg9381

I think you're on the right track.
Excessively reduced timing can result in big EGT spikes. This was one of my mistakes on my first turbo, I thought I'd run too little timing to be conservative within pinging, but I didn't recognize that the result would be big EGTs that essentially coked my dino oil inside the turbo.

If your base timing is OK, you can still check to see if your timing goes up when you rev the motor.. I don't know exactly how the stock timing map works, it could be very RPM based - IE it might be easy to confirm. If it's load/rpm based, then it's going to be hard to figure out.

Anyway you chould have slipped a tooth on cam timing.. This would impact your EGTs also.

MonsterMaxx

Measuring fuel pressure on the rail w/ Snap On's Remote Master Gauge (an ebay find
I'm seeing exactly what the injectors would see.

I know plugs are normally lean looking, but these are excessively lean looking.

If I'd slipped a tooth on cam timing wouldn't that have thrown the timing off too? Also wouldn't it have a big impact on compression?
Both of which being 'normal' would seem to indicate that neither of these are the problem and that it's not a 'mechanical' issue.

Timing does what it's always done when I rev the motor. Nothing seems out of the ordinary.


Sort of reminds me of a Chevy truck which did a similar thing many years ago. Chevy finally traced it down to a cracked ring on the distributor which was feeding the computer bad data. Did a lot of damage before it was finally diagnosed.

dcg9381

Lean could be an issue also, but I've found that mixtue doesn't impact EGTs as much as timing does.


Yes, It would throw your base timing off. It might not impact compression at all, depending on how far off it was.



Which is what exactly? If it's a timing issue, a decrease in 10 degrees of peak timing might drive your EGTs that high. Thing is, it's hard to imagine something that would cause a decrease in peak timing that wouldn't impact your base timing...

That would do it.. Although the distributor pulse isn't the only thing that determines timing on that motor. It's ashame that we don't actually have a timing map for it or know what factors play into determining timing. I could just be RPM and AFM setting.. don't know for sure. Have access to another 3.0L truck? Rev it up to 3k and measure what the timing is. Figure out if it differs significantly from your motor...

^VooDoo^

Maxx, Please put your vehical info in your sig, It helps alot.

1. How old is the timingbelt/tentioner ?, It really sounds like a jump on the bottom. (And will still time normal)
2. Fuel pressure is good under load?, Not just idle or neutral rev.
3. Look for airleak in your intake tubes, a good jerk like that could have torn one and its opening up as you load the engine.

MonsterMaxx

dcg, I'm with you on this, guessing something in the distrib is fubar. Now the question is: how do I test it. The test in the FSM does nothing. I think I need a scope so I can watch the signal and I don't have such a critter.

VooDoo, it would make my sig a mile long. This truck's had nearly everything possible done to the engine and that's just scratching the surface.

It's a '94 highly polished 3.turd. The motor has everything imaginable except a computer replacement. It's got suspension, diffs, bumpers, interior, stereo, lights, wheels and all the other upgraded goodies. A whole pile of $ has been dumped into this pig.

dcg9381

Maxx, I'm with you on this. I have an EE degree and I barely remembered how to use a scope. I had to borrow one and then still had to call and ask for help just to remember how to use the darn thing.

If you need a scope, might ask any of your friends that work at places that do electronics repair... Maybe a friend of a friend.

Again, I'm most familiar with the 22RE - but the 3.0L is the same basic setup. I'd be very suprised if it's the distributor. If you check your cam timing and base timing, the distributor is basically a system that triggers the spark 6 times per engine revolution. The distributor is fixed - no advance built into it. It's a simple system that triggers a sensor. Disconnect it, hook it up to a volt meter and spin it. Expect to see signal (continuity) 6 times per revolution. If you pull the rotor, you'll see where the inductive pickups are.

What you want to scope is the output from the ECU to the ignitor.. Even then, I don't think you'll learn much as we're not privy to the way the ECU decides to do timing. That's why I suggest you compare to a non-modified V6. Rev them both up to 3k at no load and compare timing number.
What helps here is that you have a timing light with a dial where you can easily figure out what the timing is at... If you had a vac leak or other problem with the AFM flapper, it might make you run lean and with conservative timing.

MonsterMaxx

I consider myself pretty smart on this stuff and am stumped, took it to a local shop who thinks he's pretty smart.

He's been at it two days and has checked a variety of things including cam timing and replaced the distributor.

NO DIFFERENCE. Pound the throttle, you can hear it open up, but all you get it boggggggggg.
Get it up in the 3krpm range (where it's always been a screamer) and it's nothing but bogggggg. And immediatly EGT heads for the ceiling, quickly passing 1400, 1500, and heading higher when I back off.

WTF else could it be?

He's thinking check EGR, but as I understand it, the EGR on these 3.slows has very little impact.


It kind of feels like a massive vacuum leak to me, but shows none of the other signs.

mudbutt

So did you ever unbolt the exhaust? Ive melted new cats as fast as old ones. If your rich, they bitch