Assorted Engine Troubles: A Thesis and a Cry for Help (2 Viewers)

[Marvelicious]

I'd bet it's been cracked for awhile. Sure, your poking around might have made it worse, but any leak is no bueno.

Right? If it opened up like that, it's probably been leaking for a while.

 

[Aloha80]

For folks’ future reference, pictured above is 17881-66060.

Existing one is jankily covered in duct tape while the new one is in the mail. This latest idle problem seems solved by patching up the hose.

Will update thread when I get a vacuum tester to start working through EGR testing. I’m an “unbolt broken stuff, bolt on new stuff” type of mango tree mechanic, so applying more serious methodological rigor to the EGR system will be a new venture for me.

Huge thanks to everyone who has replied so far. I’ve had my nose in the FSM trying to understand how these systems work before I start ordering parts and tearing into things (which is how I end up with torn hoses, for example).

 

[ozarkmud]

I think the under throttle bogging issue could easily be a fuel pump / clogged fuel filter sock. Rebuilding the engine would obviously not help there.

Fuel filter could also be suspect. If you can verify the fuel pressure while you have the issue, it would help diagnosing it.

 

[Aloha80]

x2 on the idea that the air intake hose had been leaking for a while. What’s infuriating is that I checked it before. It must have been cracked in between the ribbed sections where a quick look and feel didn’t show anything out of the ordinary. The engine overall feels more responsive and snappier under throttle.

The bad news is that the “lurching” problem is still around. Only happened a few times on my morning commute thus far, but it’s not gone away. So there are still lots of variables to check:
-Double check ECU for decay
-Ensure transmission kickdown cable… cables properly?
-Functions checks on EGR gizmos
-General checks of wiring looms (the one next to the EGR looks fine, but hey, I said that about my intake hose too)

Fuel filter is relatively new—do these go out fairly quickly?

How about transmission solenoids, are these a known high-mileage problem area?

No new codes yet, but if past experience is any indicator, it’ll throw me something relatively soon.

 

[Aloha80]

Well, MIL/CEL 12 and 71 are back.

Only other update from this week is that the truck performs terribly in the mornings, but normally in the evenings. The only thing I can think of that would affect it is that the ambient air temperature is lower in the morning than the evening.

That, and the EGR component circled sounds awful (loud buzzing) until it turns off when the truck warms up a bit.

 

[ZackR]

That circled part is the PAIR system.

 

[ajax1]

You can remove the pair system and move your o2 sensors up into the manifold. I left the old ones in their original spot as plugs and bought new.

 

[BILT4ME]

Well, MIL/CEL 12 and 71 are back.

Only other update from this week is that the truck performs terribly in the mornings, but normally in the evenings. The only thing I can think of that would affect it is that the ambient air temperature is lower in the morning than the evening.

That, and the EGR component circled sounds awful (loud buzzing) until it turns off when the truck warms up a bit.View attachment 3483488

Do a diagnostic on your coolant temp sensors.

It sounds like it's running bad when in open loop. After it warms up it's in closed loop and the ECU allows the computer to use the O2 sensor data to control fuel.

It may be getting a bad signal until it's in closed loop.

But, yes you can delete the PAIR if you're in a state that does not do smog testing.

 

[Malleus]

You never metioned whether or not you verified the operation of the IAC. Poor cold idling with fair/good warm idling is the sympton of a sticking IAC.

 

[Malleus]

Before you throw the PAIR system away, you might want to know what it is and what it does:

These pages are from the 1994 FSM, but the 1993 version is the same. I used these because I had it open at the time.

 

[Malleus]

I think the under throttle bogging issue could easily be a fuel pump / clogged fuel filter sock. Rebuilding the engine would obviously not help there.

Fuel filter could also be suspect. If you can verify the fuel pressure while you have the issue, it would help diagnosing it.

IME, the fuel pump filter is more likely to be clogged to the point that it will affect performance than the downstream filter. At least in the US. I've pulled downstream filters off trucks that were running well, and the filters were full of fuel varnish. I think those things are so large, it'd take Africa fuel to kill them. The tiny little in tank fuel sock is another story entirely. And, as an added bonus, you can actually get to it, without enlisting a 12 year old's hands.

 

[Aloha80]

Do a diagnostic on your coolant temp sensors.

It sounds like it's running bad when in open loop. After it warms up it's in closed loop and the ECU allows the computer to use the O2 sensor data to control fuel.

It may be getting a bad signal until it's in closed loop.

But, yes you can delete the PAIR if you're in a state that does not do smog testing.

I did check the coolant temp sensor voltage at the ECU when I was suspecting something was up with transmission lockout, and it was showing the correct voltage per FSM.

Are you referring to different sensor(s) or a different method of checking them? I’m all ears—hypothesis makes sense.

 

[Aloha80]

You never metioned whether or not you verified the operation of the IAC. Poor cold idling with fair/good warm idling is the sympton of a sticking IAC.

Thanks @Malleus, the idle issues went away after replacing the cracked air intake hose. Unfortunately, the RPM-drop-under-throttle problem persists. It appears to be more frequent when the engine and ambient temp are cold. Regardless, IAC functions check is still on my list of things to do, if only to begin narrowing down variables.

This thread sounds very similar to my issue, although the temperature correlation is inverse: OBD1 / 1FZ-FE Troubleshooting Help! - https://risingsun4x4club.org/xf/threads/obd1-1fz-fe-troubleshooting-help.29130/

That seemed like it was a VAF issue at the end of the day, but the post isn’t totally clear.

Separately, I started more thoroughly checking hoses and the hose from the intake to the PAIR system was cracked. Unfortunately, temporarily sealing it with duct tape while I order yet more stuff didn’t change the problem.

 

[Bigtoepfer]

You can remove the pair system and move your o2 sensors up into the manifold. I left the old ones in their original spot as plugs and bought new.

I was under the impression that the O2 Sensors are NLA for the 93/94. I have my PAIRs and EGR deleted. My O2 are in the original spot and I've got block off plates everywhere else. But I'm getting the lean code after long trips, like 3+ hours. And the same bad idle described here.

Might try cleaning the IAC valve and see if that nets me any improvement. Fixing this would make me feel so much better about all the work I've put in to it. Having it stumble at idle after practically a top end rebuild and new head gasket has my wife madder than hell for something I sold a perfectly running GX470 to buy.

I have faith though.

 

[Aloha80]

Update: I’ve been limping the truck along, giving it ample time to warm up in the mornings. This has reduced the frequency of issues, but the past couple of days have been pretty rough.

Because I had some free time this weekend, I went ahead and read over the FSM and came up with an attack plan.

Ordered the following:
-90079-60004: Fuel Injection Idle Air Control Valve Seal
-22271-66010: Fuel Injection Throttle Body Mounting Gasket
-25627-66010: EGR Valve Gasket

These are to remove and clean the IAC, the throttle body, and the EGR valve.

To replace my cracked air intake to PAIR valve hose (discontinued), I ordered the Tacoma radiator hose 16572-07040.

I also ordered the following because why not:
-17801-66030: Air filter
-12204-35040: PCV valve
-90480-18001: PCV valve grommet

I’m still confused about the RPM signal code, because the conditions specified to trigger that code are “no NE, G1, or G2 signal to the ECM within 2 seconds after cranking the engine.” Those signals, if I read the wiring diagram correctly, go straight from the distributor to the ECM. As the distributor has all new parts, all I can think of is a wiring issue I’m not visually seeing or a faulty ECM (please no). I’m unsure if the RPM signal code could be somehow erroneous and related to the much more believable EGR issue. Besides checking wiring or opening and inspecting the distributor, I’m not sure what else to do here.

Thanks guys and I’ll update as I work through each system.

 

[Malleus]

It's easy to check those signal paths for continuity. The FSM has the location of the ECM terminals for each. The engine harness is the conduit for the signals so you can go straight from the distributor to the ECM.

Even if you have an ECM problem, it's likely as not bad cap(s). That can be fixed easily enough.

 

[WrongsideDaily]

I was under the impression that the O2 Sensors are NLA for the 93/94. I have my PAIRs and EGR deleted. My O2 are in the original spot and I've got block off plates everywhere else. But I'm getting the lean code after long trips, like 3+ hours. And the same bad idle described here.

Might try cleaning the IAC valve and see if that nets me any improvement. Fixing this would make me feel so much better about all the work I've put in to it. Having it stumble at idle after practically a top end rebuild and new head gasket has my wife madder than hell for something I sold a perfectly running GX470 to buy.

I have faith though.

She should be mad since she and myself both said getting into an 80 was a mistake, and then you proceeded on buying the absolute WORST truck that was on the market for 3x what anyone would pay after I wasted two of my personal weekends to try to help you by pointing out good and bad on tangible vehicles, again, while wasting my personal time. I wish I had done her a favor and closed my door and left you to argue in the parking lot while the truck continued to boil over because you are the type that pops the hood on a truck, misses no less than four heater hose clamps dangling, loose, then proceeds on coughing up cash ignoring the front cover drip, and not even noticing it was a factory locked truck until it was overheating a couple hours away when you had no choice but to stare at it while it cooled. Where you still didn't notice all the loose coolant clamps I fixed in the first minute of opening the hood.

You don't need faith, you need more money than you make. You need to listen to understand and stop listening to respond when you don't. Helping you was the biggest mistake I've made in fourteen years, and I've made a lot of mistakes. You're an extremely selfish person. I've known you longer than I've known your wife, I hope she figures it out sooner than I did.

 

[BILT4ME]

She should be mad since she and myself both said getting into an 80 was a mistake, and then you proceeded on buying the absolute WORST truck that was on the market for 3x what anyone would pay after I wasted two of my personal weekends to try to help you by pointing out good and bad on tangible vehicles, again, while wasting my personal time. I wish I had done her a favor and closed my door and left you to argue in the parking lot while the truck continued to boil over because you are the type that pops the hood on a truck, misses no less than four heater hose clamps dangling, loose, then proceeds on coughing up cash ignoring the front cover drip, and not even noticing it was a factory locked truck until it was overheating a couple hours away when you had no choice but to stare at it while it cooled. Where you still didn't notice all the loose coolant clamps I fixed in the first minute of opening the hood.

You don't need faith, you need more money than you make. You need to listen to understand and stop listening to respond when you don't. Helping you was the biggest mistake I've made in fourteen years, and I've made a lot of mistakes. You're an extremely selfish person. I've known you longer than I've known your wife, I hope she figures it out sooner than I did.

This kind of crap needs to be done in a PM, not mucking up someone else's thread.

If you're not helping, get out.

 

[Aloha80]

Okay. Various parts came in, started with the lowest hanging fruit to avoid me tearing into things unnecessarily.

To reiterate, my problems at this point are:
-Hard start (feels like delayed ignition)
-Rough/stumbling idle
-Occasional, jolting RPM drops at speed
-MIL/CEL codes for RPM signal and EGR malfunction
-Lower ambient temp seems correlated with more instances of symptoms. Warming up the truck seems to make it operate more toward normal

Replaced the following and while it gave me warm, fuzzy feelings, it didn’t change anything:
-PCV valve and grommet
-Air filter
-Hose from air box to PAIR valve (prior hose was cracked)

Moved on to checking timing (engine normal operating temp, in N, lights and A/C off):
-In non-diagnostic operation (E1 and TE1 *not* jumped), timing mark moves in a range between 2° and 13° — normal per FSM. I’ll note that the timing mark was usually more toward 13°.
-In diagnostic mode (E1 and TE1 jumped), timing mark erratically hovers around the 3° mark with 1°-2° variance — not normal per FSM.

In the spirit of addressing lowest hanging fruit first, I moved on to testing pickup coil resistance. The terminal and wiring looks newish and clean. Forgive me for not jotting down the numbers, but the results are:
-G1 and G: normal
-G2 and G: no signal
-NE and G: normal

Not sure if this is in any way conclusive other than validating the MIL/CEL code for RPM signal. Does it sound like this is as simple as replacing the distributor housing, or could there be an upstream/downstream problem I’m not anticipating?

More testing and evaluation updates to come.

Thanks for everyone’s patience as I slowly become more acquainted with Land Cruiser science (as opposed to just banana-handing everything).

 

[DrDuc]

My truck was having some of the same issues that yours is experiencing. It was the VAF.