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Matt, if you disconnect the battery for more than 60 seconds, the ECM should clear any trouble codes set.

Get the min idle speed (with IAC disabled) as close to 750rpm as you can. My 3.4 was really fussy until I got the idle speed and TPS voltage set to a Gnat's Ar$e. As close to .5V as you can.

It's possible the MAP sensor could be damaged from backfiring, so you should probably check that out.

Here's some good info on that:


Also make sure the timing was adjusted with the ESC wire in the console unplugged from itself. The black wires with white stripe and a white connector. See attached pic. Note that the ALDL wires (white with blue stripe) are normally disconnected unless you're running a diagnostic or doing the IAC/TPS procedure to drive the IAC pintle all the way in. The other way to put the ECM in diagnostic mode is to jumper together the 2 pins in the corner of the ALDL plug.

How's the injector fuel spray look? With a 14psi spring, you should have more than enough fuel to make a stock 3.1 happy. Definitely check all the vacuum lines, a leak somewhere will mess things up royally.

Any more issues with the engine oil? That sounded scary.

Hand Motor vehicle Automotive tire Hood Gesture
 

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1989 Isuzu Trooper
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Discussion Starter · #22 · (Edited)
Thank you as always Ed. I will dial in the idle and TPS voltage as best as I can with the new TPS sensor (it might help if I had another person to help me unlike last time 馃槀) and I'm going to test the MAP sensor too. My vacuum pump just broke so ill have to grab another one at harbor freight. I did set the timing with that white ESC plug undone and I have identified the ALDL plug as well.

One thing I keep reading is that the timing and idle adjustments should be done with the engine warmed up and in closed loop. How am I supposed to know the engine is in closed loop besides seeing the coolant temp gauge hold steady in the middle of the readout?

Video of the engine reving up from idle and then stalling out when I try to accelerate:

Also, the injector spray seems pretty conical and even; I can see it pulsing and it does sputter a little after quickly opening the throttle. Although, it does looks like there might be excess fuel spraying from the injectors and it does occasionally spit fire out of the throttle body after opening the throttle abruptly. So maybe there is too much fuel? I've already checked the fuel pressure going into the throttle body and it measured an even 13psi (figured it should be 14psi..).

Video of the Injector spray and backfire:

Yeah I was planning on changing the engine oil and hoping it didn't turn creamy again, hopefully it is just a little bit of excess moisture and metal shavings in the engine from when we initially tore the engine down.

Thanks in advance.

Matt

Added a ton more photos to the thread!
 

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Yeah, that's pretty strange how the Check Engine light comes on instantly when you give it some throttle. I'd say about the only things that could make it do that are TPS and MAP sensors. Nothing else on the 2.8 TBI system would respond that fast.

If you can't get it in Closed Loop to adjust timing, at least if it's warmed-up you can still get it done. But you do need to disconnect that ESC wire in the console, or you don't know what the setting is. Most times it's impossible to read the timing scale if Electronic Spark Control is disabled.

I think you'll find an issue with one of the sensors. Otherwise maybe the ECM's screwy. I'd definitely pull the trouble codes out and see what's happening.
 

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1989 Isuzu Trooper
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Discussion Starter · #24 ·
Figured it out...

The trooper lives again...

The ECM ground wire that goes to the engine block was loose.

There is not the same ground location on the 3.1L engine block as there is on the 2.8L (See picture). We used an oil pan stud to ground to and the nut must've came loose after the first 16 mile drive, giving us a weak/intermittent ground to the ECM. I tightened up the nut and it drives around great! I will definitely need to find a much more suitable ground location moving forward.

Now that the ECM is grounded correctly, we drove it around town a bit and the engine eventually threw codes 13 and 33 (O2 Sensor and MAP Sensor, voltage high). I was already planning on converting to the heated O2 Sensor, but I was reading Geoffinbc's heated sensor how-to document and wondered what the best 12v switched positive lead (hot in run) would be on the trooper? Could I use something out out of the fuse block?

The Heated O2 Sensor How-To:
https://9839f16c-3fad-4d37-89f6-38d...d/a62d6a_c81bf44980dc43159cdb64da7f582da0.pdf

Thanks in advance.

Matt
 

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Yeah, that's a big ol' mess of ECM and engine control ground wires in one lug, that will cause a lot of pain if it's not connected or loose. Ask me how I know! When I did the engine swap I had pushed those wires into the fender well, out of the way. Took a while to figure out where to put them.

The 2.8 had a bolt hole in the pssgr's side of the block where you could fasten the ground wires. I used the crank sensor bolt on the 3.4 to do the same thing. If you can find a solid grounding point right on the block, it would be a better & more reliable connection than on the oil pan.

As I recall on the heated O2 sensor, there was a suggestion to tie into the power windows circuit at the fuse block. If your rig doesn't have power windows, then you could hook right into the empty PW relay socket. It's a high-amp, switched source of power. The heated sensor doesn't draw a lot, at any rate. I have mine all installed and the "hot" wire run up to the engine compt, haven't figured out what to hook it too yet. My LS has power windows. Will just have to find a convenient source of switched +12VDC and splice it in.

If the engine is running well, and the MAP sensor tests out, I'd ignore it. I get an occasional "check engine" light with EGR code on my 3.4. Probably 'cause the 2.8 computer is expecting a certain amount of exhaust flow/change of exhaust mixture when it opens the EGR valve when driving down the road to test how it's working. When the light goes on, if I turn the ign off then on again the light goes away. Just an irritation, it's not affecting how it runs.

Anyway, glad you finally got to the root of the problem. Now you can concentrate on other things!
 

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1989 Isuzu Trooper
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Discussion Starter · #26 ·
Yeah it was quite the discovery! I was dumbfounded when I figured out that was source of the problem. Anyways, I found a solid location for the ground wire, ended up using small bolt on the underside of the passenger side motor mount. Cleaned up/removed the paint off of the mount surface, bolt, ground washer at the end of the wire, and used battery terminal grease. Should be much better now.

I'll see if I can wire the positive 12V power lead for the O2 sensor into the power windows circuit (the trooper does have power windows).

Changed the oil and it looked absolutely terrible. It was a light milky brown/grey colored. I saw a lot of fine metal shavings in the oil and I'm pretty sure it was in there because of the metal work we (stupidly) did with the intake manifold off. At least, that's what I'm hoping its from. IIRC the oil that was in the 3.1L when we got it was not milky nor had any metal shavings in it, just dark oil. Fingers crossed it doesn't look like that again. Could coolant be leaking into the oil around the intake manifold gasket? I'm not too confident that was put on as well as it could've been. Is it common to have a leaky intake manifold?

I need to get the trooper registered and plated, and in my county I need to pass emissions, but the trooper didn't have a muffler when we bought it. About a 3ft section of exhaust is rusted out between the catalytic converter and the tail pipe; its almost as if the muffler rusted right off at some point 馃槀. I feel like this is a good time to upgrade to the larger free flowing exhaust if its not too much $$$. Given my current setup (3.1L, bored Intake and larger TBI), should I get a 2" or 2.25" diameter exhaust?
Do I need to replace everything up to the headers including the y-pipe or can I just replace the catalytic converter and do a cat-back exhaust?
I'm going to take it to a muffler shop, but I need to know what tp tell them to replace.
Recommendations on a budget free flowing cat and muffler?

Thanks in advance

Matt
 

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Hi, Matt, yes, intake manifold sealing is critical. Use Permatex Ultra Grey RTV for sealing purposes.


You might want to put a very thin bead around every water port. And a bead of course at the front and rear, this manifold uses no gaskets there. Make sure you torque it down to specs, if you can't get at a bolt with your torque wrench, use your own good judgement to get it as tight as the others that you can torque.

Note that some bolts extend right into the cooling system, and you need to put a bit of RTV on the bolt threads to help seal them.

Here are some very good installation tips from Fel-Pro:


On the exhaust, you don't really need to replace the downpipes coming out of the exhaust manifolds; they are 2" which is plenty large for this engine.

You can, however, get rid of a big restriction in the system by having the muffler shop cut-out the exhaust wye.

I used a Walker dual-inlet cat on my 3.4 LS, but they're getting terribly expensive. This cat with dual 2" inlets is only around $55 shipped on eBay:


This cat has a bung for the O2 sensor built-in. So the sensor will run hotter and this will make the engine run even better.

On the pssgr's side, the downpipe comes down and has a 90-degree flange where it connects with one side of the wye. When we cut out the wye, we left a stub at that flange and welded a 90-degree elbow to the stub. The elbow was routed right to the cat, and was the 1st side welded. This helped locate the cat, and all that was needed to run the driver's side downpipe into the cat were some slight bends.

Any competent shop should be able to do this, easily. And a lot better than we did, laying in the driveway! If you get a mandrel-bent 2" 90-elbow, you'll have better flow. Or a shop that can do mandrel bends.

The rest of the exhaust is easy. Use a reducer on the 2.5" outlet side of the cat, down to 2.25", to the muffler and tailpipe. 2.25" a good size for mild performance build, and won't kill your low-end torque.

I used a Dynomax muffler, but there are any number of cheap 2.25" mufflers available on eBay and elsewhere. If they have a decent price on a generic turbo muffler, use that.

Here's a 2.25" P/N 17747 Dynomax Super Turbo "long body" muffler on eBay:


These mufflers have a good tone, nice growl at lower speeds and idle, but don't drone on the hiway. That open-box one I linked is $56.06 shipped, a decent deal.

On mine, we hung the muffler temporarily so I could drive the rig to the local muffler shop. They bent up a new, larger tailpipe and properly hung the system. It made a huge difference on mine, over the terribly restrictive stock setup.

Anyway, there's a few thoughts. Hope you get your oil contamination issue under check..........ed
 

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1989 Isuzu Trooper
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Discussion Starter · #28 ·
Wow Ed, I can鈥檛 thank you enough. Your vast knowledge and research on these troopers and engine swaps continues to surprise me. Thank you.

That sounds like a super solid plan for the exhaust and I like it a lot. Thanks for explaining that out. That cat you linked seems to reconfigure the new exhaust system quite nicely, especially for the price. The 3.1L seems to have more power (than the worn out 2.8L) and revs up pretty fast for what it is, but I'm hoping the improved exhaust can give the trooper a little more grunt and torque.

On to the oil contamination, I am a little more convinced that coolant got into the oil via the intake manifold gaskets. I've decided I'm going to remove the manifold and replace the gaskets with new ones, RTV around the water passages, and reinstall the manifold with the right torque specs and sequence just to be sure.

I am also going to check the valve lash too while I鈥檓 in there. Is there any benefit or reason I wouldn鈥檛 want to replace the pushrods and lifters while I鈥檓 in there also?
I found a great price on new pushrods and hydraulic lifters from EngineTech on Rockauto ($8 and $21 respectively).

Any preference between intake manifold gaskets? I'm thinking on the Fel-Pro MS91022 (only $5 on Rockauto), but I've read that the Victor Reinz 111061501 is preferred from another thread that I read.

Thanks in advance.

Matt
 
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