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Discussion Starter · #61 ·
Welp, the Trooper just barely failed smog due to high NOx at 25mph. So now I'm going through the EGR system to make sure that is all working as it should.

EGR is opening about 2mm when I open the throttle. Pushing the EGR open causes the idle to stumble and if I open it all the way the engine dies. I'm only seeing a maximum of about 2 inHg of vacuum when I tee off the vacuum line between the EGR and BPT. I verified that about 20 inHG of signal vacuum is reaching the BPT when the engine is warm and the blue TVV and throttle are open. The vacuum amount changes depending how open the throttle valve is, as it should.

A couple things I haven't been able to find after a lot of searching here is exactly how much should the EGR be opening and/or how much vacuum should it be receiving and when. I've taken off the EGR pipe just to double check it. It has no obstructions. When I was checking the EGR port on the exhaust manifold I saw an obstruction which I'm not sure is carbon build-up or a duct of some kind. Anyone know off the top of their head if this is normal? See pic:



I also sprayed in some seafoam before I took everything apart and all the smoke it created indicated an exhaust leak where the manifold meets the down pipe. Not sure if that's enough to cause a fail. I also checked the catalytic converter with my IR temp gun. incoming pipe was 390F, outgoing was 480F which should indicate a healthy cat. I think the cat only has about 17k miles on it.

Also I inflated the tires to 35 PSI. They are super old and I was worried about blowing them out until I can get new ones.
 

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That looks like carbon buildup to me. Have you tried to attack it with a small screwdriver or other suitable scraping tool? I bet it crumbles away.

Since you're borderline-fail, anything that blocks the normal amount of recirculated exhaust gasses might throw the emissions test off.

Let us know what you find........ed
 

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Discussion Starter · #64 ·
I'm still having trouble passing smog due to high NOx at 25 mph. I think I've found the issue to be that my timing is too advanced due to the harmonic balancer having slipped.

With the timing marks aligned, the HB mark should read 0*BTDC, is that correct? Here's how mine looks:





It looks to be reading 6*BTDC when the mark is aligned, so whatever I set the timing to it's actually 6 degrees advanced from that.

Edit: Wait, I think I have that backwards. It would actually be retarded by 6 degrees. If I set timing to 12*BTDC based on the mark, the engine is actually firing at 6*BDTC. Well there goes that theory!
 

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takemehome4LOroads said:
I'm still having trouble passing smog due to high NOx at 25 mph. I think I've found the issue to be that my timing is too advanced due to the harmonic balancer having slipped.

With the timing marks aligned, the HB mark should read 0*BTDC, is that correct? Here's how mine looks:

It looks to be reading 6*BTDC when the mark is aligned, so whatever I set the timing to it's actually 6 degrees advanced from that.

Edit: Wait, I think I have that backwards. It would actually be retarded by 6 degrees. If I set timing to 12*BTDC based on the mark, the engine is actually firing at 6*BDTC. Well there goes that theory!
Yes, timing would be retarded. But you really don't know what the exact value is, because lining up the cam timing mark is a quite inaccurate way to positively determine TDC. I'm assuming that the belt is properly aligned with the crankshaft internal timing mark on the engine block cover (under the lower timing cover).

Your best solution for that dilemma is to replace the harmonic balancer, since it obviously has slipped.

I'm wondering how old is the catalytic converter? Because most postings in which they were unable to pass emissions testing, the problem was solved with a new cat.

I found a site with comprehensive instructions on how to test for a failed cat. I'm gonna bookmark this one because it's one of the best I've seen:

https://axleaddict.com/auto-repair/How- ... -Converter

I found a P/N at Rockauto for a replacement harmonic dampener, Dayco PB1400N. This was the only one they had in stock, around $121 plus shipping. These are a-plenty on eBay, Amazon, etc etc for around $140+.

There's also listed a Dorman 594-805 and Summit Racing has 'em for $102.99 with a shipping delay:

https://www.summitracing.com/parts/rnb- ... eid=srese2

The Dorman website has a lot of good info including OEM part numbers:

https://www.dormanproducts.com/p-106329-594-806.aspx

There's one on eBay, too: https://www.ebay.com/itm/New-Harmonic-B ... 4542697650

Jerry Lemond is a good resource, I'm sure he can get these too. From what I've heard, he's feeling a bit better, and that's a good thing!

HTH.........ed
 

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Discussion Starter · #66 ·
Thanks Ed,

Man, I had a whole post with all the details about this but I accidentally deleted it.

I did put a new cat on. It looks like it improved my numbers, and cut down NOx @ 15 mph in half, but not quite enough @ 25 mph.

Here are the results for the tests I've done. On the right I've added notes of adjustments I've made, and the results of plugging the numbers into Smog Lamba Calculator. And I've put in what I think the actual timing was set to in parentheses.



I was fiddling with the EGR valve today and I can't see it opening too much. I'm trying both the original EGR valve, and a new EGR valve. When I tee a gauge between the EGR valve and BPT I get like 1 in/hg of vacuum, with either valve. If I clamp off the hose between the EGR valve and BPT, the vacuum rises to 15-20 in/hg. I think I don't see much vacuum because the BPT is regulating that vacuum. The BPT needs exhaust back-pressure to "turn on" and send vacuum to the EGR valve. If the EGR opens, it lets exhaust gas in, and reduces back-pressure on the BPT which, in turn, reduces vacuum.

The new EGR valve came with a bunch of orifices to mimic the OEM configuration, but I didn't use any and threw them out. So I wonder if the EGR needs that orifice to help keep the back-pressure consistent.

New harmonic balancer is on the way!
 

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Man, that is just ridiculous that you have to smog a 31-yr-old vehicle! And failing by 33 Parts Per Million!!! Unreal!

It looks like the NOx output is really sensitive to engine timing, maybe once you get the damper on there and get the timing "tweaked" in it'll do better. BTW when you're replacing the damper, it wouldn't be a bad idea to pull the lower timing belt cover and confirm that the belt timing marks are still aligned. Murphy Never Sleeps!

Here's a few good tips for passing smog tests that I didn't think of, like inflating your tires to the high-end, makes the engine work less!

https://axleaddict.com/auto-repair/Tric ... -Smog-Test

https://www.smogtips.com/eight_things.cfm

On the EGR, if you manually pull a vacuum on the EGR valve and it moves, does the engine idle poorly? If so, at least you know you're getting flow thru the valve and it's having some effect.

The shop manual also says you can depress the EGR valve diaphragm to get the valve to move, but watch out, use gloves as it'll likely be Hot! Don't ask me how I know this!! :wink:

The manual says that with the engine warmed and vehicle stopped, you should be able to get the EGR valve to lift at 1/4-1/2 throttle. So if it's not doing this, maybe there is a problem with the back pressure transducer.

I can post some EGR troubleshooting pages out of the shop manual if you need them.

Good Luck!.......ed
 

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Discussion Starter · #69 ·
Super interesting read there. I think my BPT is functioning correctly.

I ran some smoke through the intake and found the my original EGR was leaking air through the stem. So it definitely needed to be replaced.

I got a new EGR valve with all the orifices today, and actually read the instructions this time. Turns out it explicitly says that you need a #25 orifice for the Isuzu 4cyl EGR. The orifice will restrict the flow of exhaust into the common chamber, preventing exhaust backpressure from falling, keeping the BPT "on", and letting vacuum reach the EGR valve. Phew! Hope that makes sense.



Once I get the harmonic balancer, I will throw all this stuff on, set the timing to stock and take in for another shot and let you know how it goes.

In the mean time, I'm rebuilding my distributor, as it is leaking a bit of oil into the cap area (could also be contributing to smog troubles). Thanks to the kg4miq who did a write-up on it.



One thing I was not able to find, that I know others were curious about is what the size of the bearing in the distributor is. Well I took it apart today and measured it. It's 30 x 10 x 9 mm. That's O.D. 30mm, I.D. 10mm, and W 9mm. I bought a replacement on amazon which should be here tomorrow.
 

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Discussion Starter · #70 ·
I guess while we're waiting on parts, I can talk a bit about the roof rack I made. I looked a while for used Thule or Yakima systems, but looks like roof rack are in high demand right now. I couldn't find a pair for less than $200, and I wanted at least 3 cross bars, maybe 4.

I decided to build them instead. This was my first real metal project I've done from start to finish. I got some 1x1" 16ga steel at a local metal supplier. 2x 10' lengths for about $16. I bought some universal rain gutter weld-on mounts on eBay. They were simple CNC'd vertical pieces with a clamp piece and some nuts and bolts to join them.

I decided to flip them upside down compared to how the eBay seller advertises them. I also found that the clamp piece was too deep and would hit the side of the car before offering any clamping power. So I also flipped those upside down and hammered them to fit the slope of the of bottom of the rain gutter a little better. After that they fit perfectly. However, there wasn't enough clearance to have a bolt head sticking out against the car on the inner portion of the mount, so I just welded the bolt to the mount and ground it flush.

I had enough material to build four crossbars so I built four!





I painted them with black satin epoxy paint. Then I painted the edges that touch the car with some plasti-dip. My girlfriend and I invested in a rooftop tent a while back, and it was always planned to end up on the Trooper. Being sensitive to the high center of gravity on the Trooper, I went ahead and splurged a bit on the lightest RTT I could find, the Roofnest Falcon, which weighs about 140lbs. We took it on a trip up the Eastern Sierras this past summer and it was great. It looked comically oversized on her Mazda CX-5, but fits the Trooper quite nicely. Now it will live on top of the trooper on my new custom built roof rack.


 

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Looks sharp! Is the automatic pretty snappy with the Jerry Cam?

Sounds like you'll have the EGR problem whipped.

Sooner or later you'll have touched everything on the rig and shouldn't have to fix it anymore!!! :mrgreen:
 

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Discussion Starter · #72 ·
Ed Mc. said:
Looks sharp! Is the automatic pretty snappy with the Jerry Cam?

Sounds like you'll have the EGR problem whipped.

Sooner or later you'll have touched everything on the rig and shouldn't have to fix it anymore!!! :mrgreen:
It seems pretty quick to me, but I can't compare it to the original, since I never drove it with the stock cam. I can get up to 60 mph on the freeway on-ramps OK. I haven't taken it up any of the steep freeway grades around here yet, but I've seen other 1st gen troopers in the truck lane with their hazards blinking, lol.

That's the goal. I don't have a lot of money but I do have time and some wrenching skills. All I want is a dependable rig that'll get me out in the middle of nowhere, and hopefully back home too!
 

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Discussion Starter · #73 ·
Exciting news as I was able to get the ol' gal to pass smog!

I think the deciding factor in it passing was that I was using the wrong thermostat. I had bought one on RockAuto that said "OE Temperature" without double-checking what that actually was. It was a 88*C t-stat, and my temp gauge always settled to about a needles width past middle, a little warm. I searched the Planet, and found many posts recommending an 80*C t-stat, so I bought one and did the simple job of swapping it without any issues....

Just kidding! The new t-stat must have moved out of place when I was tightening down the the outlet, and a big chunk on the thermostat housing broke off. Ugh. Off to the junkyards. After striking out at a couple yards, I found an intact t-stat housing off a '94 rodeo for $10, and it even had a bleed screw. Sometimes you gotta love the absolute glut of old cars in SoCal.

Other things I did: I got a new harmonic balancer, and when I compared it to my old one I found it had not slipped at all. So when the cam mark is lined up, the crank is about 6*BTDC. I took off the timing belt, lined up the marks on zero, and now the belt seemed about a half tooth off. I am using a block that was resurfaced and a new cylinder head. My memory is everything lined up fine when I first put the belt on months ago, but I figured after a few hundred heat/cool cycles and re-torquing the head bolts, the geometry must have changed slightly. So I decided to drill a new hole in the cam sprocket that aligned with a groove instead of a tooth and filed a new mark on it.

From this:


To this:


Now, my focus is shifting to the suspension and getting some new tires. I'm a total ignoramus on these topics, and I wonder if anyone has suggestions for what would be a good way to go, or a good thread to read. My goal is to be able to drive mainly on dirt trails and be able to get across moderately tricky sections competently when needed. I definitely won't be rock crawling in Moab or anything like that. I'm thinking of throwing some stock size General Grabbers on, but when it comes to suspension I'm lost!

Also, I got to really test out the Jerry cam the other day on the steep Conejo Grade between Camarillo and Thousand Oaks. I got in the truck lane and was able to cruise up easily at 55 MPH around ~3000RPM. I still had room to downshift and go up to 65 if needed. Nice!
 

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Just read through this entire thread again, glad to hear things are moving along. I really like this trooper. My opinion on the tires are to keep the 235's or go to 31's. Get an LT rating with all season capabilities. I ordered mine on Amazon and they have worked out very well.
Did you ever sell that fuel pump for the 6 cylinder? I would be interested
 

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Discussion Starter · #75 ·
hessmess said:
Just read through this entire thread again, glad to hear things are moving along. I really like this trooper. My opinion on the tires are to keep the 235's or go to 31's. Get an LT rating with all season capabilities. I ordered mine on Amazon and they have worked out very well.
Did you ever sell that fuel pump for the 6 cylinder? I would be interested
Thanks, and yes I do still have it. I'll send you a PM.

I did end up going with a new set of General Grabbers AT/X in 235/75r15. I was a little worried about straining the 4 cyl with larger tires. I've decided that if I ever find the 4.77 gears, then I will use that as an excuse to upsize. That oughta buy me at least a couple years.

I snapped a couple pics with the new tires on my way to a local trailhead.


 

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Good choice on the tires, man that Trooper is sweet! I have switched to 31's on both of mine. My Spacecab has the 2.6 also. Trooper is converted to a 3.4. I run nothing under 5000 feet and it they both do just fine. I am so glad I don't have to deal with smog. On the pickup I run the snowflake wheels that are just a tad wider than your stock wheels.
 

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Awesome post and work on the LS. I think we have twin trucks ('89 LS with the pure white over pewter color scheme and the cargo cover) although the body is much cleaner on yours from the pictures.

Congrats on passing smog! Mine is exempt here. Just got it registered and driving.
 

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I did end up going with a new set of General Grabbers AT/X in 235/75r15. I was a little worried about straining the 4 cyl with larger tires. I've decided that if I ever find the 4.77 gears, then I will use that as an excuse to upsize. That oughta buy me at least a couple years.

I ran the General Grabbers in the same stock size for a good 4 years and loved them! Also curious as to suspension (shocks) recommendations.

Beautiful Trooper man!!
 

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Discussion Starter · #79 ·
Getsducks said:
I did end up going with a new set of General Grabbers AT/X in 235/75r15. I was a little worried about straining the 4 cyl with larger tires. I've decided that if I ever find the 4.77 gears, then I will use that as an excuse to upsize. That oughta buy me at least a couple years.

I ran the General Grabbers in the same stock size for a good 4 years and loved them! Also curious as to suspension (shocks) recommendations.

Beautiful Trooper man!!
Thanks! After doing a bunch of searching on here, It seems like Old Man Emu are considered some of the best suspension components, although probably too expensive and you can get away with something much cheaper like KYB and it will perform just fine. Well of course I decided to go with OME shock absorbers and rear leaf springs. I've ordered new leaf spring and sway bar bushings from Energy Suspension. For the front end, I'm getting new Moog Problem Solver ball joints, control arm bushings, and tie-rods (HD mod, link in sig). Once I have everything apart, I'm going to check out my CV axles, which have torn outer boots. If they still look good I will reboot and reinstall. I'm also currently looking into new bearings since I'll have everything apart. And of course the big brake upgrade too!
 

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Discussion Starter · #80 ·
Redoing the front end all at once. New bearings, seals, ball joints, tie rods, etc.

I read here not to replace the lower control arm bushings unless you HAVE to. Decided to ignore that advice and paid the price.

Lower control arm bushings: Not even once!



After taking a whole day to remove them, I was surprised to learn that my replacements for the front (Moog, Made in Japan) were too small. Now I did clean up the housing it sits in with some sandpaper, but I don't think I took THAT much off. So I welded three little nubs into each housing, and then eased them over with a Dremel tool, and that gave me a nice pressed in fit.

Everything else is moving along nicely. Just waiting for a few more parts to arrive and should have everything done this weekend.

 
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