This is the Build Thread for 1991 TSi AWD. Reply below.

Currently working a full engine rebuild. Timing belt broke so no better time to refresh the whole thing. 270k miles on the virgin bottom end, so it is definitely due. I'll try to keep things updated here!

Following, did you find out the cause of the timing belt failure?

Dericsh said:

Following, did you find out the cause of the timing belt failure?

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Found a remnant of a ps belt inside the cover. It was either that or a shitty gates belt.

Time to start updating this build. Going way way back, I purchased my stock DSM in 1999 from my brother who bought it in '95. Original Colorado car (still in CO today). About a year after I bought it the harmonic dampener separated while idling in the driveway. This was my first repair but was relatively easy to fix even in the rain. Local dealer hooked me up. Weren't those the days when dealers had parts in stock!

A year or two later I had to install a new clutch. Good ol' vfaq walked me through it and from there I stumbled into the CODSM community. Great club, did some meet-ups, found lots of parts and met some cool people. It got me hooked on DSMs. The club eventually slipped into the Facebook pit so I wandered the desert for while, doing my own thing just to keep it on the road.

Going back to sometime around 2002/03 I blew out 2nd gear syncro and ventured down the rabbit hole of transmission rebuild. Bought another used trans to limp by on and carefully rebuilt my original. Took me about a year to get it done but turned out great. Couple more mishaps like blown turbos, idle issues galore, and many other things too long to list. Nothing overly complicated except a head swap. I kept at it, driving it daily for the most part.

Fast forward to 2021. Blew out 2nd gear syncro AGAIN. I knew I could fix it pretty easily but started to feel the weight of discontinued parts. I found Jacks Transmissions stocked almost everything I needed. That is, until I noticed my output shaft and transfer case coupler splines were completely worn and on the verge of imploding. Jacks hooked me up with a new OEM output shaft but that coupler...not so much. Completely discontinued part. At that point I joined Tuners to see what the community could offer. No bites on my WTB ad so I contacted every DSM transmission shop I could find. To the rescue was @twicks69 who hooked me up with a good used one (Thanks Tim!). Crisis averted (for now).

At around 270k miles on the ODO, the timing belt broke in March 2022, which is where this build picks up. The bottom end of the engine was still virgin and I had a spare virgin head with 220k miles on it. Perfect candidates for rebuild. And so it starts...

Time for pics! I'll have to start of slowly and show my older stuff first. More to come as time allows!
Transmission output shaft completely wore out! Replaced this with a new OEM.


old transfer case coupler, replaced with a good used one.


Old leaky transfer case yoke

First look at the piston tops


Yuck!

My garage


Removing crank


Looks pretty good for 270,000 miles, doing some dead end throw cleanup


Pistons removed. They've seen better days.


Head before machine shop



Block before machine shop



Deck surface after machine work, needs a little cleaning


Showing the plastic gauge of my crank journals


Prepping block for paint.



Primer


Paint



Tape removed and new freeze plugs


Oil port mod, I might have gone a little overboard





Valves installed and lapped


2nd gen pistons installed

ARP headstuds


Head installed


Assembly


All assembled, primed and ready to drop in

Looks great! What paint and primer did you use for the block?

Dericsh said:

Looks great! What paint and primer did you use for the block?

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Thanks Deric. It's Dupli-Color engine enamel

IT RUNS!!!! I literally had a dream come true. Almost like I'm still dreaming.

It's been down since the end of March and all that time, effort, money, blood, sweat, tears, and a lot of swear words, it's back. Another DSM saved

I finished getting it all back together yesterday. It had a fuel leak at the rail that just needed a new o-ring. It started pretty easily after that but I found the brake booster vacuum line was unhooked. Got that line hooked up, let it warm up, set the idle and ignition timing and took it out for a spin through the neighborhood. Now a coolant leak! A pesky leak running down every crossmember and the source wasn't obvious. Turns out I forgot to tighten the lower radiator hose clamp at the water pipe. Got that all tightened down and so far so good. Power steering isn't working but that's my fault. I rebuilt the pump and I think I installed the flow control valve upside-down. I'll have a look at that after work.

Drove it to work today, getting those rings to seat with wastegate actuator boost pressure and no super high RPMs. It's quite a lot different feel than pre-rebuild. I went from 1g pistons that had a lot of blow-by to 2g pistons with higher compression and hopefully no blow-by. So much more low-RPM torque is going to make it more drivable (and fun) on the street.

It could just be the angle of the photo, but do you have the correct timing belt tensioner arm installed in the long block assembly pics?

1999RSfwd said:

It could just be the angle of the photo, but do you have the correct timing belt tensioner arm installed in the long block assembly pics?

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Must be the angle. That's the original arm.

It must be. The tensioner plunger looks too inboard on the tensioner arm

1999RSfwd said:

It must be. The tensioner plunger looks too inboard on the tensioner arm

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Maybe. I did grind the arm flat at the tensioner to clean up the contact area.

What machine shop did you use for the work on the block?

Madcap Racing Engines in Lakewood. The owner also owns Carz Performance.

dwb said:

Madcap Racing Engines in Lakewood. The owner also owns Carz Performance.

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thought you would say, I need to pay them a visit and get started.

I got my idle and power steering fixed last night. Everything coming along nicely....until this morning on my way into work.

I noticed some smoke coming from the engine bay and then my oil light started flashing and then lit up solid. Oh shit! WTF just happened!?! I killed the engine as soon as the light went solid. Oil all over the road, dripping from the front of the engine. I figured I blew a front case seal or maybe the BS plug, really no idea at this point. On the side of the road I crawl underneath and to my amazement the oil cooler bolt came loose. So I pull the oil filter and hand tighten the bolt since I had no tools. I crank down the filter as best I can to put some tension on the OFH and hopefully seal it up. My wife brought me a fresh jug of conventional oil, which fortunately I had set aside for my 2nd break-in oil change. I filled it back up, crank it without the MPI fuse to build a little oil pressure, then reinstalled the fuse and started it up. No obvious leaks, no oil light, and oil gauge starts showing pressure. YES!!! Back on the road, everything seems OK.

So SO glad I noticed that dummy light and killed the engine immediately. Not exactly how I wanted to do an oil change but catastrophe averted (for now). So much for inspecting that first break-in oil.

Was the PS issue what you thought it was?

Nice save. Glad it worked out.

I had that happen to me once before as well. I make a point now when changing oil to torque down that fitting before putting on a new filter.

Dericsh said:

Was the PS issue what you thought it was?

Nice save. Glad it worked out.

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Yup, I installed the flow control valve and spring upside down in the PS pump. That's right under the high-pressure joint. So the spring goes in first, then flow control (small end fits into the spring), then thread in the high pressure joint. Super easy fix, minus the ATF mess.

I'm glad it worked out too. I'll definitely be looking up the torque spec of that OFH bolt so it doesn't come loose again. I was too concerned about crushing the OFH so I went kind of easy on it.

Small update, been running pretty good for about 220 miles.
Some minor issues:

A minor oil leak from the timing belt area that's going to be a PITA to figure out. Long weekend coming up so that'll be a good time to pull the lower timing belt cover.

Slowly losing coolant so I need to track that down. I think it's a leak on the top end tank of the radiator. Its a copper aftermarket radiator so I'll try my luck patching it with solder.

Idle has been driving me nuts. Sometimes it's rock sold at 750, then other times it has a mind of it's own. Worse with headlights, blower, rear defrost, etc. all running. Sometimes wants to die at initial stop at a stoplight, but it usually catches. I have an old thread on this I'll have to resurrect at some point.

I was running direct wastegate actuator boost pressure, which ended up being about 7-8psi. So I reinstalled my manual boost controller, up to about 9 psi now and need to see where I can go without much knock. 2g piston compression but 1g timing maps, so I need to be careful here.

Stumbled across your comment from the beginning of the month - I know it's late but perhaps it is helpful to you and others following along.

dwb said:

Small update, been running pretty good for about 220 miles.
Some minor issues:
idle has been driving me nuts. Sometimes it's rock sold at 750, then other times it has a mind of it's own. Worse with headlights, blower, rear defrost, etc. all running. Sometimes wants to die at initial stop at a stoplight, but it usually catches. I have an old thread on this I'll have to resurrect at some point.

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Do you have your Injector Battery Voltage offsets correct since it seems to get worse the more load you put on the electrical system.

19Eclipse90 said:

Stumbled across your comment from the beginning of the month - I know it's late but perhaps it is helpful to you and others following along.

View attachment 680709

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Thanks, I did get that bolt torqued to 30ft.lbs. with a 24mm deep well socket. All good so far.