I'll start off by saying, I love the wealth of knowledge contained on this forum. Looking at all these old posts gives me a sense of "Anemoia". Most of the pictures are long gone and many users inactive, I'm roughly 18 years late to the party. I figured I would document what I do to my car here and contain my rantings to a single thread. Maybe it will encourage others to slightly revive this section of NICO beyond troubleshooting posts.

Background:
this is my first vehicle. It was a graduation present and at the time I had no idea what was in my possession. All I knew is that it was a nice car that needed some work and had a big engine.
I only drove it for a few months before it started having some transmission issues. The vehicle held on to second gear for too long; wouldn't shift until reaching almost 40 mph. This alone was concerning but being a brain-dead teenager I kept driving it and roughly a week later I got the dreaded transmission malfunction message. The vehicle was now in limp mode. I ended up putting it aside for a while. My focus at the time was purely on collision repair. I had absolutely no inclination to go about removing the transmission or diagnosing the true cause of the problem. Getting into a rebuild was inconceivable. Simply opening the FSM in the trunk was too much to bear. I liked the car and resisted parting it out or selling it purely on the sentimental value.

Fast forward 6 years to 2021, I started reading up on transmission rebuilds. Having moved on to the mechanical side of automotive repair I was beginning to get an idea of what my vehicle really was. After discovering this forum, and reading some articles touting the Q45 as the golden boy who never was I got a sinking feeling in my stomach. I simply couldn't believe how I had mistreated this vehicle. I felt disgusted and started planning its revival.

Digging into the transmission issues:

I got my snappy franchisee to get me an OBD connection for those old Nissan vehicles to get a rough idea of what was happening.

As far as diagnostics go it was pretty cut and dry
First thing I did was drop the pan and service the trans. After changing the filter I kept the vehicle raised and hopped in to see how it reacted to the new fluid. At first I couldn't believe it, it was shifting perfectly and I had a glimmer of hope for getting this beast back on the road with next to no effort. That was short-lived however; once it was actually on the ground I immediately got the transmission malfunction light and I was back at square one

I performed the self test and got 11 codes. Every single one was for an open/short circuit so logically I figured I had left something disconnected when I did the initial service all those years ago. I started off with the one that sounded the most important which was a communication error with the ECM. I checked the communication wires by the book. They were fine ~.03 ohms each. That seemed strange as the manual doesn't have much for that code beyond the continuity and a visual inspection. I moved onto the other codes anyway the solenoids were next, which of course were fine as well. So far all the wiring seem to be pretty tight. All the pins looked good and I was puzzled it's not often that the module actually goes bad. It's normally an external factor that causes it to act out. Next I checked the powers and grounds, verified all the voltages according to the full service manual. Again all of it was within spec. Obviously I had my suspicions by this point but what really locked it in was what happened after verifying the circuits. The next day I performed another self test and it would read "OK" but as soon as I shifted it into any gear I would immediately get the transmission malfunction light as well as a no communication error code 54. This went on for a while. I must have triple checked the wiring between the ECM and TCM trying all sorts of different positions for the plugs maybe there was an intermittent false contact going on. The results didn't change and I finally concluded that the module was indeed toast.

Luckily I found one that was matching numbers for dirt cheap and as soon as it came in the mail I plugged it in and voila! Everything checked out okay but it still had that shifting issue holding on to second gear. I just needed to be absolutely sure before ordering a 93 module for that first gear start. Didn't want to risk any compatibility issues.

I am running some seafoam transmission additive as a last ditch effort in case there is a sticking valve or something. Admittedly I know absolutely nothing about automatic transmission functions but it worked wonders for my 88 F150 so it was worth a shot. Less than $20 to possibly postpone a rebuild. It came highly recommended by the machine shop I use and it not only improved the shifting but it doesn't slam into gear anymore. It is much more responsive at highway speeds and the guy says it saved him from replacing a transmission in his personal vehicle. Honestly I thought it was snake oil but I am now a believer (within reason).

I think your TCU failure is the first I've heard of - but with a 22 year old car, no failure surprises me. Good work!

On any vehicle this old the electronics seem to have issues. Keep in mind that the Q45s had issues with both the fuel pump control units and the Bose amplifiers when new, so it's not surprising to me when I find some control module with problems. I just recently found that my original ECU wasn't triggering the EGR solenoid at all, so it wouldn't pass emissions. Installing a used ECU fixed the problem.

What do you guys think about a temporary ABS delete? I was reading up on some old posts and a DIY repair for the modulator doesnt seem feasable. The same thread mentioned people spending roughly $1300 (adjusted for inflation) on a reman unit. Amayama shows a couple for 2k. I feel like the money is much better spent on other improvements in the mean time. This thing is bleeding like a stuck pig and obviously any used part is susceptible to the same failure. It seems like I would just be tossing money away if I bought used. I was checking out a few aluminum brake proportioning valves. They can easily be adapted without mangling the original lines. Thoughts?

No1Dad wrote: ↑

Mon Mar 14, 2022 5:41 pm

What do you guys think about a temporary ABS delete? I was reading up on some old posts and a DIY repair for the modulator doesnt seem feasable. The same thread mentioned people spending roughly $1300 (adjusted for inflation) on a reman unit. Amayama shows a couple for 2k. I feel like the money is much better spent on other improvements in the mean time. This thing is bleeding like a stuck pig and obviously any used part is susceptible to the same failure. It seems like I would just be tossing money away if I bought used. I was checking out a few aluminum brake proportioning valves. They can easily be adapted without mangling the original lines. Thoughts?

I think your story is a good reminder for why the brake fluid should be flushed every 2 years, regardless of mileage. It does seem like the Kouki units are less susceptible to leaking than the zenkei's
not sure if they directly interchange or not, but that perhaps could be another option since you seem comfortable with redesigning the brake system.
I see you have an old F150, I have a '77 dentside. As it happens, I am in the middle of replacing 45 year old brake lines. But I'm reticent to just start changing things, even on such a simple non-ABS design. For example, I haven't decided if I'm replacing the combination valve yet.
I did buy a brass (Chineseium) universal/GM valve that has same form factor (well reasonably close) to my factory Kelsey-Hayes valve. I do highly recommend using Ni-Cu lines (very easy to work with, and don't leak because the soft copper will nicely mold to a perfect seal with the compression flare (bubble in the case of our G50s) fittings. Buy the good "eastwood" tool (Amazon has it for about $175).

Unfortunately at the time I didn't know better, now that I do it's too late LOL. And yes I have a fair bit of experience making brake lines from scratch. Not too hard just time consuming. I had no idea the Q used bubble flares..... That may complicate things a little bit.

Thanks for the material recommendation, I dont know what's sitting at the shop. They're just these massive unlabeled rolls in various thicknesses

I vaguely remember reading that the 94 - '96 modulators would fit with some minor changes. I'll have to double check and edit this later

EDIT:
link to the thread in question
abs-actuator-leaking-on-a-1993-infiniti ... 97-30.html



Logic says that i outright upgrade to the newer actuator. However I do have the hankering to rebuild the old unit, as time consuming and aggravating as it may be. I believe the later models are cheaper as well.

I was working in the service dept. of an Infiniti dealership in 93-94, and the techs were replacing leaking ABS units under warranty on a regular basis even back then. The one on my 90 has been leaking since long before I’ve owned it, but I found a nice dry one in a wrecking yard that I’ll be swapping in soon.

Ryantzer wrote: ↑

Tue Mar 15, 2022 8:15 am

I was working in the service dept. of an Infiniti dealership in 93-94, and the techs were replacing leaking ABS units under warranty on a regular basis even back then. The one on my 90 has been leaking since long before I’ve owned it, but I found a nice dry one in a wrecking yard that I’ll be swapping in soon.

That's interesting, so the 94 to 96 models aren't much of an improvement? I already pulled the trigger on a used one thinking that it would take care of everything.

As a former service advisor I'm sure you are very familiar with the flimsy sun visors. What did you guys end up doing to remedy the situation outside of replacing them outright? I have six of them and five are broken

I wanted to fix a couple but the retaining nut (cap?) Is stripped. This car is going to end up looking like Frankenstein's monster by the time everything works properly. I read about tapping some threads onto the outside of the post and just slapping a nut on there. are you familiar with any other techniques? Id like to get the mirror flaps working as well

I vaguely remember the seals being updated in the later part of the 90-93 run. I've been hoping for a 92 or 93 to appear at the pull-a-part for a spare. I should have done that about a decade ago when these cars were still frequent flyers there.

Started the teardowns last night. The guides were all intact. Very surprised about that. I even tried to break one and it flexed! They weren't brittle at all... 97k miles build date is 2/90. In my infinite wisdom I completely overlooked the fact that the cooling system would also be neglected. Water pump is seeping at the weep hole and there is a lot of crud right in front of the thermostat. I have plenty to do while its open. I should also take care of the valve covers but if I do that I might as well do the entire timing job vs just the guides.

I’ve found it recommended in numerous places to reuse the original timing chains unless they have stretched or show signs of damage. They almost never fail, and the original timing chains will be ‘polished’ and run with less friction than new chains.

The general consensus was to replace the oil pump chain because they tend to stretch, but keep the others unless they're damaged.

Engine looks good! Don't forget: 271 lb-ft on the crank bolt.
As for the thermostat housing, yeah it's crusty, but that's a good thing. both it and the mid-pipe (the one between the 'elbow' hose attached to the t-stat housing and the lower rad hose) are the sacrificial anodes to protect the aluminum pieces from galvanic pitting.
Amayama had those pieces last i checked.

Noted. I guess just the guides and oil pump chain it is. I figured I'd be replacing a decent amount of hoses and misc. plastic bits but WOW I was still caught off guard. None of it is holding up at all. Which shouldn't surprise me, it's well past its expected lifespan. Including the car! I've been getting a checklist together of all the hoses ill need to replace while cleaning the solid inch of oil/dirt mixture that has accumulated.

Found this jiffy lube service reminder. I thought it was neat since I have 0 service history. It was wedged underneath the air filter box. The first number is for the next oil change which is 16,34 _ _ miles. The second is for the air filter 18,892 MI the date on that is October 1993.

3Q Jay wrote: ↑

Wed Mar 16, 2022 8:18 pm

Engine looks good! Don't forget: 271 lb-ft on the crank bolt.
As for the thermostat housing, yeah it's crusty, but that's a good thing. both it and the mid-pipe (the one between the 'elbow' hose attached to the t-stat housing and the lower rad hose) are the sacrificial anodes to protect the aluminum pieces from galvanic pitting.
Amayama had those pieces last i checked.

Are you yanking my chain?? You mean like the rods in a home water heater? I didn't know that was something implemented into vehicles... Much less this one. My torque wrench only goes up to 250. Maybe this will justify an upgrade to the latest model.

Power steering high pressure line!
I stopped by my local hydraulics store. I can have them made for roughly $140 including tax. Is this the best price ill get? I don't believe in paying the nearly $300 everywhere else is asking for. If there are any cheaper solutions please let me know. Or if you want one for roughly that price get in touch with me. Id be willing to send them out if you arent close to someone eho can manufacture them.

I got the modulator in the mail today, looks like its going to be a relatively simple install. Both are infact inverted flare and everything minus a mounting hole in the bracket and the output lines are the same. The newer modulator has the outputs on the top vs on the sides. Not 100% sure how I want to go about adapting the lines. There are 90 degree elbows made by dorman and I'm thinking that might be my best option. I might even be able to use the same lines without modifications if i go that route. Also the old unit has some padding on the bottom where it sat on top of the bracket. This one is smaller and sort of "floats". I assume the padding is there for a good reason. Wondering if I should lower the entire unit so it sits on some rubber like the old one

No1Dad wrote: ↑

Sat Mar 19, 2022 7:07 pm

I got the modulator in the mail today, looks like its going to be a relatively simple install. Both are infact inverted flare and everything minus a mounting hole in the bracket and the output lines are the same. The newer modulator has the outputs on the top vs on the sides. Not 100% sure how I want to go about adapting the lines.

oops. I thought they were all bubble. Guess my recollections need a verify step. Well, at least inverted flare are easy. Are you sure you don't want to first try and reseal your original unit?

I suspect I'll be doing this some day. Jay, you mention resealing the old unit. Have you done this, or do you have an idea of what's involved? I have a core on hand, but no desire to do the surgery until I have to. The conversion to the newer style also is interesting.

Q451990 wrote: ↑

Sun Mar 20, 2022 9:17 pm

I suspect I'll be doing this some day. Jay, you mention resealing the old unit. Have you done this, or do you have an idea of what's involved? I have a core on hand, but no desire to do the surgery until I have to. The conversion to the newer style also is interesting.

I have not taken apart an ABS solenoid/valve unit.
I've done re-seals on two different active/PS hybrid pumps which have an attached solenoid block to set the active system pressure. on those, I carefully disassembled while keeping things clean, and found that it was really just a bunch of old, compressed o-rings that would no longer hold a seal. So I *don't* know specifically whats involved on the ABS unit, but most any size o-ring can be sourced (assuming the unit works and it just needs re-seal).

No1Dad wrote: ↑

Thu Mar 17, 2022 8:31 am

Power steering high pressure line!
I stopped by my local hydraulics store. I can have them made for roughly $140 including tax. Is this the best price ill get? I don't believe in paying the nearly $300 everywhere else is asking for. If there are any cheaper solutions please let me know. Or if you want one for roughly that price get in touch with me. Id be willing to send them out if you arent close to someone eho can manufacture them.

Sounds expensive, but everything is expensive now. Here's a thread from 2005 when I did this. I can't believe the pictures still work.

new-ps-hose-made-for-40-t4470.html

Here's a quote from a different thread who only paid $36 in 2019.
post6794235.html?hilit=power%20steering%20hose#p6794235

dnudelman wrote: ↑

Wed Jul 03, 2019 2:05 pm

Power Steering Pressure hose.

I just had my pressure hose rebuilt at Pacific Rubber Inc. in Seattle 206-262-6800.

They braze your banjo fittings onto a hydraulic hose. Works great, same day service, $36.00

3Q Jay wrote: ↑

Sun Mar 20, 2022 9:28 pm

I have not taken apart an ABS solenoid/valve unit.
I've done re-seals on two different active/PS hybrid pumps which have an attached solenoid block to set the active system pressure. on those, I carefully disassembled while keeping things clean, and found that it was really just a bunch of old, compressed o-rings that would no longer hold a seal. So I *don't* know specifically whats involved on the ABS unit, but most any size o-ring can be sourced (assuming the unit works and it just needs re-seal).

When you put it that way it's probably worth a shot. Worst case scenario I just go ahead with my original plan to replace it outright. The hydraulic shop I visited had some nice o ring kits (P/N:. K212X20N90) but I didn't see any made with compatible materials, all of them were nitrile. Buying individual o-rings would be a PITA.





Update:
I called a few places and got bounced around before finally being referred to a place called swan engineering. I asked for a brake fluid compatible o-ring kit and he was surprised, says that never in his 32 years has someone asked for something like that. He mentioned I can stop by with the old rings and have them all measured. More than likely he has everything in stock. If someone else is doing all the measuring I'm all for it. I will start the tear down sometime this week and I'll let you guys know what ends up happening. With pictures of course.

My understanding is that brake fluid plays nicely with most types of rubber, so I would think that generic o-rings shouldn't pose any issues.

Ryantzer wrote: ↑

Mon Mar 21, 2022 9:14 am

My understanding is that brake fluid plays nicely with most types of rubber, so I would think that generic o-rings shouldn't pose any issues.

Forgot to mention about the posted graph, on a scale of 0-4 with 0 being the least compatible and 4 being the best option, the regular (Buna-N) nitrile rings are ranked pretty low. The guy at swan engineering confirmed this and mentioned that unless you're using DOT 5 nitrile rings are not an acceptable substitute. Not that its a good idea to switch over anyway since DOT 5 is not suited for use in abs systems. Ethelyne - propelyne is what he mainly stocks and what came recommended. According to him of course im no expert.

I have limited personal experience with this, customers have come in after using ATF as a substitute for brake fluid. It's not pretty. The brakes are unresponsive and pedal turns squishy like a stress ball.

.... And its apart. Tbh nothing crazy complicated in terms of disassembly but it does have a stupid amount of o rings. One thing to note, either due to torque specs or corrosion some of the bolts are very snug. You will need at a minimum a vise and a torch. No im not joking some of those bolts needed a surprising amount of persuasion. I managed to round one off before whipping it out. Now to catalog every ring and head on over to the specialist some time soon.



I would say getting the cap off for the main bolt was the most "fun"

By the way a good pair of needle nose pliers was invaluable for getting some of the pieces out as well. Full step by step after making sure it all works first.

Oh man, this is getting good!

The ABS unit on my 1990 has apparently been leaking for some time, as the mounting bracket has bubbling paint and rust forming on the area beneath the unit. I found a used unit that was completely dry from another 1990 and have it ready to install in the next few weeks when the rest of the brake system is getting an overhaul. Good to know that a rebuild is not outside the realm of someone with decent mechanical skills, should the used unit end up being a leaky mess as well.

No1Dad wrote: ↑

Mon Mar 21, 2022 5:30 pm

Knipex Pliers, and Nitrile Gloves - in this messed up world, they both cost about the same thing! We won't even mention the Snap-On ratchet. As a buddy of mine used to say "rich guys doing rich things..."


In all seriousness, I've spent a good bit of the last year sorting through a lot of vintage tools that I inherited from my Dad. I've learned a lot just researching what's "ebay-able" and really enjoyed using quality stuff instead of my previous collection of Harbor Freight specials.