‘91 complete tune-up

[Suavest]

My father passed away, and his ‘91 has been sitting for over 8 years outdoors (160k miles). I finally got it to start by replacing the battery and jumping the clutch interlock switch. I don’t have an NSX tech in town (Nashville), but I have found a shop that did a tune-up on a ‘95 that had been sitting. That ‘95 had been in good storage conditions though. When I started the ‘91, I noticed the brakes have lost pressure and it seemed an engine cylinder was not firing. I didn’t keep it on long, just enough to turn the car around to put on a trailer.


Please provide advice on all the items I should get replaced/checked. I would like to keep the car and drive it as long as I can. Thanks in advance.

 

[SWFL_NSX]

Hi, and sorry to hear about the loss of your father.

I'm assuming you have experience working on cars and a set of basic hand tools/jackstands/etc. If that's not true then the best first step is to take it to a garage and have them do an inspection. Nashville is a big town so I'm sure somebody has NSX knowledge. If nothing else, the Acura dealer will probably have a certified tech who can baseline the car for you.

First, download the factory service manual by clicking on the link in my sig line (below). I'd start out by refreshing the brakes, probably starting with a new master cylinder, and then bleeding them. If you don't get a solid pedal feel after that let us know and we'll troubleshoot further.

Next is to change oil and gasoline fluids and filters. Drain the oil and re-fill, install a new Honda oil filter and crush washer. After that, drain the gas from the tank and change the fuel filter (strainer) that is in the engine bay. Pull the injectors and have them sent away for cleaning as well.

After that I would start working on the cooling system. This is really critical because the process is very different for the NSX vs. other cars, and because these engines are aluminum an overheat can quickly blow a head gasket and warp the head. Rather than spell out the process, take a look at the wiki here: http://www.nsxprime.com/wiki/Coolant_Flush_and_Fill

One more note on the cooling system. You're going to want to replace all of the coolant hoses (about 20 of them) because they degrade over time. I wouldn't drive the car very far, and would keep a laser focus on the temp gage until this is complete.

If the car is still running rough pull the rear bank of coils (it's a coil-over-plug setup) and look for water marks or burning. Water gets into that area and the coils go bad. If that's the case then you'll have to replace them.

Assuming you've done all of that, you now have a car that runs, stops, and probably won't overheat. There is a lot more to do for preventative maintenance (you're going to want to tackle the timing belt, get the valves adjusted, etc.), but hopefully this lets you get a baseline on the car.

Last thing-these cars are going up in value and this one has a personal connection. Don't let somebody scare you into selling it by showing you a big repair bill. Yes, they can get expensive but they are DIY friendly and this is a good community. Good luck!

 

[Suavest]

SWFL_NSX , thank you so much. I appreciate you putting together this list. I'm confident I can tackle these. I'll provide updates and tag links/videos for others.

 

[Suavest]

Post Outline: (A) Update (B) Work Items (C) Questions
A:
After obsessively reading the manual, NSX Prime, and looking over the car, I've decided to take it to a local shop for a couple of reasons. (1) I want to drive it ASAP. (2) Replacing hoses myself will overlap with labor the shop will do anyway changing my belts.
My budget is not infinite, but I want to get all the critical items done now that will save me time in the long run. Everything from here on out I will be DIY.

I called around and found a local shop in Franklin, TN (20min from Nashville) called Reliable Automotive. They've worked on 5 NA1's and their most recent (June, 2020) was a complete maintenance shakedown of a '94, which they quoted as being $3,800. If anyone is interested, I heard that '94 is for sale, it's got low mileage and has been sitting in a collectors facility - let me know if anyone is interested and I can ask the shop for the owners info.

B:
Here's what the '94 had done for $3,800:
1. Replace all belts
2. Replace Water pump
3. Air, Fuel, Oil filters
4. Valve adjustment
5. Coolant flush
6. Brake flush
7. A/C controller replacement
8. Spark Plugs
9. Oil change
10. General inspection: injectors, coils, suspension

What I am adding to the list:
11. Coolant Hose replacement (purchased from SOS)
12. Coolant Temp sensor replacement (TW sensor) - Error code (6)
13. Injector cable replacement (chewed by rodent) - Error code (16)
14. Clean coils/injectors if needed
15. Pedal Stops - (original blue ones are gone, and I can't reach the clutch)

C:
Should I go ahead and get these done?:
16. Replace thermostat?
17. Replace oil cooling hoses?
18. Replace fuel hoses?
19. Replace brake hoses?
20. O2 sensors?
21. Anything else I am missing you guys suggest getting done?

Can’t post pictures: can’t identify a cable. Comes into the top right of the engine bay from behind the passenger seat. It is above and to the right of the engine harness entrance.
Based on the manual, it seems to be a grounding cable. I am also missing the ground connection to the bottom right of the starter motor mount – I assume that’s where it goes.

 

[drew]

Seems underpriced. Make sure you get all your parts. And tell them you want to inspect the engine with the timing belt off...look for leaks at the cams/crank.

Here's what the '94 had done for $3,800:
1. Replace all belts
timing belt too?
2. Replace Water pump
Ok, so timing belt is included.
3. Air, Fuel, Oil filters
4. Valve adjustment
5. Coolant flush
6. Brake flush
ALB needs to be included.
7. A/C controller replacement
This is a $900 part.
8. Spark Plugs
9. Oil change
Oil pan gasket too.

10. General inspection: injectors, coils, suspension

What I am adding to the list:
11. Coolant Hose replacement (purchased from SOS)
Yes. Need oil pedestal figure-8 o-ring

12. Coolant Temp sensor replacement (TW sensor) - Error code (6)
Check for rodent damage first.

13. Injector cable replacement (chewed by rodent) - Error code (16)

14. Clean coils/injectors if needed
Coils are a replacement item. If you have reason to replace coil connectors you may consider migrating to the 3-pin version and get the new set of coils for $150 for a set of six. Also need the coil covers.
Injector cleaning is $300. Plus you should replace the o-rings and pads.

15. Pedal Stops - (original blue ones are gone, and I can't reach the clutch)
OK, but I'm not sure that will fix the clutch access issue.

C:
Should I go ahead and get these done?:
16. Replace thermostat?
Yes.
17. Replace oil cooling hoses?
Not unless there is a problem
18. Replace fuel hoses?
Not unless there is a problem
19. Replace brake hoses?
Not unless there is a problem
20. O2 sensors?
Maybe, they are a wear time though. I would wait to as it will be one less thing to diagnose if something goes wrong.

include:
harmonic balancer shield.
ALB fluid change
valve cover gaskets
rear cam belt plugs (SoS)
Get a quick compression check BEFORE and AFTER the timing belt change. It is real easy to get the timing belt off by one or two teeth, this test will verify that.

consider:
a timing belt idler pulley and spring.
harmonic balancer

 

[Old Guy]

Oil cooling hoses? Do you mean the small hoses that connect the OEM oil cooler (mounted on the base of the oil filter) to the engine cooling system? Those would normally be included in the complete cooling hose change. Or has the car been retrofitted with a separate remote mount oil cooler? As noted by Drew include the little figure 8 gasket for the oil cooler pedestal. Larry B provided an excellent list of parts for major maintenance intervals in this thread

Need part numbers for a complete timing belt kit job (nsxprime.com)

Given the age of the car I would be inclined to replace the brake hoses. You are going to be flushing and bleeding the brake system so its an ideal time for the hose replacement.

As Drew notes, the Climate Control Unit is a pricey item. It is common to have the CCU capacitors replaced (NSX Erepair does this) if the CCU is misbehaving. Wait to confirm that the CCU actually has a problem before sending it out for repair if you want to conserve money.

I differ from Drew in not viewing the coils as a replacement item. The rear ones are subject to corrosion which can be confirmed by visual inspection. I would wait to determine whether there is a problem rather than replacing preemptively unless you have surplus cash hanging around. A complete set of 6 later 3 pin coils is available by using part number 06300-PR7-305. The price of 06300-PR7-305 is less than purchasing a single 2 pin coil (go figure that one out). The problem is that the 3 pin coils will not fit under the original coil covers which requires the later coil covers at about $220 each. You need to do the calculations to determine the low cost path for you.

Tough decision on the O2 sensors. At 30 years and 160,000 miles a failing sensor would not be a surprise. However, on the early cars the sensor can sometimes be a problem to remove, breaking in place and leading to a decision to just replace the manifold with a later OEM or aftermarket header. Wait to see if the ECU generates an error code.

 

[Old Guy]

An additional note. If your 1991 has the original water pump the design of the water pump was revised requiring a new cover, or a cover modified by drilling a weep hole. If you check around Honda had a 'kit' consisting of the later pump including a revised cover. This kit used to be lower in price than just the pump itself. I think that ship has sailed; but, the kit is definitely lower in price than buying the pump and cover separately. The kit is not listed in the parts catalogs; but, if you search Prime you should be able to find the part number.

Also, check the cooling system expansion tank. They can develop cracks / leaks. A pressure test on the cooling system would determine whether the tank has issues.

As noted, refilling the cooling system on the NSX can be tricky in terms of getting it burped. If the techs use a vacuum refill device this can eliminate / reduce the burping requirements.

 

[drew]

coils: the outdoor storage concerns me, I would presume all the rear coils are sus. A bad coil can cause cylinder wash and wreck the engine fairly quickly. Factor in rodent damage and, well, you have a lot of known unknowns.

oil cooler lines: my mistake because they don't exist (I was envisioning my FD)...really the A/C condensers should be the oil coolers. The oil filter pedestal/cooler should be removed as it makes dealing with the timing belt a lot easier. The timing belt on the NSX is extremely difficult under the best of circumstances and making it any harder is a non-starter.

My concern about the quote is that the $3800 doesn't leave a lot left over for labor...which is a big part of the job.

I recommend to shelf your desire to "drive it ASAP" and conduct a several-month mechanical restoration of your vehicle in your own garage. Anything overlooked will just cause a lot of heartache and be incredibly expensive. Just removing the CCU (A/C climate control unit) involves a couple of thousand dollars in plastic that is easily broken and any shop won't cover. Replacement of cooling hoses needs to be with care as an errant hose removal can be costly and won't be reported by the shop.