• Protip: Profile posts are public! Use Conversations to message other members privately. Everyone can see the content of a profile post.

Performance not consistent?

Joined
12 May 2003
Messages
5
I'm still learning about the power delivery of my recently purchased '92. The only modifications are DC headers.

My car's power does not feel consistent from day to day. Some times it feels great and pulls very hard from 5-8k and other days it just doesn't seem to have the same seat of the pants oomph. Any suggestions of things to check first? It's almost like sometimes I feel like the vtec isn't kicking in?

Also, if I stand on it near 5k, the car usually feels great. But when I stand on it near 4k (obviously low rpm and not in vtec range for anything exciting to happen) and the revs increase to 5,6,7,8k it doesn't seem to ever reach that same type of acceleration. It could be my seat of the pantometer is confusing the linear power delivery, but I'm fairly certain it's not as it just doesn't feel all that fast (sometimes).

Any ideas?

Jackson
 
Well - some things to consider that can affect performance:

- amount of gas in tank / octane
- passenger / luggage weight
- ambient temp
- elevation
- gear you are in (time to RPM is much quicker obviously in lower gears)
- tire condition

Maybe you could borrow someone's GTECH or even use a good stopwatch and a higher gear to quantify your concerns.

My bet is - if you don't have a CEL - everything is probably your perception.

If you really concerned - I would start with checking the air filter, fuel filter, fuel pump, injector cleaning, plugs, throatle body cleaning, valve clearances, and ignition coils.
 
Nick's advice is right on as usual.

matteni said:
If you really concerned - I would start with checking the air filter, fuel filter, fuel pump, injector cleaning, plugs, throatle body cleaning, valve clearances, and ignition coils.

Note that many of these items are part of routine scheduled maintenance for the NSX. Has your car had its maintenance performed on schedule?

BTW, a common culprit among these items, and an easy one to check, is a dirty air filter.
 
Are you sometimes romping on it before it is thoroughly warmed up? Until the engine is properly warmed up, the V-tec does not operate. If you are always warmed up before attempting full-throttle accelerations, maybe your temp sensor is flaky so sometimes you aren't getting V-tec performance. One way to tell is where the rev limiter kicks in. If you get rev limited at ~7K, then it could be a function of the temperature or temperature sensor. If it feels sluggish, but still goes to 8K rpm, then I think it is probably something else. Dirty Air filter, plugged injectors, dirty fuel filter, bad gas, fouled spark plugs, faulty plug wires, are all possibilities.
 
Thank you for the suggestions. The car is always warmed up, so the cold 7k rev limiter wouldn't be it. I have all previous records and it has been maintained well and on schedule. I am ready for the 45k though so will do the following in the next few days:

air filter, oil/filter, fuel filter, plugs, techron injector cleaning and throttle body cleaning. I'll start with that, see what happens and then probably have the valves adjusted by a tech. (Side note - what is average price to have that done?)

How do I go about checking the coils?

I pulled the diagnostic code and I had 2 long flashes stored in the memory...o2 sensor if I'm reading the FAQ charts correctly. I reset the computer and ran it hard for a few days and it hasn't reappered. I did notice some interesting comments in the service done about 2 years ago on the car (timing belt, cam seals, water pump, etc.)

It reads:
"Upon road testing the vehicle malfunction indicator lamp lit on freeway decelration. The lamp cleared upon shutdown/restart and did not relight on the completion of the test drive. Upon return and checking the PCM for codes a code #2 (rear oxygen sensor) was found stored in memory. Note: prior to timing belt and valve cover gaskets replacement it was noted that the rear oxygen sensor was severly oil contaminated due to oil leakage from the rear valve cover gasket. The technician cleaned the oil reside from the head and rear oxygen sensor in the hope of saving the oxygen sensor. Upon checking the sensor on a lab scope it was noted that the sensor slowed down at higher rpm. A followup test drive was made and no recoding occured."


What could a possibly interminttent sensor do? If it was a problem, wouldn't I be getting another check engine light? Is it possible to test the O2 sensor?

Thanks!
 
Hey Buddy,

Something else you may want to try\have done regardless is the following. NSXModified did this to my car about 2 thanksgivings ago a few months before I got my (1st and present) turbo.

1-Remove and thoroughly cleanse and hone the intake manifold and throttle body.

This REALLY made a difference in my NA 3.2 setup at the time. With a K&N cold air intake and comptech headers and exhaust, the car was REALLY snappy, it made a BIG difference. For lack of a better term, I would describe it as "Sooper- right-on" if this makes any sense. In other words, if you are used to machines, you can feel when they are COMPLETELY optimized, mine was at that time.

Good Luck!!
 
Jackson said:
I am ready for the 45k though so will do the following in the next few days:

air filter, oil/filter, fuel filter, plugs, techron injector cleaning and throttle body cleaning. I'll start with that, see what happens and then probably have the valves adjusted by a tech.

I think doing all these things is a good idea, including the valve adjustment, which is recommended for every 15K miles.

Just a side note - some of these items (air filter) are normally replaced at 30K and 60K, and others (fuel filter, plugs) are normally replaced at 60K. If you do them now, you might want to keep track of these services individually so that you don't do them again at 60K (unless you're running into the same problems at that time) but do them when the appropriate interval has elapsed (at 75K or 105K or whatever). (And no, I'm not forgetting that there is a time interval as well as a mileage interval for these services.)

Jackson said:
what is average price to have that done?

Typical price for a 60K service, which is similar to what you're considering because it includes valve adjustment, air filter, fuel filter, and spark plugs, as well as two fluids you didn't mention - transmission fluid and brake fluid - is $900-1100.

Typical price for a 45K service, which does not include air filter, fuel filter, spark plugs, transmission fluid or brake fluid, but which does include a coolant flush (which you did not mention), is $600-800.
 
If you are planning on doing a lot of stuff yourself and just want the valves done by a shop, I think I paid about $340 a couple of years ago if my memory serves me correctly $85/hr for a 4 hour job as I recall.
 
Back
Top