Before you ask, I've done some searching and come up with a potential problem with it thinking the car is in neutral and artificially sets the rev limiter lower. Now, I'm pretty sure it feels like the rev limiter as I used to be able to rev to 8k and just a little past it and voila! hit rev limiter. I understand this happens when the car is in neutral or if the car isn't up to oil temps yet but this is happening to me at warm temps and with the car in gear. I can't get past 7.5k rpm in 1st, 2nd, 3rd,.... haven't tried 4th or 5th (think it might be going too fast to try it). Are there any issues that could potentially be causing this problem? I know I recently changed out my vehicle speed sensor because my speedometer just kept working, not working, working... but this problem was present before the speed sensor took a crap. Can anyone give me any direction on where to look for what causes the ECU to artificially do this to the car? I can drive the car fine but it does feel annoying that I can't exactly push the car like I should be able to.
-
Protip: Profile posts are public! Use Conversations to message other members privately. Everyone can see the content of a profile post.
Problem with car not letting me rev past 7-7.5k rpm... Why?
- Thread starter funnieguy
- Start date
What does it idle at?
I would guess clogged fuel filter.
I've already tried the simple things. I've reset the ECU by pulling the clock fuse. I've pulled the battery, then tried to start it and found I couldn't until I pulled the clock fuse. The car idles fine. There is no problem during normal driving. The car goes into vtec just fine too. I just can't get past 7.5k roughly. I can't imagine it being the fuel pump cause the car does start up and drive fine. I might be concerned about the fuel filter but I'm not sure either. This sounds and feels like the rev limiter. I even tried hammering that rev limiter and nope, no luck. I repeatedly get turned back. The only thing I can think of is I did jumper the hood latch so the factory alarm wouldn't arm and go off repeatedly at really bad times when I open the door with the key. I wonder if this is preventing me from getting to 8k rpm. Does anyone else have this issue?
Dumb question...but is the engine at operating temperature? Cold engine = 7k rev limit
If the new 'limit' keeps dropping (ie to 5,000 RPM, then to 4,000, etc) I would definitely say fuel filter. How hard is it to change on an NSX? It's incredibly easy to do on my 240SX, I just have to do it every few thousand miles.
Car is up to operating temps when I try to do it. I didn't have any CEL other than for the speed sensor which I already fixed. The rev limiter doesn't move anywhere but 7.5k roughly. It also wasn't the hood latch either, just tested it. Car drives perfectly fine otherwise... I will have to look at the coolant sensor though? Car does go up to normal operating temps though as indicated by the temp gauge... So I'm not sure if this is a symptom of a bad fuel filter. I'll take a video some time of this.
Do you know when the last time the fuel filter was changed?
if its old perhaps change it and eliminate it as a source.
Have you shorted the service check connector and read the error messages?
That may provide a clue if an electronic part has failed.
Fuel shuts off at 8300 but perhaps a bad sensor may result in an earlier shutoff?
if its old perhaps change it and eliminate it as a source.
Have you shorted the service check connector and read the error messages?
That may provide a clue if an electronic part has failed.
Fuel shuts off at 8300 but perhaps a bad sensor may result in an earlier shutoff?
- Joined
- 15 May 2004
- Messages
- 6,898
These are two separate sensors, one for the gauge, on for the ECU.
It's highly unlikely it's a clogged fuel filter as you would have problems in other rev ranges too or significantly less power.
That wasn't the case when mine was clogged. And it makes sense too. Higher rpms require more fuel pressure. It will work fine at WOT until a certain point, as the fuel demand is less (think, with all rotations having same amount of fuel in each [at equal throttle], less rotations per minute = less fuel demand). It should start to lose power not more than a few hundred rpm's from the limit as the mixture goes leaner and leaner once the (lowered) maximum fuel pressure is being put to use.
- Joined
- 15 May 2004
- Messages
- 6,898
You're correct, the ECU corrects for having less fuel than expected, so it can be undetected for a long time but one should be able to feel that the car has less power. I think that if the rev limiter kicks in the ECU is already going crazy with adjustements, so you should feel it a little bit sooner.
But anyway, if the OP has no record of idea of when the fuel filter was changed, it's not a bad idea to rule it out.
As for a comparison: people with weak fuel-pumps report hesitation below 4k rpm. The hesitation is obvious but what IS more obvious is that the car lacks low-end torque. But a long as it runs fine people think it's ok.
But anyway, if the OP has no record of idea of when the fuel filter was changed, it's not a bad idea to rule it out.
As for a comparison: people with weak fuel-pumps report hesitation below 4k rpm. The hesitation is obvious but what IS more obvious is that the car lacks low-end torque. But a long as it runs fine people think it's ok.
The S14 ECU must be less clever, then. I assumed when he said rev limit that it was not like a redline limit that will bounce but a limit that will it will struggle to reach and will fluctuate at. I was hitting a "rev limiter" in that sense when mine was bad. If it bounces like an electronic limiter, then I would not guess fuel filter.
Yeah, without a record, it'd definitely be a good idea to change since it's so cheap and easy.
Yeah, without a record, it'd definitely be a good idea to change since it's so cheap and easy.
Last edited:
^Agree with this. My car had the same symptom when I bought it. Bad temp sensor was the cause. See page 11-48 in the '91 manual. Disconnect the harness and measure resistance across the sensor with the car fully warmed up. You should get 200-400 ohms. I'm guessing you'll read higher than that.
I wonder which sensor this one is. I think I purchased the right one, but I hear we have 4 different coolant sensors. I've done a search and they seem somewhat confusing as to which one does what, but it looks like one is underneath the throttle body... and another to the left of the thermostat? I'm not exactly sure where the other 2 are.
- - - Updated - - -
Well, I tried the one to the left of the thermostat and I found I had purchased the wrong kind of sensor?
And this is what I bought...
Are you using the OEM tach to measure the engine speed? If so, are you sure that the tach is correct? It is possible that the tach meter movement is out of calibration, getting low voltage or that the tach drive circuit is buggered (less likely). If your car is OBDII, you can pick up the engine RPM as freeze data and compare it to the tach reading. If you don't have a code reader, you could do the engine RPM, drive ratio, wheel size calculation and compare it to the actual vehicle speed (use a GPS as your speedometer could also be out of calibration if you have low instrument voltage). Fuel limiting in OBDII cars is supposed to occur at 8300 RPM according to the service manual. Operation of the rev limiter does not appear to be captured in freeze data according to the service manual; however, I expect that it might be there. Also, you should be able to see the injector pulse widths which would give you a sure indication if the ECU was initiating fuel shut down.
I think he'd notice if the tach was just reading wrong. I don't even use mine a lot, I just go by the engine note...
I'm thinking Old Guy's idea is worth checking out. Don't most shops have an induction-based sensor that they can just clamp around a spark plug wire and read the RPM?
And I'm not so sure you could hear a difference of 800 RPM if you were used to the car turning 8300 when the tach reads 7500.
And I'm not so sure you could hear a difference of 800 RPM if you were used to the car turning 8300 when the tach reads 7500.
Is the CEL on?
No, the CEL is not on. I did find the temp sensor underneath the throttle body and replaced that one. Unfortunately the problem still persists. I will probably try the other one on the rear bank of cylinders next. I don't know what kind of sensor that green one I initially pulled is but it plugs up just like a coolant temp sensor. I just don't know where to find one that has a hole on the end instead of a small shaft.
- - - Updated - - -
I mean the one below the thermostat.
