My Car Idles Like An American V8

[S2G-Unit]

***05/14*** SOLVED***

I finally drove my 1994 (manual) this week after it being stored since December. At idle the car started off shaky & sounded like a V8. There was no check engine light at all though.

In the last few years, here are some items that have been changed:
-Spark Plugs: May 2011 & May 2015
-02 sensors: June 2014
-Fuel filter & valve clearance adjusted: April 2012 (when timing belt was done)
-Main Relay: June 2014
-Ignition Switch: June 2014

A few years ago, I wiped down the inside of the throttle body (i didn't remove it though)

Yesterday, I cleaned out the K&N air filter (I didn't over oil it in my opinion & let it dry overnight)
Today, I cleaned the Air Intake Temperature sensor (seen here
http://www.nsxprime.com/forum/showthread.php/159564-Is-your-NSX-failing-smog-Read-this

After cleaning out the Air Intake Sensor, after the first startup the idle dropped lower than normal as if it wanted to stall but then returned back to around 800rpm. If I tap the gas, again the idle would drop & it's like the car wants to stall but it doesn't stall. I took the car for a quick drive for 3-4 blocks & it the throttle felt much more responsive. I also noticed since driving the car this week that the car a faint smell of possibly fuel.

I've also reset the clock fuse twice.
I've never changed or checked coil packs (I remember reading some people have cleaned off rust or replaced coil packs)

-Should I drive the car a bit to let the ECU re-learn the air fuel mixture?
-I'm guessing the throttle body needs to be cleaned again according to many threads?
-Could it be because of bad gas from sitting on a battery tender & not being driven/started for a bit longer this year (horrendous weather this winter)?
-I see mention of this 36450-PR7-AO1 here: http://www.nsxprime.com/forum/showt...lve-location-and-Part?highlight=36450-PR7-AO1. It seems to be discontinued?


***05/10 I did the O2 sensor test & the car still has a faint, quick, puttering sound****
***05/11 Here are pictures of my front coil packs. All 6 coil packs test exactly at the proper 1 ohm resistance indoors. 1 rear coil pack had some moisture on it, one seemed normal & the final rear coil pack had a huge amount of rust on it. I'm guessing it needs to be replaced but I can anybody answer why it still reads the proper resistance??
***05/14 2 of my 3 spark plugs & coil packs had corrosion from water entering the rear cover. I've replaced the 3 spark plugs & removed the corrosion from the coil packs for now & the car runs really well. I will have my garage remove & clean out the throttle body. This week I will also clean out the Fast Idle Valve & EACV. I've also ordered gaskets to replace the older one's on the coil pack cover to prevent more water coming in.
***05/13 I ordered a fuel filter & rear coil packs from www.amayama.com & they should be here in about 1-2 weeks but car is fine now.

 

[DocL]

I'd start with bad gas, possibly contaminated from condensation in the tank.

 

[S2G-Unit]

I'd start with bad gas, possibly contaminated from condensation in the tank.

My 2 main ideas were bad gas or throttle body needs cleaning.


Anyway, drove the car tonight & went on the highway. There is no more RPM drop when the car is started or when I tap the gas. The car seems to stutter or struggle if I try to roll through a stop in 2nd gear. Doing so causes the car to come very close to stalling, which it never did before.

On the highway at about 60mph & 3000rpm, it feels like there is a very slight jerkiness in the car. The feeling is somewhat similar to when cruise control starts & takes over the pedal, only it's more faint. Almost like there is a ton of wind resistance from time to time.

Still no CEL even after driving for a while. Is it possible I lost the code for good with all the ECU resets or should a CEL come back orshow up after driving the car for a bit?

 

[BAVARIA]

S2G -- my /94 sits in my garage for a good 5-6 months over the winter on a battery tender. Car has 53K miles. Never had an issue w/gas in that length of time. This is very unscientific and I'm sure there is a way to check a bunch of things to figure out the issue but anecdotally a few years ago I had a slight stutter when accelerating from low rpm which sounds similar to what you describe in post #3 above. It turned out to be one bad spark plug. There was likely no good way to figure this out other than replacing all 6 plugs which is what we did. Coil packs getting pretty old on these cars and sometimes as you probably know develop hairline cracks or worse. Could one or more of those be on the way out? Just my 2 cents FWIW. Best of luck.

Jeff

 

[docjohn]

the only time my car ran something like that was when I ran the car on 5 cylinders , had to pull one of the spark plug/coils due to failed valve springs....of course I replaced the engine ...

 

[Old Guy]

My car went into storage mid October and I pulled it out April 22. On coming out of storage it restarted exactly like it starts every day. Unless you put the car into storage with gas that was already 6 months old, your period of storage and being on a battery tender should not be an issue. The NSX has a closed Evap system so if it is working correctly, the car cannot accumulate moisture in the gas during storage like old pre emission control cars can. As a note, I don't bother with a battery tender, I just disconnect the battery.

I would be inclined to remove the idle air control valve and clean it. You can find a number of threads on Prime describing the removal and cleaning of the valve. A good place to start would be to get the service manual for the car (link on the red bar at the top of Prime web page) which describes removal and I expect testing of the valve. Wiping the inside bore of the throttle body won't hurt; but, probably doesn't do much. Its all the little passages in the throttle body that need to be cleaned out. Again there are threads on Prime discussing cleaning of the throttle body.

As an observation, when you pull the clock fuse, you clear all existing error codes and you wipe the saved fuel trim values. If your car was running with high fuel trim values, resetting the trims to zero could result in poor operation. It may take a significant amount of driving over the full engine operation range to re establish those trim values. High trim values may be an indication of other underlying issues. If your trim values get really high the ECU should generate an error code. Unfortunately, you have a pre OBDII ECU so you can't access your trim values to see if they are an issue.

As long as you don't damage something like the cover gaskets, pulling the ignition coils to check for contamination or signs of flashover might be a useful thing to do. This may be a particularly good idea if you are one of those people who love a sparkly clean engine and wash it down at every opportunity. If everything checks out good reassemble with dielectric grease applied to the little rubber boot on the coil snout to keep everything happy.

Your pre OBDII ECU does not have the coil voltage misfire detection circuit. The misfire error codes are probably generated by an ECU algorithm that monitors the rapid, brief changes in crankshaft RPM that occurs during misfire. To prevent false error codes (driving on very rough roads can trigger the error code) the ECU has to record a number of misfire events before it generates an error code. As such, it may take a bit before you generate an error code even if you are having misfires. Check the service manual to see if there is a way to retrieve stored codes on the pre OBDII ECUs. You might want to investigate that to see if you have any stored misfire codes.

My personal opinion is that oiled element air filters are an invention of the devil and offer no upside relative to the OEM pleated paper air filter. However, that is just my opinion.

 

[docjohn]

agree on that last statement..

 

[BAVARIA]

+1 as regards second sentence of first paragraph of Old Guy's post. Exactly same as my car. First turn of key. No smoke, no idle issues, no funny noises, no strange smells. I do love Mother Honda.

 

[S2G-Unit]

I ordered the spark plugs & 2 new O2 sensors this morning.

By the way, my gas mileage is currently terrible. I could probably only do about 150 miles or so with this problem. Maybe an O2 sensor, coil pack or on of the different sensors & valve's that need cleaning.

I'll update as I go but will still take anything tips on what to clean or check.

Thanks

 

[warrenw]

If the battery was disconnected or the clock fuse removed, it will idle a bit rough until the ECU re-learns.
I put fuel stabilizer in my fuel before 6 months of storage and it runs a bit rough in the spring, but once warm it is fine.
Multiples of 1200 RPM, this engine is a bit rough. 1200, 2400, 3600 RPM. It has to do with the number of cylinders and the 90 deg V design.

 

[Old Guy]

O2 sensors that have gone bad will definitely cause high fuel consumption. The ECU reads a lack of voltage from the narrowband sensor as a lean fuel mix and cranks up the fuel pulse width in an attempt to correct the mixture back to normal. However, if that is happening, you would expect the rich fuel mix to show up as a color change on the tips of the spark plugs. Pulling the spark plugs to check the color of the tips would be a useful indication that you have a mixture problem. If the plugs come out the normal white to slight buff color, you probably do not have a fuel mix problem. Also, if the O2 sensors are faulty, you would typically be running a lot of fuel trim and that should show as an error code (mixture out of range or something like that). If you have been driving a bit since you last reset the ECU, I would check to see if you have any stored error codes. If the plugs look good and you don't have any stored fuel related error codes, I would hold off on the O2 replacement, unless you like to do that sort of thing. If you changed the O2 sensors in 2014, 4 years seems like an incredibly short life unless your engine chronically runs rich and consumes oil. Those factors tend to shorten O2 sensor life. MY 2000 NSX, 2003 pilot and my son's 2005 RSX are all running on their original O2 sensors with no issues to-date.

 

[Kaz-kzukNA1]

Before the storage, any sign of similar issue?


First thing in the morning when you start the engine (rpm would be around 1,500rpm), does it sound the same like when you are having problem at idle rpm?
During warm up sequence, it's out of idle control loop.


Even with full OBD2, misfire detection is not guaranteed so no CEL doesn't mean you don't have misfire.
Already seen several OBD2 NSX with distinctive misfire (random but frequent pop at the tail pipe, intermittent hesitation while driving, etc) yet no CEL for a long time/miles.


Before replacing the O2 sensor, pull 7.5A Clock fuse out for more than 10sec, place it back, disconnect both Front and Rear O2 sensor connectors and then start the engine.
You will immediately get CEL.
This will first reset the ECU and then force it into Open loop mode with base map with default adjustment.
It will run rich.

If your issue is still the same before/after disconnecting the O2 sensor connectors, the cause of issue is very likely to be not O2 sensor related.
Once done, re-connect the O2 sensor connectors, reset the ECU again before starting the engine.


Fuel filter 6 years ago???
How is your fuel pressure?


Even with dirty TH body, EACV, etc, normally you will get rough idle control but without V8 sound.

From what you wrote, seems more like misfire.


You may have bad IG coil, intermittent ignitor module failure, dirty INJ, dirty EACV, etc but start with the easy bits.

Kaz

 

[S2G-Unit]

Before the storage, any sign of similar issue?


First thing in the morning when you start the engine (rpm would be around 1,500rpm), does it sound the same like when you are having problem at idle rpm?
During warm up sequence, it's out of idle control loop.


Even with full OBD2, misfire detection is not guaranteed so no CEL doesn't mean you don't have misfire.
Already seen several OBD2 NSX with distinctive misfire (random but frequent pop at the tail pipe, intermittent hesitation while driving, etc) yet no CEL for a long time/miles.


Before replacing the O2 sensor, pull 7.5A Clock fuse out for more than 10sec, place it back, disconnect both Front and Rear O2 sensor connectors and then start the engine.
You will immediately get CEL.
This will first reset the ECU and then force it into Open loop mode with base map with default adjustment.
It will run rich.

If your issue is still the same before/after disconnecting the O2 sensor connectors, the cause of issue is very likely to be not O2 sensor related.
Once done, re-connect the O2 sensor connectors, reset the ECU again before starting the engine.


Fuel filter 6 years ago???
How is your fuel pressure?


Even with dirty TH body, EACV, etc, normally you will get rough idle control but without V8 sound.

From what you wrote, seems more like misfire.


You may have bad IG coil, intermittent ignitor module failure, dirty INJ, dirty EACV, etc but start with the easy bits.

Kaz

Ok, thanks Kaz I will try your tips & I will do the O2 sensor test.

Before storage there were no issues with the car but I remember now, that I did start the car & move it back & forth a little bit about one month ago at the end of March/beginning of April. When I did that the engine sounded like it always has, (no delayed puttering like a V8). I did go on vacation twice for a few days & when I got back the battery was dead because I didn't put on my battery tender.

I checked the battery voltage in the morning yesterday & it was at 12.46 volts.


***05/10 I did the O2 sensor test & the car still has a faint, quick, puttering sound. Should I not drive the car anymore until this is fixed????****
Since my last ECU reset, the car has no more issues of low RPM when the car is started or if I tap the gas. The only issue now is the faint but pretty quick puttering sound.

****05/11 All 6 coil packs test exactly at the proper 1 ohm resistance indoors. 1 rear coil pack had some moisture on it, one seemed normal & the final rear coil pack had a huge amount of rust on it. I'm guessing it needs to be replaced but I can anybody answer why it still reads the proper resistance??

***05/14 2 of my 3 spark plugs had corrosion from water entering the rear cover. I've replaced the 3 spark plugs for now & the car runs really well. I will have my garage remove & clean out the throttle body. This week I will also clean out the Fast Idle Valve & EACV.

 

[Old Guy]

The measurement of resistance is just an indication that the primary winding is intact (no open circuit or bad connection). It is not an indication of the integrity of the high voltage insulation on the coil or flash overs on the nose of the coil which would lead to failure of the spark plug to ignite the fuel mix. Without the use of a scope, there is no way to visually confirm compromised internal insulation that is causing a high voltage flashover. External flashover on the high voltage terminal of the coil (the snout of the coil) will typically result in carbon tracking on the surface of the coil. Examine the snouts of the coil to look for tracking. I am curious about what that grey stuff is that is on the outside of the coil snouts.