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Hesitation and Random starting failures

JAKiii

JAKiii

Registered Member
Joined
9 April 2003
Messages
47
Location
Hermosa Beach
Here's one for the Braintrust:

I have experienced the same hesitation under 3k RPM as some other threads discuss. The car feels like it's' running lean and rough until I give it more gas and then the power will pop back in. The problem only happens between 1k and 3k RPM. My coil pack check was strange, I got a 1.4 reading on every pack, front and back. Even though this is above spec, the consistency of the readings suggest to me that there is no one bad coil, or that my meter was off. I removed some of the rust from the rear packs, applied electrical grease and put the car back together, but this did not solve my problem.

I'm reading that some people have solved this problem by replacing the O2 sensors, so maybe this is my next move. But there is one other symptom:

Every couple of weeks I will try to start the car and it will not fire. I will crank a few times, waiting 30 seconds, and try again. Every time this has happened I have eventually been able to start the car. It happens in warm and cool weather, when the car has been recently driven and when it has sat overnight. The frequency of this failed start is increasing slightly.

I wonder if these problems are related? I have Comptech headers and exhaust, otherwise stock. '92 70k miles.

Thanks for any insight,
jamie
 
ok, I will try cleaning the connector, or more accurately, I will try finding the connector and then cleaning it. Do we think a dirty connector would cause the starting failures? That one seems like a fuel supply issue to me...

jamie
 
Try taking the car out for a test drive. Accelerate and decelerate in 3rd gear from about 10mph to 60mph and back down to 5mph. Do this a few times in 3rd and also in 2nd. See if this produces a CEL 42 or 43, which would indicate a possible O2 sensor problem.

.O2 :)

DanO
 
When you start the car, let the fuel pump fully prime, then turn the key over and see if you get anymore starting problems.

Let us know how things turn out.
 
I was plagued by "hard starting" for quite a while. It got worse and worse over time. I let the pump prime (I could hear it) over and over again and it still had hard starting. Sometimes it would start right up, sometimes not and sometimes only on the second key off/on.

You really should consider having a main relay in reserve for the non-start issue. Just keep it in the car and you can replace it one day when your car completely dies...just like mine did (at LAX, in the passenger drop off lane, with security giving me a hard time, the entire time).

It did take a few months for the car to completely die. It did it one day driving home: the engine just cut out. I reached back and banged on the relay and it took off again. Once more at a light and then a week later it completely died (at LAX).

Fortunately, I had managed to order a new relay and have it in my trunk. I prowled the forums for the likely cause. When it failed I popped off the top rear bulkhead cover, pried up the entire relay, used a key to disengage the connector clip and clip in the new relay. Later when I had a 10mm wrench I removed the old relay and properly mounted the old one. I did this all while under scrutiny at LAX and having them come over every couple of minutes to "make sure I was okay".

If am wrong: you need to keep a replacement MAIN RELAY in the trunk anyways. Especially when it is giving you this kind of warning...

If I am right: you will get to be towed to your local dealer, two days down time while they order the part.
 
well I orderd some parts today so I should be swapping by tomorrow night: an O2 sensor, a main relay, and a fuel filter. Who thinks the failed starting problem is related to the hesitation problem? How do I read a CEL code? Why do main relays go bad? What's a main relay? What's the best way to look cool when your Japanese supercar won't start in the Ralph's parking lot?

thanks for all the input,
jamie
 
I don't know how the main relay fails, but I took it apart. It is very robust and well made...should never fail. But it apparently does.

As for looking cool. It is a great reason to go up to some hottie and [humbly] explain how your really expensive car has failed you again and could she please help you [with something, it is not important what]. Always ask for her name first, if she is even slightly "interested" she will ask your name in return. If she doesn't ask for your name: she isn't interested [don't waste your time or hers].

As for the CEL, it is really called a Malfunction Indicator Light (MIL). Instructions are easy and they are avail either on NSXprime, the forums or your manual.

Use penetrating oil on the o2 sensor a day or two in advance. It is necessary to use a tight fitting wrench or you may round the nut. Do not slowly pull...just a quick "jabbing" motion to loosen it.

That's all I know about life dood. Good Luck

Drew
 
JAKiii said:
well I orderd some parts today so I should be swapping by tomorrow night: an O2 sensor, a main relay, and a fuel filter.
Click to expand...

I’d replace the main relay first because that’s the easiest. Because you have headers, replacing the O2 might be a difficult job, especially the front one. I don’t thing the fuel filter is the culprit because you say the car runs fine above 3k, which is where I think fuel flow would be restricted the most but if the filter is due for replacement then it’s a good idea to change it anyway. Have you performed the road test that I mentioned above? If you do get a CEL or MIL as drew says, it will be the “check engine” light on the dash. You can “pull” the code by jumping (a paperclip works) a connector under the glove box and read the series of flashes that the indicator makes (see service manual pg. 11-18).

You might be able to tell if the two symptoms are related by disconnecting the connector to an O2 sensor connectors and see if the hesitation persists. Disconnecting the sensor will produce and immediate check engine light but the car will be ok to drive for short distances because the ECU goes into a default mode where it supplies a pre-programmed fuel mixture instead of reading from the O2 sensors. The car will probably idle badly at startup. Take it for a test drive to see if the hesitation is persists. If it does, then it might not be O2 related.

If you plan on replacing the O2 sensors, it might be worthwhile to invest in a specialty O2 sensor wrench (22mm). Let us know if you plan on replacing the front sensor so we can give you tips and service manual pages as it might require some amount of part removal.

Good luck,

DanO
 
I drove to work this morning and tried the O2 sensor test, accelelrating to 60 and back down to 5mph a few times in 2nd and a few times in 3rd gear. No CEL. The test was not perfect as traffic and roads were not perfect, but I got 2 or 3 cycles in, if that's sufficient. I guess the first thing to try is disconnecting the O2 sensor and see if the hesitation goes away. I will change the main relay and keep the old one as a spare even if that doesn't solve my non-starting, which has started perfectly every time since this thread was born. The fuel filter needs changing anyway.

jamie
 
Update: It looks like the Main Relay was to blame for my non-starting issue. Thanks to the braintrust for this diagnosis. I learned from Drew that you can smack the panel behind the passenger seat if the relay isn't cooperating, and sometimes convince it to try harder. Good trick. Tonight I replaced the part so we'll hope this problem is history. I will work on the hesitation this weekend.

jamie
 
I've narrowed my hesitation problem down to the front O2 sensor. However, as predicted I am having trouble removing the part. I have partially stripped the sensor despite using what I think are the correct tools: alternately a 22mm wrench and an O2 sensor wrench. Does anyone have a good idea how to get this thing out? There is no easy way to remove the Comptech header section so I really don't want to do that. Photo attached.

jamie
 

Attachments

  • front o2 sensor.jpg
    front o2 sensor.jpg
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theres a o2 sensor tool has an opening on the side, that way you can use a wrench.

btw if you are going to throw out the old "BAD" main relay I would love to have it for a few bucks and will pay for shipping. I've had a few bad relays before but I threw all the bad ones out... just want to do an autopsy on it :)
 
nsxexotic,
I was going to keep the old relay in my trunk as a backup, even though it was not working very well. I used the O2 wrench with the hole in the side, but to no avail. In fact, that tool flexed under pressure and I found a 22mm was better. But I was stripping the O2 sensor with both tools. -jamie
 
Jakii: regarding seized O2 sensor...you should get the "gas wrench" and heat up the bung. Apply vice grips and violently ( sledge hammer style) apply turning strokes.

It probably rounded off because you went "slow" when trying to loosen it.

nsxexotic: the main relay is pretty darn simple. Not much to it and bench testing showed the relay making contact. Didn't get the VOM out, but I suspect the contacts get slightly corroded or out of sync. I am thinking about just keeping a pinout of the connector so I can bypass it in a time of need.
 
UPDATE:
Strangely, since I was unable to get that O2 sensor out of the car, my hesitation problem has gone away completely. I had disconnected both O2 sensors and driven the car briefly, so maybe this reset something? The only other thing I did was spray contact cleaner on the sensor connectors. It's too early to declare the problem solved, I just thought I would report on this development...

jamie
 
Last edited:

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