Recurring issue

[Ryan Singh]

So this has been happening ever since I got my car back in July 2001. No one's ever given me a solid answer as to what it is...most people suspect boost leak but I've had it tested for that on many occasions and it's always come back as good.

What happens is that it starts up fine, runs completely normal...but then at certain times under acceleration it hesitates. I give it gas, the rpm's rise to about 3500 or so and I can hear the turbo spooling, but then the rpm's stop rising and they fluctuate up and down in an ever so subtle fashion. The turbo continues to spool with the more gas I give it, but the sound of the exhaust gets deeper and deeper at this point and the a/f reads rich. I let off the gas completely, hit it again and it's fine.

My plugs are in great condition, gapped to .28 and are NGK BPR6ES
Fuel is always 94 from Chevron, I always cycle the tank completely...from full to empty never topping up in between.
Engine is stock with a K&N, T28, 3" dp and a GReddy cat back

I've done injector cleaning and replaced my fuel filter but it didn't make a difference.

What else can I do?

Thanks

[Jason Harwood]

Timing or Crank Sensor.

[Greg Durban]

Check your ECU to. I don't know how the 2g's are with stuff like that but it's worth a shot.

[Brett Haviland]

get a datalogger or OBDII scan tool that reads data and look at what your various sensors are doing when the problem occurs.


Personally to me it sounds like a bad o2 sensor.

[Jason Harwood]

get a datalogger or OBDII scan tool that reads data and look at what your various sensors are doing when the problem occurs.


Personally to me it sounds like a bad o2 sensor.

He would throw a CEL and the car would go to base maps. Wouldnt cause it to run funky like that. I would know! I had a bad o2 on mine haha....

[Ryan Singh]

Thanks guys, I will look into that.

[John Hartman]

as his is an early OBD2 car it most likely won't throw a CEL unless the event happens for a long enough time, or more frequently.  If you DO get it to turn on the light, you can not only pull the code, but the freeze frame data(data on the other engine sensors at the time that the light went on)  this data can be quite helpful determining what is going on.

For example, if the car had been running for a while and was warmed up, but suddenly the air fuel ratio was in the 9's and the coolant temp sensor for the ECU was reading -45, this will be your biggest clue 

As well, not sure what you mean about base maps, but if you mean limp mode, depending on what is actually wrong, again, it might not if its not for a long enough time frame.

It may be something temporarily plugging the exhaust such as a broken catalyst substrate.

It could also be in the transmission possibly, something holding the engine back?

It could easily be a connection at a vital sensor like the maf or the ECU plugs being partially loose or corroded.

Without driving it, its hard to diagnose something like this.

[Ryan Singh]

Thanks for the input John...it's definitely not throwing a CEL code, but my money's on the tranny. It's been fucked since day one, but it just won't die to the point where I have to replace it...so I wait...for its death. :::thunder::: mua ha ha ha ha ha!!!!!!!!

LOL

I don't think it's the exhaust either because...well I don't really have a reason to think that besides the fact that I love it too much. Lol