As you can see by the wideband review I have a hesitation in the 5k rpm area. It seems to only occur in 3rd gear and when the engine is cold it doesn't do it. The a/f is steady it just seems to pause for a second and then keeps on reving. It doesn't always do it at 5400 like in the pic but always in the 4800-5500 area.

I thought it might be timing but I put a resisitor in the KS and same results.

Any help would be appreciated.

 

I believe that's the switchover on 2K2-2K3 manifolds.

Check Studmans' dyno, he's got a dip at 4800ish rpm on these two:
http://maxima.theowensfamily.com/ima...-20031010a.jpg
http://maxima.theowensfamily.com/ima...-20031010b.jpg

And then at about 3900rpm on this one:
http://maxima.theowensfamily.com/ima...-20031010c.jpg

 

All of those pics you listed are under 4k I get that one too but only in 1st gear. After that the shift is above 4200 so the VIAS switchover only happens once.
This is a new one I never had it before a couple of weeks ago.

In that pic the shift is now at 4800 because of the raised limiter but even if I let the trans shift itself the dip is still there.

This is what is used to look like before this developed.

 

Look again between 4500-5000rpm right where the hp/tq cross.

 

I tried tieing the VIAS open and still the same result so its not the VIAS.

 

I was thinking maybe your clutch was slipping, but that's after the torque peak, correct?

Just guessing Jime...I don't know.

 

Darn, here I thought you were going to straighten me out.

Its an auto, no clutch. It doesn't feel like anything slipping, its more like the engine is being held back temporarily.

 

Haha...clutch.

I need more information, OBD scans maybe?

Also, you *MIGHT* have a tech do a ride-along with you and a Consult-II to figure it out.

 

Just an update, I still have this problem, its always only in 3rd gear (auto) but not always at the same RPM unless I let it shift by itself. It does it approx 300-400 RPM above what the RPM is after the shift, if I shift at 7k its over 5k but if I auto shift its around 4300.

I have monitored the timing, a/f etc etc and nothing seems to change when the occurs. Its not too noticable unless you look at the chart but you can feel it if you pay attention. I don't think its hurting my 1/4 times that much, I did four 13.6 runs yesterday and every one did it because I kept everything warm so it would be consistent.

I am runnng the IHRA Summit Series this year. Its a 15 event season, (0-14.99 sec cars) and I am racing n the MOD class so some pretty fast cars and mostly all V8 guys. http://www.torontomotorsportspark.com/dragway/home.htm

Got rained out yesterday after I got 4 time trial runs in. I am somewhat reluctant to spray while this is happening but I am going to try a small shot this week just to see what it does. Otherwise I will just race N/A until I get it figured out.

Right now I am going to start monitoring the trans fluid temp before and after cooler to see if its temp related and maybe I can cure by bypassing the stock cooler or adding another external. Just not sure if the trans ecm would do that if the temp was hot or not.

 

I believe its the TC locking up bc mine did the same thing and only in 3rd gear. Next time this happens throw the car into 4th and see what happens. It should unlock the TC and the rpms will jump like 500rpms or so. I believe its pretty normal, all the 02 Autos that I have come in contact with have done this. Mine did it once the car warmed up also.

 

Funny it didn't do it before but then I wasn't holding in 3rd like I am now, it was always in drive. I didn't think it locked up at WOT but whatever, if it cures the problem I will leave it in D until it gets higher in the rpm band in 3rd then shift back down to 3rd to hold it from shifting at the normal 3-4 shift point.

I will check it out today, Thanks Matt.

 

I've also done this on the dyno to see what the dyno would read and it spikes the dyno like 3-4whp when this happens. Basically I leave the car in 3rd(D) and right when the hesitation starts I knock it over into OD. When this happens, to me it felt like the TC unlocking again but if you try to go back into 3rd again it will hesitate again. Its very weird thats all I can say.

 

Update: Just went out to try it, had 2 days of rain so couldn't check earlier.

I made 3 runs until it started to do its usual RPM drop in 3rd gear.

Then I left it in 4th and like magic no RPM drop.

Did another run in 4th and after it got over the point where it usually drops I shifted it back to 3d with no hesitation or rpm drop.

Repeated the above another couple of time with similar results.

Thank you Matt, I owe ya, it was driving me nuts.

 

Sounds like the torque converter locking up. Is it supposed to lock up when you have the shifter in 3rd?

edit: nevermind I'm retarded. I didn't read through the whole thread just remembered the initial post from back when it was new. didn't know you guys had already figured it out.