Engine Hesitation

[Qshipsta]

hey guys,. i've been having some problems,.(well more like anoyances) with hesitation,..whenever i go from a dead stop,. it seems that between,..1600rpms,. and 2200rpms the engine doesn't seem to be doing much at all,. if anything, .although the tac is moving,. it does this even in 1st gear,. and doesn't do it (that i've noticed) when the engine is cold,....any ideas???

[Chally]

Get your codes checked out first. If all is OK, make sure the connectors are clean on the Coolant Temp sensor, MAF sensor & CAS (crank angle sensor)

Chally

[Q45tech]

32 valve small displacement [274 cu in] V8 are optimized at 1200-2500 rpm for economy and really don't start producing power till 4,000 rpm...........the way they are designed.Get you cake and eat it too, at least as idle and cruise economy is concerned while providing the power of a 20% larger engine at high rpms.........something has to give and it is the low to mid rpm responsiveness!

More low rpm grunt requires more cubic inches like the 350 Chevy or the new 343 ci QX5.6 engine or a 5 or 6 speed transmission optimized to shift at 30 mph instead of 50 mph.

Just when Nissan gets the 5 speed working Lexus/MB/ BMW/Jag and others jump to the 6 speed automatic!......to cover / recover from the problems in the 60-70 mph range [when 5 speed shifts occur]

[elwesso]

Check your ECU codes...... Do a search for that.....

I can bet you'll have the infamous code 34- knock sensors!

[elwesso]

However, on further reading of your post, it sounds like the engine timing is being retarted from the ECU, from running too hot..... Replace the Tstat definitely.....

[Chally]

Mine did the same until I replaced the K/S's, thermostat & Temp sender for ecu.As you say, the tacho is moving but there ain't no Grunt until 4000rpm.With all running OK, you should have reasonable grunt with SERIOUS grunt from 4000rpm.When you plant the pedal from a standstill, the rear tires should at least chirp, if not spin, & there should be fun all the way to 7000rp.

[rover3l]

How easy is it to replace the KS?

[elwesso]

Not fun!!!! It requires doing the plenum job!!!

I am still psyching myself up to doing this!!!

[nuQ]

i just bought the KS's that wes notified us about on ebay. gave serious thought to doing the plenum job myself, but, don't think it's within my capabilities (plus i don't have a garage, or a serious set of mechanics tools). my options in getting it done boils down to keith vanmeter (a now independent, master infiniti tech), or an ex-mechanic who is a friend, charges around $50 an hour. i'll get the under plenum kit from joe, and probably the O2 sensors (anyone know joe's price on these?????). can't wait to make these changes, and can only imagine having more power in my Q. the power from 4000rpm and up is incredible, but would love to have a little more in the 1k to 4k range. i can still spin the tires from a start though, so there's alot of hope!!!!!!!! any opinions?

[elwesso]

You could bring your car down and help me do both!!!!

If you want to wait until Im done and for my writeup, that might be better... Ive spent hours researching this, and I dont think its gonna be too bad, just very time consuming..... But, at least you have the resistance to bite the bullet and have someone do it.... Thats not an option for me, though

Youll be into a lot of labor if you go that route.... Figure at least 10 hours to do it right.....

I wish I could spin the tires..... Im thinking about replacing all 3 of my temp sensors while im in there (cal model)....

Really, you dont need a lot of tools for this.... Just some sockets, wrenches, a torque wrench, and a hose remover (invaluable).....

[nuQ]

when do you plan on doing yours wes????? since the KS's are on the way, would love to tackle this soon, if i had access to a garage would seriously consider doing it myself. a detailed write-up would be invaluable, though,,,hint-hint, wink-wink!!!

[elwesso]

You know its coming!!! Ive promised so many times, I wouldnt be allowed back if I didnt.....

Anyway, at my grandparents house they have a marina next door (which they own) and they have a huge heated shop...... With over 50 years of accumulated tools, plus a brand new parts cleaner (state of the art).... Im doing it over christmas... I should have it done by new years day.....

[nuQ]

CAN'T WAIT!!!!! LOOKING FORWARD TO THAT DETAILED POST! wish i could bring the Q so we could do a double-fix-up!!! your post will determine my decision!!!

[elwesso]

Well if you can my doors will be open!! Just give me the word and you can bring your Q to my place!

This will have a TON of pictures and diagrams!!!!! Anyone will be able to do this!

[nuQ]

YOU DA MAN!!!!!!