Prom tune in the Northeast

[91MinuteMan]

Originally Posted by ZR-1 Mack

Out of curiosity is there a problem or are you just adding some custom features on the chip you have? The reason I asked is adding the custom feature is only $100 while the dyno tune is $200/ hr. (1/2 consultation and 1/2 facility charge) plus the travel expense.

No major modifications in the works--it is just that beneath the sound of the exhaust and tire road noise I am almost sure I hear steady knocking on acceleration, but honestly I wouldn't bet my life on it. I am going to pull the plugs this weekend and replace them with one step cooler plugs and see if this helps. I also am not happy with the idle as it occasionally, randomly and infrequently has started to fluctuate. The car also tends to crank 3 or 4 times before it starts, warm or cold, although sometimes it starts quicker. Overall the runs pretty good and I always have to consider that I may be too critical.

[FU]

Knocking or pinging ?
One range colder than stock is good for a car that is stock or some top end mods.
Red Line injector cleaner may help out a bit.

[91MinuteMan]

Originally Posted by FU2

Knocking or pinging ?
One range colder than stock is good for a car that is stock or some top end mods.
Red Line injector cleaner may help out a bit.

I would say ping is a better description. The engine is mostly stock with a K&N filter and port matched intake plenum and exhaust. I will try the red line.

[91MinuteMan]

Originally Posted by FU2

Knocking or pinging ?
One range colder than stock is good for a car that is stock or some top end mods.
Red Line injector cleaner may help out a bit.

Well, the colder plugs are in and I've done a few high rev blasts down the Mass Pike with the red line in and it sounds a lot better. New question, I have a habit of drifting to a stop clutch in with gears in neutral (dating myself, I learned on a 3 on the tree and this is how my dad taught me to drive, so it is now well engrained). From the time I put in the clutch until I come to a stop the revs run at about 1200. When I come to a full stop they go down to about 700, which is the normal warm idle speed. The Z is my first manual with a computer controlling the engine so any thoughts whether this is typical?

[tomtom72]

I think that the idle speed "hang" in neutral @ coast down is a program that reduces exhaust emissions upon de-accleration. Back in the old days, around the early 70's, some cars had de-accel valves. I know my 72 V6 Capri had one. It did the same thing that my 90 Z does when you coast down from speed in neutral to a stop, I'm that old too!

It seems that the program will not let the motor return to idle speed instantly but rather the idle speed seems to come down in two steps & takes a few seconds to get back to 6-700 rpms as I coast down to a stop in neutral in my Z. I even notice that if I coast down to a stop in gear it seems like I loose my compression breaking for brief periods & then it's there & then it's not & then it's there again. I figured that since my ECM was not setting any codes that this must be part of the emissions program?? I don't know enough about EEC motors to say for sure but mine does this all the time and it's passed emissions testing two yrs on a dyno here in NYS so I just figured that it is "normal". I would think it prevents a rich condition during closed throtle de-accleration??? I know that's what the idea of the "de-accel" valve was in my Capri, rich emissions prevention @ de-accleration.

[91MinuteMan]

Sounds like a reasonable explanation to me. Knowing that this happens to at least 1 other Z takes it off my mental check list. Thanks.

[ZR-1 Mack]

Nothing wrong with getting the most out of your car. I was thinking about a Haibeck chip but I don't think I want to do it until after I change out my existing OEM injectors first $$$$. I replaced a bad primary injector last May and the next time one goes I'm doing all 16.