Bogs for a second and then takes off

[StickWalker]

First off, I replaced the injectors with new FIC injectors and pinned the secondaries open with Hiabecks chip for 2ndy deletion. I did this swap around 500 miles or so ago and also changed the fuel filter at the same time.

Now the issue starts after a few minutes of driving before that it runs great. (Never has an issue from a stop) When the issue occurs I am in a gear coasting (foot off the gas) at around 2-4000 rpm, and when I hit the gas pedal it bogs down for a second or so and then takes off and pulls to 7000 no problem. It only ocurrs after a moment of high vacuum once its warm. I have replaced the MAP sensor and hose with no change, drove around with a fuel pressure gauge on the windshield which shows around 41 psi with the foot off the gas, and goes up to 51 when I press on the gas.


I've checked for vacuum leaks and cant find any. The only thing I have noticed is that #4 cylinder plug seems like it's running rich, Ohm's 16 when cold, havent checked when hot.

If anyone has any other ideas without just throwing parts at I would appreciate it.

Thanks,
Don

[Roadster]

IMO, it may depend on what gear you are in at the time you hit the gas pedal, and the speed that you are traveling. When I first got my Z 6 months ago, I noticed a similar situation, but found out that if you drop a gear or two and bring up the r's, no problem. I thought that at any gear with the LT5 it would be instant, and again depends on your speed and what gear you are in.

I don't think that one plug even if running rich would cause that situation, IMO, it would have to be loaded and fouled out for you to feel anything.

Just had ours out today, always a great ride.....have fun.....

[XfireZ51]

Did this happen before the 2ndaries were deleted?

[StickWalker]

Dom, this didnt happen before the secondaries were deleted, and there is not bogging for 5 minutes or so after starting it. Then ,only after coasting with the foot off the gas and like your slowing down for a light and then you get back on it, it falls on its face for a second and then takes off like it never happened.

Don

[We Gone]

I'm sure the secondary injectors are not on in the first 5 min. after start up as the temps have to be up before they will go active. This may be why you don't have an issue in the first 5 min. or with no secondary's are the injectors all working from start-up?

[StickWalker]

Steve, I believe the secondaries are all on all the time with the deletion chip. Plus this didnt happen for the first 3-500 miles after I deleted them. After searching some older threads I'm wondering whether an O2 sensor has died since the car has 100K miles on it.

Don

[We Gone]

Ok, was not sure what went into the prom after reprogram, If you can get a scanner to look at your 02's would help alot. I had a small hesitation when cold checked with scanner and found my right 02 was not cross-counting correctly numbers were all over, replaced both and it runs much better.

[XfireZ51]

The secondaries are active after 20C. At closed throttle, only the primary injectors are firing, however once TPS% is over ~ 1.2%, secondary injectors come on. However, the stock calibration has a delay for allowing the secondary plates to open. That's not necessary with secondaries disabled. When you close the throttle, you could be going into DFCO (Decel Fuel Cutoff). Did Marc disable this? With high vacuum of closed throttle, fuel is sucked out. You need some extra pump shot (AE) to make up for that fuel once you step on the accelerator.
Have Marc review your calibration.

[BennieC.]

My customer's car is doing the exact same thing as well. Marc also did the chip for the secondary elimination. I'm going to check it this weekend and try to find out exactly why it's doing it.

[StickWalker]

Bennie, I have been driving the car and it still does it but not as bad when first noticed. I really dont notice it when I am doing any spirited driving. It just happens like I said when decellerating/coasting and then hitting the gas. If I keep my foot just on the gas pedal its doesnt happen at all. So it just seems to act like it runs just a bit lean when coasting and jumping back on the the throttle.
My wife and I took it to the beach for the weekend a couple weeks ago and ran great. Good Luck

Don