So I have a lovely little situation that I'd appreciate some advice/guidance in. I recently tuned my V6 Base with VAP's tune - and I requested two files, one with extra pops.

I loaded the extra pop tune on my car and all things were GREAT! No problems. Then, on a long drive to San Francisco, I got hit with injector failure - cyl 5 & 6. Car towed to shop.

Replaced all 6 injectors to be safe, oil change, and sent me on my way. All was fine. I also changed my tune to the non-pop tune. $4,500 bill with a $600 tow included.

Now, I have other issues. Here's what I think happened - the pop tune had a weird effect down certain hills, the car wouldn't stop "popping" off throttle. Now, when my injectors failed, and going down a hill, I believe the car was straight DUMPING fuel even off throttle into my cylinders - and now, I have a crazy misfire problem that is ERRATIC - in certain situations, high load usually, I can trigger misfires again - I believe that I had a damaged cat on the 5/6 cyl bank side - from the excess fuel dumped into my cyl from the pop tune.

I can't always get it to happen, but now my car lags/stutters in certain scenarios. It's infuriating, it almost never triggers a CEL. I got a code for catalyst efficiency or damage from the shop, but we cleared codes and they haven't come back. I'm going to try and "Italian tune up" the car - but right now this is Strike 2 of 3, and one more strike and I'm getting rid of the car.

Any thoughts or advice?

 

Sorry you're having these issues. Just to add a datapoint, my car has always popped and crackled off throttle while descending. Also, I know OzXFR uses a product called OxiCat a couple times a year to keep his cats and lambda sensors clean. You could try adding that to a tankful. I believe its easier to find Cataclean in the states, which I suspect has the same cleaning effect. Let us know how it goes. I hope you can sort this out.

 

Why did you just straight to the cat being the issue? First thing I would look at is the spark plugs to see if you've fouled them. Cat damage is unlikely to cause a misfire.

I will note, these cars get cat efficiency codes all the time. I've had to replace O2 sensors 4 different times for that particular issue, and its never cat damage.

 

They replaced the spark plugs with the injectors.

 

did you experience the misfire issue before the plugs and injectors were changed?

 

Nope!

 

Maybe I should reload the stock tune...

 

I get the stuttering/misfires in specific load situations, just after a downshift, sort of "lugging" - example, cruising in D on the freeway at 65, push on throttle to trigger a single downshift, boom - misfires.

 

NOT every time though.

 

Certainly try reloading the stock tune. See if the problem persists. If you still experience the misfire, logic dictates that the problem is w/ the injectors or plugs. Take it back to the shop and have them sort it out. If the stock tune clears up the misfire condition, then hit up VAP for some troublshooting. Good luck.

 

Never had an issue before the injector failure with the tune though.

 

Correct, its possible that the issue has to do with whatever work was performed (replace injectors / plugs) ie an issue w the repair. The only other option is that the issue has to do with none of this and the injector fault codes were a red herring. I think we can eliminate the tune if all was well before the injector failure.

 

Why do don't ask VAP?

 

I don't get it with all the desire for pops and crackles. Back when I rode modified motorcycles, especially H-Ds, pops and crackles in the exhaust meant that the carb tuning needed some work. That noisy exhaust is the least attractive thing in an F Type. Just my opinion, of course.

 

Blasphemy - Bold stance indeed sir! I literally bought it for the sound - nothing else - don't get me wrong it has some great features and I'm working on some custom stuff but the noise got me.

 

First place to start with is VAP, surely?
Story doesn't make sense that you'd replace parts etc and spend $5.1K, then ask a forum for advice, to me at least?

They are very good when it comes to giving technical assistance with their products and a lot more knowledgable than us ;-)

 

I actually don't think it's the tune. I'm wondering if my symptoms (stumbling on load/misfires on acceleration) are indicative of catalytic converter damage.

 

The pops are reminiscent of the highly tuned naturally aspirated engines with carbs or mechanically driven fuel injection systems that had fixed high lift/ long duration cams that purposefully flushed raw fuel to the exhaust to maximize combustion charge and cool the valves.

 

That doesn't make any sense... You could knock the cat internals out entirely with a broom handle and it wouldn't make your car stumble or misfire.

 

Sorry if this is way off, but on my older 2010 XJ 5L cylinders 5 & 6 are on different banks with separate cats. Are they on the same bank in your v6?