Inconsistent Performance

Hey guys,

I'm about to start parting out, so before I waste all this cash, I want to see if anyone has any last minute opinions.

I made a post about a month ago but with no luck.

I've had issues with my car since a stage 2 upgrade a few months back. Prior to the upgrade, car ran great.

Recap from the previous post: Upgrade included TSP Long tubes, 18 Manifold, 47 Pound injectors, GT350 CAI, and Flex fuel tune.

The biggest problems that I have with the car that I think might serve as the biggest clues:

1. Surging at idle, between 500-1000 rpm.
2. Stalling when coming to a stop. RPM drops to ~300 then the car just gives out.
3. Occasionally there's ticking that sounds like it's coming from the manifold when revving passed 3k. It goes away when disconnecting the IMRCs.
4. Lastly, main thing I want to address and the strangest of them all: Inconsistent performance. Sometimes the car will run great, i.e. no surging, pulls fantastically, and feels overall much quicker than stock. Then, even after changing no variables mid drive, the car just craps the bed and goes back to its sluggish, no torque, and surging self. It's totally unpredictable when the car will decide to work or not and I can't control when it'll happen.

I just feel like not many things can cause inconsistent performance like this. I can live with the surging and stalling (surging is not ideal obviously but it's driveable and not worth a huge hassle to address and the stalling doesn't happen that often). I can't live with a car slower than stock because that just doesn't make any sense. Even my girlfriend noticed lol.

We've checked all vacuum connections, throttle body connection, and swapped gt350 CAIs. Today he's swapping the my 18 manifold with another that doesn't have any issues. I have the harnesses.

Any other ideas suggestions? Thanks guys

I'd try locking out the Manifold. If you really want to keep the IMRC's I'd suggest hard wiring instead of using the harnesses that are out. That could be where you're inconsistency is coming from. Could be some connection issues between the two but not bad enough to where it trips the CEL. Just food for thought.

It could be the manifold

Brianh922 said:

I'd try locking out the Manifold. If you really want to keep the IMRC's I'd suggest hard wiring instead of using the harnesses that are out. That could be where you're inconsistency is coming from. Could be some connection issues between the two but not bad enough to where it trips the CEL. Just food for thought.

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this.

Brianh922 said:

I'd try locking out the Manifold. If you really want to keep the IMRC's I'd suggest hard wiring instead of using the harnesses that are out. That could be where you're inconsistency is coming from. Could be some connection issues between the two but not bad enough to where it trips the CEL. Just food for thought.

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If I ask him to lock them out, I'm assuming I'll need a re-tune correct? As long as we can determine if the issues are resolved with the lockout before a retune then that's fine.

Can try a different tuner as well, but as the others said my first suspect would be the manifold.

aleccesarenriquez said:

If I ask him to lock them out, I'm assuming I'll need a re-tune correct? As long as we can determine if the issues are resolved with the lockout before a retune then that's fine.

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Yes you will need to retune the car for lockouts

Angry50 said:

Can try a different tuner as well, but as the others said my first suspect would be the manifold.

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I'm going to try and be cost effective as well. I would love to try out a Lund tune but I want to make sure all other variables are accounted for before I spend 500 on a new tuner.

I've been thinking about trying out the stock tune to see if the tune is the problem. How should I go about testing the stock tune considering I have the headers and injectors? If I can just run it to see if the surging goes away, it'll tell me if it's the tune or mechanical.

Only thing left after the manifold are the headers. Oddly enough someone recently posted about sluggish performance after TSP headers install. Maybe they are the root cause of all this.

I really want to avoid the part out.

I originally posted about the car being sluggish. But my logs say otherwise after really comparing them to my older logs without LT's. I picked up 2 degrees timing up top and 3-4 lb/min MAF. I think it's just all in my head with the added sound and humid weather we've been having in VA lately. I have my dyno session to confirm everything Saturday. I think I lost a little down low but that's expected being locked out and with the longtubes.

Brianh922 said:

I originally posted about the car being sluggish. But my logs say otherwise after really comparing them to my older logs without LT's. I picked up 2 degrees timing up top and 3-4 lb/min MAF. I think it's just all in my head with the added sound and humid weather we've been having in VA lately. I have my dyno session to confirm everything Saturday. I think I lost a little down low but that's expected being locked out and with the longtubes.

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If your logs have a time stamp, see if they corroborate. You'd think extra timing and MAF flow = quicker but check time if you can.

Regarding the OP's point, have you checked for possible knock from the headers hitting something?

I haven't been able to look at the logs myself since the Livelink drivers aren't working on my computer, but if there is knock, I hope my tuner would've noticed something when he did the dyno runs (although maybe the car happened to be working fine during that time, which has been the case in the past. It seems like every time I take it to them, the car doesn't want to act up)

Mustang_Lou said:

If your logs have a time stamp, see if they corroborate. You'd think extra timing and MAF flow = quicker but check time if you can.

Regarding the OP's point, have you checked for possible knock from the headers hitting something?

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Good point. I know my logs all start at a different RPM's but I guess I could just use a certain range to check.

LOCK OUT THE MANIFOLD NOW!!!!!!!!!!! DO NOT part it out over this, its the IMRC's being funky. Been there, fought it, locked out and am loving the car again! Also, like posted by others, check to make sure your headers and exhaust arent touching anything. I also just went through this and finally got it sorted and the car is much happier for it.

Matt

66sprint6 said:

LOCK OUT THE MANIFOLD NOW!!!!!!!!!!! DO NOT part it out over this, its the IMRC's being funky. Been there, fought it, locked out and am loving the car again! Also, like posted by others, check to make sure your headers and exhaust arent touching anything. I also just went through this and finally got it sorted and the car is much happier for it.

Matt

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Matt, are you experiencing any issues at all with the IMRC's locked out? Any bucking or surging down low in the RPM range during normal driving?

Lock out the IMRC and have him retune for that. If that doesn't fix it, then find another tuner who knows what they are doing.

SQ