It'sOver9000!!

Please help, looking for advice/insights:

Took my 98 Vette in to Speed Inc. at the start of August to do heads/cam and dyno tune, plus install a new clutch. Due to the new clutch, the next few weeks consisted of gentle driving to break the clutch in. Got about 300+ miles with no problems (including a good amount of city driving) as of this past Friday, so I finally decided to have a little fun and go WOT for the first time since the install to actually experience the new power.

The car instantly went into limp mode and the DIC flashed "Reduced Power" "Service Traction Control" and a check engine light. Pulled over and pulled the codes which consisted of P1514 and a slew of lost communications codes. I restarted the car and it started up fine, and drove normally. Didn't go WOT or anything, but I did try a little spirited driving and it was okay.

Yesterday I decided to try going WOT again for the second time... and sure enough, it instantly went into limp mode with the same DIC messages and all. Pulled over, restarted and all was fine.

Did some research on the forums and I know P1514 is related to the Throttle Body, but could also be related to the tune (related to calculated vs. actual airflow). I contacted Speed Inc. and they immediately said it's a failing Throttle Body. I asked if they would look at the tune again but they insist that it HAS to be the Throttle Body, not the tune.

My buddy has a WS6 T/A and that should have the same Throttle Body as mine, and he's willing to work with me to temporarily swap them to see if we can repeat the issue. However, if it's Throttle Body, apparently GM discontinued making the stock parts, and as far as I know there is no aftermarket replacement except ported Throttle Bodies. Which means a matched intake. Which means another dyno tune. More money after JUST having a tune done.

I just wanted to ask some of the experts on this forum: does this sound like a tune issue, or should I go straight to checking out the throttle body?? I don't think I'm being unreasonable about wanting my tune to be double checked... Also, does anyone in the Chicago-land area have the ability/knowledge to tell me if my tune is okay and are willing to look at my car??

For the record, I'm not bashing Speed (they do great work and have many positive reviews on here), but I just want to drive my car and actually enjoy it to it's full potential after spending so much to do heads/cam, without having to spend tons more...

robmiz

It's been a while but I had a same problem after a cam installed. Using HP Tuner, I slightly increased the gram max values by 0.01 on throttle position for 75% and above on "Calculated Airmass vs. TPS vs. RPM - P1514 Error" table under Engine Diagnostic tab.

acuevo

If I'm not mistaken the F body LS1s used cable actuated throttle while our Vettes have drive by wire so I donmt think you'll be able to compare with your friends Trans Am throttle body.

It'sOver9000!!

Most of what I've read and understood seem to point to this as being the issue. Problem is, I don't have HP Tuners to take a look at it. Was your car professionally dyno tuned before you started having issues?

It'sOver9000!!

Crap...

Beast

If I ever get a heads and cam installed, I'm doing the whole thing, pushrods, rocker arms, ported throttle body, port my ls6 intake, stock injectors might not be big enough, how about coil packs. Those are still original on mine.

I'm sure speed inc. can port your throttle body, just get it done

It'sOver9000!!

I mean... no point in doing that if my throttle body is actually bad. If it does turn out to be the TB, then I'll be searching for a stock one. I JUST spent money on a tune, not really keen on spending more money so soon after just to tune it again because of this.

And if it's the original tune that came with my heads/cam... a ported throttle body won't fix that either. Just need the assistance of someone with HP Tuners and some know-how to check on it, which is the hard part.

nsogiba

You should find another local C5 owner and swap throttle bodies (easy 10min job) to rule out the throttle body.

It'sOver9000!!

I'm hoping the forum can help out with that. I currently don't know any other C5 owners near me in real life unfortunately.

v6turbo87

How did they do a dyno tune if it keeps going into limp mode??? Was you there to witness the dyno tune???

It'sOver9000!!

I was there to witness one of the pulls and there were no issues. Went to 4th gear and it certainly sounded like WOT.


For all I know it could be the throttle body going bad, and maybe it's just coincidental that it just so happened to go bad right after getting a tune done with no issues prior.


Won't know for sure until I can get the tune looked at, or find someone to swap throttle bodies with. Or if I can get access to something like a diagnostic manual and attempt to troubleshoot the part myself, but I am no diagnostician by any stretch of the imagination.

acuevo

After checking the definitions for P1514 I'm kind of leaning towards what robmiz said about the max values for air flow relating to that specific trouble code. If that IS the case I'm not sure how the shop could have missed it while tuning. If the shop is adamant that they think its the throttle body and refuse to even double check the tune I'd be tempted to ask another dyno shop with LS experience for their opinion and see if they can look at the tune. Then if that does prove to be the problem, see about getting the first shop to reimburse you for the second tune.

Either way keep us all posted, I'd like to see how this turns out for you. Good luck!

feeder82

i have had lots of experience with Speedinc, they have tuned thousands of LS vehicles, and they stand behind their work. I have no doubt if you take it back they will fix the tune no charge.

knewblewkorvette

They "should" fix you issue at no charge.

It'sOver9000!!

So an update:

Met up with a former co-worker of mine who has a 2001 Z06 and we swapped throttle bodies today. The result is:

It's not the throttle body.

My car repeated the issue and went right into limp mode with the P1514 code (along with C1278, TCS Temporarily Inhibited) when trying to hit WOT using the Z's throttle body, and when we tried my throttle body in his Z he was able to hit WOT multiple times no problem. So in a way that's a relief.

Next up will be looking at the tune. Turns out I do know someone who has EFI Live, so the plan is for him to come by tomorrow after work and start looking through the tune, specifically that C6101 table. Might be worth it to fork over the cash to buy a license for my vehicle and update the table with 25% greater values to see if that clears up the issue.

If it turns out NOT the be the tune... not sure where to go from there. Maybe the MAF sensor is misbehaving??

And also because I know we all love pictures, I've attached a pic of our cars from earlier today.

acuevo

Glad its not the t-body, maf sensor is a possibility but I really think this shop should be standing by their work and take a look at it for you before you start forking out money. Now that you've tested their theory they have no excuse.

Also, just out of curiosity, what cam and heads did you go with and what kind of numbers did it lay down? I'm pretty much stock now on my 99 but 8'm hoping to be doing heads and cam next summer.

It'sOver9000!!

My mods are as follows:

- PRC Stage 2.5 LS6 Heads
- Speed Inc. SI5 Cam, 231/237 .589 .595 112
- XS Power LT Headers
- LS6 Intake
- Callaway Honker CAI.

Put down 433 RWHP / 397RWTQ on the dyno after the tune.

As far as my current issue, I agree that Speed SHOULD be reviewing my car, and I do plan on informing them of my TB findings but I want have my ducks in a row first before doing so (because I don't feel that I should be paying diagnostic fees, and I'm almost positive they would charge me for that since I'm taking time away from other cars. They already tried to upsell me on a ported TB, Intake and retune when I first reported the issue).

Validating the TB was one part, and the other part of that involves going through my tune (hopefully tonight) and screen-shotting the C6101 tables. Comparing values with my buddy's Z06, posting my table in the Tech section to see if others have any input, etc.

And for the record, at the moment I'm not bashing Speed Inc. They've done good work for me before and lots of people here speak highly of them. I just want to do my homework to try and understand the issue (with helpful input from this forum) to reduce my chances of getting taken for a ride, so to speak.

acuevo

REALLY nice numbers there, good to hear because i'm planning a similar setup to yours but with a milder cam and ls1 ported heads instead.

Keep us posted here, hopefully its something simple and it will be sorted out soon.

Sydwayz

Have you talked to the place that did the work and tune? Man, I wouldn't TOUCH the car with another tuner/computer until they have had a chance to diagnose it. Once you mess with it, they likely will and should wash their hands of it.

That's so much better than you throwing darts, in the dark, blindfolded, backwards, while hammered, in a wind storm.

It'sOver9000!!

My current plan is to use EFI Live to just look at and take screenshots of the C6101 table (which seems to be the major culprit of issues similar to mine based off research) and then post it to the Tech section here and maybe on LS1Tech to try and get some feedback on whether it looks way like it could be the cause of my issues given the mods I have. Then with some knowledge on it I'd go back to Speed Inc.

I wouldn't change anything on the tune. I just don't want to go in completely blind and get misled by fancy terms. I don't think they would intentionally do that, but with how confident they are that it ISN'T the tune it doesn't hurt to be somewhat prepared.