ttypecamaro

iTrader: (2)

My brother has a trans am with a 383 LT4 engine in an LT1 car with stock wiring harness and computer. He got a mail order tune on the computer, and he has tunercat to tune it himself. We set the BLM min/max to 128, and nothing changed. It seems like no matter what we do to the VE tables, it doesn't run any different than before.

I was thinking there must be some mechanical or other 'not-tuning related' problem. When it warms up, the idle is really bad (it idles well when cold) and the car will buck REALLY bad where the tires will actually lose traction at 2000rpm.

He recently changed the spark plugs because they had too short of reach (Advance gave him the wrong plugs he found out). If any one has any ideas, questions or similar experience please let me know. Thanks.

zipfast

iTrader: (2)

Without knowing anything about your / his "tune".
What temp does it run good at? What temp does it start to run bad at?
I would think it runs good in Open Loop (cold). Then when it goes into Closed Loop and the choke times out you loose all the extra fuel, which makes it run baaaaad.
Try adding fuel in the Base Pulse Constant Multiplier Vs. MAT
Just add say 0.200 to the temps where it starts to run worse.
Just a thought! See if it helps or hurts.

ttypecamaro

iTrader: (2)

tunercat does not have the "Base Pulse Constant Multiplier Vs. MAT" table in the lt1 (ee.tds) definition file. I have attached a link to download our current .bin and the stocklt1.bin
.
https://jshare.johnshopkins.edu/aschlot1/TransAm%20ecu
I think it starts to run bad around 180 degreesF (t-stat temp). The weird part is that it doesn't happen gradually. It will go from great to terrible in under a minute of driving. If you stop and wait an hour for it to cool down you can drive it again.

3.8TransAM

Obvious and dumb, correct injector constant in the tune? Or at least fairly close?

Have u tried making a fairly large change to the VE table? Not just locking the BLM?

Any access to a wideband to see what your true closed loop AFR is doing?

I've also seen Opti's fail just like your describing as well, gives the car a real on/off type of issue. The ones that didnt fail were alot better when cold(richer) than they were when in close loop(leaner)

later
Jeremy

ttypecamaro

iTrader: (2)

the injector constant is correct, 44lb/hr. we've messed with the VE tables a lot. I've increased it by as much as 15% and decreased parts of it by 50%. It seems to have no effect on the way the car runs when hot. It kind of sounds like a bad optispark to me too, but it is fairly new. By new I mean... It was installed, driven to florida (from Maryland 1000mi), then the stock motor pushed a rod through the block on startup in a parkinglot in FL. It was towed home and sat for two years in the car before it was installed on the lt4. I looked at it recently and it (optispark) seems to be covered in oil? My brother must have screwed something up? either the o-ring or the intake sealant.

ttypecamaro

iTrader: (2)

My brother took off the optispark and He couldn't turn it by hand.

He called a local shop that works on 4th gens and they said the reason it runs bad when it warms up is because there is some resistance that can change due to heat when the optispark is bad.

That guy said he put a new optispark (that was on a shelf for a while) into a car and it was bad right away.

For those who haven't replaced one, is a big job.

rooster433

Did you guys do that to the coolant temp spark compensation table?

Some tuners liketo hide thier work wiht adders... That table looks downright scary in your file.

ttypecamaro

iTrader: (2)

Oops.. I was playing with the offset in the constants table to see what it did and forgot to set it back to stock. I updated the file in the above link. Thanks for noticing that, before I flashed it to the pcm.

The optispark literally fell apart after the cap was removed. It was filled with Aluminum shavings and had two sheared off bolts that are supposed to hold some disk.

A new Optispark will go in tomorrow. $290

does any one know anything about an optispark with some magnetic mechanism instead of the two vacuum lines?

3.8TransAM

Great idea poor execution, ruined the Opti, the Quad four, the Fiero and the poppet valve type vortec 4.3 port setup. :-(

Such a shame.

Yeah I had the experience of swapping a new "bad" Opti into a car, that really makes u want to punch something :-)

Well since that seems like your issue, come back when you retest it after u get the car back and lets see where u stand.

later
Jeremy

ttypecamaro

iTrader: (2)

Car runs better than ever. Optispark: $150 at Salvo's, claims to be new (not reman.). Another $150 or so for the MSD cap and rotor. The MSD uses a magnet where the rotor touches the cap instead of a ball bearing. My brother had a really hard time getting the harness connector to plug into the new optispark correctly. Still has tuning issues around 2000rpm. Thanks for the suggestion of the optispark!

ttypecamaro

iTrader: (2)

Salvo optispark went bad after a week, got a replacement, it went bad after 3 minutes. Dragged it to the dealer with the van just to make sure, they said that the only problem is the Salvo parts, $1000 to replace it.

Any suggestions? Summit has one for $289 can it be trusted?
Isn't there some external coil pack kit for LT1/LT4? Is it worth it? can it be tuned?

kevm14

Try calling Dal.
877-448-5451

The coil pack systems are Delteq and LTCC. LTCC mimics an LS1-type ignition and Delteq is more standard GM pre-LS1 DIS (I prefer the Delteq for some reason).

ttypecamaro

iTrader: (2)

Problem solved...heres how:

the catch with those coilpack systems is that you need a properly functioning optispark, or we'd have to pull the motor to put in a standard distributor.

After the stock opti w/ 76kmi (lasted a week), 2 salvo opti's (3 minutes each), and one Summit (AC delco) optispark (15 minutes), 4 opti's in total, I asked my brother what was going on with that crap. he said they were all mechanical failures, i.e. broken bolts on the rotor and slotted wheel thing, or bearings. So my dad looked at it for him (i'm at college). The whole time the problem was the pin on the camshaft was sticking out too far. How much?

My brother has 2 stock LT1 cams, and a cc-306-8 which is in the car. He measured the pin on each of the stock cams: 19/32"(1996) and 13/32"(1995). hmmm? then he measured the CC-306-8 pin...20/32". so which one is right? he's using the '96 timing cover so one would expect it to be closer to 19/32". He measured it out and found he needed to tap the cc-306-8 cam pin into about 15/32" to fit with some clearance. the latest optispark has lasted about 3 days so far with no problems.

Oh, and he somehow got all of his money back for all of the optisparks, the only thing he didn't get back was his original core, which was trash anyway.

Now he has a spare $150 MSD cap and rotor used twice, for a total of 6 minutes.