HPTuners, Predator, and other tuners in here please!!! [Archive] - GrandAmGT.com Forum


View Full Version : HPTuners, Predator, and other tuners in here please!!!

06-13-2005, 05:38 PM
Our 2001 Grand Am GT with the 3.4L engine is having some problems. Today I took the Diablo Predator that is married to my 1999 Trans Am and hooked it up to the OBDII port on the Grand Am. It was just to mess around to see how hot the coolant temps were and IAT temps, but was amazed at what I found. I noticed that during wide open throttle the car had MASSIVE amounts of knock retard. I logged up to 8.5 degrees at the worst, but averaged around 6.5-7.5 at WOT. I also see 1-2 degrees of knock retard at 75 mph cruising. THIS IS BAD!!!!!

Now, within the past year let me give you a maintainence history on the car.

New plugs NGK TR55 gapped to .055
New Delco wires
Two new ignition coils, left the third original as it had no corrosion buildup like the others.
Seafoamed the engine to clean carbon out
Currently using Auto RX in the oil to clean out the crankcase of sludge/varnish buildup
Also, the lower intake gasket has been replaced twice and the engine was replaced once by GM warranty. The lower intake gasket failure the first time killed the engine due to overheat.
One injector was replaced under warranty due to failure
I do add injector cleaner to the fuel for preventive maintainence

Now, I thinking that I simply need to replace the third ignition coil to solve the problem, but I could be wrong. She has been complaining that the car has no power at higher speeds like it used to even worse when she floors it. Well, she was happy when I told her what was happening, but now I need to know what's causing it.

I was hoping that someone who has experience with tuning on this engine could help me with my problem.

H.O. Driver
06-13-2005, 05:48 PM
On the stock PCM I would have to run 89 octane to see 0* KR. However you might have just got a tank of bad gas, its possible. (specially since you are seeing KR at cruising speeds and under minimal engine load)

What was the temprature outside when you were doing this? I know on hot and humid days most stock cars will see KR do to heat soak and things like that from being ran for a long time.

Scan it again when you get a fresh tank of gas and try some higher octane to see if it reduces the KR too.

There is more to check but since its a stock car it can be narrowed down more.

06-13-2005, 06:17 PM
That did cross my mind as a possibility. I will fill the car with 93 octane next time with some kick but injector cleaner to see if the problem goes away. If it doesn't I will try the new coil.

06-13-2005, 06:23 PM
I'd stay away from the oil and fuel additives too. Most of them are gimics that don't work and can actually make your engine run worse. Good gasoline from big name chains already have a cleaning additive in them too. Using good gas and quality oil, and also changing the oil filter and fuel filter on schedule, can go a long way towards the car running better and longer. You don't need the other stuff. As long as there isn't anything else mechanical wrong with the car (ie. that would make it run too rich, burn oil or coolant, etc) then you won't have any build up.

I'd deffinitely try running a tank of 89 octane and see what that does. Especially since you live in a southern state where the day time temps probably get pretty high. You might also want to try getting a lower temp thermostat (and maybe drilling it too) to help it run cooler.

06-13-2005, 07:23 PM
Does the Diablo Predator have a way to caputure a log?

Any way you could provide a log with the following parameters:

Intake Air Temperature
Engine Speed (RPM)
Throttle Position
Long Term Fuel Trim (Bank 1 only if more are availabe)
Vehicle Speed
Knock Retard
Current Gear

Also, for kicks, disable the traction control using the button on the dash and scan again...

06-13-2005, 08:12 PM
8.5 degrees seems high to me... the only time I got KR that high was when the PCM was detecting too much power and sent KR in order to reduce the timing (down to 4*!! with 15* KR), however this only happened at WOT.

Now I'm only getting about 3* (time for headers).

It might be some crappy fuel, but do you think crappy fuel would account for 8.5?

06-13-2005, 08:34 PM
Octane? I'll get occasional knock in the 1-2* range cruising on the highway with crappy gas when its warm out. The car burns real lean at cruise, so the combustion chambers are pretty darn hot, so without good octane, you'll see a little knock. Same thing at WOT, without good gas, a lot of these cars will see some to a lot of knock retard. I used to see 4-6* of KR with 87 octane going wot, probably more now that its summer, but I run strickly 93 octane now, as per DHPs reccomendation with their PCM. I rarely see any knock at all with the good gas, and usually its only after extended crusing when the combustion chambers are really hot. BTW, what where the IATs and outside temps?

06-13-2005, 09:56 PM
The outside temps were a very humid 95 with IATs in the mid ninetys as well. Do you think that a colder thermostat would help this problem with reprogrammed fan settings? Coolant temps avg about 198-200 degrees cruising on the highway.

06-14-2005, 12:48 AM
Aside from octane, what BRAND of fuel are you running?

Stations that cut their fuel with ethanol can cause trouble for some of the newer cars that aren't bi-fuel compatible. Aside from upping the octane/brand I'd suggest that you test your catalytic converter. If your cat is clogged up it can cause exhaust gasses to back up into the cylinders and cause a great deal of knock. Sometimes it gets so bad its obvious on WOT acceleration.

Whenever a car comes into my shop with a complaint of "Lack of power" that screams of bad cats.

06-14-2005, 12:59 AM
It might be some crappy fuel, but do you think crappy fuel would account for 8.5?

Yes. I've pulled fuel from the tank of a suburban that was completely black. You couldn't see through it at all. The amount of uncombustable materials that fuel left after a burn test was unlike anything I've ever seen before.

A bad tank of fuel can raise hell on a modern car. Several.... or DAILY tanks of bad fuel can ruin the fuel system.

06-14-2005, 06:46 AM
merged the threads - try not to double-post in the future :thumbs:

06-14-2005, 08:39 AM
Well, she likes to put in 89 Octane from Citgo, but when I drive it I put in Amoco (BP) 93 octane. IMHO it does run better with the Amoco, but since you mentioned clogged cat I think you may be on track. I was thinking about removing the stock cat and resonator for a high flow car sound/magnaflow cat and installing a better sounding muffler. I might have to try this to see if it fixes the knock problem.

Is the factory resonator a straight though device or chambered?