Bigblu1

2000 Tahoe swapped from an lm7 to lq9, with a summit 8712r drop in truck cam. I only used the long block. All other dressings were from my lm7 throttle by cable. (The LM7 ran perfectly fine, no issues at all I just wanted more power and torque) I did install new knock sensors (from dorman as a kit with harness) I ordered a mail order pcm from Michigan Motorsports. I had an idle problem the iac was at max so I drilled the throttle plate hole and now idles great. My issue this combo has the same power if not a little less than my 250K mile stock LM7. Idle sound is flat. I did get a ses light from knock sensor voltage after 30 miles of driving. (Then it really wouldn't accelerate) I reset the pcm and it got the same power back. Like I said it runs fine just feels so weak. I was expecting some serious power increase. It literally feels like it might have 250 horsepower, my kids 2000 ford ranger 4x4 4.0l will out run it. I'm almost convinced my cam is off a tooth. Even though I checked it 5 times. Any advice or people who went through similar situation? Were not talking a small lack of power this thing is a dog.

G Atsma

Did you get it retuned for the bigger long block? It will never run right if you don't tune for the new displacement.

Bigblu1

Yes, I filled out the questionnaire , I attached the form. I have been in communication with the tuner. But he's vague at best.

If this is an engine swap application, please detail your vehicle setup here: 5.3 LM7 swapped to LQ9 6.0

Fuel System- Stock throttle by cable


Octane Fuel Used- 89


Engine Details- LQ9 6.0 from an 03 Escalade


Camshaft(s)- Summit 8712R1


Head(s)- Stock LQ9


Injectors- Stock


Intake Manifold- Stock


Throttle Body- Stock Cable


MAP Sensor- Stock LM7


MAF Sensor- Stock LM7


Headers- Stock Exhaust Manifolds EGR


Transmission- 4L60 Stock


Torque Converter- Stock


Shift Firmness- Medium


Rear end gear ratio- Stock 373 4x4

Bigblu1

It literally feels like my old lm7. Just shifts harder and revs to the moon before a shift, I power brake it and floor it and it's just a pitiful mmmmmmmmmmmmmmmm

G Atsma

You should have just grabbed the Escalade ECM and used it.

Spamfritter

iTrader: (1)

The 2000 Tahoe's LM7 injectors are 24.8lb./hr. versus 25.2lb./hr. on the LQ9. I don't know if that makes any difference but with a bigger cam you can probably benefit a bit from larger injectors. The bigger issue is that the mail order tune is likely insufficient to get that engine running like it should. Were the cam specs provided to the tuner?

Bigblu1

Yes I provided a copy of the cam card. The knock sensor codes keep coming back. I really think this tune is wrong, or the cam is off a tooth. Can the tune really make this big of a difference? My first modded injected Ls

Spamfritter

iTrader: (1)

The tune is everything in fuel injected engines and especially in cases where the engine is either heavily modified or if the engine isn't the original engine that came with the vehicle.

Bigblu1

The tuner emailed me it's impossible for the tune to set knock sensor voltage codes. I find it strange that both set p0332 and p0327 at the same time every time, over 90 percent throttle at over 60mph going up a hill.

CattleAc

iTrader: (7)

The only way you're going to get this figured out, is to get someone local to you with a decent scan tool,.take a look at it, and see wat's going on...

01WS6/tamu

iTrader: (37)

Find a local dyno tuning shop head there let them sort it out. It's the only way you wont pull your hair out.

RonSSNova

iTrader: (3)

Put the OEM knock sensors back in. The Dorman sensors are junk. They WILL show knock when there isn’t any.
I’ve dealt with this many times when folks don’t put real GM sensors in.

Spamfritter

iTrader: (1)

Some of the Doorman stuff is fine but a lot of it isn't. There are times where going OEM really is the best option. (I can't tell if this is one of those cases, I have no experience with non-GM knock sensors.)

Bigblu1

Pulled a plug, about 100 miles on it, checked fuel psi 55psi, checked compression on 3 and 4 both 190. Looks like its LEAN

Kawabuggy

iTrader: (1)

I know this is going against the grain here... and against what is commonly practiced, and I find myself typing this quite a bit on replies.. you said "I power brake it and floor it and it's just a pitiful"... here's a thought.. how about until you sort the problem out and get the motor running correctly you might wanna lay off intentionally abusing it. Right now, you might just have a tune issue, or fuel delivery issue, or minor mechanical issue. You keep stomping the gas pedal to the floor and holding it there and potentially it could get really expensive very quickly. Do you have a scan tool? Can you check your fuel trims while driving it just to see what the PCM is doing for the fueling? Have a friend that has HP Tuners so you can data log it?

Where are you located?

Bigblu1

I power braked it once, as a test. I have an appointment with a dyno tuner on Thursday. I checked fuel trims, st is bouncing between -5 and 7 at idle, lt is 9 and 11. Timing at idle is 22, hold 50 at 3k with no loads. Mal showing 12in vacuum, compression is 180ish to 190 ish all cylinders. The tuner and I spoke in depth and he feels it is just a bad tune.

Bigblu1

Well took it to the Tuner - Docs Performance in Las Vegas, truck now has all the power I expected. Drove it 30 miles home in traffic in 105 degree heat and it ran flawless. He stated the tune was off quite a bit. Super happy now. No more SES light or pending codes.