tuning problem ?:

hi guys i got my pcm flash by a local guys here im canada .
specs are a truck engine 6L 2003 with a 2005 4.8L truck engine pcm and Harness the truck was drive my cable and old style cam crank sensor .

im looking at a 80% engine load at idle and 23g/sec MAF its reading 18ish Inhg of vacuum but on my gauge ( hand held ) im getting max 10 inhg of vacccum when the engine is surging because of too much gas ... if i test my map sensor ( ls1 style ) with key on engine running it varie the way it should . i checked for vaccuum leaks and didnt find any i blocked all vaccum ports too. ALso an other problem i have is that if i touch the throttle the car goes up in rpm but i dont control it ... it does this trouble seen i took the pan off for a bad strainer ORING. i didnt remove the intake on that job...
i have screen shots of the freeze frames of my scanner . it is coding MAP sensors out of range and and other one of the map .... i dont have a good used sensors to test with

I think you are not getting much of a response because there are a number of potential problem areas.  I feel like I would need quite a bit more information to even begin to guess at what is going on.

With so many differences between the engine and ECU you might be better off starting by having a new tune essentially built from scratch.  Perhaps find a quality local tuner with a shop and dyno who knows GM LS based tuning very well, and have him help you try to sort through things.

I know that doesn't offer much help, but tuning is one area where spending the money to have it done right usually pays off.  A bad tune will cost power and driveability, and can destroy an engine.  A good tune will make more power, improve driveability, and help your engine live a long life.  It is usually money well spent.

A final possibility might be just to spend the money on tuning software for yourself.  After spending some time working with an excellent local tuner on my Evo, I decided at the rate I was modding the car, it would be best for me to learn to tune it myself.  I picked up the needed gear and software, and then spent about a year slowly getting comfortable with the process.  I started with small changes, and eventually retuned the whole car switching from gasoline to e85 (but keeping an emergency 87 octane backup gas map - I could switch from e85 to that with a hidden switch) and changing from 513 cc injectors to 1000 cc units.  At that point I also began making lots of mechanical changes that needed to be tuned for.  Things like an intake, exhaust, larger turbo, GM boost solenoid, MAP sensor, head work, cams, larger fuel pump, etc.  As I made those changes I needed to retune after almost every modification.  In the end I had probably close to a hundred hours worth of road tuning, backed up by some quality time on a dyno.  And all of that double checked by our local Evo tuning expert.  By the time I was done the car ran like stock in temperatures from -40 f below zero to over +110 f on hot summer days.  No CEL lights, no odd behaviors, no backfires, no bucking, no problems with hot or cold starts, nothing that required an excuse to any passenger.  It was a lot of work, a bit of cost, and required quite a bit of reading and study, but in I felt it was very much worth it.  I drove that car from Canada to Texas, as well as a number of other road trips (and track time), and it was always great to drive.

Sorry for the long ramble.

I guess without knowing that you actually have a good baseline to start from, it is really hard to know exactly where to start.

ls1tech.com might be a good place to research and/or post your question.

If you haven't already, I'd try [You must be registered and logged in to see this link.]

He programmed my PCM, mine was a similar set up as yours (4.8 van computer), but a 5.3 LS with a different intake, injectors, cam, etc.

it can take a long time for him to respond to questions, but if you send him $ and the PCM you will hear from him within a couple days- he spent a lot of time on the phone with me sorting out the issues-

I'm guessing you have already looked at his website (lt1swap.com), but if not, it's a good resource-

He sorted me out, and so far so good

it could have a tuning problem, but you may have other issues id look into first before blaming the tuner.

first off, what are you using to scan it?

at idle, when the maf is showing 23g/sec what is the maf frequency? (its shown in Hz).

what are the codes that are being set for the map sensor? the actual code number will help us out.


ive seen in some gm computers where they have a map code and its dead (or unplugged) and still has a reading on the scan tool. thats the pcm guessing what the map should be showing. being you have codes you need to get those sorted out before going any farther.