Just Installed PCM on GMC Envoy 05

Hi there,

Got my PCM order last week:) , but my schedule was really busy:crazy: , so didn't get a chance to install it until this week. Installation was easy, but was not sure once I restarted if was normal for the system to start revving so high and then slow down. I was able to test it out and notice the difference in shifting and on the gas pedal. Okay, so here are the following questions concerning the tune up.:worried:

- It is normal for gas to burn more after tune up? Reason, I had a full tank, reset the trip odometer when installed the PCM. Just notice after starting the ENVOY about 3 times all day gas was down 1/4 tank:confused: . Trip was at 33 miles, not heavy on the pedal. Before tune up I could reach 50 or so at 1/4 tank. Tires are in correct PSI. There no heavy object except me in the ENVOY. Is this normal or there some sort of problem.

- Second, I have a K&N Drop in Filter, no air intake except OEM. Throttle body is clean, and notice the sound on the engine was much louder after installed the tune-up PCM. It used to be quite, but I am not sure if that normal or not. I will try to get a sound file for this. There was a time where the engine started; you could not tell if the engine was on. Now you could hear it about 20 feet or so. Is that normal?

Everything else is fine. I know it almost time for me to change the oil, but I don't think that could be a problem. I am using 87 for fuel and I picked the medium in fuel, so I could use 87 or 89. Any help would be great. Thanks

Transmission fluid was just changed, but didn't get a chance to drop the filter. Too cold, so I would take care of that once the weather is much better.

Order was for Rendon

you only get 50 miles to a 1/4 tank??!!!:weird:

I get almost 100 miles! :crazy:

My impression was that it could take a couple hundred miles of driving for a new PCM (and tune) to adapt to your driving style and vehicle environment. Break it in first, then take data and make observations on changes.

Well, with a full tank and driving in the city I get about 200 miles or so. If I am in the highway then I get more. Actually, I used to get more, but lately I have been getting a lot less. Summer time I've gotten about 300 or more. I am not sure if is due to winterize fuel or maybe something else. I have extended warranty and before the tune up I wanted to take it to the dealership to get it check out about the fuel. I had a problem with the fuel gauge and it was replaced. It kept giving me false reading. It would tell me I was low on fuel when it was a full tank. Problem is fixed and now I am getting less on my tank. I Did not think it was problem, but a friend suggested I get it checked out. Plug where changed in the in the summer to Bosch Plt 4, but I heard bad things on Bosch and the envoy. I am going to replace them back with AC DELCO Iridium. I had NGK Iridium but once installed engine sound was really loud. Gap on plug was set at .055. I was told the correct gap is 0.044. I going to try it again with the correct gap, but once the weather is much betI would break in, but I am just concerned about the fuel part and the loud engine rev when driving or just in idle. Any other suggestions.

You will not get worse gas mileage with our tune. flat out..

You probally just have a mix of a few things going on.. winterized fuel, learning period, and just looking too hard into it. Also did you send your PCM in for reflashing? IF not you will need a case relearn which can effect mileage.

I also reccomend a little more scientific method when determining fuel mileage. like miles traveled/gallons required to fill back up.

I got the core. Tomorrow I am heading to Philly and I will see how the miles are on it. As for the engine rev noise being much louder is that normal. I know I need to break it in, but the noise came after installing the PCM. I will do the case relearn tomorrow. The Envoy went on without a hitch, but I will do the case relearn just to be in the safe side. If I take it to the dealership could I leave the Tune PCM or swicth it back to the OEM? Just curious. I will let you guys know how much I need it to refuel when traveling. I know about winterized fuel and effect it has on miles. I see the difference, but I guess it just to soon to say anything. Thanks

I got the core. Tomorrow I am heading to Philly and I will see how the miles are on it. As for the engine rev noise being much louder is that normal. I know I need to break it in, but the noise came after installing the PCM. I will do the case relearn tomorrow. The Envoy went on without a hitch, but I will do the case relearn just to be in the safe side. If I take it to the dealership could I leave the Tune PCM or swicth it back to the OEM? Just curious. I will let you guys know how much I need it to refuel when traveling. I know about winterized fuel and effect it has on miles. I see the difference, but I guess it just to soon to say anything. Thanks

Yeah, its probally too soon to say anything. You will not get any worse gas mileage than stock. Most if not all report an average of 1-2 mpg better.

You don't have an option of getting a case relearn, it is required if you didn't get your orginal PCM tuned. Your tuned PCM will have to be in the truck when you have a case relearn done.

As far as the noise, I would guess it is your imagination but could be relatedto you not having a case relearn done.

Hey Alvin,
got my OEM PCM back " and hate it " cuz my car is in for service, this is the last service under warranty, and i did not find any place that does " or even know " what a CASE relearn :no: so can i send my OEM one for a tune then send you the one you guys tuned for me back to you ?? :crazy: kinda like the loaner program ? :undecided thats the ONLY way i can get a CASE :(

Hey Alvin,
got my OEM PCM back " and hate it " cuz my car is in for service, this is the last service under warranty, and i did not find any place that does " or even know " what a CASE relearn :no: so can i send my OEM one for a tune then send you the one you guys tuned for me back to you ?? :crazy: kinda like the loaner program ? :undecided thats the ONLY way i can get a CASE :(


Ah, I see. You put the stock PCM back in because you didn't want them to find it or something? There is a big difference between a tuned computer and a stock computer isn' it!

Get in touch with Kelly.. She should be able to get you setup on a loaner program.

Ah, I see. You put the stock PCM back in because you didn't want them to find it or something? There is a big difference between a tuned computer and a stock computer isn' it!

yeah, and they DIDNT !! and i swear your TUNED PCM is 1000 times better !! i swear guys !! after i installed the old one, i was like what the ....!!! i hated it !!!! the TUNED one is AWESOME !!! thank you Alvin and Kelly for an awesome awesome job :yes: :woot: :thumbsup: :thx

Well I have a question concerning crankcase relearn. When the tune PCM was installed, engine was able to start without a problem. I understand if you get the core you need to do a CASE relearn. I followed the steps, but how do I know if I did it correctly. Also, gas miles where corrected, I am getting about 85 miles per 1/4 of the tank, acceleration is much better and performance is a lot better:) , but the engine is still running rough.:confused: I don't know what else could it be. I might just have to take it to the dealer and see what they tell me. I know it take time to break it in, but the sound is driving me crazy. My son keeps asking was wrong with the truck. So, I know it not just me. I am going to change the oil since it due, so I will wait to see. I doubt it has anything to do with it. The only thing that was just changed was ATF. Could that be it?

JR4815D2, have you tried reinstalling your OEM PCM to see if the problems go away. From what I have heard the Bosch +4 plugs are junk for the I6 engines.

When you put your new PCM in you did a security relearn, not a CASE relearn, you can't do one of those yourself unless you have a LOT of money for your own Tech II machine.

I would say reinstall the OEM PCM since that is quick and easy to do on the I6, if it corrects everything maybe the tuned PCM is defective, if it still runs rough then change the plugs, if it runs better that way reinstall the tuned PCM.

Sparty,

I would try it tomorrow. I got some instruction from PCMFORLESS on CASE relearn, but I am not sure if that correct. I could take it down to some one who has the right tools for security relearn. I know that Bosch are no good for this engine, but it too cold to changed them. I going to get the ACDelco iridium, but first I am going to try to put back the OEM PCM and see if the rough sound goes away. If not then this weekend I will work on it. I wasn't sure if I need to take it to some one to get all these relearn done.

Sparty,

I would try it tomorrow. I got some instruction from PCMFORLESS on CASE relearn, but I am not sure if that correct. I could take it down to some one who has the right tools for security relearn. I know that Bosch are no good for this engine, but it too cold to changed them. I going to get the ACDelco iridium, but first I am going to try to put back the OEM PCM and see if the rough sound goes away. If not then this weekend I will work on it. I wasn't sure if I need to take it to some one to get all these relearn done.


There are two relearns that need to happen

Security (you can do it yourself)

And CASE or crank angle relearn. (you cannot do yourself)

take a look at the literature we sent to you.. It should make this a little more clear.

You realize the CASE relearn and the SECURITY relearn are two totally different things.:confused: If you put the new PCM in and the vehicle started, you don't need to do a security relearn at all.(and if it hadn't started, you can do the security relearn by your self) If you are using a PCM that did not come with the vehicle from the factory, you will need a CASE relearn. A CASE relearn requires special tools to do, and not all mechanics will be able to do it.




EDIT: Alvin beat me to the post!

Okay, tomorrow I will look for an auto shop that has the correct tool for the CASE relearn. There are few shops in my parent’s area, so I would try to take care o f it. Maybe once the case is done, the engine rough will go away. Thanks for clearing things up...

Got CASE done today and the rough sound is still there, but it's not as bad as before. I am thinking it might be spark plugs.. I paid 45.00 to do it. I will see if I could change the plug this weekend to ACDElco or the NGK iridium. Will let you guys know how it goes..

FYI, the new GEN 2 Dashhawks can do CASE relearns on GM vehicles....nice feature.