Update your PCM!!

[gchemist]

I installed the GM original Jimmy ECM sent to www.wait4meperformance.com on Thursday. WOW!! I noticed the idle change right way! The updated spider loves the changes. Engine revs past 5000 RPMs on WOT shifts. Tranny shifts are awsome. The 4 door Jimmy jumps out of the first gear. Accelleration is great! Downshift and jumping on to the freeway are no problems at all. No hesistation when I stomp the throttle. I have to feather touch the throttle because it's sensitive. The corrected speedo is nice too. Best $85 spent on the Jimmy!! The tank was 1/4 gone so I can't report on milage improvements. I'll report back later.

If you own a 4 door, get the PCM updated!! 2 doors will like the performance even more. The 4.3 responds very nicely to the changes.

[likaroc13]

few questions....what year is your Jimmy? Have you done a lot of other mods to the engine? How long was the wait for the PCM? Thanks

[Mickey_D]

And do they send you a new one so you can continue to use your vehicle while waiting?


Oh, and just where is it in the vehicle? If you tell me behind the glove box, I'm screwed....

[gchemist]

I sent my original PCM. I was able to park my 96 Jimmy for a week. I sent the PCM out on Wed. It arrived a week later on Thursday. Any 96 and later GM vehicle is easily upgraded. Good reading on the upgrade.

You don't have to send the original PCM. However the cost is higher. They can send you a PCM for $159.00. After you install it, you will need a crank relearn procedure performed. The new PCM needs to know the position of the crank. Some people get by without the procedure. However, it is recommended so the PCM can work the timing properly. The procedure can be done by a dealer or a good shop. Costs an additional $70+. If you send the original PCM, costs are only $75 + 9.00 for shipping. The crank relearn procedure is not necessary because it is saved prior to upgrades. Once you upgrade any PCM, you can send it back for more changes or upgrades for free. You just pay for shipping.
Modifications that can be done: torque management is reduced, better tranny line pressure, torque converter lockup above 45 mph, egr valve cycle after the engine is turned off, code clearing, fuel map updated for octane used, speedo can be changed to match tire size, top speed limiter removed, and other small changes.
Read the link above for great details on the service. If I had a V-8 from 96+, I would do the same service ASAP.

My Jimmy has been updated with a new FI spider. I removed the poppet FI spider. I also removed the plenum air restrictor under the throttle plate. Tire size 255/60R17. Added a K&N filter. Everything else is stock.

The PCM is located on the passengerside fender well. Right next to the battery, bolted to the top of the overflow tank. Five electrical connections (all color coded) and four bolts. The PCM is easily removed.

[gchemist]

I can report milage at 80 MPH. I took a round trip to El Paso. 1200+ miles. At 80 MPH, the Jimmy pulled 20.5 miles per gallon. Wow!! I wonder what it will do at 70! A little slower and it goes up. I 'm running 255/60R17 (29") tires. The 4.3 had no problem turning the large tires. The extra power and fuel map sure does help.

Now, I'll be running in the city. As soon as I can go through a full city tank, I'll post milage.

[gchemist]

Alright!! Went through the first full tank after having the PCM reprogrammed. Normally MPG were 16-17. The first tank put out 18.5! Or about 1+ MPG more. Even with being stuck in dead stop traffic for 1 hour. At that rate, the $85 will pay for it self quickly. Not bad for a 4 door and simple modifications done to the Jimmy.

[Mickey_D]

Well, I e-mailed them back on the 21st of May and still no response. Just as well. I'm selling both the truck and the Blazer, so no need for the PCM to be done for me...

Glad to hear you're having a good experience out of it.

[BurnoutNova]

what years is this for? i have a 92 and wouldnt mind doing this.

[gchemist]

96 and later GM vehicles for sure. Anything older I'm not so sure. You are better off by calling. They get swampped with work sometimes. With fuel prices through the roof, I'm sure he is getting a lot work right now.
I'll keep posting updates. Next week, I'll get a chance to drive 200 miles at 70 MPG. My average speed in city driving is 35 to 45 MPH. A little freeway now and then too. Lights fortunately are spread out too. Block to block traffic lights are uncommon unless I drive downtown.
Oh, note that I'm driving 29" 255/60R17 wheels too. The tires raised the Jimmy nearly 2"!

[Pyrotechnic]

Man, $85 is really cheap for a tune. Of course it isn't like those hand held programmers, and you gotta put the vehicle down for awhile, but thats still a good price.

[gchemist]

Update: The Jimmy has a solid 22+ MPG with PCM programming. It was close to 21-21.5 prior to reprogramming. It pulled 335.4 miles on 15 gallons. The gain is close to OD expected gains from the 4L60E.

I don't know how much the ram air will affect results. I'll post more results after running the ram air setup.

[BurnoutNova]

so it doenst sound like the mileage is much better at all, only .5 mpg?