Fuel economy low on OBD I car - Gremlin?

[The_Eric]

Lots of good input!

I will check:

-Knock retard (I don't think there is any, but will double check)

-Check for EGR call to operate


Originally Posted By: mechtech2
She did not get 30 MPG in winter with E10 with that car.
Maybe you should not argue with her about that!

Any tire size changes? Is the pressure OK? How about brake drag? And alignment is a hidden but crucial factor!


Well, she's sitting next to me right now claiming that she would get at least 28mpg...???

Tires are of the correct size and at the correct pressure. The alignment is a darn good point! Oddly enough (now that you mention it) the mileage drop somewhat coincides with the last alignment - done at my shop (but not by me) on our archaic stone age equipment. I've actually been meaning to have it double checked by some more modern gear.

So, you guys have given me some great stuff to look into and I'll report back as answers come in.

One last question: On my scanner, I have a pid value "trim cell" what in the world is it???

Thanks guys!

-Eric-

 

[jetmech1]

Quote:
She did not get 30 MPG in winter with E10 with that car


+1

I got a friend with a '01 Monte with a 3.1 My 1990 Buick 3800 gets an honest 28 Hwy on non-ethanol in the winter which beats his 3.1. (A very sore point that I remind him of frequently) LOL

 

[jetmech1]

Quote:
One last question: On my scanner, I have a pid value "trim cell" what in the world is it???


That's parameter ID's. I haven't gotten into that, but here's a webpage that explains it. Hope it helps...

Auto scanner PID & Interpretation

Scroll about 2/3 down the page and it explains fuel trim cell.

 

[cchase]

Not sure what you guys are doing to get the low fuel economy on these engines.

 

[mechtech2]

Blocking off the EGR helps throttle response, but actual MPG may suffer.
Why? Timing will be reduced if there is a knock sensor or from other parameters, and the engine acts smaller when cruising with EGR systems intact. Less vacuum and better MPGs are the result.

 

[The_Eric]

Okay, I've got some data collected. Does anybody know how to post Snap On's ShopStream Connect as a video?

Otherwise I could try and post random snap shots...

 

[Vikas]

Did you purchase the ShopStream?

 

[Garak]

Originally Posted By: OVERK1LL
Thank you!! I thought I was the only one! LMAO!!


Me, too. I was trying to figure out how a Gremlin could be OBD I compliant.

 

[The_Eric]

Originally Posted By: Vikas
Did you purchase the ShopStream?


No, it was a free download from Snap On.

Originally Posted By: Garak
Originally Posted By: OVERK1LL
Thank you!! I thought I was the only one! LMAO!!


Me, too. I was trying to figure out how a Gremlin could be OBD I compliant.


Yeah, in retrospect, I probably could have picked a better thread title.

 

[Vikas]

free download? what is the hardware? I thought ShopStream is a standalone device like Verus or Modis. Is ShopStream based on ELM27 or something like that??

I thought you decided to purchase a fancy one from Snap On instead of the fancy Autel.

- Vikas

 

[The_Eric]

Originally Posted By: Vikas
free download? what is the hardware? I thought ShopStream is a standalone device like Verus or Modis. Is ShopStream based on ELM27 or something like that??

I thought you decided to purchase a fancy one from Snap On instead of the fancy Autel.

- Vikas


ShopStream is Snap On software that allows you to transfer and view files from your scan tool, which in my case is the Solus Ultra to your PC or laptop.

I'll see if I can get some shots up in a little bit.

 

[Vikas]

OK, so your new toy is called Solus Ultra! Too many Snap On names to remember ( I can only admire them from a distance

 

[The_Eric]

Here's a snap shot of the ShopStream software and of my wife's vehicular vitals... Not sure what I was doing at the time but I have 1999 more pictures I can take...

So, if you look at the PID list, you can see that the EGR valve is at least calling to operate and there is no knock retard.

Another poster mentioned TCC slippage and I don't think there is any? TCC slippage RPM is usually around 15. If I accelerate, but not enough to unlock the converter, the slippage remains the same. It only goes up when the TCC is NOT engaged.

 

[The_Eric]

Okay, so I'm going to dig this thread up from the deep...

The car has been averaging a fairly consistent 24-25 mpg, with a couple of 26mpg runs in the mix on E-10 fuel.

About 2 weeks ago, I finally decided to give in and replace the (missing) catalytic converter to see if the thoughts of increased volumetric efficiency was contributing to her lowered mileage. This is somewhat correlated by the fact that when I finally pulled a plug, I found it to be a few shades lighter than I remember.

After picking up a Magnaflow converter for cheap, I had to modify the modified flange on the resonator (because when I removed the converter, I replaced the flange due to deterioration and it wasn't quite the same). Once installed, we fueled the car up (E-10) and headed out for a night on the town. About a week and a half later (about a 70% hwy/30% city mix), the moment of truth was upon us... After tallying the numbers, we came in at.... 24.24mpg... Bummer.

We did some more driving and racked up a fair amount of hwy miles (about 80-90% hwy), so she went and fueled up at the same station and checked the numbers... 31mpg!!!

Maybe you guys talking about increased V/E are on to something and the computer just needed some time to reset it's parameters? We'll keep monitoring economy to see if the trend continues or not and report back. I'm also having her switch to non ethanol blended fuel to see if her economy increases enough to justify the increased price tag.

So, to all the nay sayers who doubted her mileage, maybe, just maybe you'll be eating crow...

 

[The_Eric]

One last report...

After more monitoring of fuel mileage, it was still pretty inconsistent. High 20's to low 20's. Even a few low 30's in there too.

So I was about to give up on it and have her just drive it till it drops...

In the past I had noticed the occasional gas smell. Checked all the lines and fill/vent hoses. No leaks. One day I happened to smell it towards the front of the car and chased it to the vapor canister. In a fit of frustration, I shotgunned a new AC Delco canister from Rock Auto and a new Standard purge valve on the car.

The mileage went up and stayed much more consistent. She's now averaging 26-31, depending on her driving habits and locations (city-hwy).

So, I feel this is probably a case closed (Thankfully).

Thanks again to all who contributed!