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Question: 89 Consumes lots of fuel after new injectors installed

Toy4Hal

Well-known member
Joined
Jul 10, 2003
Messages
140
Location
Los Angeles
Corvette
62 Maroon, 03 Anniversary Convertible
A short while back I joined in a post that was about a 90 which would not start when hot. I had what seemed to be a similar issue with a friend's 89. It turned out to be not quite the same issue (I think).

My issue was an engine which would "die on acceleration" when the car was hot. It continued to get worse until it finally would not start at all when hot. I did a lot of stuff to the car, based very much on excellent advice from people on this forum. My thanks to all. It got the car running.

There is a recap of all that was done below. With all these stuff done, the can now runs and runs very well. However, it is consuming a lot of fuel.
The folks at SouthBay Fuel Injectors suggested checking some sensors to see their settings. The note from SouthBay Fuel Injectors is:
"Try checking the following: All sensors: If there is something wrong with The air and H20 sensor it will tell the computer to put more fuel in. Check the 02 sensor and the timing."
So, my question/request: Can anyone provide me with the correct sensors and settings for these sensors so I can get them tested? Thank you.

I suspect I'm going to hear from some to buy the service manual. And, I will. I thought I was done with this car but obviously not. However I need the data now. Thanks.


The following was lifted from the prior post as background:
I thought it appropriate to post the continued status on the 89 I spoke of which would not continue to run and was finally was diagnosed with 2 very bad injectors. I did buy and install a set of Bosch III injectors from SouthBay Fuel Injectors.

I can't say enough good things about these people. They were available at all hours to help me (my 1st time doing this) get the injectors installed right and not leaking.

The instructions previously posted by someone else on this site were very good; a few variants such as a solid vacuum line to the brake booster and the need to disconnect a few more parts at the front in order to get to the inside bolt on the passenger side of the fuel rail. But, all in all, if you take your time, anyone can do this. Just don't rush!!

So, the car is back together, runs good, idles nice, etc. However, fuel usage is way up!!! I don't personally have a history driving this car but I was a little concerned with fuel mileage while I drove it for the few days after the job. But, I was driving on city streets and putting my foot into her to see if she died on hard acceleration. Nope. She runs fine.

The owner of the car is now telling me she is seeing freeway mileage in the high teens while cruising at about 60, where she was used to seeing high 20's in the same circumstances. So, back to my "experts"! Any advice?






Let's recap what has been done (in this sequence)
  • Ignition module replaced.
  • Cap, rotor, and coil replaced.
  • Fuel filter replaced.
  • Fuel pump replaced.
  • Throttle control valve replaced.
  • ECM was replaced (by the dealer).
  • Original factory injectors replaced by Bosch III 22 lb. injectors.
This is where she sits. Runs great, runs strong (for an 89). But using a lot of fuel. Ideas?

Thanks again for all your help.
 
S

steelhorse

Guest
Did you use math to figure out the mileage or just go by the readout?
I did similar work to my 86 and it was several gas tanks before the readout was correct. If I just divided miles by gallons I always got the correct mileage even though the readout said less. The readout is now correct.
No idea why it took it a while to correct.
 

Toy4Hal

Well-known member
Joined
Jul 10, 2003
Messages
140
Location
Los Angeles
Corvette
62 Maroon, 03 Anniversary Convertible
Did you use math to figure out the mileage or just go by the readout?

Mostly it's using the readout. However, "gut feel" of how often it now needs fuel for periods/trips that used to take far less fuel. It's a friends car but she knows her car very well. I will have her do some math to be sure. Thanks.
 

vetteoz

Well-known member
Joined
Jan 20, 2004
Messages
1,564
Location
Not in Kansa anymore
Corvette
1990
For the sensors in question the only real way to check them and ECM operation is to run the engine with a scanner hooked up so you can see what it is actually happening
A bad O2 sensor for example could prevent the ECM going into closed loop
 

G Winter

Well-known member
Joined
Aug 21, 2004
Messages
2,177
Location
NW Iowa
Corvette
1990 red convert 6 sp
Not to insult you but we all forget things. If you checked the timing be sure you reatatched the EST wire. You did disconnect it to set the timing, right ?

Glenn
:w
 

Toy4Hal

Well-known member
Joined
Jul 10, 2003
Messages
140
Location
Los Angeles
Corvette
62 Maroon, 03 Anniversary Convertible
Not to insult you but we all forget things. If you checked the timing be sure you reatatched the EST wire. You did disconnect it to set the timing, right ?

Glenn
:w

Glenn, I appreciate the comment. No insult taken (never wil be). Thank you!

I did not do anything with the timing through this process. That's not to say the dealer (who replaced the ECM) did not set the timing. I can't say. I do know the car "pinged" a lot going up hills prior to the ECM being replaced and does not ping now. It's worth checking. Thanks.
Hal
 

redvett

Well-known member
Joined
Dec 16, 2001
Messages
486
Location
AZ
Corvette
2001 Convertible
If the new injectors are not the same flow rate as the OEM the average fuel counter will be wrong. The calibrations in the Memcal are set for the OEM injector.
 

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