Corvette C4 Forum 1984 through 1996

programmed chips?

Old 11-10-2014, 10:02 AM
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Default programmed chips?

I have a 1989 Corvette standard base convertible. Will my gas mileage be improved with a programmed chip?
Prior to rebuilding L-98 engine and 700 R4 transmission, my overall gas mileage was near 27.5. Now I'm barely at 24.0. What's the best solution? I've tried oil viscosity, tire air pressure and can't seem to get close to the pre-rebuilt levels.
Old 11-10-2014, 07:59 PM
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Default Details?

The first question is during the rebuild did you take it back to oem spec or did you do a little 'enhancing'? How about letting everyone know what you did to it. Power and economy typically are an inverse proposition, add more of one will result in a loss to the other.

If you changed nothing, then something isn't right with the rebuild or the settings used.

That's my opinion.
Old 11-10-2014, 10:40 PM
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Welcome to the forum.

I agree with hcbph.
Old 11-11-2014, 08:54 PM
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Everything went back as standard. I did remember changing fuel pump, injectors and fuel pressure regulator while trouble shooting my problem.
I was losing oil pressure when the engine got warm, which cut-off the fuel pump. I gave no consideration that maybe the fuel pump, fuel pressure regulator and injectors needed to be uniform. Should they have been? Are there any options?
Old 11-17-2014, 07:11 AM
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Default Mileage

OK, so you took it back to OEM, or as close as possible. It's been years since I rebuilt an engine so take this with a grain of salt.
This all assuming your mpg numbers are highway related. Get out your fsm as I'm sure you're going to be using it before you're done.
First thing I'd recommend is check if there are any codes set, that could be a lead. In addition to that, I'd fill the tank and take it on the highway at a set speed using cruise for about 100+ miles. When you get back, fill at the same pump and work out the mileage.
Assuming none of this gives a lead, I'd do a good visual on everything. Insure every vacuum hose and electrical connector is hooked up where it should and no cracks etc in them.
Next I'd read the sparkplugs. Pull them one at a time and see if there's a difference in color on them.
Insure the torque convertor is locking up on the highway. Also check things like brakes, you don't want any dragging on you.
On the injectors, fuel pump and regulator - did you go back to oem sizings? Bigger injectors or higher fuel pressure could result in a reduction in mileage.
Another would be is the timing set properly along with any emissions related equipment?

Just some thoughts for the moment. Hope it helps. Good luck.

Last edited by hcbph; 11-17-2014 at 07:14 AM.
Old 11-18-2014, 06:16 PM
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Thanks for your help. I've tried some of these suggestions, there are some I'd not thought of. Your suggestions are most welcome.
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