77' 280 acceleration problem

[brento_1488]

Ya once I get my buddy out this weekend to check it out, if we figure it out ill letchya guys know what the problem was. In. The meantime, any more troubleshooting ideas why it would still be running so lean?

[FastWoman]

Well, after you eliminate all the simple stuff -- and also the not-so-simple stuff -- then you're left with the ECU. What a few of us have found is that the ECU can drift over time in the pulse widths it delivers to the injectors. This drift always seems to be in the direction of a lean mixture. So after you've ruled out everything else, you can modify your coolant temp sensor circuit with an inline resistor to up-regulate fuel delivery, richening your mixture. If you use a variable resistor, you actually have a means to tune your fuel/air ratio.

... but we're getting ahead of ourselves.

[cozye]

what's your fuel pressure ?

[brento_1488]

Ya I was reading that in some of ur other related threads fastwoman. CozyeStill waiting to get paid to order the fuel pressure gage.

[FastWoman]

Cheap fuel pressure gauge (under $10): Go to your local hardware store, and find a cheapo Chinese generic pressure gauge. I found one at True Value for under $5 with 1/8" NPT threads. I then found a 1/8" NPT "T" fitting and some 5/16" nipples to go in the remaining two ends of the "T." I think my total cost was $6 or $7. It's surprisingly accurate. I got the thing to install (permanently) inline between my fuel filter and fuel rail. If it doesn't hold up, no biggie (as long as it doesn't spray fuel!).

[brento_1488]

true that. ima check that out tomarrow

[brento_1488]

wooow. the shitty part about living on an island... Ace, Napa, and Carquest all dont have anything even close to what i was looking for. what a bunch of assholes... my machanic buddy i ran into said its prob the MAF sensor but im ganna continue with trouble shooting before i go and spend $200 on something i potentionally dont need...

[brento_1488]

wooow. the shitty part about living on an island... Ace, Napa, and Carquest all dont have anything even close to what i was looking for. what a bunch of assholes... my machanic buddy i ran into said its prob the MAF sensor but im ganna continue with trouble shooting before i go and spend $200 on something i potentionally dont need...

[cozye]

There isn't a mass air flow sensor on the car. There is an air flow meter, but it operates differently than a MAF. you can test every part of the fuel injection system with a voltmeter, however you can really test anything until you verify proper fuel pressure. It's the first step. There are many people who have had the exact same symptoms as you, caused by a bit of rust settled in the fuel tank and clogging the fuel inlet, or a dirty fuel filter. No way to know until you visually verify proper fuel pressure.

There is a factory service manual available for download that has a very thorough and detailed section on fuel injection system troubleshooting, you might take a look at that just to understand the system and prepare for what you will need to do once you verify consistent fuel pressure.

Think about it like this. Fuel injection is like taking a water spigot and opening and shutting the valve quickly. The amount of time the valve is open in a given condition is constant (say at 3000rpm at operating temp). The fuel pressure should be consistent at that condition so that the exact amount of fuel is injected that is supposed to be injected. If you drop the pressure in half, you would only be getting half the liquid out of the spigot. On the fuel injector, it would be half the fuel, causing the motor to run lean, or starve for fuel.

Edited June 10, 2011 by cozye

[brento_1488]

ya i realized i wrote maf sensor instead of AFM. on with the tinkering i go. thanks

[brento_1488]

somethin like this for the T fitting? http://www.summitracing.com/parts/MRG-2975/

[cozye]

somethin like this for the T fitting? http://www.summitracing.com/parts/MRG-2975/

That one should work, but this is the one I used http://www.summitracing.com/parts/SUM-G1710/

Realize that 3/8" is a little larger than your 8mm fuel line, but it's close enough that with a little lubrication you can slide it on.