87 2.9 won't stay running.

luftwaffle · Aug 4, 2016

Hey everyone. My poor old 87 has been sitting for about 2 years as I have to travel a lot for work. I would like to get it road worthy again. When I parked it, it had a lope to the idle almost like it had an aftermarket cam, but besides that it would run and drive.

Anyways, it will idle fine for like 5 seconds and then bog really bad and die unless I floor it, then it sputters, revs up and tries to die. I've noticed a burning smell and small amounts of smoke coming out of the oil filler.

I have replaced the spark plugs and wires, & cleaned the IAC valve.

Can anyone point me in the right direction as to what I should try next?

Thanks!

RonD · Aug 4, 2016

When you start it cold does the computer go into Choke Mode?
Idle above 1,000rpm, advanced spark and rich fuel mix

The high idle is the easiest to spot, lol.

If not then computer may be getting the wrong engine temp reading, so doesn't know engine is cold.
2 wire ECT sensor is what the computer uses for that, this has no connection to dash board temp gauge, that's from a SENDER, not sensor.

When engine is warmed up shut it off then take off the intakes air "tube", open throttle and see if you can smell gasoline, you shouldn't.
With fuel injection, when you turn the key to OFF the injectors stop that instant, engine keeps turning so pumps out any fuel smell from the intake.
If you smell fuel then you may have a leaking fuel injector, or leaking fuel pressure regulator

luftwaffle · Aug 4, 2016

RonD said:
When you start it cold does the computer go into Choke Mode?
Idle above 1,000rpm, advanced spark and rich fuel mix

The high idle is the easiest to spot, lol.

If not then computer may be getting the wrong engine temp reading, so doesn't know engine is cold.
2 wire ECT sensor is what the computer uses for that, this has no connection to dash board temp gauge, that's from a SENDER, not sensor.

When engine is warmed up shut it off then take off the intakes air "tube", open throttle and see if you can smell gasoline, you shouldn't.
With fuel injection, when you turn the key to OFF the injectors stop that instant, engine keeps turning so pumps out any fuel smell from the intake.
If you smell fuel then you may have a leaking fuel injector, or leaking fuel pressure regulator

Yeah, if I start it ice cold it idles for maybe 30 seconds really high. Then it has terrible throttle response and tries to die. Thanks for the info, I'll try your suggestion this weekend and report back.

RonD · Aug 5, 2016

IAC Valve seems to be working if idle goes high at startup.
It does read like ECT sensor is telling computer than the engine is already warmed up, so computer lowers idle and leans out fuel mix too soon for a cold engine, so it struggles to stay running.

And just as a heads up when diagnosing fuel injected engines.
Pumping the gas pedal with a carb meant you were squirting in more fuel, so it really was a "gas" pedal
With fuel injection the "gas" pedal is now an "air" pedal, there are no jets or an accelerator pump, so pumping the "air" pedal lets more air in.

That's how the IAC valve works, computer opens it to let more air in to increase idle speed.

luftwaffle · Aug 5, 2016

RonD said:
IAC Valve seems to be working if idle goes high at startup.
It does read like ECT sensor is telling computer than the engine is already warmed up, so computer lowers idle and leans out fuel mix too soon for a cold engine, so it struggles to stay running.

And just as a heads up when diagnosing fuel injected engines.
Pumping the gas pedal with a carb meant you were squirting in more fuel, so it really was a "gas" pedal
With fuel injection the "gas" pedal is now an "air" pedal, there are no jets or an accelerator pump, so pumping the "air" pedal lets more air in.

That's how the IAC valve works, computer opens it to let more air in to increase idle speed.

I actually have a new ect sensor for it around here somewhere. I had my brother turn it over and I could only hear the fuel pump on the rail prime. Should I go ahead and replace the in tank one?

RonD · Aug 5, 2016

Fuel pump will only run for 2 seconds when key is turn ON, that is normal.
It won't turn on full time until engine RPMs are above 400

You can turn key on, count to 3 and turn key off, then repeat that 2 more times.
That will get 6 seconds of fuel pump run time which should put 35psi at the rail if it was 0psi to start with, spec is 30-40psi for your system.

You can NOT over-pressurize the system, it has a fuel pressure regulator(FPR) on the fuel rail, that will send extra fuel/pressure back to the gas tank on the Return Fuel line

Fuel Pump relay is on the fender in engine bay, it has a Green Base, Brown base is EEC relay, Black is WOT relay(optional, for Air conditioning).
Computer controls the fuel pump relay, to send power to the in tank fuel pump, when key is turned ON the green base relay will click ON and the after 2 seconds click off.
After engine starts it will click on and stay on, you can feel it "click" with your finger.

Brown base relay will also click ON with key ON, but it will stay ON until key is turned OFF

87 2.9 won't stay running.

luftwaffle

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RonD

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luftwaffle

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luftwaffle

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