2.9 stumble

[10strokin]

Hi all, I have changed the throttle position sensor, oxygen sensor, coolant temp. sensor, and cleaned the throttle body on my 87 2.9, but when i hit the gas from idle, there is a noticeable stumble before it revs up...any ideas? Thanks

 

[10strokin]

By the way, the idle is fine, its only when u hit the gas, it bogs for a second, then accelerates....

 

[PGHFord]

Did you scan for any codes?

 

[RonD]

The EGR and IAC(idle air control) can affect from idle acceleration.

Don't replace them test them, hardened vacuum lines can get cracks

 

[lodden758]

low fuel pressure can affect it to. check fuel pressure and fuel pressure regulator.

 

[J281v8]

Did you change the fuel filter yet? When was the last time you changed the plugs and wires? How many miles on the engine? What kind of air filter do you use? Just trying to get some background.
Jim

 

[10strokin]

Forgot to add, plugs and wires are brand new. IAC was cleaned up nicely and reinstalled. I cannot get any codes to come up at all on my tester, have no idea why. i have a new filter up by the engine, but dont know the condition of the one on the framerail yet. Engine runs pretty decent other than this. 129,000 miles. No smoke and all cylinders read between 120-140

 

[PGHFord]

Push down on your fuel injector plugs to the injectors make sure there isnt one that has come loose. my truck always sorta did the stumble thing just as your about to go when the truck is cold, I was reading just now about just like such an issue on another site, said one of the injector plugs was loose. Im seeing how my truck runs now for a week before I fiddle anymore with it, seems to be fine since I replaced IAC and MAP and fixed no start with a new TFI. Might consider next weekend taking off EGR and doing a routine clean for maintenance.

 

[10strokin]

What exactly does the MAP sensor do?

 

[RonD]

MAP stands for manifold absolute pressure.
This sensors gives information to the Engine computer so it can meter the fuel injectors.

Fuel injected engines need some way to determine the most efficient amount of fuel to add to the available air flow, that's what the MAP does, tells the ECU the air volume pressure.
Carburetors used "jets", as air passed by the jets fuel was sucked in to the manifold, the wider open the throttle the more air so more fuel was pulled in.

The MAP sensors isn't the only sensor used for fuel mix, engine temp and air temp is important as well.

MAF stands for mass airflow, this is a similar sensor to the MAP, a manufacturer usually will use one or the other, but both can be used

 

[10strokin]

Excellent info, thanks! I will look into changing this next and checking the injector plugs....