can't let off gas or it dies


nannon37
08-30-2004, 05:33 PM
i have a 94 jimmy that is using a lot of gas. when i let off the gas to slow down it will die. i have been told the erg valve looks new so i should change the o2 sensor. however, another told me it is probably the spider injector. any way to check on these things before i start dumping money into things. thanks for any help.

JSayre
08-30-2004, 09:09 PM
Sometimes the EGR valve gets stuck open & causes that problem (it happened to my 96 OFTEN). You can take it off (2 bolts) and see if there is a chunk of carbon stuck in it. I had to do that a couple times a year. You might want a new gasket handy in case you wreck it taking the valve off though.

Teaman3
08-31-2004, 03:34 AM
What size engine and injection type ?

First it would be an idea to check the state of the plugs. Black sooty plugs is an overly rich mixture, grey/white lean.

Has the idle speed screw been adjusted ?

What is the condition of the air filter ? Old ? Recent ? Dusty ? Greasy ?

Clean the EGR as JSayre suggests.

Check the ignition timing. There should be a label stuck to the slam plate or radiator cowl giving the requirements and data for that.

If the AIR injection pump also pipes to the inlet manifold, you'll need to check the valves and electrics. Air should only be injected during sudden throttle closure. Normally, no air should be injected.

Check the output of the Throttle Position Sensor. No throttle: at least 1/2 volt. Open the throttle to full slowly and observe output: it should rise steadily. If not it's a fail.

The Idle Air Control valve seat should be cleaned. It's at the base of the throttle body. Ignition only, on for 5 seconds then off, then start/run engine for 10 seconds to reset.

What type of gearbox and speeds ?
If automatic, drive at 55mph engine warm. Brake GENTLY to 50mph. Feel/listen for a soft downshift ? From 0mph to 60mph count the number of "upshifts". Most automatics are fitted with torque converter clutches that are engaged above a certain speed, and can be disengaged by the brake pedal operating. If it doesn't disengage, stalling can happen.

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