350 TBI troubles

[bigdogkrug]

Ok, so my truck has recently been running poorly intermittantly. Seems to happen both when the engine is hot and cold, it will just start loosing power like its running out of gas, and almost feels as if its misfiring too randomly. Always seems to happen on light acceleration from a stop or while driving at speed. Mostly after slowing down to make a turn then accelerating after. If I accelerate harder or floor it the engine picks up normally as it always has. Seems to idle fine, twice in last few weeks I've had to hold the throttle down to get started, but mostly starts up fine.... its starting to happen more frequent and I'm worried. I've changed the fuel filter, EGR solenoid, plugs, plug wires, distributor cap & rotor, and ignition coil all within last year... I'm stumped, the check engine light doesn't come on at all.... Appreciate any help guys

 

[smier]

Does your check engine light work? If so, have you tried to pull any codes? So many possibilities here... You're going to have to eliminate a few... I started with the free/cheap ones. Everyone has given me similar symptoms, but I'm betting on the EGR valve or fuel pressure issue...
1. Pull the codes.
2. Check your new plug and wires etc... and make sure they are all connected properly and not burnt or cracked allowing them to arc/short out.
3. Check your fuel pressure.
4. Check your EGR valve. I'm surprised you replaced the EGR solenoid instead of the EGR valve.
5. Check your IAC or idle air control may be malfunctioning or gummed up.

So many more possibilities, but those should get you started. Don't just throw new parts at it, check the stuff out so you don't waste money. Let us know what you find, and we will try and help you out. Intermittent problems are tough, especially if you can't duplicate them.

 

[Jessie James]

I agree with pulling the codes. Quick, easy, free.

The EGR valve can easily be tested and inspected. If it's stuck open you could have a problem. FYI - You likely would not be able to pass smog using a dyno if the EGR is bad.

IAC valve only comes into play at idle. I don't think that is the issue.

Here is what the manual says to check:

> Air filter
> Fuel injectors. Both should be spraying when the engine is running. Disconnect them both and turn the engine over. There should be NO fuel coming out.
> Timing - remove the EST wire (tan with black stripe) from the distributor first.
> Fuel pressure - should be 9 to 13 PSI. You could have a blocked fuel filter or bad fuel pressure regulator.
> Injector wires grounded at air cleaner.
> Alternator less than 9v or more than 16v
> Timing
> Compression
> Worn camshaft (remove valve covers and inspect valve movement)
> Low transmission fluid or bad torque converter
> EST - the brown with black stripe wire which goes to the distributor. You have to test that whole system, which is more than I can type out! Google perhaps?
> Restricted exhaust

You can also easily test the MAP sensor. Start the truck, unplug the electrical connector. If the idle improves, you have a bad MAP sensor.

I hope that helps!