won't stay running

[SAM CARUSO]

SUV runs for a few minutes, shuts off and then won't start. Replaced MAF and TPS sensors. While running in neutral it idles smooth, drop into gear, rpms drop to 200 and idles very rough.

 

[Rhett]

Check the Idle Air Controller (IAC) -- these can get gummed up and can be (sometimes) successfully cleaned.

Your standing idle should be about 650-700 rpm

Also make sure all vacuum lines are connected.

 

[SAM CARUSO]

Check the Idle Air Controller (IAC) -- these can get gummed up and can be (sometimes) successfully cleaned.

Your standing idle should be about 650-700 rpm

Also make sure all vacuum lines are connected.

cleaned IAC, all vacuum lines are on

 

[bigred4x4]

Getting any lean or rich codes?

Id also check fuel pressure.
I've also seen a cracked spark plug cause the engine to miss under load but idle fine
And you also might want to check your exhaust could be a clogged cat. But any codes you can pull will be helpful.

 

[J_C]

Which engine? Beyond OBDII codes being pulled, it might help to hook up a scan tool capable of showing live data for the few minutes it runs. I suspect it's too lean, and you've replaced the MAF and cleaned IAC so I'd do a fuel pressure check.

While it shouldn't be needed now, eventually it might be good to unhook the battery to reset the computer to relearn with the new MAF sensor present. I could be wrong, have seen conflicting info about whether this is really needed but I'd error on the side of doing it, and as a bonus, it might run for a few minutes longer while the engine still runs richer.

When you wrote that it shuts off, I assume this happens if it's just left sitting idling, that it is not necessary to put it into gear to get it to stall?

 

[Rhett]

Which engine?

Since he has a '95, it's OBD-I. I know of no scanner that can pull live data from an OBD-I, outside of maybe an old Ford star tester or something like that. I don't think TweeCER lets you do live captures

 

[Rhett]

cleaned IAC, all vacuum lines are on

Before you start spending lots of $$, take a look at the throttle adjustment screw on the base (pass side) of the throttle body. Sometimes it falls out, or wiggles out of position. When it does this, the throttle plate closes too far, not allowing the engine to ingest enough air at idle to run.

 

[J_C]

DOH... '95. Like my furnace, just a little too old to tell you what's wrong with it. Mentioning the throttle plate on one this age makes me wonder about checking for carbon buildup too.

 

[SAM CARUSO]

DOH... '95. Like my furnace, just a little too old to tell you what's wrong with it. Mentioning the throttle plate on one this age makes me wonder about checking for carbon buildup too.

Cleaned the throttle plate, still does it.

 

[Rhett]

Cleaned the throttle plate, still does it.

But did you take a look at your adjustment screw?

No joke, very commonly I have seen the screw wiggle off or move to where the throttle plate is closed too far. It only takes a tiny bit of movement to throw it out of whack.

 

[gatzdon]

How long is a few minutes? A bad engine coolant temp sensor (not the sensor for the gauge) would result in being able to start a cold engine, but difficulty running a warm engine and approaching impossible to drive a hot engine. When the sensor corrodes up, but before complete failure, it can result in reading significantly colder than the engine really is.

 

[Ashley31]

Having the same kind of issue with mine, starts up cold lovely but when it’s hot takes an age to sgart and is very rough plugged into a comp and it was showing ECT at nearly 280!!! Unplugged and it started first time so I’d change your ECT Sensor first it’s what’s im doing then possibly the thermostat....also does the temp gauge move at all ?