Hard to start,ragged idle and sputtering/jerking intermittently

[WhiteSplash93]

I have a 93 splash, 5 speed manual,with a 2.3 four banger.
Ive been having problems with it starting lately,but it eventually will sometimes. Once it cranks,it will idle fine and off you go. Then suddenly it will sputter jerk and backfire like crazy, but once the rpms climb it clears up and runs smoothly. Once I upshift it does the same stumbling,back firing,jerking. Again once you reach a certain point it clears up,but its difficult to reach the proper rpms because of the peoblems. Ive tested the tps,voltage is .98 at closed throttle and steadily increases until it hits 4.97 at wot. I disconnected the iac valve and the idle seemed to level out,but it stalled in the driveway and I couldnt test drive it with it disconnected. The plugs and wires are brand new,they were fouled and needed replacement anyway. I should also not that the exhaust is open right after the cat,because I cant keep it running long enough to get it fixed. Not sure if it could be related,but information is key on these forums. Any help would be appreciated.

 

[BreadPigeon]

I assume there is no engine light on?

 

[RonD]

Can't really test IAC valve until engine is warmed up.
Warm idle should be about 700-750 with manual trans
When you unplug the IAC valve RPMs should drop to 500 or so or engine may stall out, either is good it means IAC valve is working and no vacuum leaks.
If idle stays high then most likely a vacuum leak but could be IAC valve is stuck.

Does it only do this struggling when cold?

The fuel injection computer runs in Choke mode until engine warms up
High idle 1,100+ RPMs, the colder the outside temp the higher the cold idle
Rich fuel mix
Advanced spark timing

Choke mode is started by the computer seeing cold coolant temp from the ECT(engine coolant temp) sensor
If this sensor is giving the computer the wrong temp then computer may think this is just a restart and engine is already warmed up, so no choke mode and engine would struggle until it did actually warm up.
ECT sensor is fairly easy to test, but not expensive to replace, but ONLY if this is a cold start issue

 

[WhiteSplash93]

The cel is on. Had been for ages,and no one can read theseobd1 codes. I disconnected the iac and rpms dropped til it almost stalled so thats likely good then right? I disconnected the maf and it runs right. Does that mean my problem is the maf sensor?

 

[WhiteSplash93]

Also would the ect cause the intermittent problem with starting? Because if I leave it sitting a day or longer it cranks right up,without an issue. Then it warms up and starts acting up again.

 

[RonD]

yes, IAC Valve is probably OK

So it only does it warmed up, then not ECT.

And you have a CEL which means computer could be running in OPEN loop all the time.

So first you need to get the codes, easy to do and you can do that yourself.

Video here: https://www.youtube.com/watch?v=X07hu0kAuzE

More info here: http://www.therangerstation.com/tech_library/OBD_I.shtml

And codes are here, yours will be 3 digit codes on a '93: http://www.therangerstation.com/tech_library/3digitcodes.shtml

Codes are not literal, they can't tell you if something is "bad" just that there is a problem with voltage or range in a system.

So don't go replacing stuff.

After you have the codes and are sure you got them all and wrote then down correctly, disconnect battery for 5 minutes and that will clear current codes and CEL should be off next time you start the truck.
Then see how long it takes for the CEL to come back on, if it happens right away then it is an emission code, usually EVAP system.
If it doesn't come back on until engine warms up then could be sensor or control issue, so shut down engine and get the codes again, that will give you current issue

The older TFI spark system was known for having issues when warmed up, this generally wouldn't set a code.
Coils can also get heat sensitive

 

[WhiteSplash93]

It does come right back on. Ive had the battery disconnected for extended periods quite often these days. (New flywheel,new starter,new headlights, etc.)

 

[RonD]

Then get the codes, need those first.

Could just be filler neck on gas tank has a leak or EVAP vacuum system


And code could indicate MAF sensor voltage issue, which is why it ran better without that sensor connected, but could be wiring or the sensor, code might be a clue to which one

 

[WhiteSplash93]

1,5,9: MAF is/wasout of range-MAF
5,5,8:EGR vacuum regulator/solenoid failure EVR or PFE or solenoid

 

[RonD]

159 code and engine running better without MAF connected would indicate wires to MAF or MAF itself is bad.
Give a good look at the wires and connectors, no frays or corrosion, if they look good replace MAF.

558 code is for the EGR solenoid not EGR Valve, if you follow the EGR Valve's vacuum hose it will go to the EGR Solenoid
EGR Solenoid is an electric valve activated by computer, pulsing voltage to open it a little or a lot.
It will have 2 wires and 2 vacuum hoses
One hose goes to EGR Valve, the other goes to intake manifold(vacuum source)
Make sure both hoses are air tight, no cracks or leaks
You can test solenoid with 12volts or even a 9volt battery
With no volts you shouldn't be able to blow thru either vacuum port, its closed
With voltage then you should be able to blow thru either, its open
Solenoids have no polarity(+ or -) so you can hook it up either way for testing.

 

[rednik]

Did you check the fuel pressure?


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