SPFI Starting and idle issue

[Ledheckman]

I have an 89 gl that's been having this issue since I got the car. Upon attempting to start it will fire then immediately die you have to pump the gas to get it to start. If you pump the gas get it started then hold the car at say 3,000 for a moment it will stay running.Once the gas is depressed it will then idle at 1,000 rpm and once warmed up will have light idle surge im stumped. I've checked vaccum cleaned IAV and engine has had a full tune up.

[Dee2]

I think the key words are "idle surge".  This can come from many possible sources.  A good article for diagnosing is here:

 

https://www.2carpros.com/articles/engine-surges

[DaveT]

Another thing to check is the CTS .

[Ledheckman]

What's the best way to go about checking that sensors operation?

[DaveT]

Ohm meter. Either run the engine up to normal temp, and check the reading as it cools down, or remove it and use water in a small pot and stove, etc.

The fsm has a little chart of temperature vs ohms. It should be steady, maybe drift, depending on which method you use, not jumping randomly. I don't have access to a fsm until tonigh.

[Ledheckman]

Ok I will look into this. Could this be the culprit of the gas needing to be pumped on start up as well?

[Ledheckman]

Ohm meter. Either run the engine up to normal temp, and check the reading as it cools down, or remove it and use water in a small pot and stove, etc.

The fsm has a little chart of temperature vs ohms. It should be steady, maybe drift, depending on which method you use, not jumping randomly. I don't have access to a fsm until tonigh.

[Ledheckman]

Is there any way I can shoot you a video of the cars behavior? You seem to know your stuff and I'd really like to get this sorted out I'm new to these old subies.

[DaveT]

How big is the file?  Over 10mb won't go by email.  I'll have to see if I still have my drop box account active.  youtube works, if you have  / set up an account.

 

The description in the op could be CTS, or Idle air, or a few other things, or a combo. 

 

Jumpy idle I have experienced due to flaky CTS. 

Engine dying when the gas pedal is released, I have seen caused by IAC valve dead.  But the car would run when I manually controlled the idle with the gas pedal.

 

Going by theory, if the CTS is telling the ECU the engine is at one temp, say hot for example, and it's cold, it's going to be hard to start, and keep running, until at least some heat builds up.

The pumping of the gas, well, it's not the same as carburetor engines.  In carbs, there actually is a mechanical pump that squirts fuel down the throat when the gas pedal is pushed down.  This is needed to keep the mix balanced  - the air flow increases a lot faster than the fuel vapor.  With out it, the engine stumbles until everything levels off again.   In our SPFI, the ECU reacts to the pedal position, and signals the injector as needed, so no need for a pump.

It's likely just holding the pedal down a good bit may have a similar effect.

Also, something to note - in the event of the engine getting flooded [which I've had happen a few times since 1988]  The method [it's part of the programming in the ECU] use to clear it is hold the pedal most of the way down, and crank.  Take a break, and crank.  Hope you have a good battery.  And it will clear, and start firing, then finally catch and run normally.