TBI high Idle

[350xryder]

Thanks to all the great info on this board I installed a tbi from a 1990 Blazer on my 75 scout ii 345. The scout drives great down the road, I cannot get it to idle below 800 rpm. And at 800 rpm it dies when I put it in gear, so I have the idle set at 1000 rpm to keep it from dying. I have followed the tbi setup FAQ and cannot seem to get the system to maintain a low idle.

I suspected a vacuum leak, so I did all the usual fixes. Propane, around all mating surfaces including throttle shaft with no solution. I replaced the intake gaskets recently during a top end rebuild. I also replaced tbi to manifold gasket and egr gasket. The brake booster doesnt seem to be leak vacuum. PCV in valley pan is connected to vacuum port on rear of intake manifold. MAP sensor is connected to center port on rear of throttle body. All other ports on TB are pluged

With laptop running winaldl the temp sensor seems to be the same reading as dash temp gauge. IAC at initial start up is 145 then counts down to 0 where it stays during idle. TPS is reading .58v during idle. Timing is set a 0 degress with bypass disconected.

Can this be timing related? Possibly a bad ignition module, or incorrect reluctor phasing?

Any help would be great! I seem to be stuck.

[Bill usn-1]

Do you have any data logs and BLM data?

Have you set the min idle speed?
What happens when you drive the IAC closed to set the min idle?

[350xryder]

I will log some data today

When i drive the IAC closed and set minimun idle speed, the engine will die below 750 rpm.

[scorp1us]

You're getting way too much air.

I'm suspecting your throttle plates are open too far. You're idling too high because you're getting more fuel because you're running lean. Your IAC is 0, it should never be that. That's telling me it's trying to choke itself off. There is a table called "IAC air flow vs temp" (if memory serves, or something to that effect) You'll see there is no 0 entry, meaning that IAC should always be non-zero. I'm running a later PCM, which can calculate this in percent, but you should still have a table.

Re-do the initial setup procedures. Your throttle plates should be more closed than they currently are. This in turn, will change the TPS so then adjust that. In that order.

[350xryder]

I found my reluctor was off a couple degrees. I then went through the initial startup procedures. Set timing at 0 with bypass disconnected. Engine will still only idle at 700 rpm any lower it dies. So I set it there and logged some data. My IAC is still reading 0 at idle.

Here are my specs
Fuel pressure 14psi
tps .56v
21 in Hg vacuum
ecm 1227747
ANLX
5235206*RPD injectors

the scout drives good, just doesn't want to idle low.
I have attached my data log. Thanks for any help.

[Bill usn-1]

You only attached the BLM table. Do you have the data log?

[scorp1us]

How did you get through the initial setup procedures if you can't get less than 700rpm?

During the ISP, you should be able to get down to 500-525 rpm, with the throttle plate almost shut and the IAC at 0. Then you should adjust the TPS and hook the IAC back up.

Then when the engine is running, at idle, it should NOT have an IAC of 0. The reason why it is zero is there is too much air getting into the engine, the IAC as closed to try to bring down the idle. You want the IAC to not be zero, so it can choke it off if needed. But it's fully out and can't lower itself any more.

It's trying to lower your idle, but there's still too much air getting in. But, you're showing 21" of Hg, which makes no sense. It is showing your throttle plates are being effective. Take the vacuum from somewhere else to be sure.

[350xryder]

Thanks for the replies. I cannot seem to find my data on my laptop. I will keep trying.

I got through the ISP by settling with a high idle and moving on. I took vac readings from two places on the TB. I will get a reading off the intake. Could low voltage cause this? My alt light is on at idle and my voltage readings are 12.6 with the key on. I bought a 105 amp alt. today and should have it going tomorrow.

My data is somewhere......

Again thanks for there replies

[350xryder]

attached is a screen shot of my winaldl folder. I realized I am using vista. Should the data log be located in this folder?

[scorp1us]

Have you made or bought a cable?

Use TunerPro for logging.
You'll need a couple files, and ASD and ADX. Together you'll read data out of it by hitting the log button. This will let you/us read exactly what is going on.

If your idle isn't set right in the ISP, it definitely won't be set right after.