'93 5.7 TBI problem at slow crawl speed

She runs great at all times other than the old parking lot crawl speed. Anything 5 MPH or under she seems loaded up, almost like she is getting too much gas, happens whether she's cold or hot no change. Idle is perfect anything above a crawl she is great, but very annoying in parking lot for sure. Never stalls but seems likes she wants too, but never does.

Any ideas to look for?

She runs great at all times other than the old parking lot crawl speed. Anything 5 MPH or under she seems loaded up, almost like she is getting too much gas, happens whether she's cold or hot no change. Idle is perfect anything above a crawl she is great, but very annoying in parking lot for sure. Never stalls but seems likes she wants too, but never does.

Any ideas to look for?

Any codes.
Check base timing.
Pull air cleaner and check for injectoir flooding.
A timing light helps check injector pattern.

sounds like one of the injectors in the tbi unit is slobering. usually it is the orings between the body and injector not the injectors themselves. BUT check codes, do some diagnosis, etc. The obd 1 is not very smart, so codes may not do you any good, good ol fashion diagnosis is best here.

thanks guys

It appears no codes have thrown, however the problem exsist. Agree the OBD I not near as informative.

I take a look at the timing and maybe pull the EGR and clean her up a bit. Sometimes you can get rid of some of the carbon build up on them.

There is a idle speed sensor on your TB that may be your problem, also I hear they sell a gasket kit for TB cause gaskets fall apart with age. You may also have a vac activated EGR valve and vac solinoid may open or close EGR at incorrect times. Just more for you to check. Luck

There is a idle speed sensor on your TB that may be your problem, also I hear they sell a gasket kit for TB cause gaskets fall apart with age. You may also have a vac activated EGR valve and vac solinoid may open or close EGR at incorrect times. Just more for you to check. Luck


you mention the idle speed sensor, I went to Auto Zone website the reference a Idle Air Control Valve and then a Throttle Position Sensor. I do not find an Idle Speed Sensor. Is either the ones I mentioned the same as the ISS

Idle air control is correct. You may want to look at info in package or buy book. As I recall there is a learn proceedure its been some time since I changed one ask at parts store they may also know.

Idle air control is correct. You may want to look at info in package or buy book. As I recall there is a learn proceedure its been some time since I changed one ask at parts store they may also know.

agreed, there is an requirement to ground the ALDL(data link connector) or better known as where we connect the OBD I tester. I still have to find it's location somewhere under the dash, big SOMEWHERE:lol:

After changing idle air control on my 93 caddy with 350 chevy eng. I believe the pinnacle can be made longer or shorter by turning and I think you need to measure then adj to hit bottom in TB correctly. But I seem to remember driving at 40 MPH for a specified time which the ECM learns and it makes final additional correction. I think the IAC comes with info,thats why I said check book or with parts store.

Okay slow progress. I did change out the Idle Air Control last night. What was strange to me, Online you can print information about repairs direct from Autozone, it indicated ground at the diagnostic port and turn key to on but not Start position for 30 seconds. However when I went to Autozone to purchase the printable instructions indicated to do nothing. Nothing meaning just unplug, take out, replace, and plug back up. Nothing extra. So ran it for about 10 mins down some roads but did not seem to do anything.

So here I ask, does it take time for the ECM to learn something new, does it need to be run for longer to actually reset? Or is it just possible my problem has nothing to do with this?

I would like to add an observation. Now that we have some cool morning, it really seems she runs perfect while cold, example this morning I was backing out and started down the road slow and she was running great.

Can the throttle position sensor have anything to do with this problem above.

thanks

The new IAC valve's pintle needs to be adjusted to the proper length. Measure the new valve's length from the tip to the mounting flange or threaded end. If it is greater than 1.102" then use light finger pressure to slowly retract the pintle into the body to the designated length. Hope this helps!

is there are correct length? or just less than you measurement?

I have no idea why the istructions don't specify this

Thanks again

The reason for no instructions on it is because it should be set right from manf.
So double check it.

As long as it is not any longer that 28.0mm or 1.100" in. from tip to mounting surface it is ok to install it.
If longer push it back to 1.100" in as instructed in upper post.
They are self adjusting but if the plunger is to long before installing it can damage seating surface.
Also make sure the new VALVE MATCHES THE OLD ON ON PLUNGER SISE AND SHAPE.
key on should set it.
But start engine and turn it off and back on and see jow it does.

If it does not idle right after installing you may need a engine scanner to check it out for proper operation of pcm control of it.

The reason for no instructions on it is because it should be set right from manf.
So double check it.

As long as it is not any longer that 28.0mm or 1.100" in. from tip to mounting surface it is ok to install it.
If longer push it back to 1.100" in as instructed in upper post.
They are self adjusting but if the plunger is to long before installing it can damage seating surface.
Also make sure the new VALVE MATCHES THE OLD ON ON PLUNGER SISE AND SHAPE.
key on should set it.
But start engine and turn it off and back on and see jow it does.

If it does not idle right after installing you may need a engine scanner to check it out for proper operation of pcm control of it.



Well, without the above input I did install her last night and she idles great, but the original problem has not ceased. So onward I guess. I have the EGR and the EGR vaccum sensor next I guess.