3.1 Engine hesitates after restart when hot

[Meridivs]

Recently our '92 TS has developed a strange problem - it pulls and runs fine but once we stop the engine when hot and restart it it doesn't run right and hesitates (power comes and goes in waves, regardless of acceleration).

If we keep the engine on, cooling fan cycling, it runs fine with no issues but once stopped it hesitates after restarting hot.

Have you experienced this? What might be the case for such strange behaviour?

[Jeffrv]

How long does the engine run poorly after it has been allowed to shut down and heat soak all the components?

[Meridivs]

It runs poor indefinitely or until you shut it down and allow it to cool.

Originally Posted by Jeffrv

How long does the engine run poorly after it has been allowed to shut down and heat soak all the components?

[Jeffrv]

How much fuel do you have in the fuel tank when it does this? The 3.1 engine is throttle body, which operates at a much lower fuel pressure than port injection ( spec is 9 to 13 PSI ) They are also much more tolerant than port injection of operating with lower fuel pressure, to a point.
When the engine is running normally, take the air cleaner cover off and look down the throttle body, you should see both injectors spraying fuel consistently and in a nice pattern, Look at it again when the engine acts up to see is the spray pattern has changed, to more of a dribble than a spray. This would indicate lower fuel pressure. Be careful doing that though as if it is not getting enough fuel, it will run lean and could backfire, not good if you are looking right over the opening.
Try keeping at least a half tank or more of fuel in the van, it allows the fuel to cool, preventing vapour lock, as well as keeping the fuel pump itself cool.

[Blue Bowtie]

That's a good piece of advice, but it would be more effective to connect a fuel pressure gauge to monitor actual pressure. I've had TBIs do the same thing, and almost always fuel pressure was a problem. That vintage will probably require an adapter to be connected at the inline fuel filter in order to read fuel pressure, since there is often no test port provided from the factory.