93 chevy conversion van hesitates when starting out

Skmet, Have you had a full tune up lately, including an injector cleaning. Problem could be a misfire, have a good Tech scan for codes, diagnose and estimate repair. Check the attached links,instruction and guides, Good luck
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1999 Chevy Astro Van Hesitation Issue
AstroSafariVans com
Astro Van hesitates when cold 1 2 EricTheCarGuy EricTheCarGuy Stay Dirty
http://www.automotiveforums.com/t546930-_96_4_3l_s_10_misfires_or_hesitates_at_constant_speed.html

Pull the axles & take to an auto parts
store to R&R the axle bearings

Try to get it running a bit to warm up the exhaust. Take a point and shoot thermometer and take the temp of the cat. If temps exceed 400 degrees I would start to suspect a plugged cat.

Back firing is usually an indication of a timing issue

The timing chain is most likely worn & jumped a couple
of teeth or the distributor was installed wrong,if you recently
had work done

lol everything but the actual cause of the problem. The big clue here is your gauges. What sensor going bad will cause the gauges to jump? Ask your mechanic that wasted all your money replacing good sensors. Then you may want to find a good mechanic. The problem is a wiring problem. Probably the main hotline running from the ignition to the fuse block. Somewhere in that area. If you have the spark circuit on a scope you would find it flat line when it hesitates.
I dont think it is a short because if it was you would have blown fuses or smoke and or electrical smell. So it has to be an open circuit that would be nearly impossible to find. If I was going to just start replacing things, I would start with the ignition switch and then the fuse block and then any hot wires to and from both elements.

if your having cold engine start hesitation,you need to check the engine temp switch,it tells the computer how cold it is,so the engine can adjust to a rich start and not a lean one.if the switch is faulty and the computer is being told it is 80degrees,you will not get a rich mixture like no choke at all

Yes...timing. Adjust the distributor...back it off a little and set the timing....also check your carb setting for rich/lean mix....air mix will cause this also.

What have you done to the system to cause this or were you trying to adjust something?

Auto Zone, Discount Auto, Pep Boys

Hello;
The injector assembly also contains the pressure regulator. Since the truck has been sitting, you may have some corrosion in the regulator and the injectors. Try a fuel cleaner and the work on the regulator.
Thanks;
Rich;
RPM Northwest

The cylinder 7 misfire is likely a symptom of the problem, not the problem itself.

Typically, the catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream 02 sensor reading should be fairly steady. Typically the P0420 code triggers the check engine light if the readings of the two sensors are similar. This is indicative of (among other things - such as faulty sensors in the "emissions loop") a converter that is not working as efficiently as it should be.

I do not believe that it is a problem with a valve/head gasket or cam.