2000 Astro misfire/missing when cold

[tntv]

Only in the morning when engine is cold does it really hesitate...misses. After it warms up it seems to run well. Replaced the fuel filter. What can I do to diagnose? Fuel injectors? On a range of 1-10 with 10 being most difficult, how hard is it to DIY replace fuel injectors if needed? I've run a few bottles of Techron and Lucas already. Thanks!

2000 Astro Van 4.3L LS

[Leeann_93]

When's the last time plugs/wires/cap/rotor were looked at and/or replaced?

[redfury]

You should check your fuel pressure first, see how well the van is holding it. If it isn't holding pressure well, then it could be an injector/regulator issue. If the regulator is leaking fuel, it will dump it down the intake runners for the rear most cylinders as they both share the same intake port in the upper part of the plenum, which is directly below the regulator.

You can try cycling the key 3 times to let the fuel pump build up pressure and see if that does anything good or bad to your initial start up.

Generally, on a cold start up the van is going to be set at default settings for sensors like the O2, etc until they have come up to operating temp and then come online. They can then trim the fuel/timing to clean up any problems that may be mechanical in nature ( physical problem instead of electrical/sensor issue ).

I'd also look to see if there are any codes stored.

[tntv]

Thanks....I don't think the plugs, wires, etc. would only show symptoms when cold. I did replace them a number of years ago. I'll figure out how to check the fuel pressure, etc.

[Leeann_93]

Moisture could be getting under the cap (it's common on these), which would increase when it's cold outside, causing a harder start/misfire when cold. When it warms up, the moisture is burned away and it runs better.

So yes, it could cause your problem and they do need to be checked.

[mkj54]

If it's been a couple years since you changed the plugs, they're due to be changed before you spend time doing anything else.