Crazy Astrovan

astro
chevrolet

#1

I have a 96 Chevy astro van, and its has the following symptoms…Check engine like comes back as “multiple Misfires” The plugs, wires, rotor and rotor cap were replace about 2 years ago, but the van has occasional lurchings, and a misfire can be felt.

IT originally came back as needing the front two O2 sensors as having issues

Can i still be the O2 sensors or, the vacuum hoses or the timing chain?( both OEM)


#2

These are excellent vans by the way.The only problem I had with my 98 was the fuel pump…had to cut a hole in the floorpan to get at it instead of dropping the tank.In your case,I would spray some water on the spark plug cables to see if the van misfires.


#3

I used to own a couple of Astrovans years ago. They both had ignition coil failures. You might want to check that out. I recall that they both had a hard time after splashing through rain puddles.


#4

It might be worthwhile to remove the distributor cap and inspect it and the rotor. Especially the under side of the rotor where a red or grey tracking indicates voltage is arcing through. Eventually all rotors fail but many after market brands have a short life especially if one or more plug wires are deteriorating.


#5

Already put a multi-meter on the coil
The numbers were dead center


#6

Already checked the rotor, it looks brand-new


#7

For a misfire to occur there’s a problem with one of these

  • spark
  • ignition timing
  • fuel/air ratio
  • compression

A visual check for a healthy spark during cranking makes sense. Next, idle the engine at night where it is very dark. Do you notice any sparks jumping around in the engine compartment? Next up, check the ignition timing, the fuel rail pressure, then check the fuel trims and do a compression test.

That’s a good test, but coils can fail intermittently, especially with increasing temperature. An o’scope test of the ignition system might show that up.


#8

How do you check for timing? Look at the timing chain?


#9

By “timing” I’m referring to ignition timing, not valve timing. Valve timing is set by the timing chain. Checking valve timing is more complicated. Ignition timing is usually pretty easy to check. For ignition timing on my early 90’s Corolla there’s a marker on the crank pulley I check with a timing strobe light. How it is done though varies car to car. I think cars w/OBD II the ignition timing can usually be read out using a scan tool.

Checking the base timing at idle is important on some engine designs b/c they base all the other timing assuming that is correct at the specified idle rpm. That’s why the idle rpm and the idle ignition timing has to be correct for the rest to work. Newer engine designs (usually using a crank position sensor and often a cam position sensor) are less particular about idle rpm and idle rpm timing b/c they can make use of more sensors to set the ignition timing.


#10

I should mention that the check engine light has a habit of coming on and then disappearing


#11

The computer has spotted a problem with one of its sensor readings, but it must be just on the edge of acceptable. Changes in temperature, engine load, driving circumstances may be what makes the CEL go from on to off to on … etc. The computer can’t say what the actual problem is, its not that smart. But it can provide very valuable clues to help your shop figure it out quickly.

btw, if that CEL ever starts flashing non-stop, best to immediately stop at the next safe location and turn off the engine and have it towed to a shop. Flashing CEL’s mean there’s something seriously amiss (no pun intended) and that expensive to repair engine or exhaust system damage may occur if you continue to drive.


#12

Yes, yes, and maybe.

The possibility of bad oxygen sensors is obvious. Their outputs can, however, be checked.

Vacuum hoses on a 21 year old engine are always a possibility. There are ways to test them using a vacuum gage and/or even spraying them with ether while the engine runs. If there’s a leak, the engine’s idle will race when the ether hits the leak. But IMHO vacuum line by the foot is so cheap that if they’re suspect it’s better to just change them one by one and see what the result is.

Timing chains: while they’re a very stable way of timing the valves, if your engine has Variable Valve Timing oil pressure problems can cause valve timing problems. And chains can stretch over time.

Which brings me to the valves. Sticky or worn valvetrain components, including lifters, rocker arms, weak springs, etc can and do cause problems on old engines.

And then there’s erratic injectors. And bad compression.
Gotta go now. My REPLY button is disappearing.