So I just got this 2000 Astro Van I know its not a blazer but its got the same engine anyway lol.

Engine fires up and idles like dog crap read the codes for random cylinder miss fire. when you give it gas it barely throttles up but does real slow and then bogs out and almost dies around 2k rpm.

Replaced spark plugs and wires
Replaced distributor
New cap and rotor
reset timing to TDC when new dizzy was installed
Did a fuel pressure check
Did a leak down test
swapped coil

When the fuel pressure gauge was connected and was running the gauge was jumping around between 55-60 psi like crazy it was basically skipping back and forth in sync with the way the engine was idling.

After everything I've done it still idles the same exact way.

I got a good deal on the van because the guy said it "ONLY" needed tranny work but seems as if the engine is in worse shape than the friggin tranny.

Any ideas?

If I spray starting fluid in the throttle body while its running if I sray it just right I can get the engine to smooth out and basically idle perfect but as soon as I stop spraying the starting fluid it goes back to running like a tank.

Honestly just bought the van because it had decent cargo shelves in it that I wanted for another one of my business vans lol.

Read online that bad Crank sensor and cam sensor would give a no start condition and if the fuel pressure regulator was bad it would fail a leak down test witch it didn't

Any help would be great I'm about to call Pick-n-pull to come get this thing before I take a sledge hammer to it lol

 

Spark plugs, distributor cap & rotor need to be AC Delco.
Is the check engine light on? If so, what codes are in memory?
Spraying starting fluid is extremely dangerous and not recommended. One stray spark and BOOM, instant flash fire! Carb cleaner is much safer.
Follow the steps in this link and post all 4 readings: https://blazerforum.com/forum/2nd-ge...eakdown-88305/

 

Everything is AC delco

Only code coming up is P0300 Random cylinder miss fire

Okay so I just hooked up the pressure tester and here's the results

At the service port:

Turn ignition on psi is 60
Shorty after it's done priming drops to 55 psi
after 10 min was at 45 psi

So guess there's a leak for sure

Gonna go to Home depot tomorrow and buy the fitting for the fuel filter leak down test to see if leak is in tank

So if leak is under plenum then its the pressure regulator or one of the spiders that are leaking?

I was kinda thinking that it was the pressure regulator all along

Any good threads you can point me to for the plenum removal and regulator/spider replacement

Thanks

 

Did you try pulling one plug wire at a time to see if related to one cylinder more than another? I know the code was for ramdon misfire, but just asking.

Are the plug wires in the correct positions at the distributor? They go in order on the even side, but out of order on the odd side.

 

Yes, please do complete the fuel pump testing and post the results. However I wouldn't buy a new spider just yet. I think a lot depends on the type of injection spider that you have in there right now.

If it is original (injectors requiring pressure to pop off and deliver), they are very sensitive to fuel pressure and could easily be the cause of your miss. However, if it has already been converted to injectors that are electronically acutated (MPFI), a leak down of 55psi to 45psi in 10 minutes through the fuel pressure regulator (or back through the pump) in itself should not be the cause of a misfire (in my opinion). The new style spiders are not nearly as touchy or troublesome as the earlier versions. This is the reason why people go to them.

So I think you need to finish the fuel pump testing and pull the intake plenum and see if the injectors have electrical connectors on the end of the spider legs so you know what you are working with. Don't lose any of the orings for the fuel line connections and DO NOT bend the fuel lines. Make sure the electrical connector is fully unlocked before you try to pull it off. Other than that it's just brackets and bolt removal.

One thing you mentioned that bothered me is that the fuel pressure was fluctuating when idling. If this is a rapid and severe up/down fluctuation of pressure, that would seem to indicate a severe fluctuation in the vacuum signal to the pressure regulator and could possibly mean a bad valve or valve spring in the engine. Please explain what you mean more carefully and completely.

Also of concern is that you reset a new distributor to "TDC" during install. Please advise exactly how you did this. You might just have the distributor rotor out of position, causing the misfire. Timing is not set at the distributor, it is set by the computer and only distributed to the correct plug wire. If it isn't pointing exactly to the correct terminal, then misfire can definitely ocur. There are two timing marks on the balancer. With the correct one pointing to the mark, the distributor is dropped in with the rotor pointing to the #6 stamped into the top of the distributor housing. Then you check camshaft retard with a scan tool with engine running to make sure is ±2° of zero. Also of concern is that you got the firing order right. On the driver's side of the cap there are two that are switched from what you might think. In any case the cylinder numbers are labeled on the distributor cap. LannyL82 mentioned this.

Pulling the spark plugs (keep them in order) and looking if they are carboned, etc can help to tell a lot. You can do a compression test while they are out.

So this is why I think you may want to not jump to big conclusions about the spider too early. It's a pretty pricey item.

Last thing to remember is that you may have multiple problems needing rectified, but only one thing causing your miss. For example your fuel pump could be on its way out and test bad, or leak down in fuel pressure regulator could be more than designed - but rotor timing or crossed plug wire could be causing the miss. Note this is just an example, and not what I think is wrong with your vehicle. Point is to find something that makes good sense, and check all the basics if there is significant expense involved in a part replacement.

Good luck!