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My Astro is Misfiring! codes P1351 and P0300. Advice Needed

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10K views 34 replies 9 participants last post by  konybravo  
#1 ·
I turned the key and it started up for the first time in maybe a couple of weeks. It ran well for the first 2 minutes until the engine warmed up a little.

Then I heard occasional misfires and then they began more frequent and I turned the engine off. A few hours later I started my Astro and it did the same things as before.

I used my scanner and it showed P1351 and P0300.

Almost a month ago I decided to do some preventative maintenance on my Astro and changed the spark plugs (ACDelco Iridium) and wires and then my van wouldn't start. I installed a new ignition coil, ignition control module, fuel pump, distributor, cap and rotor.

I know how to do some "remove and replace" things but it takes me about 10 times longer to do than many people. I am not good at diagnosing problems.

Any suggestions on why my Astro is misfiring or what to try first?
 
#2 ·
Did the van run fine, before the tune-up?Did these codes appear the moment it started misbehaving, or before?If the van' s been running fine on startup, I assume, you did not misplace the wires @ the cap..?Are you sure, you installed the distributor correctly- have you marked the rotor's position, prior to removal, or did you do it by the book- cylinder #1 at TDC, etc? The engine would run even a tooth off.Have you checked your ICM, and coil connections, and wires(a wiggle, when running)? You may give the ignition system the "fireworks test", since sometimes the components come bad out of the box(especially wires). If the above don't give any answers, you may need to check your fuel pressure, and the electrical connections @ the pump.Many reported issues, are due to bad crimp conections there.
 
#5 ·
GM General Motors P1351: ICM Circuit High Input Conditions Details: With engine speed less than 250 rpm, ignition control enabled, the VCM detected that the ignition control circuit was more than 4.90 V

https://www.engine-codes.com/p1351_chevrolet.html
 
#6 ·
Yeah, thats a strange one as those codes point to the things you already replaced.
I would go back over those things to double check it all, make sure all the plug and coil wires are fully seated and double check the distributor install, set the engine to #1 tdc and see where the distributor is pointing.
 
#9 ·
konybravo said:
Did the van run fine, before the tune-up?
The van van perfectly before I decided to change the really old spark plugs for ACDelco Iridium and installed new spark plug wires. I bought a new set of a different brand spark plug wires that I hope to install today. Maybe it was the wires...

konybravo said:
Did these codes appear the moment it started misbehaving, or before?If the van' s been running fine on startup, I assume, you did not misplace the wires @ the cap..?Are you sure, you installed the distributor correctly- have you marked the rotor's position, prior to removal, or did you do it by the book- cylinder #1 at TDC, etc? The engine would run even a tooth off.
The codes appeared as soon as the engine started the first time after installing the new distributor. The wires on the cap are not misplaced. I installed the distributor by the book, cylinder #1 at TDC, etc.

I think that I might need a scanner to read cam retard/advance ("CMP" reading from OBD2 but from what I was able to find is that only the expensive $400+ ones do that. Then I could adjust it to +/-2 degrees by twisting/rotating the distributor like in this video:
.

konybravo said:
Have you checked your ICM, and coil connections, and wires(a wiggle, when running)? You may give the ignition system the "fireworks test", since sometimes the components come bad out of the box(especially wires).
I have checked my ICM and coil connections and they are both receiving power. Should I try spraying some electrical connector cleaner in them? I haven't tried the "fireworks test" yet but will add it to my "to do list".

konybravo said:
If the above don't give any answers, you may need to check your fuel pressure, and the electrical connections @ the pump.Many reported issues, are due to bad crimp conections there.
I replaced the fuel pump with a new ACDelco a couple of weeks ago and checked the fuel pump assembly connections at that time.
 
#11 ·
Wimpazz said:
GM General Motors P1351: ICM Circuit High Input Conditions Details: With engine speed less than 250 rpm, ignition control enabled, the VCM detected that the ignition control circuit was more than 4.90 V

https://www.engine-codes.com/p1351_chevrolet.html
That link says- Possible Causes:

Faulty Ignition Control Module

Ignition Control Module harness is open or shorted

Ignition Control Module circuit poor electrical connection

I installed a new ACDelco Ignition Control Module a couple of weeks ago.

I wonder if it was just a bad one from the factory or if the (excessive?) cranking trying to get it to start since then overheated it.

Do you think I should buy a new Ignition Control Module?
 
#12 ·
1lowcab said:
Yeah, thats a strange one as those codes point to the things you already replaced.
I would go back over those things to double check it all, make sure all the plug and coil wires are fully seated and double check the distributor install, set the engine to #1 tdc and see where the distributor is pointing.
Yesterday the distributor was pointing to the arrow at TDC/#1 but I think it's a good idea to try it again.
 
#13 ·
dchan51360 said:
Earlier He mentioned that he had done the spark plugs and had one of the wires in the wrong place.

Also when he installed the distributor, I think he mentioned that it was off by a tooth. I don't think there was a follow up to that.
Yesterday I was able to get it so that it wasn't off by a tooth and now at TDC/#1 the rotor points to the arrow.
 
#15 ·
If you can turn your distributor (not keyed) you really need to get a live stream reader to set CMP retard.

I replaced my Distributor with the Accel billet unit which does not have a "key" so it does allow me to turn the distributor in place.

Scandata.com sells a Bluetooth OBD scanner with an app and enhanced GM data set for about 240.00 I don't know if there are any promotions running but I got mine for 215 (10 percent off first order) you can try promo code "10first"

It will read the CMP retard as well as view real time all the trim and other sensors.

It will not do a case relearn however. I had to take my vehicle to a shop for this. You do need something like a TechII or more advanced scanner for the case relearn procedure. This is where having a good working relationship with a shop comes in handy. My regular mechanic that handles the jobs I don't want to do, and my wife's BMW, did my case relearn for no charge when I was having a routine oil change/fluid change.

DC
 
#16 ·
I got my Tech 2 for $235 shipped. Why spend $215 for something that doesn't do everything the Tech 2 will do?

You need a scanner that will do live data, even if you don't spring for a Tech 2.
 
#18 ·
Mauring said:
That link says- Possible Causes:

Faulty Ignition Control Module

Ignition Control Module harness is open or shorted

Ignition Control Module circuit poor electrical connection
You hit 1 of 3 so far, how about these other 2?

Mauring said:
I installed a new ACDelco Ignition Control Module a couple of weeks ago.

I wonder if it was just a bad one from the factory or if the (excessive?) cranking trying to get it to start since then overheated it.
Doubt that greatly, but bad unit is possible.

Mauring said:
Do you think I should buy a new Ignition Control Module?
Quite the opposite... stop throwing parts at it and find data. AK is right on the money, if it was fine before then ya did something wrong or got bad parts.
Also, Did you clear the ECM codes after you replaced all that?
 
#19 ·
Update:

Today I hooked up my $20 OBD2 scanner and used the Android app Torque Pro and had the app set to "Timing Advance".

The first time that I started my Astro today it said -12.5 degrees

I then rotated the rotor by one tooth and started it and it said -20.5 degrees

The third time I rotated one tooth and it said 0.0 degrees and wouldn't start.

I don't know what the Torque Pro means when it says "Timing Advance" or if the numbers from today are any type of clue as to what is wrong with my Astro misfiring.

I haven't done any of the people's suggestions yet, it got dark and I got exhausted.
 
#21 ·
Timing advance and CMP retard are two totally different things.

The computer adjust the timing to where it is programmed to (if it can). When you advance or retard the system using the distributor mechanically, you will reach a point that either too far advanced or too far retard, for the engine to run.

IIRC the engine at about 1k RPM /cold idle should be sitting right around 20degree before tdc. And when I first tried to do this also not knowing that the computer would try to compensate, I turned my distributor, and it stayed right at 20degrees I kept going until it started to run real rough but still was clear it was trying to stay at 20degrees TDC. That's when I realized what was going on.

Watch the videos again. Set the harmonic dampener so that the timing mark is right at TDC. Then adjust the distributor gear so that the rotor is pointed where it is supposed to be.

If you have the "keyed distributor" this should be all you can do. If you have a distributor that you can turn and adjust, you need to load the live data stream and adjust the CMP Retard to read 0 +-2

If you have the keyed distributor, I'm going to guess that you should go back one tooth so the computer can hold the timing at idle to 20 degrees. Just to verify I just started up my van and read the timing.. it's sitting right at 19-20degrees and climbs to about 35 if I rev to 2500rpm.
 
#22 ·
Wimpazz said:
Mauring said:
That link says- Possible Causes:

Faulty Ignition Control Module

Ignition Control Module harness is open or shorted

Ignition Control Module circuit poor electrical connection
You hit 1 of 3 so far, how about these other 2?
I don't know how to fix or check for an open or shorted Ignition control harness. How do I do that? I would like to do all 3 of 3.

The last one "Ignition Control Module circuit poor electrical connection" is something that I can do.

Wimpazz said:
Quite the opposite... stop throwing parts at it and find data. AK is right on the money, if it was fine before then ya did something wrong or got bad parts.
Mauring said:
Do you think I should buy a new Ignition Control Module?
Wimpazz said:
Quite the opposite... stop throwing parts at it and find data.
I agree. That is a good saying.

After the Astro wouldn't start after I changed the plugs and wires, I hired a mobile mechanic who pulled out his ($5,000?) SnapOn scanner the size of a laptop and diagnosed that my Ignition Control Module was dead. At that time I also replaced the Ignition Coil.

I figured that both parts are 20+ years old and I didn't want my van to not start when I am camping 30 miles down a dirt road.

Wimpazz said:
and find data.
I am trying to find data. That is why I am asking for help on AstroSafari.com. I didn't have a father or any friends who knew how to work on cars. I still don't.

This last month I have spent hundreds of dollars on diagnostic tools that I have never had before and only know how to use from Googling.

The "stop throwing parts at it and find data" saying is very common in this forum and in every car related forum.

Personally I find the saying hurtful every time that I read it.

I am trying my best to diagnose, fix and maintain my Astro.

I may ask stupid questions but I really don't know how to do much of the things mentioned in this forum.

I am trying hard to learn.
 
#23 ·
1lowcab said:
Your LAPS can test that ICM for you, for free. It would rule it out.
Does the LAPS need it to be on the van? My Astro misfires so badly that I am afraid to drive it anywhere in case it blows a head gasket or something.

1lowcab said:
Also, Dashcommand will read the CMP if you download the GM enhanced PIDS for $9.99.
All you need is an elm 327 and then DL the Dashcommand program onto your Android, Apple or Windows device.
Thanks! I will buy it. :D
 
#24 ·
dchan51360 said:
If you have the keyed distributor, I'm going to guess that you should go back one tooth so the computer can hold the timing at idle to 20 degrees. Just to verify I just started up my van and read the timing.. it's sitting right at 19-20degrees and climbs to about 35 if I rev to 2500rpm.
Thanks for all of the advice in your post. I like the quoted part, it is good to know that your Astro runs good at 20.
 
#25 ·
Relax, you see us all here trying to help, right?

The "stop throwing parts at it and find data" saying is very common in this forum and in every car related forum.... because its true. Its expensive and rarely nets results. Thats why everyone says it. Now, let's start by answering questions and finding that data. Taking things off the table is narrowing it down, so lets do that.

1) Did you clear codes to see which ones come back?
2) Did you use an AC Delco module or something else?
3) When you are setting TDC, are you aligning both the upper and lower mark on the main pully, or just one?
4) When you set in the distributor, set the rotor just barely behind #1 firing position so that when it drops all the way in, it will align.
5) Are you engaging the oil pump rod when you set it in? That means it sits completely flush to the engine block.
6) Make sure you didn't knock loose the knock sensor wire.
7) When you get back to it all, check the connections on each side of the module for anything obvious, like dull metal, garbage, oxidation, burned, loose, etc.

Do the research, learn and you will be fine, not to fret. Most of us aren't mechanics either, we learn by doing and so will you.