# 99 Chevy Astro Misfire runs rough code P0301



## Hardway

99 chevy Astro Van anybody know how to test a fuel injector to see if it is causing a misfire? 6 cyl eng runs rough. P0301 code.


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## joecaption

http://www.youfixcars.com/testing-fuel-injectors.html


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## 47_47

P0301 is cylinder 1 misfire. Check the secondary ignition first (wire, coil tower, spark plug). You can measure the resistance of #1 injector and compare to others. All should be ± 10% of each other. To go further, you will need specialized tools.


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## Hardway

Hardway said:


> 99 chevy Astro Van anybody know how to test a fuel injector to see if it is causing a misfire? 6 cyl eng runs rough. P0301 code.


This is a spider aray under the intake and the resistance will not tell you if the injector is clogged. I am looking for a way to activate the number one injector. Wire, coil, spark plug good and plug fires.


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## 47_47

You can install a fuel pressure gage and manually PWM the injector with a tester, measuring and comparing the fuel pressure drop between injectors. You can also use a noid lite to check the ECM output and wiring to the injector.


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## cjm94

Those spider injector assemblies have poppet valves on each hose that are common to plug. There isn't much that works to clean them without an injector flush machine that will pulse the fuel psi and that only works half the time. Gm has an updated assy. that gets rid of the poppets and uses regular injector tips on the hoses.


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## Hardway

cjm94 said:


> Those spider injector assemblies have poppet valves on each hose that are common to plug. There isn't much that works to clean them without an injector flush machine that will pulse the fuel psi and that only works half the time. Gm has an updated assy. that gets rid of the poppets and uses regular injector tips on the hoses.


cjm94 so is there a way to acess the injector to check it with out taking the intake off? I should have never taken it in for repair. I should have bought a few test items. Because they replaced the MAF, Computer, fuel pump, cap, rotor and then some. damaged the gas cap, the air box. Needless to say they are done. I have since purchased my own OBD scanner, Fuel pump pressure gauge. I have It narrowed dow to number one fuel injector. Cold here now and no garage.:wink:


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## cjm94

No way to get to them with the intake on. It's not a very DIY friendly set up. I know people think dealers are a rip off but for about a hundred bucks you would have had a good diagnosis instead of a couple thousand dollar mistake. I hope they stood behind there mistakes. I'm not saying dealers don't make mistakes but good ones would not have charged for the stuff they misdiagnosed.


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## Hardway

cjm94 said:


> No way to get to them with the intake on. It's not a very DIY friendly set up. I know people think dealers are a rip off but for about a hundred bucks you would have had a good diagnosis instead of a couple thousand dollar mistake. I hope they stood behind there mistakes. I'm not saying dealers don't make mistakes but good ones would not have charged for the stuff they misdiagnosed.


Taking the intake off is not an issue, just wanted to make sure it is an injector. This all started out at the dealers, they went out of business. From what I understand $1,500.00 to replace the injectors. I can do it my self. I should have bought a few test items and did the trouble shooting my self.


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## cjm94

Taking the intake off is the hardest part of that job. You should be able to find the injector assy for 200-500 depending if you go with the old style or the updated ones


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## Hardway

cjm94 said:


> Taking the intake off is the hardest part of that job. You should be able to find the injector assy for 200-500 depending if you go with the old style or the updated ones



$250.00 online

P0301 code is a misfire on number 1 cylinder so would I be wrong assuming the problem is something dedicated to cylinder number one?



I still have to check compression.


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## cjm94

If you have spark and compression you are pretty safe with the injector. A cylinder leakage test would rule out a burnt valve but injector poppets are very common on those


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## Hardway

cjm94 said:


> If you have spark and compression you are pretty safe with the injector. A cylinder leakage test would rule out a burnt valve but injector poppets are very common on those


That is what I am thinking, bad injector.


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## Hardway

Will I need any special tools to replace the fuel injectors?


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## cjm94

No you shouldn't just basic tools


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## Hardway

*Injectors*

Ok thanks for all the info, I will research replacing the injectors before I start. I will take pix so if I forget where something goes. It is just a matter of starting the process.:thumbsup:


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## Hardway

Update, done nothing so far. But now it is running so smoothe, can't tell it is running idling at a red light. Check eng light has not came back on yet. So I don't know.


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## paintdrying

Dude, do not get into that spider system. On an astro it is able to be done but is very tight. You should take it in for a fuel injection cleaning, you have a poppet stuck. If the dealer did not use ac delco parts than pull all those off. Also replace the wires. I can not stress enough that you need to use ac delco parts on that van.


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## Marqed97

I had one of them in our shop awhile back for a misfire that would come and go (P0307 - Cyl 7 Misfire). The owner had it another shop and they replaced a ton of parts. All that was left was the injector spider. I have worked on so many Chevy 4.3/5.0/5.7's that I have boxes of spare parts. I threw on a distributor cap that I knew was good and that took care of the intermittent misfire. It had been replaced already. And it was an ACDelco part. Those caps were a terrible design to begin with (they cross conductor paths in the cap so that the wires come neatly off each side). Maybe a defect in the cap, maybe the guy who put it in dropped it, maybe the box got dropped during shipping, etc, it doesn't take much. 

In my experience once the spider poppets plug up they don't usually come back on their own. I've had 50/50 luck using a high pressure injector cleaning tool. But replacing the spider assembly isn't very difficult. I'd use the new design if at all possible...much better design (no poppets). 

I had a 99 Astro AWD for 2 years. It was awesome in the snow, I'll say that. And I'm not a Chevy guy. But finally sold it off as the gas mileage was rotten and the wife wanted a sliding door on both sides (we had just had twins).


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## Hardway

Marqed97 said:


> I had one of them in our shop awhile back for a misfire that would come and go (P0307 - Cyl 7 Misfire). The owner had it another shop and they replaced a ton of parts. All that was left was the injector spider. I have worked on so many Chevy 4.3/5.0/5.7's that I have boxes of spare parts. I threw on a distributor cap that I knew was good and that took care of the intermittent misfire. It had been replaced already. And it was an ACDelco part. Those caps were a terrible design to begin with (they cross conductor paths in the cap so that the wires come neatly off each side). Maybe a defect in the cap, maybe the guy who put it in dropped it, maybe the box got dropped during shipping, etc, it doesn't take much.
> 
> In my experience once the spider poppets plug up they don't usually come back on their own. I've had 50/50 luck using a high pressure injector cleaning tool. But replacing the spider assembly isn't very difficult. I'd use the new design if at all possible...much better design (no poppets).
> 
> I had a 99 Astro AWD for 2 years. It was awesome in the snow, I'll say that. And I'm not a Chevy guy. But finally sold it off as the gas mileage was rotten and the wife wanted a sliding door on both sides (we had just had twins).


 
Have not had the P0301 code or any code since my last post. I agree with you that a plugged injector is not going clear up and the reappear. I also have read several articles on the after market caps. Still runs rough at idle thou. Who sells Delco caps?


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## paintdrying

Rock auto is my favorite for parts. Those 4.3 can run rough on idle. Might be your egr valve. Or that air control valve is dirty. I do not even worry about miss fires anymore. Astros run bad longer than most cars run


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## Hardway

paintdrying said:


> Rock auto is my favorite for parts. Those 4.3 can run rough on idle. Might be your egr valve. Or that air control valve is dirty. I do not even worry about miss fires anymore. Astros run bad longer than most cars run


Yeah I looked at Rockauto, buy a lot from them. Even with the shiping, $20.00 less then local patrs store. I will order cap and. rotor and go from there. EGR tested good! When you say air control valve meaning Mass air flow it was replaced. It has been in the shop a few times and they replaced a bunch of stuff. I gave up on them, "just bring it back" got old!


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## toolaholic

Air idle control valve. You can clean this w/ throttle body cleaner.


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## Hardway

Up date:
I have not done anything because of cold weather. I let the gas run down to less then an 1/8 of a tank and filled the tank. On the way home from the gas station the check engine light came on. I drove it a short distance and back home check eng light still on. Next day I started it and the check eng light was off. I am driving it; still rough idle at the stop light. I did not check to see what code is stored as of yet. I will get around to changing cap and rotor with OEM Delco. 15 degrees at the moment, I will post when I do something. I thought I would just update! :whistling2:


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## paintdrying

Never below a quarter of a tank of gas, you will burn that pump up fast. I tested this theory on an astro I had and burned the pump up in less than a week.


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## Hardway

paintdrying said:


> Never below a quarter of a tank of gas, you will burn that pump up fast. I tested this theory on an astro I had and burned the pump up in less than a week.


I don't doubt what you say, I used to run close to out of gas all the time. The OEM pump lasted 13 years 120,000 miles. Just saying:thumbup:


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## Hardway

Update:
I never got around to doing anything.
The check eng light reset and has not came back on. So I don't know what it can be. I will update if it changes.:thumbsup:


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## Hardway

Never did do anything other then basic maintenance and the check engine light has not came back on. Still idles rough stopped at the light. The dealers never figured out the rough idle they would test drive it with me and tell me they don’t notice it. Needless to say the dealers is no longer in business. So just updating.:thumbsup:


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## cocobolo

ALL Chevy 6's and 8's really love a good ignition. If there's something wrong with your distributor cap, rotor, plug wires, plugs etc., it could very well cause the trouble you are having. Having read your whole thread, I would lean toward an electrical problem, all of which is easy to fix.

Have you pulled the valve covers to see if any of the rocker arms are slightly loose? Occasionally a cam lobe will start to go flat and cause trouble, but not any too often.


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## Hardway

cocobolo said:


> ALL Chevy 6's and 8's really love a good ignition. If there's something wrong with your distributor cap, rotor, plug wires, plugs etc., it could very well cause the trouble you are having. Having read your whole thread, I would lean toward an electrical problem, all of which is easy to fix.
> 
> Have you pulled the valve covers to see if any of the rocker arms are slightly loose? Occasionally a cam lobe will start to go flat and cause trouble, but not any too often.


distributor cap, rotor, plug wires, plugs etc, all new.
No have not checked the rocker arms.
In the past a lose rocker would chatter. I put a vacume gauge on it and no flutter.


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## cocobolo

Something else I just thought of. You can get some sort of cleaner for your fuel injection, which you just introduce into the intake system somehow. It has been years since I did that, but it helped. Might be worth a try. Mine was a 4.3 as well.


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## Hardway

Update as I stated all summer no check engine light. I was up north for ten days, it got down to 48 degrees and I got a check engine light. I drove 50 miles back to the property and parked it. On the way home I hit 68 degrees about a 100 miles from the property and the check engine light went off and stayed off 250 miles home.:laughing:
I will scan it in the morning and post the code.


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## Hardway

P0301 misfire number one cylinder!:no:


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## cjm94

Good chance it's the injector sticking. They are very common to get carboned up and stick more so cold.


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## Hardway

I just hate to pull the top and replace the spider assembly and have the same problem. I ran a few cans of GM heavy duty fuel injector cleaner thru it. Did not improve it though. I have looked into purchasing the equipment to inject thru the fuel rail. I will call around and see who does the injector cleaner and cost?:thumbsup:


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## cjm94

Don't expect to much on the flush it's not a guarantee. In almost 20 years of working on cars I'm at probably 40% of flushing injectors fixing anything


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## Hardway

cjm94 said:


> Don't expect to much on the flush it's not a guarantee. In almost 20 years of working on cars I'm at probably 40% of flushing injectors fixing anything


I pretty much concur on the flushing.
I don't have a garage and this is my main ride.
I like working on cars, just don't like to be rushed.
It being van with engine cover makes it a little more involved. 
Not going to take it in anymore, they charge too much and mess something else up. Like when they replace the fuel pump and dropped the tank without disconnecting the filler neck. Damaged the OEM cap and trim around the fill neck. "Oh we did not do that because we did not disconnect it" "All we did was lower the tank." really?

I will keep ya updated from time to time!:thumbup:


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## davey68

Did you manage to fix it? 
Just wondering whether putting some Super Unleaded is going to help the car. After all, they got some of the injector cleaning stuff, too.


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## Lotek

Hardway said:


> I pretty much concur on the flushing.
> I don't have a garage and this is my main ride.
> I like working on cars, just don't like to be rushed.
> It being van with engine cover makes it a little more involved.
> Not going to take it in anymore, they charge too much and mess something else up. Like when they replace the fuel pump and dropped the tank without disconnecting the filler neck. Damaged the OEM cap and trim around the fill neck. "Oh we did not do that because we did not disconnect it" "All we did was lower the tank." really?
> 
> I will keep ya updated from time to time!:thumbup:


Astrovans get the hose disconnected from the neck at the tank, it won't come out otherwise. If you don't have the updated injector assembly, it's a good investment if you are keeping the van. Possible sticking valve though...if the misfire happens under load or at high speed, it's something to consider.


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## paintdrying

I was thinking weak valve spring as well. You could try running a half quart synthetic oil on the next change. If the filler neck is leaking might trying running some Heet through it.


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## Hardway

Mid October, I did a full tune up my self AC Delco parts.
coil, cap, rotor,plugs, wires.
Cleared all codes and did not recieve anymore codes.
Still rough idle in drive stopped at a light.


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## Hardway

So far no codes!


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## Fix'n it

Hardway said:


> Still rough idle in drive stopped at a light.


these 4.3's are not the smoothest idlers. but a clogged egr will make em idle really bad, and is a common problem.


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## 1995droptopz

I had a 1998 Blazer with the 4.3, the truck had 175k, and when running it would feel like a misfire. I found the distributor gear had worn out to the point that many of the teeth had 1/16" of wear on them. I know of one other person who had this same problem. It causes your timing to shift, and can cause a misfire.


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## brotherGood

Just read the last page of it. Glad you don't have anymore codes. A rough idle could be a vacuum leak, clogged injector..something like that.. I wouldnt think itd be a worn distributor gear unless you were having the stumble all the time. Have you replaced your fuel filter? 

Also, double check your plugs. I'm betting they'll show a lean condition, but I'm not good with fuel injection..So I could be wrong


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