2000 Astro stumbling at 20mph and 50mph

[fowler]

Hello, this is m first post but I've looked at this site many times over the years and gotten alot of good tips.

Anyways, I have a 2000 Astro with an issue that I have not been able to diagnose. It stumbles at about 20mph, then it's fine until I hit about 50mph. After 50mph, it stumbles all the time. The stumbling only kicks in when the van gets warmed up. I've gotten a p300 code for random cylinder misfires. I've changed the plugs, wires, cap and rotor, new ignition coil a year ago and a new fuel filter just last week. None of this has made a change.

I took it to the dealer this weekend for a diagnostic. Needless to say, they weren't very helpful. I did manage to get them to check the fuel pressure and it was fine. So I don't believe it's a fuel system issue at this point. They didn't seem to check anything else for me, nor did they even drive it and get it over 50mph to experience the stumbling. They ended up telling me they think it could be a partially blocked catalytic converter. I had that checked out at a muffler shop today. They called and let me know that they do not think this is my problem. So I'm ruling the catalytic converter out now.

So I guess I'm at a loss as to what may be causing the stumbling. EGR valve? Bad distributor? Vacuum leak?

I'm waiting to hear from the dealer's service manager right now, as I want them to do a real diagnostic, rather than tell me "I think it may be a partially blocker catalytic converter." I paid $100 for nothing.

[astro355]

Hello,

there are no other codes present?

What were the fuel pressure readings?

how does the air filter look?

have you tried unplugging one sensor at a time and driving the van? such as the IAC, then MAF, then EGR, etc

[fowler]

Fuel pressure was 63psi I believe. It was normal. The dealer mechanic didn't seem like the best. No other codes. Air filter is fine. Haven't tried unplugging one sensor at a time. I might try that tonight though.

[astro355]

What was the fuel pressure at idle?

What was the fuel pressure at cruise?

What was the fuel pressure at WOT?

What was the fuel pressure after the van was shut off?

You really need to know all of those to know if the fuel system is ok or not. Also, I should point out that when you unplug those sensor and run the van, you will (should) get a code.

[fowler]

I called the dealership and they told me he went through all the items described above on the fuel pressure test and everything was within spec. So I'm not sure. Spoke with 2 other mechanics and one said it could be the EGR possibly the other told me if it was, it would throw a code. So I'm still at a loss. I guess the only other thing to do is to go through all the plugs and wires again to rule out anything there and then try unplugging the IAC, MAF and EGR or just pull the EGR and clean it up and put it back in if there's any carbon build up. I won't get time to do that until this weekend though, so I'll keep you posted after that.

[Masstro]

I have a 2000 as well. I know u said u replaced stuff but my ignition system has been really finicky no mater what i do. I have used several dis caps and used extra insulated wires to no avail. I have similar things happen usually every 30000 miles but sometimes less and it only happened when the van was cruising at low rpms(maybe 20 and 50 are the lower rpm ranges of whatever gear ur in at that speed?) Check for arcing under the hood at night to see if the ignition system is not insulated somewhere. If it is there will be a faint blue glow.

Jay

[rev_les]

You guys are using di-electric grease on the spark plug and coil wires right? and making sure they're seated thoroughly....especially the coil wire, with the P0300. To the OP, when you did the cap and rotor, was there any slop in the rotor at all? The drive gear on the distributor seems to wear on some vans and not as much on others, but if it gets slop it'll cause erratic misfiring. Just another avenue to research.

[fowler]

So I ended up taking it back to the dealer as I had paid $100 for them to tell me they "thought" it was the catalytic converter. So with this second go round, they basically tell me it's my transmission. I asked them how my transmission would cause a p300 code and the service manager made up some **** about the engine vibrations etc....blah blah blah. Needless to say, I will never take it back to the dealer or purchase a vehicle from them due to this incident.

So I called a couple transmission places today to get an idea of the cost on a rebuild (since I am having a trans issue with shifting from 2-3). I explained to the first shop the issue and he told me I need to figure out the misfire issue first, as the trans won't cause a misfire.

So I'm still at the same place I started. I have noticed that once the Astro is warmed up, I do not get the stutter at 20mph anymore, yet the stutter still happens consistently after the 50mph mark. My plan is to replace all the plugs and wires this weekend with Delco parts and test the distributor to see if there is any play in the gear. I'm also gonna check out the EGR valve and see what it looks like and clean it up if there is carbon on it. I'll check to see if there is any slop in the cap when I replace it again this weekend.

[rev_les]

try firing it up at night and see if you have any arcing, it's never a bad idea to check the plugs. Something you may want to do, is drop the dealer's name at Pissedconsumer.com
It's a website that highlights consumer complaints. Check that coil wire really good and make sure it's not chafed and grounding out at certain speeds due to various factors like the wind underneath, vibration, etc... Rule out the free before you go buying parts, unless they're needed.

[astro355]

I'm not so convinced that its an ignition problem. I would really want to know what those fuel pressure readings are. I worked on a Bonneville years ago that had a very intermittent stumble that was caused by a crankshaft position sensor that was on its way out.

[rev_les]

I'm not so convinced that its an ignition problem. I would really want to know what those fuel pressure readings are. I worked on a Bonneville years ago that had a very intermittent stumble that was caused by a crankshaft position sensor that was on its way out.

I agree with you, I'm just trying to help rule out things before he goes plopping down cash. That crank pos. sensor can cause you to pull hair out too, definitely something in need of checking, as well as the OP seeing the fuel pressure with his own eyes......especially with the qualifications that dealership's mechanics seem to have.

[astro355]

I'm not so convinced that its an ignition problem. I would really want to know what those fuel pressure readings are. I worked on a Bonneville years ago that had a very intermittent stumble that was caused by a crankshaft position sensor that was on its way out.

I agree with you, I'm just trying to help rule out things before he goes plopping down cash. That crank pos. sensor can cause you to pull hair out too, definitely something in need of checking, as well as the OP seeing the fuel pressure with his own eyes......especially with the qualifications that dealership's mechanics seem to have.

That's the problem I see also. I've never heard of a transmission causing a misfire.

[rev_les]

Exactly....makes you wonder if the engine running right might fix the transmission problem. My first indicator several times on some of my GM's that I was gonna lose a fuel pump, is they suddenly act like the transmission's keeling over.....Or it may have a trans problem too.

[astro355]

Exactly....makes you wonder if the engine running right might fix the transmission problem. My first indicator several times on some of my GM's that I was gonna lose a fuel pump, is they suddenly act like the transmission's keeling over.....Or it may have a trans problem too.

What transmission problem? I didn't hear anything about a transmission problem. But this is a perfect reason why these vans should have come with tachometers. I'd better it has more to do with the rpm of the engine as opposed to the speed of the vehicle.

[rev_les]

So I ended up taking it back to the dealer as I had paid $100 for them to tell me they "thought" it was the catalytic converter. So with this second go round, they basically tell me it's my transmission. I asked them how my transmission would cause a p300 code and the service manager made up some **** about the engine vibrations etc....blah blah blah. Needless to say, I will never take it back to the dealer or purchase a vehicle from them due to this incident.

So I called a couple transmission places today to get an idea of the cost on a rebuild (since I am having a trans issue with shifting from 2-3). I explained to the first shop the issue and he told me I need to figure out the misfire issue first, as the trans won't cause a misfire.

So I'm still at the same place I started. I have noticed that once the Astro is warmed up, I do not get the stutter at 20mph anymore, yet the stutter still happens consistently after the 50mph mark. My plan is to replace all the plugs and wires this weekend with Delco parts and test the distributor to see if there is any play in the gear. I'm also gonna check out the EGR valve and see what it looks like and clean it up if there is carbon on it. I'll check to see if there is any slop in the cap when I replace it again this weekend.

This one !

[astro355]

So I ended up taking it back to the dealer as I had paid $100 for them to tell me they "thought" it was the catalytic converter. So with this second go round, they basically tell me it's my transmission. I asked them how my transmission would cause a p300 code and the service manager made up some **** about the engine vibrations etc....blah blah blah. Needless to say, I will never take it back to the dealer or purchase a vehicle from them due to this incident.

So I called a couple transmission places today to get an idea of the cost on a rebuild (since I am having a trans issue with shifting from 2-3). I explained to the first shop the issue and he told me I need to figure out the misfire issue first, as the trans won't cause a misfire.

So I'm still at the same place I started. I have noticed that once the Astro is warmed up, I do not get the stutter at 20mph anymore, yet the stutter still happens consistently after the 50mph mark. My plan is to replace all the plugs and wires this weekend with Delco parts and test the distributor to see if there is any play in the gear. I'm also gonna check out the EGR valve and see what it looks like and clean it up if there is carbon on it. I'll check to see if there is any slop in the cap when I replace it again this weekend.

This one !

I was being sarcastic. The trans issue isn't a trans issue. Although invented by the dealership, even the trans shop suggested fixing the misfire first.

[rev_les]

I missed the sarcasm there

[fowler]

So I went over to my buddies house yesterday to look at the EGR valve and replace the cap & rotor and plugs. He replaced the cap & rotor for me and upon connecting all the plug wires back, he noticed that the first plug wire was recessed a little bit. So he pulled it out with some pliers, connected it to the cap and we took it for a test drive. Ends up, that's all it was. I guess I never noticed it during the numerous times I checked the wires connected to the cap. I guess the dealership never even looked at it either. Anyways, runs fine now except for my transmission issue, which I'll tackle next.

Thanks for all the advice. I've found plenty of info on the site over the years that's helped me with my Astro.

[Leeann_93]

I hope you bought that buddy some beer for that - and I'm really glad you got it fixed