Reduced Power & Poor Fuel Economy Problems

Reduced Power & Poor Fuel Economy Problems

Postby Corsemoto [OP] » June 4th 2008, 8:09pm

Hello, been here in the past for a few years with my older '97 Safari AWD but changed e-mail and user accounts since then, so greetings again all!

I'm having some issues with my 2004 Astro LT AWD.

Started on a trip back from Texas towing a small enclosed trailer, check engine light came on and had what seemed to be a significant reduction in power and really poor fuel economy. Got home and had codes scanned and showed Mass Air Flow Sensor fault (don't have code handy, can post later today...) and so I replaced MAFS with a new original from dealer, removed code, reset computer, replaced paper air filter, fuel filter and installed a new fuel cap (from dealer) for good measure.

However, the van still has what feels like a serious reduction in power and poor fuel economy, especially under load climbing hills (haven't towed a trailer since first incident). It seems as if exhaust flow may be obstructed, like the catalytic converter may be clogged and causing problems. Any other suggestions on this matter?

I've been looking at Magnaflow replacement converters (part # 94009) on eBay. What I don't know is if the small pipe in front of the main converter body is a resonator or some sort of pre-converter that would need to be replace as well?

Thanks.
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Re: Reduced Power & Poor Fuel Economy Problems

Postby davesyo » June 5th 2008, 2:27am

Best way to tell is to make the exhaust leak ahead of the converter to see if power comes back .You could also check for exhaust restriction with a vacuum gauge.Check for low vacuum , also if you have vacuum readings lower at 2000-2500 rpm than at idle you have an exhaust restriction
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Re: Reduced Power & Poor Fuel Economy Problems

Postby Corsemoto [OP] » June 18th 2008, 4:56am

Thanks for the reply.

I ordered a Magnaflow weld-in replacement catalytic converter and cut the old one out yesterday - completely clogged! Also removed the pre-converter to have a look, which turned out to be fine. Removed the downpipe from the manifolds, welded the pre-converter back in place, reinstalled the downpipe and welded the new Magnaflow converter in place, new exhaust gaskets, tightened everything up, checked for leaks and test drove.

Wow! :deathmetal: It sure is nice to have full power back again in my Astro - best $75 I've ever spent on a vehicle for sure and fuel economy has definitely improved.
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Re: Reduced Power & Poor Fuel Economy Problems

Postby meetthespeakers » June 18th 2008, 4:00pm

I just ordered the same Magnaflow universal Hi-Flow Cat, did you get the standard or high-flow? Any tips for doing the job? I have AWD to, I take it you need to take the Y-Pipe off? If so I can tell thats already gonna be fun.
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Re: Reduced Power & Poor Fuel Economy Problems

Postby Corsemoto [OP] » June 18th 2008, 9:20pm

meetthespeakers wrote:I just ordered the same Magnaflow universal Hi-Flow Cat, did you get the standard or high-flow? Any tips for doing the job? I have AWD to, I take it you need to take the Y-Pipe off? If so I can tell thats already gonna be fun.


It wasn't too bad of a job with the front jacked up and on jack stands. I purchased this one on eBay from these guys - If you make a Best Offer, they give you a discount code to use at checkout, like 7% off or something and shipping was quick as well.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=220244229850&ru=http%3A%2F%2Fmotors.shop.ebay.com%3A80%2F__%3F_from%3DR40%26_trksid%3Dm39%26_nkw%3D220244229850%26_nd1%3D%26submit.x%3D0%26submit.y%3D0%26_fvi%3D1

Magnaflow Hi-Flow 3" Part # 94009

We started by cutting in front of the main catalytic converter and unbolting at the Tri-flange in front of the muffler and removing the clogged catalytic converter. Then we decided to cut the pre-catalyst out before removing the Y-pipe. Really, we should have just removed the Y-pipe before cutting out the pre-catalyst which isn't too bad with some extensions, swivels, a bit of penetrating lubricant and some finesse when wiggling out. Reaching the 02 sensor connectors was probably the most difficult part of removal/installation...

After checking the pre-cat, which looked good, we welded it back in place and welded a lip to the end of the pipe (where it was cut in front of the main catalytic converter) in order to match the new Magnaflow converter pipe ID. We were going to take it to an exhaust shop and have them flare ends of the pipe where they meet the Magnaflow converter, but it was late and we ended up where we needed to be with a bit of welding/grinding, etc. We refit the Y-pipe and measured/test-fit the new Magnaflow converter. Trimmed a bit of the tubing from the ends of the Magnaflow converter to get it where we wanted it and then welded it to the remaining Tri-flange pipe and fitted it in to weld the front of the cat to Y-pipe.

It's tough to say if it is better than a good stock converter as it's been months since my van has run well, but for around $75 and a day's work, I absolutely cannot complain - performance is outstanding and I actually smile while driving my van again. Yes, I just said, "I enjoy driving my Astro AWD." :thumbup:

Hit me up if you have any other questions. Oh, and you shouldn't need to remove the Y-pipe if you are just going to cut out the main converter and replace, there is enough room (tight, but enough) to weld all the way around with everything in place.
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Re: Reduced Power & Poor Fuel Economy Problems

Postby meetthespeakers » June 18th 2008, 9:27pm

Yea I scored one off ebay for $72 free shipping for the high flow version. I was hoping I could just cut the old cat out and slip this one on without having to remove the y-pipe from the car. But I guess I will see when I get into it. I am hoping it breathes a lot better and gives me a deeper tone with the catback/intake I have. Thanks for writing back. I feel you on the AWD. I love it, but hate it at the same time, especially when it came to lowering it. I hope maybe next year if I am totally bored finding a shop to weld a custom bag setup.
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Re: Reduced Power & Poor Fuel Economy Problems

Postby Corsemoto [OP] » June 18th 2008, 9:40pm

I edited my post, you may not have seen it. I don't think you will have to remove the Y-pipe if you are just replacing the main cat. I don't think my ''97 Safari AWD had a pre-cat like the newer ones, so your '98 should be cool. Let us know how it works out, my van seems to have a bit more bark to it even with the stock muffler. I had a Flowmaster on my '97 and while I like it around town, didn't do anything for me on the highway or idling all day at the track with the A/C or heater on!
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Re: Reduced Power & Poor Fuel Economy Problems

Postby rosslato » November 20th 2008, 10:46pm

DiModaCorse wrote:Hello, been here in the past for a few years with my older '97 Safari AWD but changed e-mail and user accounts since then, so greetings again all!

I'm having some issues with my 2004 Astro LT AWD.

Started on a trip back from Texas towing a small enclosed trailer, check engine light came on and had what seemed to be a significant reduction in power and really poor fuel economy. Got home and had codes scanned and showed Mass Air Flow Sensor fault (don't have code handy, can post later today...) and so I replaced MAFS with a new original from dealer, removed code, reset computer, replaced paper air filter, fuel filter and installed a new fuel cap (from dealer) for good measure.

However, the van still has what feels like a serious reduction in power and poor fuel economy, especially under load climbing hills (haven't towed a trailer since first incident). It seems as if exhaust flow may be obstructed, like the catalytic converter may be clogged and causing problems. Any other suggestions on this matter?

I've been looking at Magnaflow replacement converters (part # 94009) on eBay. What I don't know is if the small pipe in front of the main converter body is a resonator or some sort of pre-converter that would need to be replace as well?

Thanks.


my 98 was doing the exact same thing, replaced MAF sensor that scanner said was bad but still had same problem so bought the same converter off ebay and had it installed, BINGO! the old converter was clogged up. it runs like a champion again. thanx for the info.
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