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Old 12-29-2008, 02:57 PM   #1
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Default Horrible engine stumbling may need ATL Mechanic any suggestions

I have a 93 with a Greddy turbo kit, rx7 ic, bipes, vortech, 1.8 injectors, walbro, and 02 clamp. I bought it with most of these things installed and it was pushing 10psi. Ran great for about a year all the sudden I get up to 10 psi and it won't accelerate any more and it sounds maybe like a back fire but not very loud almost a popping (not like detonation popcornish sound). I got a little scared and took the boost down to 5 psi and it starts to do it there too. I put up a post and everybody said buy a wideband, so I did. Got it in the mail AEM yesterday but I don't have a DP with a second bung so I have to find a way to weld it in. It's gotten to the point where I can barely make it up my driveway the hesitation is so bad. This has just become my daily driver and I need it fixed fast. I'm going back to school and do not have my company car any more so I NEED WHEELS.

I've tried leaning out and going with more fuel with the vortech with no luck. Could it be timing? Could it be a bad narrowband 02? Could it be the 02 clamp failing or disconnecting? What about plug wires? If anybody knows of a mechanic in ATL that can help me out I would really appreciate it. Thanks guys.
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Old 12-29-2008, 03:01 PM   #2
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Did you check the sparkplugs? I've learned to always check the spark plugs.
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Old 12-29-2008, 03:08 PM   #3
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Default Yep, new plugs put in a few weeks ago

Yep, new plugs put in a few weeks ago. And I took the gap down so that the spark is not blown out.
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Old 12-29-2008, 03:25 PM   #4
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I was having a similar issue and after I swapped to my 190HP Walbro it drove like a porsche. I assume it was my fuel pump eating ****. Maybe worth checking out your fuel pressure?

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Old 12-29-2008, 04:07 PM   #5
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im having this issue right now....
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Old 12-29-2008, 04:22 PM   #6
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Sounds like a failing Air Flow Meter? or a major leak vacumm leak. if that is not it check timing belt make sure it didnt skip a tooth, or if you have cam sprockets it didnt slip. GL on that.
What color are the electrode on the spark plugs? just some things to look for. black and dry = rich, white = lean, white with spots = lean and some detonation, black and oily = oil and hot spot which lead to detonation. fresh plugs with a few miles will be easier to read then old plugs

Last edited by LowBoostn; 12-29-2008 at 06:11 PM.
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Old 12-29-2008, 04:26 PM   #7
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Check the fuel pressure. Stick a gauge on it, get your pressure at idle. Kink the hose, get the max pressure it will push. Bring back those numbers so we can rule out fuel pump/filter. Does it do this on open wastegate?
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Old 12-29-2008, 04:52 PM   #8
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Default fuel pressure gauge

do I just go buy a gauge at autozone and a t connector and get the reading? That's what I'll do right now. I think i can wire the wastegate open and test that. Thanks guys.
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Old 12-29-2008, 05:01 PM   #9
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Sounds alot to me like dying fuel pump. Happened to me also. While your doing it though, might as well replace the filter. Check back in with the test results, just jump the fuel pump in the diagnostic box and test away. If I'm not here I think the specs are something like 35 psi @ idle 80 @ kink.
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Old 12-29-2008, 07:45 PM   #10
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Default fuel Pressure

First I wired the wastegate open so I didn't boost and it ran a little better. It still hesitated at low RPM's and it wasn't really easy getting up my driveway but it wasn't to bad. But it still isn't good.

OK, I got a T connector and gauge and hooked up the fuel line (not the return which should be towards the front of the car I think). I ran the jumper from F/P to Ground and I got 20 PSI from the gauge. I kinked the return line but the pressure didn't go up. I noticed something else, I use to be able to hear my walbro 190 fuel pump running, not any more. Since it is only maybe 2-3 years old with maybe 15k on it could it be the filter or one of the hoses? I'm really hoping this might be the problem because it wouldn't be a really tough fix.
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Old 12-29-2008, 07:50 PM   #11
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Here's some info I copied from the FAQ, as well as a link to the info. I seriously hated driving my car when it was having these problems. It seemed like everytime I got to 6ish or so psi it would do a "ba ba ba ba ba ba" type of bog. It didn't start happening to me until about 2 years of the car already being turbo'd. I put the Walbro in and haven't had the problem since. I also agree on changing the filter as well. Be sure to keep us informed on how it works out.

https://www.miataturbo.net/forum/t4288/

Quote:
You’ll need to connect a fuel pressure gauge on your fuel lines to do this test. $20 at NAPA can get you what you need. Ask the counter clerk that you need a temporary fuel pressure gauge and length of 5/16” fuel hose, they can get you what you need. Attachment 3821

Turn your Miata to ON but do not start it. Open the diagnositics box and put a paperclip on F/P and GND. That will run your fuel pump. With a pair of pliers, squeeze the fuel line shut that connects the FPR to the original fuel pressure regulator. When squeezed shut, the pump will be forced to maximum output. Make sure the pressure available is consistent with your intentions. In all cases, the pressure must show, in this idle test, to be about 10 psi higher than the desired fuel pressure, as the available pressure under real load conditions will be less than that measured at idle. This test does not actually prove the pump to be adequate under boost, but if it doesn’t pass this test, it is certainly a waste of time to continue with the same pump.
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Old 12-29-2008, 08:44 PM   #12
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So is 20psi too low? I will test it again when I get some light in the morning. Anybody know the best place to buy a walbro 190? Summit Racing looks like they have a universal 190 will that work? I can't find one that says its for a 90-93 miata they all say 94+ and I'm guessing those won't fit. Do I need another installation kit because I already have one? thanks guys
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Old 12-30-2008, 05:08 PM   #13
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Default Cannot get above 20psi Fuel Pressure

I have run the relay in the diagnostic and clamped the line and I cannot get above 20psi. Even when I rev it doesn't go above 20psi. I replaced the filter this morning and I am getting the same thing. I am ordering another walbro 190 because that is the only thing I can think of. Anybody have a better idea before i spend $130 bucks so I can pick it up at Summit in GA. Thanks guys.
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Old 12-30-2008, 11:37 PM   #14
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I have had a walbro fail after about a year. If you can't get more than 20psi, even if you pinch the line, it is definitely the pump. I love how they are easy to get at.
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Old 12-30-2008, 11:38 PM   #15
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You don't have to ground out the diagnostic if the car is running.
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Old 12-30-2008, 11:39 PM   #16
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Old 12-30-2008, 11:49 PM   #17
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Quote:
Originally Posted by pdt602 View Post
I took the gap down so that the spark is not blown out.
Down to what? I had to go all the way to .020.
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Old 12-31-2008, 02:03 AM   #18
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I gapped down to .020 also and it didn't fix the problem. I just picked up the pump from Summit. It didn't come with the install kit but I wouldn't think I would need one since the old walbro was only a year old. I didn't see the posting quick enough but at least I didn't have to pay for shipping. I'm going to put it in first thing tomorrow and I'll report back.
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Old 12-31-2008, 04:25 AM   #19
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The best guide that i have ever read to troubleshoot your car.

The 6 Ps: Proper Preparation Prevents **** Poor Performance

Just substitute everything 300zx related to miata
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Old 12-31-2008, 11:29 AM   #20
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Thanks man, i use to use that site all the time when I had my Z. It was a great car but so expensive to work on. I do miss it sometimes though.
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