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.

Did you check the sparkplugs? I've learned to always check the spark plugs.

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.

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 shit. Maybe worth checking out your fuel pressure?

Vash-

im having this issue right now....

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 :)

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?

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.

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.

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.

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/

Vash-

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

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.

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.

You don't have to ground out the diagnostic if the car is running.

Buy this...

Lightning Motorsports - Walbro 90-93 Miata In-Tank Pump Kit -

Down to what? I had to go all the way to .020.

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.

The best guide that i have ever read to troubleshoot your car.

The 6 Ps: Proper Preparation Prevents Piss Poor Performance

Just substitute everything 300zx related to miata :cool:

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.

AGH, so I get the old walbro out and it looks totally different from the one I bought. It has a black male harness on the top of it that just plugs into the cars harness. The one I bought is much longer (1"-2") and doesn't have the harness on top. I figured since I was swapping walbro for walbro it would work fine. The one I bought was the universal walbro and all i got from summit was the pump in a little bag. Nothing else. The top fuel connection doesn't even fit in the mounting brackets hole it is too big. Do I need to return it? Will it work? Thanks guys.

refer to post #16

I wish I had done that before I bought my down the road at summit. They gave me the external pump so I ordered the pump online and I'll return the old one. I just wish I hadn't spent the time getting to the other one. Oh well

Sorry I missed the remainder of the posts, but yes, its sounding like your pump is shot. I bought mine from lightning, and would recommend the same. Let us know how it goes.

I love my car again
 

So I finally got my new Walbro on and it is running like I remember, maybe better :) I really didn't think it could be the pump because the walbro i had was only 2 years old and maybe 10k on it so I checked everything else first and just about went insane. :vash: Anyway, thanks for your help guys.

Strange that a "well known" and respected fuel pump manufacturer's pump would go out in 10k miles. What is that all about? And what do you guys think about the cause? Is this possibly a result of running a FPR that demands more pressure than normal like us Greddy guys do?

I've had one fail on my civic in about a year. More performance, less quality control, I guess.

too much fuel.



12:1 FMU + walbro + 10psi = +120psi of fuel

look at my fueling with a 7:1 disc:

http://boostedmiata.com/wideband/7psi_265cc.jpg

IIRC I was using a 4:1 disc for 10psi

http://boostedmiata.com/wideband/9psi_265cc.jpg