AFRs are acting up - Miata Turbo Forum - Boost cars, acquire cats.

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Old 12-01-2008, 07:16 PM   #1
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Default AFRs are acting up

So, as you know I went to the dyno the other day and everything was running fine. I go to take my oldest son to his house Friday night and on the way back home, I decide to have some fun and floor the car. I'm running along with the top down having fun and enjoying a beautiful night and Dang!... I hit a ******* pot hole. What happened next has me perplexed. My car is running fine but, when I go into boost the AFRs in the gauge show 14! wtf! I changed back to my previous calibration the next day and even though it was slightly better it would still show in the 13s. So, I fiddled around with the laptop and began to see my AFRs around 11; not good but, at least it was drivable.

Today, while doing some errands in the city I get hit in the back by some ******* but apart from the sensation of being hit from the car; the damage to the car is really minimal.

The thing is: this **** with the AFRs did get worse. So here's what I thought it could be:

1) a problem with my MAF sensor (NOT)
2) A problem with my fuel pump (I suspect that is not the case)
3) A problem with my car's fuel regulator (I'm inclined to think so)
4) When I called my tuner he told me to bring the car in tomorrow to check the alternator to see if there's a problem with the battery or with the alternator per se.

Any thoughts?

Thanks
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Old 12-01-2008, 08:05 PM   #2
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try re-calibrating the wideband??? or is it a uego
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Old 12-01-2008, 08:59 PM   #3
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try re-calibrating the wideband??? or is it a uego
Yes, it's a Uego.
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Old 12-02-2008, 01:39 PM   #4
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So; I checked my fueling system thoroughly and didn't find anything. As far as I can tell, all my fuel lines, fuel pump, pressure regulator and even the generator are in perfect working order.

I'm beginning to suspect my WB sensor took a crap. Anyone has an AEM WB for sale? I'll pay shipping via FedEx too.
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Old 12-05-2008, 12:24 PM   #5
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I'm in need of some assistance. Ever since I took my car to the Dyno, I can't stop smelling fuel and every time I floor it, the car will go lean as soon as there's some fuel pressure while in boost (the AFRs on the WB gauge show 14s and 15s as soon as I hit 5,000 rpm). I took out the dual fuel rail, checked it, check the injectors and cleaned up the rail. I checked all the fuel lines (including the ones underneath the car). I found 3 of the lines connecting to the fuel rail in bad shape and replaced them. I took the car out of the shop and now I can't smell the fuel spilling on low rpms so part of the problem had to do with the lines I changed but I still smell fuel when in boost and my car will show it's really lean.

Can someone suggest what else I can check?

Thanks
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Old 12-05-2008, 12:28 PM   #6
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first of all, I hope you have a fire extinguisher in the car. I do.
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Old 12-05-2008, 12:28 PM   #7
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gas cap.

make sure fuel pump assembly is tightened down in tank properly.

also check the fuel hoses in the trunk. the fill hose and vapor hose. Have had problems there.

double check for leaks. by closing off the fuel return line and running the fuel pump. that will give you your max fuel pressure that your pump is capable off. if it's leaking you will see it then. unless of course the leak is on the hard return line somewhere after you clamp it on it's way back to the tank.
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Old 12-05-2008, 12:44 PM   #8
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Look at your injectors and see if they are leaking. Was your car going for full boost.

If you let out of it fast before full boost. ( Which is smart) this may be the problem.

You may have knocked a hole into one of the couplings or knocked somthing partially lose. There for, you map is only giving gas for the amount of boost acheived. And the rest of the air is going out the hole. I also had a filter come off one day and it changed everything too.

What type of fuel management do you have?
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Old 12-05-2008, 12:53 PM   #9
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Quote:
Originally Posted by Toddcod View Post
Look at your injectors and see if they are leaking. Was your car going for full boost.

If you let out of it fast before full boost. ( Which is smart) this may be the problem.

You may have knocked a hole into one of the couplings or knocked somthing partially lose. There for, you map is only giving gas for the amount of boost acheived. And the rest of the air is going out the hole. I also had a filter come off one day and it changed everything too.

What type of fuel management do you have?
Uhh, if he has a blown coupler and air is escaping through that the fuel being injected would correspond to that and still maintain the proper AFR. The amount of boost achieved is all the engine would be getting also so the AFR should stay stable.
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Old 12-05-2008, 12:58 PM   #10
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These won't explain the gas smell but id you check:
your factory FPR like you suspected?
the sock on your fuel filter, someone recently posted his tank was full of rust and clogged that sock
fuel filter clogged?
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Old 12-05-2008, 01:46 PM   #11
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Quote:
Originally Posted by paul View Post
gas cap.

make sure fuel pump assembly is tightened down in tank properly.

also check the fuel hoses in the trunk. the fill hose and vapor hose. Have had problems there.

double check for leaks. by closing off the fuel return line and running the fuel pump. that will give you your max fuel pressure that your pump is capable off. if it's leaking you will see it then. unless of course the leak is on the hard return line somewhere after you clamp it on it's way back to the tank.
Thanks for the suggestions to both you Paul and Todd.

I'm going to check my fuel hoses in the trunk and the fuel pump. I'll check the filter too. I thought it could be clogged but never got to check it.

I never thought about closing off the fuel return line. That's good.

I planned on taking the car this afternoon to the Dyno and make a pass to see if the WB sensor is not working properly (I already ordered one and I'm waiting for it to get here) but I don't think that's the reason. The WB gauge reads a perfect 14.7 to 14.9 while idling.

BTW. I've got a 190 ph fuel pump; could it be that?
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Old 12-05-2008, 01:49 PM   #12
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Quote:
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first of all, I hope you have a fire extinguisher in the car. I do.
No. I've been procrastinating with that decision.
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Old 12-05-2008, 02:11 PM   #13
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Quote:
Originally Posted by paul View Post
Uhh, if he has a blown coupler and air is escaping through that the fuel being injected would correspond to that and still maintain the proper AFR. The amount of boost achieved is all the engine would be getting also so the AFR should stay stable.
Thats what I was saying. 13 and 14afr wouldn't be bad, if little to no boost was acheived. ( The turbo is working, but
only a small amount of pressure may have been acheived, which wouldn't increase afr's that much) I didn't know how much boost had been acheived when he let out.

Sometime my explainations get cloudy.
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Old 12-05-2008, 06:18 PM   #14
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Quote:
Originally Posted by Toddcod View Post
Thats what I was saying. 13 and 14afr wouldn't be bad, if little to no boost was acheived. ( The turbo is working, but
only a small amount of pressure may have been acheived, which wouldn't increase afr's that much) I didn't know how much boost had been acheived when he let out.

Sometime my explainations get cloudy.
Thanks for the help Todd.

I just got back from the dyno. My WB is working properly. I cut off the pass the moment I saw 16s on the dyno's AFR chart. At that moment, my car had not even reached 5,500 rpm.

Before going to the dyno I went to the shop. I decided to lift the cover of the fuel tank and check everything there. Both fuel lines were dry (no sign of leaking whatsoever!) and the breathing lines were also in perfect working order. I took the fuel pump out and it looked pretty good. I checked the filter and I didn't have to clean it. The fuel in the tank was clear and I could see nothing wrong.

I'm going to change the OEM fuel pressure regulator and try an Automotive I bought from Mikef85 not so long ago.

Now that I think about it: I didn't make a datalog and I'm wondering if one of the injectors may be acting up.

My tuner suspects the fuel pump but I don't want to buy one until I know what's going on. I'm going to put another guy's fuel pump in tomorrow and check what happens.

Besides those 2 things; I really don't know where else and what else to check!
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Old 12-05-2008, 07:05 PM   #15
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Did you check/replace the external fuel filter? They are pretty cheap insurance.
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Old 12-05-2008, 08:08 PM   #16
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Did you check/replace the external fuel filter? They are pretty cheap insurance.
I couldn't find it!

I'll go check the manual; thanks.
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Old 12-05-2008, 08:19 PM   #17
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Long shot, but the it could be the fuel injector O-rings leaking where they snap into the (intake manifold if it's a 1.6, cylinder head if it's a 1.8). Reason I say this is you mention you smell fuel only in boost. Well, when you are boosting, the pressure inside the manifold is greater than outside the manifold, and if the injectors aren't sealing where they snap into the head or intake manifold, then it could be leaking a mist of air/fuel out one or more of the injectors, buy only under boost. And it may only leak when in boost and seal when in vacuum.

One way to check for leaky injector seals is by spraying carburetor cleaner at the bottom of the fuel injectors. If they leak, the engine will "respond" by either speeding up or stumbling. I got two injectors leaking too. Gotta fix it before I turbo.
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Old 12-05-2008, 08:32 PM   #18
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i just went through that with my fuel pump. AFR's were getting higher and higher and I had to keep retuning. Eventually it couldn't make the pressure I needed. Still doesn't explain the gas smell though.

Did you check the lines in the trunk?
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Old 12-05-2008, 09:48 PM   #19
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Quote:
Originally Posted by patsmx5 View Post
Long shot, but the it could be the fuel injector O-rings leaking where they snap into the (intake manifold if it's a 1.6, cylinder head if it's a 1.8). Reason I say this is you mention you smell fuel only in boost. Well, when you are boosting, the pressure inside the manifold is greater than outside the manifold, and if the injectors aren't sealing where they snap into the head or intake manifold, then it could be leaking a mist of air/fuel out one or more of the injectors, buy only under boost. And it may only leak when in boost and seal when in vacuum.

One way to check for leaky injector seals is by spraying carburetor cleaner at the bottom of the fuel injectors. If they leak, the engine will "respond" by either speeding up or stumbling. I got two injectors leaking too. Gotta fix it before I turbo.
I'm thinking that I can check this in the AEM (and will do so). The thing is, I took the dual feed fuel rail out yesterday; checked the injectors (found that some seals were toast and bought them and had them installed) but couldn't find anything else wrong.

I was about to take the dual feed out and try the OEM one but the mechanic stopped me. He said he couldn't find anything wrong with it.

One question that does come to mind: if I had 1 bad fuel injector; would I be seeing these symptoms? My logic says no but I have absolutely no clue.

About the smell. It's weird; when they fixed the lines next to the rail yesterday the smell went away unless I was in boost but today it was back to smelling at all times. Sorry for the rant.
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Old 12-05-2008, 09:53 PM   #20
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i just went through that with my fuel pump. AFR's were getting higher and higher and I had to keep retuning. Eventually it couldn't make the pressure I needed. Still doesn't explain the gas smell though.

Did you check the lines in the trunk?
I did check the lines in the trunk; absolutely dry.

This is my plan of attack now:

1) I'll go down to my parking spot in a little while and fire up the car with my laptop connected. I'll be able to see what every injector is really injecting.

2) Early tomorrow morning is back to the shop. There I plan on doing the following:

a) Try another fuel pump
b) Install the Automotive pressure regulator (just in case my OEM one is toast)
c) I bought 6 440cc high impedance RC injectors from a local Nissan 300 owner who has a Greddy kit installed in his since May and just upgraded his to 750 cc. I would install these instead of my current 550 cc ones.

I got nothing else I can think of.
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