AGURDI590

Hi ..My 1990 vert was running great after I did the throttlebody mod to it, ported the intake slightly and replaced all the vaccum hoses with silicone as well as new 550 cc injectors. I also added a manual choke cable to help with cold start.
the car has a new high flow fuel pump, new fuel filter, and full stainless Steel Racing beat header to muffler exhaust. I have a new AEM A/F ratio gauge
which always read 14:7 to 1 when I cruised on the highway. Now it tries to get to 12.5 to 1 and throws a check engine light and drops to 11:1 or worse. the check engine light goes off when I back off the throttle and the process repeats itself continually. gaus mileage is now 10 mpg vs 19 before

The car now stumbles terribly under acceleration as it is running way too rich gauge reads 8.5 to1 when I try to accelerate hard ..under very light accel It gets to 4800 and stumbles or bucks wildly. when it is Thoroughly warmed up ( 30 minutes of driving) It finally calms down a bit and doesnt buck or stumble as much

It throws code 17 Feedback system error no matter what I have tried ..I have replaced the o2 sensor (2 bosch) now with an NTK , Rewired the o2 sensor directly to the CPU ( which was also replaced) new NGk plugs ,New Spark Plug Wires, . I do not know what else to do ?? Any help would sincerely be appreciated.

muythaibxr

I think this is in the wrong section... moving it where I think it should go.

AGURDI590

Thanks ..are you familiar with the DIYPNP for the S5?

RotaryEvolution

iTrader: (30)

test/adjust the TPS according to the FSM and go back to the stock fuel pump, you don't need an upgraded fuel pump which will just waste gas...

open a book, do a google search, do something in regard to educating yourself prior to just tossing **** on the car. most aftermarket high volume pumps will overwhelm your stock fuel pressure regulator and force more fuel through the injectors, can you guess what the result is?

AGURDI590

thanks I will adjust TPS per manual specs and let you know

HAILERS2

For the non closed loop fault............................I'd backprobe the 02 wire at the ECU with a digital meter. Warm the car up fully. Idle the car and see what the digital meter reads on dcvolts.

Hard to say what YOUR cars idle will read on the 02 wire with the meter. With no airpump/acv I'd expect it to read in the .6 to .8 vdc. Closer to the point eight vdc.

IF it read like that and the value changes when you drive the car I'd say the ECU is seeing the 02s output which should be from zero to approx 1vdc.

IF the above checks out................I'd check and make sure the ECU is seeing the clutch switch and the neutral switch when it's supposed to see those switches. I'd also make sure you have the right boost/pressure sensor for your engine/car. No turbo sensor on a non turbo car nor vice versa.

IF the 02 wire to the ECU isnt showing a voltage..........disconnect the 02 sensor wire either from the ECU plug or any plug b/t the 02 sensor and the ECU plug and see if the o2 sensor wire has voltage on it when your engine is idling. An example would be if you installed a aftermarket 02 sensor that had a short wire on it with a connector on that wire. Pull the plug apart and see if there is voltage on the half of the plug that goes directly to the sensor. Should show zero to one volt with a fully warmed up engine. If not write back.

If memory serves all the ECU needs to go into closed loop is a input from the 02 sensor and the car actually be driven in gear over approx 1700 rpm. I might be wrong about the rpm by a couple hundred one way or the other. So the ECU has to see the transmission in gear via the neutral switch on the transmisison and maybe also the clutch switch being let off. Mabe on that last count, maybe not.

The jpg came out of the online manual. The part I'd pay special attention to is if the 02 sensor shows voltage with the o2 wire disconnected from the ECU with a fully warmed up engine.

If you have a airpump and acv then the above check of the 02 output wont be the same. At idle it would show near zero voltage. You'd have to actually drive the car to see if the 02 value changes upwards or not OR disconnect the airpumps drive belt or if non turbo just pull the blue plug off the Relief solenoid alone and leave the belt on the airpump. Then the 02 will read a voltage at idle with fully hot engine.

AGURDI590

okay I adjusted the TPS to FSM specs .. it was a little off but the idle was always very smooth. no changes. I forgot to mention I purchased an adjustable fuel pressure regulator along with the high flow fuel pump. however the car ran so well for 6 months after I did the mods I never got around to installing it. I read you cannot run an after market Fuel pressure regulator with the stock S5 fuel rail and I also read you can by running it after the secondary rail and to pull the vaccum hose off the factory FPR and attach it to the new adjustable FPR. which of these are correct?

AGURDI590

In reply to Hailers2 , My S5 car has the air pump for 5th and 6th port actuation, I checked the o2 sensor reading at warm Idle and voltage was .86. Under acceleration and deceleration it fluctuated per specs of FSM. My clutch switch is working fine. I have not been able to locate the neutral switch on the tranny yet. My map sensor is correct fo NA and checks out fine. Code 17 also listed fuel pressure as a possible cause. everything else has been checked so any help in installing the Aftermarket adjustable FPR would be of great use to me.

87 t-66

iTrader: (133)

my suggestion:

put the stock fuel pump back in
put the stock 460cc (or is it 440?) injectors back in
remove the FPR and use the stock one

then see if you are still having the issue

AGURDI590

Or I could just go out and buy a smart car ..I'll check the fuel pressure with a gauge first

AGURDI590

The Fuel pressure is High ..it reads 42 psi when specs say 32 to 39 is where it should be.
I will install the adjustable FPR and see what happens next.

Evil Aviator

What are you using to control the larger 550cc fuel injectors and higher fuel pressure to keep them from overfueling the engine?

AGURDI590

with stock ecu using an adjustable fuel pressure regulator with gauge ..now it reads 31 at idle and 39 under acceleration. Have just completed building a new DIYPNP ecu for the the car. this new ecu and the aem AFR gauge were going to control the fuel. however it is being troubleshooted for spark ..so Im stuck with the stock ecu till then ..going to add a turbo AFM As i heard that will help lean it out as well.

Evil Aviator

^ There is your problem. No way in hell is that going to work.

Don't bother attempting to tune the car until you install the DIYPNP ECU. You will not need the turbo AFM, and the new ECU will control the spark.

In the meantime I recommend that you read some books about how an EFI engine works. Piston-engine EFI books are fine. Even better, see if there is a cheap engine tuning class offered at your local community college or tech school. I don't suppose you can afford the tuition for EFI-101?
http://efi101.com/efi101.html

AGURDI590

Well the car does accelerate much better and the AFR under fulll acceleration is 10.5:1
Still the code 17 appears every 10 seconds after cruising. I will continue to lower the fuel pressure as specs say it could go as low as 32 ...gonna shoot for 36 psi under acceleration and 28 at idle

AGURDI590

Okat turbo Afm Arrived minutes ago..popped it on and .......it pains me to say you were all wrong!! at cruising AFR is now 14:7 to 1 Again !!! and the check engine light has gone away no more feedback system code error 17 ....yeah!!!!

turboIIrotary

iTrader: (9)

There is no reason to put 550s on a mostly stock n/a engine it's just a waste of money and probably gets worse fuel mileage.

Evil Aviator

... and you will pop it right off again when you install your new DIYPNP ECU.

Well, under his icon it says "Future Home Of Turbo II". Otherwise, it is a typical minor noob mistake that will not really hurt anything. The mileage should not decrease by more than 1mpg. My main concern is that I hope he doesn't try to tune the ECU himself.

SpikeDerailed

iTrader: (7)

ok so now the fueling may be close to correct, but what about the ecu's load calculation used for ignition timing? The tii afm has a stiffer spring and the tii ecu knows it, so it calculates air flow correctly, the n/a ecu(n35x) does not.

87 t-66

iTrader: (133)

just let him mess up the car...i think we have all done enough. you can lead a horse to water...

AGURDI590

Okay been a few months since I updated the Post. Everything ran great for a month or so, but then I noticed the Fuel Pressure was increasing and the dreaded Code 17 returned. I went back to the stock fuel pump and the code 17 was gone. My AFR gauge reads 14.7 to 1 again and gas mileage is a respectable 17 MPG for combined city highway. It accelerates to 8,000 rpm with no issues and is a pleasure to drive once again. A new problem has arisen that I think points to the stock fuel pump. the AFR goes lean when sitting in traffic on a mid day run. My Temp gauge reads 185 to 189 normally but rises to 195-200 in bumper to bumper traffic and the AFR starts leaning out from 13.5 to 15 ..16..17..18 before it will eventually die if I do not keep the revs up to 1500 or so. If I get moving again the temp goes down and the AFR starts to slowly return to 14.7. Also if the car sits for 20 minutes it has a hot start issue This did not happen with the high flow pump. When it sits for an hour or longer it starts right up. My fuel pressure gauge shows the pressure also drops to 15 or less when it gets hot. I'm going to try the stock turbo II pump and hope that code 17 does not return

AGURDI590

I originally planned to use an adjustable FPR ..but the s5 fuel rail must be modded to do this.
I bit the bullet and cut the old stock FPR off my fuel rail and capped the end. I can run 17 to 16 PSI now and the car idles better than ever due to the much lower pressure. she revs even easier to redline and the fuel pump wiring was loose so that solved the super lean issue when the car gets warmer. I also set my front 1800 cfm push fan (to help the stock fan) to 185 degrees and this actually lets the temp peak at 195 then drop to 190 while sitting in long traffic lines.
AFR peaks at an acceptable 15:1 at idle when hot.

MazdaMike02

iTrader: (4)

Why are you doing all this to an Na? And the computer needs to know many things to go into closed loop, including ect, rpm, iat, o2 etc.

J5sense

iTrader: (3)

+1 too much fuel

AGURDI590

I do this because I plan on doing a turbo II conversion and DIY told me my DIYPNP ECU can improve my NA driveablility and mileage plus it can also run the turbo. unfourtunately My DIYPNP does not work yet so i'm stuck with the stock CPU. This car is my daily driver and is running as well as it ever has now that I have sorted out all the issues. It does not have too much fuel or run rich any more. 22 year old technology is not what I want!