Overly rich

[96Cobra1773]

Hey guys, looking for some advice and direction. Thanks in advance!

I recently finished the rebuild on my car and took it to a tuner shop here in Phoenix. Basically he says there is a mechanical issue with the car and he could only build the base tune for it. It is running super rich, surges at idle. Tuner did not dig into it, and had no real guesses

Here is my basic set up:

1996 cobra forged shortblock
stock heads with imrc's deleted (turned off in base tune)
p1sc 3.40 pulley, intercooled
sct 2600 maf
aeromotive 340 intank pump
60lb siemens inj
bbk 65mm tb
bbk longtubes and xpipe
sct x4 tuner w/ base set-up tune

Heres how i have it set up.

Anderson powerpipe with maf, converted to draw-thru and just behind filter. Stock procharger bov routed back to powerpipe (after maf, before blower). Air intake sensor rerouted to intake tube just before throttle body.

I pulled the plugs and all 8 were jet black, just the same for the o2 sensors. Cleaned the plugs up and closed gap a little to .030. installed 4 new 02 sensors. installed new stock fuel pressure regulator. changed engine oil.

I cannot find an obvious vacuum leak anywhere. I dont know how to "smoke test" for one tho.

i have not started the car after cleaning plugs, new o2 and new regulator for fear of washing out the rings if run too long in this condition.

DTC's pulled from computer are p1132 and p1152 and p1000

I know p1000 is just the engine run cycle as its new. and p1132 and 52 means rich condition from what i read.

Fuel pressure gauge is enroute and will install upon arrival.

Basically the thing is super super rich and i cannot figure it out. Any ideas would be great!!

 

[mwolson]

Possible causes:

Electrical:
● Short to VPWR in harness or HO2S
● Water in harness connector
● Open/Shorted HO2S circuit
● Corrosion or poor mating terminals and wiring
● Damaged HO2S
● Damaged PCM

● Fuel System:
● Excessive fuel pressure
● Leaking/contaminated fuel injectors
● Leaking fuel pressure regulator
● Low fuel pressure or running out of fuel
● Vapor recovery system

● Induction System:
● Air leaks after the MAF
● Vacuum Leaks
● PCV system
● Improperly seated engine oil dipstick

● EGR System:
● Leaking gasket
● Stuck EGR valve
● Leaking diaphragm or EVR

● Base Engine:
● Oil overfill
● Cam timing
● Cylinder compression
● Exhaust leaks before or near the HO2S(s)

 

[96Cobra1773]

Question about 02 extension harnesses. I used a set for the front sensors, but the tabs on the connector did not line up. i had to grind off the tabs so they would plug in. this caused the color of the wires to not match up between the extension and the harness. Is that an issue or is it just colors dont match but the wires make the connections they need?

 

[mwolson]

On mine, the Red and Yellow/Light Blue (or Red/White, Tan/Yellow or White/Black) wires go to the O2 sensor heater wires, which are both White wires on my O2 sensors. The Gray/Red wires are the signal return wires, which go to the Gray wire on my sensors. The Red/Black (or Gray/Light Blue, Pink/Light Green or Red/Light Green) wires are the signal wires which connect to the Black wire on my sensors.

 

[96Cobra1773]

Havent had time to do any work. Tmro i am going to delete the egr and air injection system, in case something in there went bad. Car did sit for 8 years with out running... Supposed to get the fuel gauge tmro too.

 

[mwolson]

All that will happen is that you will also generate EGR and SAI DTCs too, which will really complicate the debug effort. Minimize the number of variables you are dealing with. Fix this problem first, then you can start modifications.

 

[96Cobra1773]

I know it will throw those codes, i will have them tuned out. My hope was that one of those systems had a problem, and was causing my issue. I see your point mwolson

After pulling the egr, sai system, replacing the fuel regulator and closing the plug gap, i reworked my air intake system. I added a little distance from the maf to the bov return, in case the air was swirling at the mix point. I added a few inches between the filter and the maf on the front end to smooth that out.

Fired the car and all the above was an improvement. It idles better, much smoother although too high, and did not surge at all in the 2-3 minutes it ran. I shut it off quick because when revving it raw fuel was shooting out the exhaust again.

Wondering if my pcm is bad. What else could affect fuel supply and a/f mixture?

My fuel gauge was a no-show today. Ebay ship times suck compared to Amazon...

 

[mwolson]

I'd suspect the base tune at this point. Who is your tuner? Did he put the correct injector value file in? Did he put the correct MAF value file in? What is your AFR at idle? Are you running a wideband? Etc, etc, etc.

 

[cbrown9064]

I hesitate to say this, but will anyway...does your tuner know what he is doing? Should be able to make the car rich or lean pretty easy. I am running a Quarterhorse and Binary Editor and can make the car black smoke rich or missing lean in a heartbeat. Also, a vacuum leak make the car lean, not rich.

If all other data points are correct, lean up the MAF curve. What is the computer commanding for lambse versus what are you seeing on the narrowband or wideband? Like Mark said, so many questions. But all parameters in the EEC are adjustable with the right tools, so it does not seem possible to make it run.

That all being said, you can mask mechanical issues with tuning, so make sure everything is A OK.

 

[96Cobra1773]

The tuner is Dyno-Comp in Scottsdale. Ive never worked with them before now but i saw several gt500's on their dyno. He said he made the base map on the car, based off my parts list. He seemed to know what he was doing. That being said, when they had the car, he believed their to be a mechanical issue based off the surging idle, the faint white smoke/steam (not sure which) and fluid coming out the exhaust. He said he was commanding the car to lean out, but it wasnt "responding" like he said it should.

He said they would look into it further, but at $109 an hour, i did not want to pay them to poke around. I can do some of that myself.

So the fluid has me the most concerned. Im just not confident what it is. The fluid itself doesnt smell like raw gasoline, almost has no smell. but of course its coming out the exhaust, so i do smell that. I see no coolant in the oil, and no oil in the coolant. Im wondering if its not condensation collecting all the soot and junk in the system before blowing it out. You rev it up and it does not smoke, last night just shot out some powdery soot, then some fluid after a minute or two. Remember, i popped pistons 7 and 8 in this car years ago. Filled the intake with oil and had a nice smoke show. Car sat for 8yrs until this rebuild. Everything is new and clean except the cat back is the same, so im sure there was some left over residue in the mufflers.

I take the oil cap off and pcv valve off and feel no air being forced out. It has good vacuum at idle.

I do not have a wideband or anything to test the a/f ratio myself. Was looking at the AEM kit today for about $150. That one any good?

thanks for the replies fellas..

 

[mwolson]

You can log the idle & part throttle fuel trims to see how your AFR is being controlled using SCT's Livelink software and a PC. You will only need the wideband for WOT tuning. I do recommend you get a wideband, but you can start logging some of your AFRs immediately.

When logging, use the PIDs with capital letters. They log faster than the lower case ones. I recommend you log:

Coolant Temp
Fuel Source
Both LTFTs
Both STFTs
ISC Duty Cycle
ISC Integrator
LOAD
MAF AD Counts
Battery Volts
RPM
TP Relative
Vehicle Speed (don't need this for idle, but it helps for part throttle, so I list it here)
Spark Advance
Spark Source

It is true that you have to have all of your mechanical issues solved before you begin tuning. If you tune around mechanical issues, your tune will get really screwed up. When your tuner says your car isn't responding to changes in the tune, there is a good chance that you do have a mechanical issue of some kind.

Have you checked for a leaky injector? If you put a fuel pressure gauge on the rail and turn the key on, you should see the fuel pressure go up to 39 PSI. When you turn the key off, the fuel pressure should stay up at 39 PSI for at least 5 minutes. If it leaks down fast, you may have a leaky injector or two. Just a thought.

 

[1996MysticSnake]

Did you mess with repining the MAF harness at all?

 

[96Cobra1773]

Sorry for the delay, havent had time to work on the car. Mystic, the MAF harness was extended years ago (soldered) when i installed the procharger. It worked ok back then and was not re-pinned during the rebuild.

Finally got my fuel pressure gauge hooked up. It reads 39psi at idle with vacuum line connected. 41psi unhooked. Now keep in mind its idling way high at the moment, close to 2k. I know the tuner said he increased it some to try and rid the surging, plus i deleted EGR and SAIsystems, which might contribute to high idle...? It has a new stock regulator on it, but seems high to me. 16" on the vacuum guage.

I bought another PCM in case mine is faulty. (supposedly replaced by AMP back in 2005, but who the hell knows with that shop).

Not going to hook it up, just take it with me to the tuner to swap if needed for testing.

Any other ideas or suggestions? Thanks again!

 

[mwolson]

Your fuel pressure should read about 29 PSI at idle with the vacuum hooked up, not 39 PSI. It should read 39 PSI only if you unhook the vacuum from the FPR or at WOT if you are naturally aspirated. It should read 1 PSI over 39 for every PSI of boost you have at WOT for forced induction.

The FPR is supposed to keep the fuel pressure at 39 PSI above the relative pressure in the manifold at all times. With stock cams, your idle should be at about 20"Hg. That is about -10 PSI. 39 - 10 = 29 PSI at idle.

It sounds to me like your fuel pressure regulator is not working correctly.

 

[96Cobra1773]

Because its idling so high, roughly 2k, would that not cause the higher psi and lower vacuum? The regulator is brand new about 3 weeks ago. Im thinking about putting an adjustable one on there, but would like the idle to be tuned down to normal before i do.

 

[mwolson]

What is your vacuum at idle? Divide that by 2 and then subtract that from 39 to see what your fuel pressure should be at your fast idle.

 

[96Cobra1773]

Idle is just about 1600 after a min of warm up. I see 16" vacuum. So i should be at 31psi at idle, but im at 39psi.

Thank you mwolson, for your continued help!

I have an adjustable Aeromotive FPR on the way.

 

[mwolson]

Idle issues can be a b!tch to get fixed. The PCM uses air (IACV) to do coarse control of idle but it uses spark advance to do fine control of idle. After you get your fuel pressure correct, and you know you have no leaks of metered air, you will need to log your PCM to see the spark source value at idle. If it is not a steady 9, then you have issues to fix. Don't let anyone tell you to drill your throttle plate, adjust the throttle stop or futz with the TPS sensor.

There are other things to log if you are not a steady 9 to help you figure out the issue.

 

[96Cobra1773]

Installed the Aeromotive FPR, Part #13102. The unit is backed out as far as it will go, and i read 41psi with the reference line unhooked and plugged. Plug it in, and i see 38psi.

Also, as soon as i shut off the car, the gauge immediately drops to zero rail pressure. Is that how the Aeromotive is designed? Stock unit didnt do that.

Doing some research on the 340 Aeromotive pump, do you think my stock return line is too small causing the fuel to not get back to the tank quick enough, causing high psi at the rails?

 

[mwolson]

I'd check the vacuum at the end of the hose you plug into the FPR. It is possible you have a clogged vacuum line. You can also use one of those little vacuum tester pumps to put some vacuum on the fuel pressure regulator to ensure that it drops about 1 PSI for every 2" of Hg you put on it.

When you shut off the key, the fuel pressure should stay up for at least 5 minutes. The FPR wouldn't let the fuel pressure drop right away. A bad fuel pump check valve or a leaking injector could cause that.

I doubt very much that your return line size would be causing a problem like this.

This problem is a persistent little SOB isn't it?