Idle tuning issue after engine re-build from 4.6 to stroker 5.0

Hello everybody,

I have a tuning issue at idle after engine re-build either it will go either rich or lean. It will not be stable at all. see below mods with the situation issue.

Mustang 2v modifications:
D.S.S Racing Block oversize 0.040 with 5.0 Stroker kit, Patriot Stage 2 heads, blower HP292 cams, Paxton Novi 2K with 3.5” blower pulley and 10% Innovate Crank pulley (boost at 14-15), SCT BA2600 MAF, LT headers with full exhaust system, Typhoon Intake manifold, Performance products plenum and 75mm Throttle body, 60lb Siemens Deka Injectors, return-less fuel system with Division X Stryker 340lph single pump, Kenne Bell BAP, and NGK TR6 spark plugs gapped at 0.030.

The car was tuned perfect by all mods mentioned above with same boost except the (DSS Block with 5.0 stroker and Patriot stage 2 heads only).

After the re-build I loaded the new custom tune with changing only Engine Displacement for the new cubic inch to see how the idle will be and correct the tune from there.

1st fire-up the car idle rough and A/F ratio was reading rich 12 and then after 5 mins it goes lean 16-17, then a check engine light came up with code 0602 Control Module programing error. I disabled the code 0602 from SCT Advantage software and switched off the Adaptive control and Cats Temp switches to tune the MAF by STFT1 and 2. I load the tune and the car idle way better and sounds different but the AF ratio still reading lean and goes to 18-19 while the STFT1 and 2 within the specs between 0.95-1.05. I tried to raise the MAF airflow for idle within 20% and the car still will read lean but the STFT1&2 goes to 1.1-1.2 which is adding fuel and then I decrease the MAF airflow by 30% and the car this time will read rich 11-12 AF and the STFT1&2 will go 0.78-0.89.

So, next step I tried to force it to Open loop to tune it by the AF ratio and MAF counts or MAF volt and this time the car idle at AF 11.9-12.8 so I decrease the airflow by 20% and then the car idle lean 16.3-19, I raised the Airflow by 10% and its idling at 12.8-13.4 for 3 mins and then it will go lean 15-16. So, it drives me crazy!!

I don’t know if it is a vacuum leak issue that causing the idle not reading stable or what exactly? Please your support appreciated. I am thinking to do a leak down test to see if I have a leak or not.

Your usual supports really appreciated.

Here you go an update:
i tried setting displacement and MAF transfer back to what it was setting before the rebuild. Then i gave the maf 8% more and see how it does.

Unfortunately no changes at all. The AF will read rich for 3 mins and jump to lean 17-20 and the STFT1 between 0.97-1.04 and LTFT1 0.83. After that i shut off the Adaptive and cats for temp to start adjust the maf based on STFT1 peak and vally to get the average. Still same issue no changes at all. It will read the first 2 mins 13-15 AF and then jump to 18-20.

So, i think there is possibility for leak. What do you thinks, any suggestions?

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Fueling / EFIDynoTuning Poke around efidynotuning.com might help if mechanically the car is sound.

ecu trying to correct fueling.

It sounds like you have a mechanical issue to me. Scaling the displacement should only affect load (Something I recently learned). I can see fuel being a little off given the new displacement, but it shouldn't be that bad. I'd make sure you have no leaks.

disabling a code DOES NOT fix it. You need to find out why thr code is being thrown.

put the old tune back in it and diagnose whats going on

Sure I will return the tune back without disabling the P0602 and make a smoke test for vacuum leaks and see from there. After that i will make a leak down test and look for leaks.

I forget to mention that during the re-build we installed a new spark plug inserts with red Loctite for Cyl# 6 & 8 to seal it.

I'll keep you updated.

Here you go an update

I did a smoke test from back of the Intake Manifold vacuum line and i found 2 leaks:

1- IAC Valve "massive leak"
2- EGR Valve "little leak"

Can both of those valves creat a lean condition?

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More update:

After the leak down test, i found a major leak in cylinder #6 and 8 from, the Spark Plugs insterts that the shop installed. Is it possible to be fixed and have no leaks or i just replace the heads?

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Don't sound right. Possible to try another insert. Heli-coil or actual insert?
If it were me I would just replace the heads with a set of Trick Flows.

01blckcobra said:

Don't sound right. Possible to try another insert. Heli-coil or actual insert?
If it were me I would just replace the heads with a set of Trick Flows.

Click to expand...

01blckcobra, you're right that something doesn't sound right.

I repeated the leak down test today for bank 2 head again for Cylinders 5,6,7 & 8 and all of them were reading on the Green spot in the gouge and only reading 13-15 % of leakage which is acceptable but something I did not get it that after 30 seconds of compressed air the needle will drop gradually to 8 % of leakage. What does that mean? is it sound of scaping air from insert or what?

After that I said let me do a leak down test for Bank 1 head for cylinders 1,2,3 & 4 because I thought it was ok as those heads I bought them as a second hand. Here you go the surprise as it shows in the attached photo all Bank 1 spark plugs are having a titanium inserts with cap on top and I found that all spark plugs there will go only half way and even I couldn't do the leak down test on all of them as the hose for leak down test have a half threads and can't get it there. So, I think that wat causing the engine to go lean when it get worms up and can't be tuned.

FYI, the inserts we installed on Cyl 6 and 8 was Heli-coil black inserts.

As a conclusion, the old owner of those heads repaired all the Inserts with crappy inserts. Now, I have to take the heads off and do all the inserts job carefully and make sure no leakage on them.

After I replaced the IAC and EGR valves I took a datalog and car will die once I run it. I have to hold the pedal gas to keep it running no matter what I do with the tune until it get wormed and then it will be running fine. The car smell too rich and Air Fuel ratio fluctuating like crazy between 16-20 which is lean but car will smell all gasoline. For A/F ratio I am using Innovate LM-1.

Attached is the datalog file. Please have a look at it and let me know what do you see that I am not seeing.

I guess I'm missing the titanium insert in your pic. You found you have a mechanical issue. Fix it before you try tuning it.

And it's warmed up. Not wormed up.

As you can see from this pic the titanium inster and i guess the threaded from inside like the second pic which only half threaded.

My question, can an insert like this for our spark plugs cause a major issue such as leak because not fully threaded from inside?

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An update for the P0602 error code that will not allow me to tune the car properly.

After doing the electrical wiring, modules, and PCM diagnostic we found the PCM failed and it said possibility causes by damaged PCM. I changed the PCM and the issue gone with no trouble codes. Thanks god.

Now i will continue tuning the new pcm and see how things will go.

I would like to thanks Decipha for his advice by telling me not to disable the P0602 code and see what causing this major issue. He open my eyes in something i was not paing attention to it and almost to ignore it.



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Car will crank but will not start after the new pcm.

After installing the new PCM that came from 2003 Mustang 4.6 (PCM "MPC-14F") to 2001 Mustang 4.6 (PCM "MLC-463A").

We did the PCM configuration and PATS reprogramming, the car will crank but fuel pump not priming and will not start at all no matter what we do.

After little search i found that each PCM has it own hardware platform. The 2003 mustang hardware code is MPC while the old pcm from the 2001 mustang has MLC and i think thats why we will not be able to run the car.

My question:
Is it possible to install a junkyard PCM with MLC-462A which i think came from 99 mustang instead of original MLC-463A that came from 2001 mustang?

Looking for support and advice.



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