Rough start

[acm543]

When I start the car, doesn’t matter if I leave it off for 5 minutes or if it’s a cold start, the rpms idle really high and real low. That’s anywhere from 1,200 down to almost 300. Then it once it calms down, it will fluctuate between 900 and 300. Also lambda b1 and b2 fluctuate all over the place. That is also any where from 1.15-0.50. After I let the car sit for a minute or two it calms down and is fine to drive. Nothing changes and the lambda sits at .93 unless I’m engine braking. I don’t know if it matters too much but while I’m driving the AFR doesn’t change from 14 on the gauge cluster on the dash board. I’ve tried cleaning the MAF sensor. My next thought is the O2 sensors. A friend mentioned it might be a plugged injector. Im going to see my tuner on Monday. Any thoughts from you guys?

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[ugstang17]

When was the tune installed? What mods have been done to the car? How many miles are on the car? When did you last clean the TB? When did you last inspect the fuel filter or change it? Is the car misfiring when this happens? Are there any CEL codes stored or active?

As for a fuel injector I doubt it. WHY? Because you are seeing a problem with AFR on both banks based on the limited information. If it were a fuel injector (singular) the AFR bank1 vs AFR bank2 would read fine on one side and lean or fluctuating on the other. Equally LT's for one bank would be normal and LT's for the other would be high or low if it were again one fuel injector on only one side. This indicates that whatever the problem is it is common to both sides. So you can rule out a spark plug, a COP or an injector. If there are multiple COP's injectors, and spark plugs failign on both banks then that would first be unlikely (though possible) and they would have to be failing on both banks. This also rules out a potential O2 sensor as again they are specific to each bank and the issue is effecting BOTH banks. That isolates it to air intake issues, TB issues, tune issues, fuel issues, or PCM issues common to both sides.

 

[acm543]

When was the tune installed? What mods have been done to the car? How many miles are on the car? When did you last clean the TB? When did you last inspect the fuel filter

As for a fuel injector I doubt it. WHY? Because you are seeing a problem with AFR on both banks based on the limited information. If it were a fuel injector (singular) the AFR bank1 vs AFR bank2 would read fine on one side and lean or fluctuating on the other. Equally LT's for one bank would be normal and LT's for the other would be high or low if it were again one fuel injector on only one side. This indicates that whatever the problem is it is common to both sides. So you can rule out a spark plug, a COP or an injector. If there are multiple COP's injectors, and spark plugs failign on both banks then that would first be unlikely (though possible) and they would have to be failing on both banks. This also rules out a potential O2 sensor as again they are specific to each bank and the issue is effecting BOTH banks. That isolates it to air intake issues, TB issues, tune issues, fuel issues, or PCM issues common to both sides.

I don’t know when the tune was put on the car. I haven’t had any contact with the previous owner. Car has about 64,000 miles on it. When I cleaned the MAF sensor, I also wiped down the throttle body, opened the throttle body up and wiped it down on the inside. Unless there’s more to it than that. I didn’t think about the fuel filter. So I’ll check that when I get home.The car has catless long tube headers. I have two CEL for the O2 sensors. That’s why I thought I could possibly be the O2 sensors because they both could be bad? I’m kinda new to all of this. So I’m still learning.

 

[ugstang17]

I don’t know when the tune was put on the car. I haven’t had any contact with the previous owner. Car has about 64,000 miles on it. When I cleaned the MAF sensor, I also wiped down the throttle body, opened the throttle body up and wiped it down on the inside. Unless there’s more to it than that. I didn’t think about the fuel filter. So I’ll check that when I get home.The car has catless long tube headers. I have two CEL for the O2 sensors. That’s why I thought I could possibly be the O2 sensors because they both could be bad? I’m kinda new to all of this. So I’m still learning.

What codes? The extensions for the O2's (if needed) for LT's have been known for causing issues on the S197's. Don't know if that applies on S550 aftermarket headers. Depends on O2 placement. Factory wiring can also be an issue. I have access to prints for S197 series but nothing yet for 15+ or I could give you some direction aside from trace them back and inspect for damage. It is possible that both O2 sensors are failing but not probable. I would first visit the Fuel filter. If that has debris in it you may then wish to pull the fuel pump and see if there is crap in the tank. To clean the TB you need to remove it. VMP performance has a video for how to remove and clean their twin body. Same situation just yours is a standard TB design. Disconnect the battery before breaking connections. Make sure that pressure is relieved on the Fuel system before trying to inspect the fuel filter as well. On the S197 you could pull the relay to the fuel pump, start the car and let it die and that would relieve all the pressure. Not sure if that still applies on this fancy 'eurostang' push to start system.

One last thing to check for since you have had the air box off. Make sure that the airbox is properly seated at eh TB and in any other place after the MAF. IF it is not, this will allow unmetered air to enter the fuel mix and cause weird odd lean issues on both banks. Check all connections on that air box.

 

[acm543]

What codes? The extensions for the O2's (if needed) for LT's have been known for causing issues on the S197's. Don't know if that applies on S550 aftermarket headers. Depends on O2 placement. Factory wiring can also be an issue. I have access to prints for S197 series but nothing yet for 15+ or I could give you some direction aside from trace them back and inspect for damage. It is possible that both O2 sensors are failing but not probable. I would first visit the Fuel filter. If that has debris in it you may then wish to pull the fuel pump and see if there is crap in the tank. To clean the TB you need to remove it. VMP performance has a video for how to remove and clean their twin body. Same situation just yours is a standard TB design. Disconnect the battery before breaking connections. Make sure that pressure is relieved on the Fuel system before trying to inspect the fuel filter as well. On the S197 you could pull the relay to the fuel pump, start the car and let it die and that would relieve all the pressure. Not sure if that still applies on this fancy 'eurostang' push to start system.

One last thing to check for since you have had the air box off. Make sure that the airbox is properly seated at eh TB and in any other place after the MAF. IF it is not, this will allow unmetered air to enter the fuel mix and cause weird odd lean issues on both banks. Check all connections on that air box.

I’ll check for the codes when I go to lunch. When I get home I’ll pull of the throttle body clean it and check the fuel filter. If there is stuff in the fuel pump/tank what would I do from there? I appreciate the help. Hopefully this will do the trick.

 

[ugstang17]

I'll wait for the codes. In the meantime does the car drive normal other than the idle surging? No lurching or surging or bucking or massive sputter, or massive hesitation, going down the road under normal throttle conditions? If not do you see AFR activity on the display? There will be some as the AFR is constantly correcting to maintain commanded LAMBSE on banks 1 and 2. It could fluctuate depending on the quality of the tune by .5 in blips and then return to 14.0. Just trying to get a better picture in my head of everything before pursuing a path of eliminating the probable faults.

 

[acm543]

I'll wait for the codes. In the meantime does the car drive normal other than the idle surging? No lurching or surging or bucking or massive sputter, or massive hesitation, going down the road under normal throttle conditions? If not do you see AFR activity on the display? There will be some as the AFR is constantly correcting to maintain commanded LAMBSE on banks 1 and 2. It could fluctuate depending on the quality of the tune by .5 in blips and then return to 14.0. Just trying to get a better picture in my head of everything before pursuing a path of eliminating the probable faults.

I’ve had surging happen maybe 3 or 4 times, that’s after letting the car return to normal. If I don’t let bank 1 and 2 settle down before I drive they are all over the place. So I’ll be suring and bucking a ton. AFR normally sits right at 14. The only time bank 1 or 2 change while driving is when I engine brake. That’s normal though.

 

[ugstang17]

SO that seems to indicate (without seeing them first hand) that the O2 sensors are at least reporting back data of some type to the PCM. I'm trying to help you as I can while at work. I haven't done a lot of forum trouble shooting for a while AND I am at a handicap because I do not have schematics for the S550 or tech manuals to reference. I have been trying to get a set from the service manager at the dealer I bought mine from.

I have some things running through my head but I want to know the codes before sending you off on a witch hunt.

 

[acm543]

SO that seems to indicate (without seeing them first hand) that the O2 sensors are at least reporting back data of some type to the PCM. I'm trying to help you as I can while at work. I haven't done a lot of forum trouble shooting for a while AND I am at a handicap because I do not have schematics for the S550 or tech manuals to reference. I have been trying to get a set from the service manager at the dealer I bought mine from.

I have some things running through my head but I want to know the codes before sending you off on a witch hunt.

The codes are P2251 and P2254. You’re good man. It’s hard to fix a problem when you aren’t there. So any help is appriciated.

 

[ugstang17]

Okay. I don't have a schematic so I referred to the S197 wiring schematics for he 5.0. The codes are the same failure for O2 sensor #1 (the primary O2) on bank 1 AND 2. P2251 is for bank 1 and P2254 is for bank 2. With these being the same the first thing to begin checking would be your wiring harness for nicks or any where it may have been pinched or could get burned and make appropriate repairs. If that all visually inspects well, then next thing and the more likely (unless you just had a clutch upgrade done or something similar in that area) would be to inspect the O2 extensions (usually needed with LT's) and see if they are burned. Take them out of the circuit and do a continuity check pin to pin. THEN on one end only check pin 1 ,2 pin 2,3 pin 3,4 and pin 4,1. You want to see infinity. If you read open end to end or a short on the pin to pin replace the extensions. Heck replace the extensions anyway. Many guys have had issues with these extensions on their LT's on other forums. If that confidently checks out then I would suspect that the O2's may be bad.

DO YOU KNOW IF THE CAR RUNS OR RAN AT ANY TIME ON E85? E85 will eat O2 sensors up pretty fast as I understand.

 

[acm543]

Okay. I don't have a schematic so I referred to the S197 wiring schematics for he 5.0. The codes are the same failure for O2 sensor #1 (the primary O2) on bank 1 AND 2. P2251 is for bank 1 and P2254 is for bank 2. With these being the same the first thing to begin checking would be your wiring harness for nicks or any where it may have been pinched or could get burned and make appropriate repairs. If that all visually inspects well, then next thing and the more likely (unless you just had a clutch upgrade done or something similar in that area) would be to inspect the O2 extensions (usually needed with LT's) and see if they are burned. Take them out of the circuit and do a continuity check pin to pin. THEN on one end only check pin 1 ,2 pin 2,3 pin 3,4 and pin 4,1. You want to see infinity. If you read open end to end or a short on the pin to pin replace the extensions. Heck replace the extensions anyway. Many guys have had issues with these extensions on their LT's on other forums. If that confidently checks out then I would suspect that the O2's may be bad. When I get home I will go through my notes and see what the resistance of the Or sensor across the heater and sensor should read normally. But even if these checks are good the sensor could be what is called poisoned or inhibited by a coating built up on it from something.

DO YOU KNOW IF THE CAR RUNS OR RAN AT ANY TIME ON E85? E85 will eat O2 sensors up pretty fast as I understand.

Thank you. I’ll go through that when I get home tonight. No the car never ran on E85. I’ve read the same thing you have as well, E85 eats through O2 sensors

 

[acm543]

Why does it only have this problem at start up and not all the time?

 

[ugstang17]

I stand corrected. I've spent too much time troubleshooting narrow band sensors with guys owning 05-10 models. The 11+ Coyote uses the wide band HOS2 sensor. There are 6 pins on this model. Looking at the Diagnostics section the problem eludes to the reference ground connection which is on pin 2 of the 6 pin connector. I cannot provide wire color because I am not certain it will apply since I am referencing prints for a 2011 Coyote. See my PM for reference.

I do not know the answer to your last question. Poor grounding or bad connection can cause all kinds of problems in electronics. Temp, moisture, dirt, and/or vibration effecting the connection can change and suddenly everything is fine. It's referred to as a "ghost gripe" in some worlds. The term referring to the fact that it is there and then it is not. Yours at least has some form of repetition so it can be isolated.

 

[acm543]

I do not know the answer to your last question. Poor grounding or bad connection can cause all kinds of problems in electronics. Temp, moisture, dirt, and/or vibration effecting the connection can change and suddenly everything is fine. It's referred to as a "ghost gripe" in some worlds. The term referring to the fact that it is there and then it is not. Yours at least has some form of repetition so it can be isolated.

That makes sense. Whelp guess I’ll jump under the car and see what happens. Thanks for your help. I’ll for sure keep you updated

 

[ugstang17]

Check you messages . And please give a follow up after it is resolved so others can learn form this as well.

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