idle problem
- Thread starter mustangjoe02
- Start date
I had a similar problem after installing my LT's. I cleaned my MAF and IAC along with installing a new tune and it went away. I'd suggest cleaning the MAF/IAC first since its easy and cheap.
Also, I damaged one of my 02 sensors while installing the LT's. A damaged sensor could cause similar problems.
Also, I damaged one of my 02 sensors while installing the LT's. A damaged sensor could cause similar problems.
wmburns
SN Certified Technician
+1 on clean the MAF.
Cleaning the black vented IAC isn't likely to fix the problem.
Are there any other DTC codes?
Replace the PCV valve. Check for vacuum leaks especially around the valve covers, EVAP system, and PCV vacuum lines, PCV grommet, oil dip stick, oil cap. In short, anyplace un-metered air can enter.
Are there any exhaust leaks?
Note, a low idle can also result when cylinders are not pulling their weight (power balance). Confirm that the ignition system is in good repair.
Another possible cause for a surging idle is not enough vacuum to keep the black vented IAC vent value closed. Seems more likely after an aggressive cam upgrade (or anything that reduces vacuum).
More information on how to trouble shoot idle problems.
Is your mustang stumbling, dieing at idle or idling rough? - Page 14 - Ford Mustang Forums
Cleaning the black vented IAC isn't likely to fix the problem.
Are there any other DTC codes?
Replace the PCV valve. Check for vacuum leaks especially around the valve covers, EVAP system, and PCV vacuum lines, PCV grommet, oil dip stick, oil cap. In short, anyplace un-metered air can enter.
Are there any exhaust leaks?
Note, a low idle can also result when cylinders are not pulling their weight (power balance). Confirm that the ignition system is in good repair.
Another possible cause for a surging idle is not enough vacuum to keep the black vented IAC vent value closed. Seems more likely after an aggressive cam upgrade (or anything that reduces vacuum).
More information on how to trouble shoot idle problems.
Is your mustang stumbling, dieing at idle or idling rough? - Page 14 - Ford Mustang Forums
Ok so after cleaning maf, iac, egr and retune, nothing happened. Still barely surrges at idle. Like 750-800. Then when pulling to a stop of after revving the engine at a standstill the idle drops to 550 then returns to 750 and surges. Maybe spark plugs or fuel filter?? Should I run a can of seafoam in it or is that stuff junk? It just started after the lt headers install. Can't find an exhaust leak either. What's a better way of finding a leak than just listening through a tube at all the connections??
Wow that sounds EXACTY like my surging problem after the LT install.
What kind of octane tune are you running? Did you specify that you had long tubes and an O/R exhaust when ordering your tune? Do you notice any idling surge after the engine is warmed up? The front O2's are a lot farther downstream with LT's than previous so it might take a little longer for them to warm up.
I called them and spoke to BAMA in person. We discussed all of my mods, including the O/R longtube exhaust, and they sent me the tune a few days later.
What kind of octane tune are you running? Did you specify that you had long tubes and an O/R exhaust when ordering your tune? Do you notice any idling surge after the engine is warmed up? The front O2's are a lot farther downstream with LT's than previous so it might take a little longer for them to warm up.
I called them and spoke to BAMA in person. We discussed all of my mods, including the O/R longtube exhaust, and they sent me the tune a few days later.
The surge is there all the time and the drop only comes after revving or stopping. I just replaced both o2s and got a retune. I'm not sure if they actually know my mods. I put them in online and got a tune the got the next tune after talking to them through email. Ill give them a call tomorrow so I can speak to them directly and maybe see if they want me to datalog it
nyuk98gt
15 Year Member
mustangjoe02:
Call up your tuner and ask him about increasing the O2 sensor delay and, perhaps, the heater duty cycle. The O2 sensors are seeing colder gas due to the larger diameter piping. This is a well-known issues with LT's. Increasing the heater duty cycle keeps the sensors warmer (and working 'in the zone') and the longer delay helps the computer adapt to the new geometry. (The existing delay values may not be big enough with respect to the stock learning range.) With these one or two changes, the engine will idle very nicely.
HTH,
Chris
Call up your tuner and ask him about increasing the O2 sensor delay and, perhaps, the heater duty cycle. The O2 sensors are seeing colder gas due to the larger diameter piping. This is a well-known issues with LT's. Increasing the heater duty cycle keeps the sensors warmer (and working 'in the zone') and the longer delay helps the computer adapt to the new geometry. (The existing delay values may not be big enough with respect to the stock learning range.) With these one or two changes, the engine will idle very nicely.
HTH,
Chris
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