Rough Running on initial Cold Start - keywords 07030 all calibrate calibration cylinders DTC engine foul fouled fouling hesitate idle intermittent light LLV MIL misfire miss no P0300 plug plugs

This PI was superseded to update Recommendation/Instructions. Please discard PIP4047A.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

A brief rough running concern may be experienced for a short period of time after cold starting the engine. After the first start of the day, the rough run condition will not occur again until the vehicle's engine cools to near ambient temperature, usually overnight. Typically, no DTC will be stored. This condition is likely the result of marginal fuel evaporative qualities and a new PCM calibration was released to address this concern.

Insure the vehicle has the latest PCM calibration found in TIS2Web calibrations and titled "new calibration to correct rough idle after cold start". These calibrations are designed to remedy this concern.

In some instances, the updated calibrations will drastically improve, but not entirely eliminate, the concern. Some vehicles may exhibit this condition for a few seconds after start with no stored DTC. If the SI diagnostics (Doc ID# 1720938) do not isolate a cause for this concern after the updated PCM calibrations have been installed then test the fuel injectors with the AFIT as outlined in 03-06-04-030E and repair as necessary. If there is no problem found, no DTCs stored, and the concern continues to occur for a short period of time on cold starts then the cause is most likely related to sub-standard fuel evaporative quality.

A change to a Regular Grade Fuel obtained from a high volume Top Tier Station, combined with a clearing of Long Term and Short Term Fuel Trim Memory, will improve the condition. With minimum fuel in the tank, fill with Regular Grade Top Tier Fuel and then drive for a minimum of 5 min to completely circulate the new fuel in the system. Connect the Tech 2 and record the LTM & STM on the repair order and then clear short term and long term fuel trim memory. Drive the vehicle for a minimum of five minutes after clearing and park the vehicle in a location where it can be cold started the next morning to validate the repair.

With tech 2 set up to capture a snapshot, cold start the vehicle after an overnight park. If the vehicle starts and runs acceptably then return it to the customer with recommendations to use regular grade fuel from high volume, top tier stations. If the vehicle still exhibits a Cold Start Rough Run concern then save a copy of the snapshot data and contact TAC for further instructions.

Diagnostic Process if issue persists after latest cal installed and a few tanks of Top Tier Regular Grade fuel has been run through the vehicle.

1. TAC consultant to document the following information from the dealer to the TAC case.

•	Technician Comments / Conditions when Vehicle was cold started:

•	Local Time of day at time of cold start ___________am/pm

•	Ambient temperature at time of cold start __________ F

•	Did vehicle exhibit run rough concern? Yes / No

•	Amount of time in seconds after start that rough run began to occur? __________sec

•	Amount of time in seconds that vehicle exhibited run rough concern?__________ sec

•	Vehicle transmission selection at time of rough run? Park / Reverse / Neutral / Drive.

•	Severity from 1 to 10; 1 being minor - 5 being rough - 10 being vehicle started ran a short time, quit and had to be restarted

2. Verify dealer has saved a snapshot of the cold start concern.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.