You may want to check for buildup at butterfly valve on throttle body. could be buildup of carbon that when cold is hard, and after engine warms up the buildup would soften. this would allow butterfly to sink into it.
always start with the cheap stuff!
The idle speed should be controlled by a closed loop system. The required idle speed is programmed into the ECU and the ECU should measure the actual idle speed, make a comparison and carry out adjustments to ignition timing, fuelling and air flow to maintain the two figures within a fairly close tolerance.
If the engine runs well on the road fuel supply won't be the cause of a poor and rough idle. The big question is the idle rough because of a fault and the fault is causing the slow idle or is the idle so slow it is the only reason the engine seems rough.
The possible faults/reasons for the slow idle are many but in most cases such faults would switch on the engine check light.
I suggest the engine is serviced if it is due - certainly the basics should be checked, spark plugs, sparks, air leaks, breather system, cleanliness of the throttle body and/or idle air valve, etc.
If the routine stuff doesn't cure the problem it would be advisable to hand it over to a specialist who can examine live data on a good scanner...
Have a 2nd opinion. It can be due to the cooling system low or the sensor, idle speed sensor or solenoid. A fuel filter or pump would give u trouble hot or cold temps. Get 2nd op. good luck. PS its safe to use reputable replacement parts.
Not sure if this will help you out.Troubleshooting starting and running problems can sometimes be quite difficult. This is especially true if you aren't aware if all the possible causes of a problem. This is a general guide which will list symptoms for 944 starting and running problems and common causes of those problems. It is intended to help you map out a troubleshooting plan.
Running Problems
Clark's Garage Ā© 1998..
A fuel pressure gauge, spark tester, and voltmeter are extremely useful in narrowing down the possible causes of the problem.
or try this link. What causes low rpm at the initial start of the engine Google Search
SOURCE: Engine vibrates, shakes car at 1700 rpm, smooth at 2000 rpm
Something similar happened to my van, and it ended up being that I needed to replace a tie rod in one of my wheels. Hope this helps! I know this was posted awhile ago.
SOURCE: How do I replace a fuel pump on a 2003 escape?
Check to see if the inertia switch is tripped first. Read your owner manual for location and how to reset. Just push the button. It usually only trips in an accident to shut off the fule pump in case there is a leak.
here is how to replace the pump. It's good because you don't have to drop the tank!
Remove the gas cap.
To install, reverse the removal procedure.
Not a bad job. buy pump on ebay or new at discount at tascafordparts.com
SOURCE: 2004 f350 6.0 diesel.Engine surges
Hi, i want you to clean the air intake valve and idle speed control valve, follow the procedure below.
Here are the common cause of surges, cold stalls, stalls at stops, slow idle speed, erratic idle speed, rough idle and engine hesitation (and other problems), it is in most cases the idle speed control air-bypass valve and or throttle valve and upper intake, these area's get full of gunk and combustion residue over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.
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