First thing, fix leaking exhaust, this can cause erratic idling...second thing, remove and clean IAC valve and MAF sensor..dry and replace, also try putting some SeaFoam in the petrol, engine oil and air intake, let sit for 10 minutes then go for 10-15 min drive...suggest you change engine oil shortly after driving about 5000kms, if the oil is old..
Did you get any codes on the misfire? If you did not, test ignition coils, test vacuum, test fuel injectors, verify correct plugs..That's right, anything from a fouled spark-plugs to burned cylinder head valves can cause a misfire. Whatever the root cause of the misfire, the bottom line is that one or more cylinders are not contributing to total engine power output. This leads to power loss, rough idle, unstable RPM and bad gas mileage...cheers
Thank you so much you were straight to the point about which steps to take first. sounds like a car expert to me!
Cheers mate, glad to help..
No worries mate, glad to help
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SOURCE: rough idle and intermittant misfire
I have a 2006 with 37800 miles was told today that the fan motor and radiator must be replaced. When the car started to overheat due to the fan motor not running fast enough it blew the freon out too so now a/c wont work either. The bill is close to 1000.00 Dodge offer to pay for labor as GOOD WILL GESTURE 144.00 to be exact. I have taken it in over and over with the same complaint you have described and was told to get a tune up so I did. Warranty espired exactly 3 weeks ago. My sugestiojn would be to sell the damn thing!
SOURCE: Tacoma 4cyl idles rough, heditates, multiple misfires
Possible fuel delivery problem, fuel pump, fuel line, clogged fuel filter, leaking injectors or injector O-rings, faulty pressure regulator etc. Check your fuel pressure.
SOURCE: misfire code, rough idle, full tune up complete,
The black soot on the plugs means that you are running extremely rich. The fuel injectors ma test good electricly, but they are notorious for leaks. The spider-looking thing sandwiched between the plastic intake plenum and the intake manifold gets cracks in it's "legs" and leaks fuel ito the plenum area. The fuel pressure regulator is also housed in this same assembly. if the diaphram in the regulator gets a pinhole in it, it also leaks fuel into the plenum area, causing all kinds of erratic idleing, black smoke from the exhaust, and will cause your fuel trims to drop into the negative 20s.
There is a technical service bulletin covering this subject. This procedure outlines the steps required to replace the existing Central SFI Fuel System with a new MFI (Multiport Flexible Injection) Fuel System.
It is removing the injectors which are all housed in the center body of the injector assembly and replacing them with a new version where the injectors are located where the ols "poppets" used to be in the intake manifold ports. The picture below is for a V-8 engine that is covered by the same TSB.
The poppets and the pressure regulator are available individually to fix your existing fuel injection system, but I gave up on that after replacing several poppets only to have them come back in a few months with another popet line broken. I recommend replacing the whole assembly with the new and improved version. My customers have told me after doing this that the engine never ran that smooth when it was new.
The GM part number for the new injector assembly for your V-6 engine is 12568332 it is also now available at several aftermarket parts outlets.
As for the timing chain solution posted by doodieman200, all I have to say is that I have enough fingers on one hand to count all of the failed timing chains I have replaced on these engines. If you don't have a cam/crank sync code, the timing chain has definitely not slipped a tooth.
Testimonial: "thank for tech update. due to working in a fleet bus shop i no longer get regular tech bulletins"
SOURCE: rough idle. rpms drop. misfire.
try your coil packs they go over your sparks or do plugs first and see what happens do affordable first
SOURCE: 1996 Honda Accord Rough Idle Even After tune up
Perform a valve clearance inspection and adjust if necessary. Tight or sticking valves will cause a misfire or rough running concern. Note: Perform valve adjustment when the engine is stone cold. 4cyl: INT 0.26mm EXH: 0.30mm (V6 engine are hydraulic and no adjust necessary.) Also check for a sticking or stuck open EGR valve. For diagnostic purposes only: Remove the EGR valve. Place a business card over the EGR passage and bolt the EGR valve back on. This plugs the EGR ports and if the misfire goes away the EGR valve is partially stuck open and is defective.
Check for low fuel pressure. Check for low compression. Check cam timing. Check for a weak ignition coil. Also don't over look the possibility of worn or broken engine mounts which cause excessive engine movement and engine vibration. -hope this helps
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