My 1990 sierra has a miss in it when i accelarate. I replaced plugs and wires but not the fuel filter or fuel pump.I also smell fuel outside between the bed and cab on the drivers side
Check out the distributor cap and rotor arm, - and make sure the plugs ar gapped properly - should be 1mm on 1.6 1.8, and 0.75mm on the 2 liter.
Check the oil level urgently, if it has been misfiring for some time you will have acuumulated all that unburnt petrol in the oil sump!!! (you can test this by getting a bit of oil from the dipstick and putting a drop on your fingers, rub together and sniff the oil, if it stinks of petrol change it -you need to change the oil filter too since it wil be full of petrol tainted oil also.
Once you are sure you have good oil and either it was ok after testing it from the distick "golden, clean oil"
or you replaced the contaminated oil and filter you can move on to sorting out this misfire.
- You didn't mention if you checked or replaced the HT coil -
Check for strong sparking from the main HT lead from the coil itslelf,
Pull the lead from the centre of the distibutor cap -
have someone crank the engine while there is a "spare" sparkplug in the main ht lead (ground the plug to the engine, holding the rubber insulation of the cable with pliers - Use a normal HT lead if the main coil lead wont reach a suitable grounding point with the sparkplug) -
check for solid bright blue spark, it should be regular timed, and strong EVERY time - any missing or weak sparks indicate electrical problem either - the coil is failing - or the battery is weak - or the distributor is faulty. - a faulty distributor would be expensive to replace and more so to repair, a reconditioned distributor costs around £120.
for now I assume the coil checked out fine and gave a strong steady uniform set of sparks.
With a fully functioning coil, you're left with the distributor cap and rotor arm - the distributor cap comes off with 2 screws at the left and right sides of the cap between the HT Connectors -
unscrew them - (note the original orientation of the distributor cap before you pull it off to aid refitting)
you can now pull away the cap from the rest of the distributor.
INSIDE the CAP there are four "poles" round the outside, and a spring mounted contact in the center - make sure the poles are clean and shiny with only light markings at most, if they are blackened, whitened ro rounded and pitted then replace the cap - ford dealers or local part shop, most shops will stock both the rotor arm and distributor cap for around £15-30 - phone around for the best deal.
Still on the distributor is the rotor arm, this pulls off - it has to be pulled dead straight off the distributor shaft -
once you have the rotor arm off you can inspect the metal contact on the top for general dirtiness and decay, it "should" be shiny brass/copper in colour. if it looks pretty bad, pitted or blackened/burned- - get a new rotor arm from ford dealers or from local part shop (not expensive)
Once you are sure of a clean or new rotor arm and distributor cap you can try the engine again - hopefully the misfire is gone.
If it is still there....
we are here
DISTRIBUTOR CAP - FINE
ROTOR ARM - FINE
OIL + FILTER NOT OVER LEVEL + CLEAN, NO PETROL IN IT
HT COIL - GOOD STRONG REGULAR SPARK.
If it still misfires with all these things in perfect order then you are left with: Clogged Fuel Line/Filter or
Failing Fuel Pump or
Ignition TIMING - ( 10-12 degrees BTDC) have igition timing checked and set if not correct.
OR... Faulty Distributor - pretty much worst case scenario.
Tell me how you get on -
Often it is the distributor cap and rotor arm -
If not I hope its the fuel filter!
Jan 22, 2010 |
1990 GMC Sierra