Miss-Firing, Hesitation & Rough Idle Problems (2.4)
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Miss-Firing, Hesitation & Rough Idle Problems (2.4)
Symptoms
If you have these symptoms with your Frontera 2.4 petrol or other model this should help you locate the problem quickly.
- Rough idle:
- RPM will not go above 2,000 – 3,000 RPM even if accelerator is held at constant position.
- Engine shakes from side to side under idle.
- Engine dies/stalls under load, apparent when taking off.
Engine dies/stalls on idle
The Fix:
Check spark plugs by taking each spark plug out in turn and earth it by the head. Earth can be achieved by taking the spark plug and attaching the H.T lead back on the plug and resting it on the cylinder head cover with a spanner on top of the plug to hold it in place. Make sure there is contact between the spanner and the screw thread of the spark plug. Turn the engine over and have someone check that there is spark conducting on the plug and that the spark is not arching and does not earth on the body of the plug. If there is earthing apparent the porcelain on the plug has failed and plugs will need to be replaced. If there is no spark, check gapping with a feeler gauge and adjust according to manufactures specifications. If there is still no spark check H.T lead by taking a lead off once of the other plugs and trying it again. If there is no spark still, check distributor cap for wear or corrosion clean or replace as needed and check rotary arm for wear and corrosion too. If plug fails to spark still replace plugs, if no spark after that replace or test coil pack.
If all spark plugs are working fine, clean spark plugs with solvent or 220+ grit sand papers till metal can be seen on the core. Re-fit the plugs and connect H.T leads and then start engine, let the engine run for 3 – 4 minutes then switch off. Take spark plugs out one by one and check for carbon build up. Any spark plug where metal can be seen still and no deposits are seen where cleaned will suggest a bloke or failed fuel injector. Read article coming soon on reconditioning injectors.
Check cam shaft lobes. And replace if needed.
Check timing and timing chain, if timing out adjust accordingly best to use strobe timing gun to fine tune. If timing chain needs replacing or timing cogs need replacing. It’s better to replace as a set as uneven wear can occur.
Check Cylinders for uneven or low compression using compression gauge, test cylinders on a dry test first, then do a wet test by squirting a shot of clean engine oil into cylinders, enough to cover piston head, achieved by removing spark plug. Check MAFF sensor. Do not by from Vauxhall by from after Market Company.
Check MAP sensor. Remove power lead to see if engine improves.
If uneven or low compression is evident, replace piston rings and check valve seating.
If rough idle is still occurring read section below on air leaks.
Miss Firing
Miss firing can be the same symptoms as above, except hesitation do not occur, and engine does not shake from side to side. Instead popping/miss fire can be heard, idle fluctuates between 2,000 – 3,000 RPM this is caused by air leak in the inlet system.
The Fix:
Check throttle body for gaps and replace gasket as needed.
Check hoses are secure and air tight and no splits or holes are evident replace as needed.
Check inlet manifold gasket and replace on refitting. One point to remember is if inlet/exhaust gasket has failed; replace the manifold to head bolts as these can sheer off level with cylinder head or manifold face plate. If sheer is evident normally on end manifold bolt towards bulk head, the bolt will need to be drilled out and cylinder head tap and died. If sheer is evident on face plate of manifold, as simple pair of pliers and good grip will un-screw the sheer bolt from the head. Refit back together.
Check injector plate gasket. These gaskets can be found where the front of the injectors are sealed into 2 plates sealed to the inlet manifold, just before the fuel and air enters the cylinders. Replace these gaskets before refit even if no leak is evident as this will save you time and work later.
Check fuel injector seals. As the fuel pressure regualtor relives the pressure inside the fuel rail, leaks can occur on the on fuel injector seals. Injector seals are not easy to source and would be worth your while to replace the injectors. Do not by direct from Vauxhall as they will charge you £100 per injector excluding V.A.T. a point of note would be to clean injector rail on removal and check fuel pressure regulator. And clean the 2 holes where fuel enters and return to fuel tank this is achieved by covering the valve hole in the middle and blowing trough each hole opposite. To clean fuel rail take the end plates off to gain access to the inside of the rail. Please remember to replace the square seals at each end and make sure the inlet holes for the fuel are free on debris, also replace the copper washers on the fuel inlet and return pipes on the rail these are 2 washers per fuel line pipes.
Check idle position sensor and clean power contacts to make sure no rust or debris is evident.
Hope this helps you out. If may seem a lot of work but checking all these points will save you time, money and labour at garages.
Author: Paul Laker
