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And how do the spark plugs look? Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Thu, 12 Jan 2006 05:43:10
In Reply to: 94 CSE 2.3 Turbo goes great BUT.., Mark, Wed, 11 Jan 2006 17:12:22 Members do not see ads below this line. - Help Keep This Site Online - Signup |
It sounds like you may have a few things going on.
Misfiring under boost is different from fuel cut-off. Fuel cut-off is very abrupt, like the engine shuts off - it'll pitch you towards the windshield. As turrbo says, that's due to overboosting. It may be a bad BPC, or a sticky wastegate actuator. Turrbo's comment about a weak BPC sounds right.
Misfiring is different - it feels like, well, not all cylinders are firing. When this happens under boost, I immediately think spark plugs. The higher the pressure in the cylinder, the harder it is for the spark to jump. If the plug gap is too wide, the spark won't jump, and the cylinder won't fire. So check the spark plug gap. And while you're at it, check the DI (if your car is so equipped - your comment about 98 octane fuel implies you aren't in the US market). Look for burn marks on the tops of the spark plugs, implying the spring in the DI boot isn't making good contact. And I'd pull the plastic cover off the DI (flip it over, undo about 8 torx screws) and look at the coils. The coils are the four plastic tubes. Look to see if there are burn marks on the metal ends, where the springs in the boots meet. If so, expand the springs a little to make good contact. And hold the DI up to a bright light, to see the level of the oil in the coils. They should be all about 90% full. If one or more is leaking and the level is low (or you see oil), then the DI is on the way out and may be causing most of your problems.
If you have a distributor cap, make sure the cap and rotor are in good shape, the timing is spot on, and if the spark plug wires are more than 2 or 3 years old, replace them.
If the plugs look old, replace them. If they look gunked up (fouled), you may have a mixture problem, or the rings or valves are getting old and putting oil into the cylinder.
Plug fouling could cause the startup problem. Old plugs could cause all these problems. Same with bad ignition system (DI or distributor).
posted by 192.249....
, Thu, 12 Jan 2006 05:43:10 <-- Viewing This Message, Thu, 12 Jan 2006 14:20:23
, Wed, 11 Jan 2006 22:28:56
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