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APC Posted by Ari [Email] ![]() ![]() In Reply to: APC, and heater core., Levi, Mon, 26 Nov 2001 18:51:45 Members do not see ads below this line. - Help Keep This Site Online - Signup |
It don't think it's the APC. It can only reduce you from full boost (needle up by the red) to base boost (half-way into the yellow). And when it does drop you into base boost, it's very smooth - no stuttering.
I doubt the turbo is overpressuring. You'd see that on the gauge, unless the hose to the gauge is leaking badly. Fixing that falls under looking for vacuum leaks (see below). It could be knock, but unlikely at low boost. The engine missing and stuttering can sound a lot like knock.
Without more testing, I'd say vacuum leak (what Justin said), or ignition. First, look for any obvious vacuum leaks - cracked hoses, loose hoses, hoses dangling. Next, pull the spark plugs - how do they look? They should all be a uniform grey. All white implies running leak (low fuel pressure and/or vacuum leak), and black and sooty implies running rich (fuel pressure regulator). Measure the plug gap. They should be set to the value on the decal in the engine compartment, also found in the owner's manual. If the gap is too big, the engine will stutter under boost.
If the plugs look worn, replace them. Get the NGK's specified in the manual. Now is not the time to try a non specified plug - don't try the MagnaGlow Spitfires because the guy behind the counter says they will fit. Get the NGKs. Make sure you check the gap before you put them in -they don't come from the factory gapped for your car.
Check the timing, and adjust if necessary. If the cap, rotor, or plug wires are more than a couple of years old, replace them. If it is an ignition problem, you want to limit your unknowns. Bad spark plug wires can cause missing under boost. You don't need any super-duper wires - just get a decent set of aftermarket wires from the autoparts store, and a decent cap and rotor (I usually find Bosch).
posted by 140.157....
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