Skipping under load

[Christ]

Ok, I've changed the distributor and intake box for known good ones (they ran the red car), so really the only thing I can imagine that's left is that the injectors can't keep up with the engine under load/high throttle.

Before I swap them out, is there anything else I need to check? I can't even time the POS because it dies when the timing is set anything near correctly, and won't hardly run.

The way it is now, I can drive it, but it takes awhile to take off, and if you give it too much throttle, it will start skipping and the engine will not rev even without load.

I don't normally advocate "parts switching", but I really don't feel like working on this car anymore, and the parts are known to be good, and already in my possession, so that's what's gonna happen until I get tired of it and just swap to a B8. (Don't really want to.)

[kellen302]

cam timing?

[hotrodin4me]

new plug wires

[georgeb]

Possible dirty fuel filter. Also there's a current post about someone wanting to clean injectors.

[Christ]

Possible dirty fuel filter. Also there's a current post about someone wanting to clean injectors.

I won't clean injectors... new/refurb are only $50/4.

Plug wires? Can you explain how it would rev freely with the timing advanced fully (dizzy turned fully to the firewall, but it has no power there), but cuts out when I back the timing off? I've yet to check for breakdown on the wires, and it probably needs new ones, but they're easy enough to replace with known good ones, so I'll try it anyway.

Fuel filter - I'll take it out of the line and join the lines together to eliminate it as a possibility.

Cam timing - I've thought about it, but with the piston at TDC (by a screwdriver in the plug hole) the dizzy lines up properly.

[Zanzer]

I usually start with the simple stuff first. I would double check and verify that the firing order is correct. A couple of crossed plug wires will make one run like total crap.

[georgeb]

There's a better way to check the cam timing than a screwdriver in the spark plug hole!

[Icedawg]

Sure sounds like timing, so perhaps you should open up the timing belt cover and check.

Before I swap them out, is there anything else I need to check? I can't even time the POS because it dies when the timing is set anything near correctly, and won't hardly run.

Otherwise it could be fuel supply. Faltering at wide open throttle is a first sign of a plugged fuel filter. If you can blow through it with very little effort, once the gas is out of it (done that the wrong way), then it is OK, if not it will cause faltering at load. It could also be a sign of a poor fuel pump. I just had to replace mine, at WOT it caused misfiring, and once we put a fuel pressure gauge on it we saw the pressure dropped way off as soon as the revs picked up beyond 3000 rpm.

[Movin]

You need enough fuel and enough spark at the right time to make it snappy!
There are a lot of things to test, but the basics need to be established..Test fuel
pressure while snapping the throttle, and test each plug wire that it can deliver enough spark to knock your fillings out and prevent any new dependents in the near future,
this would be about 3/4 inch...

[twopass]

"enough spark to knock your fillings out and prevent any new dependents in the near future"

Thats a pretty hot spark!

[Movin]

Yes, by my observation, most who experience this method of testing
have a slightly different narration of events but I think the interpretation
is much the same!!

[Christ]

It's not only skipping under full throttle, though. If you apply the throttle as the engine accelerates, it will NOT skip. If you apply too much throttle at once, or too much load (going up hills) then it does.

However, now, since setting the ignition timing as close as I could get it, it's actually driveable. Although with the 155/80R13, will not go over 70 indicated (approx 78MPH actual). Is that normal? My 5 speed would easily reach closer to 100... so it's really seeming like a fuel supply issue, running out of "breath" at higher RPM now.

The screwdriver in the hole is the way I've done rudimentary checks on cam timing for years, honestly. You can't set it exactly that way, but you can tell if the cam is a tooth off because the distributor won't line up properly (it's pretty obvious if you've done this for awhile). I don't care that it runs 100% just yet, because I'm not sure I'm even keeping this motor, and I've got too many other things to do with my time as yet. As long as it starts, runs, and drives willingly (without having to baby the throttle) I'm OK with it, at least until I decide what I'm doing.

[FestYboy]

would you like me to meet you half way and give you a hand?

btw, you can't trust the rotor position to set the cam timing on these engines. 8* (one tooth) will still look good at the rotor position. pull the cam belt cover and set the cam timing corrrectly before you can say "it's good".

also, look for carbon scoring around the coil tower (arcing), this will happen only under load (where the copression provides enough resistance that the spark wants to take an alternate path to ground rathe than through the spark plug).

[blkfordsedan]

The screwdriver in the hole is the way I've done rudimentary checks on cam timing for years, honestly. You can't set it exactly that way, but you can tell if the cam is a tooth off because the distributor won't line up properly (it's pretty obvious if you've done this for awhile).

I apologize, but I'm a little confused about this method. I would agree that you can find TDC (or relatively close) by putting a screw driver in the plug hole and feeling the piston movement (as long as you're on the compression stroke). I fail to see what the distributor position has to do with cam timing (i.e. camshaft to crankshaft relation). I assume when you say the distributor lines up, you mean the rotor will be pointing at the #1 terminal on the distributor? That really doesn't tell you anything, since the distributor housing rotates in relation to the rotor anyway. That method will make sure you're not 180* out of phase on the distributor and get your base ignition timing in the "ballpark", but doesn't give any significant indication of the actual camshaft position in relation to the crankshaft position. If you're off by 1 tooth on the cam sprocket, it would be very hard to tell without using some type of positive reference like the timing marks on the cam and crank sprockets. IIRC, 1 tooth on the cam sprocket is only like 3-1/2 to 4 degrees worth of camshaft rotation...which is a very small amount to notice in terms of rotor position. However, being 1 tooth off on the cam would equate to like 7 or 8 camshaft degrees in terms of true cam timing. That's more than enough to make it run like crap. Not saying that's your problem, but if there's any question the cam could be off, I'd pull the timing belt cover off and line the crank & cam marks up to be sure! :p

[blkfordsedan]

Sorry for the redundancy, FestYboy beat me to it! I started the post, then had to take a phone call before I could finish!! LOL