Finally got a chance to get my '94 Z28 to the track. Ran at Island Dragway yesterday. The temps were pretty high, at 87+ degrees.

Car has full bolt-ons. (160 thermostat, Lingenfelter cold air, Pace Setter long tubes, ORY, Magnaflow cat-back, Madz28 tune, 3.73 -EGR -AIR -ABS) 75k miles on the clock.

Best run of the day was a 13.33 at 102.8 mph with a 1.875 60'. I was running BFG Drag Radials of a set of stock wheels.

The car had a high speed miss, over 5k rpm. Wasn't a hard miss, just a light stumble. Got somewhat worse as the day went on. My last run for the day was a 13.40 at 101.93 with a 1.846 60' and the stumble over 5k rpm was pretty noticeable.

Any ideas on what could be causing it? Opti is brand new GM, brand new OTVC Taylor wires with no light show that I could see (will check again tonight), Bosch Platinum spark plugs, good fuel.

I'm thinking either (a) fuel pump going south or (b) stock valve springs have had it. Gotta dig out my fuel pressure gauge and stick it on the window to see what's going on.

 

I don't think you will find anyone knowledgable who will say the Bosch platinums were a good choice.

Other than that I think you have some good ideas to check.

Little off topic, but I grew up in that general area, on the Deleware between Belvidere and Columbia.

 

I'd be looking at burnt wires if you just changed them. Definitely look at the ones behind the power steering pump and altenator.

 

get a ngk or autolite plug, check everything for problems. Something should turn up.

 

It could be a number of things, first the ignition systems on these cars suck so I would look at getting an MSD box. AC Delco platinum plugs are they way I would go anytime you need to replace them unless you need a cooler heat range for NOS/blower. Yes it could be stock valvesprings not being able to keep up with the RPMs but I doubt thats the case at just over 5K, ive had mine waaay above that. I also dont think that you would see the fuel pump starting to fail that soon either but as with anything it can happen. Since I dont have an A4 i dont know if there is any reason to suspect a tranny problem on this but you never know. I would focus on ignition and check your fuel injectors as well. Check everything easy first cause the valvesprings and fuel pump are things you dont wanna have to replace unless your upgrading.

 

Where do you have the shift points now? Those times are really right around what it ued to run for me in similar conditions, maybe a tad bit cooler, but the car always trapped in 101 range. Now that you have done some work it should be trapping alittle higher, but it was hot yesterday. I think your on the right path by checking fuel then the springs. I thought you did the 1.6's? Maybe nows the time to do them with new springs

 

Too much gap can do it. What did you gap the plugs too?

 

what happens when you lug the motor? Is there also a miss at high load/low RPM?

 

Z07: Plugs are gapped at the stock gap.

Tillard: Can't lug it, it's an auto.

Geezer: Shift points are lowered a slight bit from what they were, maybe 100-200 RPM. I'll compare the files and see exactly what they're set at now. Didn't open the valve covers yet, so no 1.6 rockers. The over 5k miss has got to be costing me at least 3-4 MPH. On my last run I launched harder then I did before, with nearly no wheel spin, but you could feel the misfire before the 2-3 shift and on the top of the track.

Snake: I disagree on the MSD box and the AC Delco platium plugs. The MSD box is simply not needed with a stockish motor, and I've seen too many AC Delco plugs lose that platinum puck wich open the gap up way too far. I'm going to plane-jane NGK plugsto try something different. I'm suprised about the Bosch platinums, though. I usually have good luck with them.

Meangreen: The plug wires are OTVC. Once they reach the valve cover they're simply nowhere near anything that could burn them.

96caprice: Bosch platinum plugs used to be pretty good. I guess the quality has gone downhill.

 

GAH! Cheap, low quality garbage taylor wires!

Went to the garage now that it's full dark. With the lights off it's darker than a coal miner's belt buckle, so it ought to be good to see if I get a light show.

Fire up the car, and start looking under the hood. What do I see? ARCING! Dammit! The lousy taylor wires are arcing right from the wire to ground. Not from the plug boot, from the plug *wire*.

Also saw some light show right around the coil. Guess that's up for replacement, too.

Gotta place an order with summit now, I guess. MSD wires and coil, here I come. At least it's a relatively easy fix.

 

You can kinda lug it when its in 4th when the coverter locks around 45-50mph. Now that I think about it, I remember a few years back 2 rockers on the driverside were loose and I adjusted them. Don't know if that would cause a problem seeing how you found major arcing

 

opti opti opti opti opti opti

because thats always whats screwed up on these cars anyway.

 

Might replace the coil wire first.My02

 

Ironx: The Opti is brand new. If you read what I posted, it's the low-quality taylor wires I got with the OTVC kit.

Fatdog: What good would that do if I have arcing all down the length of every wire I looked at in the dark? Taylor wires are garbage; had I known that I would not have ordered the kit from TR, and I would have gone with MSD to begin with.

 

I knew it was the wires. And yes even though they are OTVC they are still routed behind the power steering pump and altenator.