Hello. First of all, I will tell you that my 2002 has been stored all winter since November. Before it was stored, it has a whisper lid, granatelli MAF, and a K&N filter. The car ran perfect, and went into storage with about 1100 miles on it.

During the winter, I installed an SLP LT header, Y-pipe, and ORP system with the 02 Simms. I also changed the plugs to NGK TR6, and the wires to Taylor Thunderbolt 10mm. The battery was unplugged for a few months during storage.

In early spring, I started up the car and took it for a run. It ran great, felt super strong, and seemed to be fine. The first time I nailed it at about a 20 roll, no problem. Then, I nailed it, and the engine started to stumble as it climbed to around 3,500-4,000 rpms.

I took it back to my shop (where I store it), pulled off the plug wires, and checked all the plugs. The gaps were fine and they looked fine, so I retightened them and made sure the wires were on good. I then reset the computer with the fuses in the hood compartment and tried it again. This time, I let it run for a while to relearn the computer settings.

I took it out, nailed it, and it ran great for several miles. Then, the misfire came back. It feels like something is holding me back, but the car will still accelerate hard even though it stumbles hard also. Once it shifts, the stumble disappears. There are no trouble lights coming on in the engine.

Anybody seen anything like this? Any ideas?

Thanks in advance.

 

Did you check your plug wires for any rips or tears?

 

Yes. I've also done some testing on them to see if they were arcing under load. I don't see any damage to them. I was thinking of putting on my old wires and trying that. The only thing is, when I reset my computer, it drove great for several hard accels...then seemed to get progressively worse over the next one hundred miles or so. That is leading me towards an air/fuel mixture problem in the computer... but why would it do that? What would make it get worse? How could I check that...

 

May be a silly question but is that fuel the same fuel that was in it when you stored it? If so add a can of heat and or Octane booter. Remember how bad the mower runs the first tank or 2 of gas after it has been stored all year. It could have moisture and after a few runs you stir it up and the miss starts.

Ozz

 

Good point. However, I emptied that tank and filled up a new tank full with 93 octane. It seems to get worse the more I drive it? After I first reset the computer, it didn't happen for a while. Then, it would gradually happen about 50% of the time. Now, it seems to have the problem almost every time I nail it from 10-30 mph. At high speeds or idle, I run fine with no misfires or hesitation at all.

You would think this problem would show itself across the rpm/mph spectrum somewhere besides first or 2nd gear (automatic)? Hmm. Maybe there IS a tear in a plug wire as was suggested by a few people. Is it possible it only shows up at the lower speeds under heavy accel?

 

UPDATE!

I took off all the plug wires and inspected them thoroughly. I didn't see anything wrong.
I checked the plug tightness and even took out a couple to see if there was anything strange. The plugs looked great, all were tight.

I reset the computer again and took the car for a drive after making sure all the wires were plugged in tightly. The miss was there, only intermittent, and only mild when taking off from a stop or a slow roll (0-20 MPH). It would sometimes kick in hard at 25-30, but nothing above that. Other times, it won't miss or stutter at all, and I even break the tires loose at 25-30 MPH in the automatic. I can really feel the power of the SLP LT headers.

Now, I took the car home and swapped my Granatelli MAF with the stock one. I tested the car again. It still did it, and again intermittent and only at slower speeds under WOT. Always under WOT. I will say this, though - I DID feel a difference between the Granatelli and the stock MAF sensor.

Hmm. I'm still scratching my head. Something in my computer doesn't like me...I only have a few things left to check: Computer, GAS (maybe some contaminants during the winter that were not ejected from the system even after 2 tanks of new gas?), and fuel filter? I also could put the stock wires back on and give it a test to COMPLETELY make sure? Hmm.

 

I posted a reply on another board to you. <img border="0" alt="[chug]" title="" src="graemlins/gr_chug.gif" />

<small>[ April 13, 2002, 04:00 PM: Message edited by: zombiedude ]</small>

 

Thanks for the help. I'm going to give it a shot with the stock wires. If that doesn't help, it might be AutoTap time...