toegead93

Only in 4th gear from 40-45mph my car feels like it's missing or stumbling. I don't know if this a fuel delivery or a tuning problem. It runs fine at any other time. I've had this issue since my last round of mods which included cam, RR's, springs, & chip...Any thoughts? I'd like to narrow the possibilities down if anyone has had a similar problem.

Alvin@pcmforless.com

IF the chip is tuned well for the cam you shoudlnt have any issues like this.

It almost sounds ignition related but hard to tell without seeing a datalog.

shoebox

Ignition misses are most noticeable in higher gears.

toegead93

I've been wanting to have the capability to record this data for some time now. From my searches, I think all I need besides my laptop is FreeScan or Datamaster software, ALDL1 cable (from Moates) and the CABL1 USB (from Moates). Is this correct? If so I think I might purchase the cables and download FreeScan. It ends up being cheaper than having a shop log the info.
Thanks.

Alvin@pcmforless.com

Yeah you can get a cable from moates or ALDLcable.com.

The software I prefer is TTS Datamaster.

toegead93

OK, I recorded data with Datamaster today. It took me a few tries before I was sure everyhting was recording properly. Can you take a look?

toegead93

Thank you Alvin again for looking at the data log and the diagnosis....

It seems my o2's are completely dead. One sits on 1 value the entire time and the other does very little switching. This is driving the fuel trims nuts and the reason why the car is flipping back and forth between closed and open loop.

Two things that might be causing this that I see...
1) I have a small exhaust leak on the passenger side collector just before the O2 sensor. It's hard to get too, but I try to use high temp silicone selant to stop it.

2) I have a 93 and never replaced the single wire O2 wires with heated wires. I'm guessing this is the problem if both sensors look dead so I'll try replacing these first. Any other ideas?

Cmr0z28

Sounds like the converter locking up is making a miss more apparent.

toegead93

Yes, definatley more appearant once it's locked up. It seems to be masked more the faster I'm going.

Chevycobb

I had a similar problem and it ended up being the ignition coil. Felt a stumble in higher gears but the faster I went the less I would feel it. replaced the coil and ran fine.