VandykeT/A

I've got a heads and cam car with a mail order tune. The car has a stumble every now and again in high gear at lower rpms. Like 2k to 3k. Its not throwing any codes and it has good top end power it just stumbles occasionally. Once when pulling out from Wal Mart it stumble in first and i noticed a small pop though the throttle body. Not anything huge but enough to tell it did it. After that I parked it and haven't started it. I've put around 500 or so miles on it. Probably less. I thought I just had a plug trying to foul but I've put two sets in it and a new set of wires and its still the same. My question is since the only tuners I know of are about 4 hours away do you guys think it would be safe to drive it that far. It starts right up and idles it just has the occasional stumble and I'm afraid of blowing it all to hell. And could it possibly be a oxygen sensor bad that just isnt' throwing a code. One of them is new and the other is factory and the car has 76k on it. Thanks

greasepunk

I had a 'stumble' on my lt1 that seems similar to your experiences; was corrected when I found/replaced my AIR pump fuse (blown), not sure your set-up tho (i.e. !AIR)

Sprayed1998

iTrader: (10)

Its more than likely your mail order tune.

VandykeT/A

But would it be ok to ride it the 4 hours to a tuner with the stumble?

BOBS99SS

iTrader: (2)

Yeah imo a mail in is just a baseline to get to a dyno,how long have you been driving on the mail in tune 500 miles is it ? that's a lot of time on a m/o tune,did you not know you needed a real tune?honest this is my opinion so you take it for what its worth ,if you can't tow it there ,drive it and take it easy,unlike the 500 previous miles.

VandykeT/A

I thought the mail order tune just wasn't as good as a custom tune. Now that I talked to a few people they said they would stop riding it and take it straight and have it dyno tuned. I was just afraid to ride it anymore at all. And it wasn't the Air pump fuse I checked it. Thanks

BOBS99SS

iTrader: (2)

yeah I mean if ya can't tow it,like I said if it is running ok and you have been driving it for this long just put it up there.its cool man we all learn something every day,just hope the car is ok.I know one guy that tried to get by on a mail in and his end result was not good.but at least now you know and you can get it fixed,you will be shocked on how much better the car will run and feel after some good dyno time,if there is a few tuners in your area ,well 4 hours away I would try and find out which one deals more with LS cars, maybe search a lil on tech and see who people might reccomend

LilJayV10

iTrader: (39)

If you aren't at WOT the computer is going to be adjusting everything anyway. As long as whoever did the mail order tune got your injector size right it should be fine. This is what Mike Norris told me when I got a mail order tune from him. I drove it for about 600 miles to break the clutch in.

You said it popped out of the T/B. Did it only do it that once or is it a common thing. If it's back firing out of the T/B that means either that cylinder is firing at the wrong time or the intake valve isn't sealing all the way and the combustion gases are getting pushed past the valve and out the intake.

VandykeT/A

It was only a one time thing. It acts kind of like an old carberated car that you stuck in high gear going 35 and floored it. Its not lugging but all the symptoms of I guess you could say. Could being off on the pushrod length cause it to do this?

SOMbitch

iTrader: (8)

Yes wrong PR length can leave a valve hanging open and cause a misfire but i would guess that is not your problemj since it is intermittent. o2 sensor and maf for a start and then look deeper... Could be tune but I doubt it.....

VandykeT/A

Well the reason I said it was pushrod lenght is because I had a friend do the install and he wasn't to sure on how to measure so i just started reading around for people with the same set up. Its got 7.450 and I'm not throwing any codes at all I've just got one old 02 sensor still in there. I'm about to take it down to Heintz racing in a couple weeks and have a ported FAST 102 and a slp maf put on when they tune it. I planned on replacing that 02 sensor before i took it anyway and ill take the MAF sensor off my camaro and see if it runs any better. Before I had just a torquer 2 and bolt onsand it ran fine then I added the MS4 and the heads and the first mail order tune I got it wouldn't run hardly at all. it was throwing tons of fuel through it so i sent it back and got it retuned and it does fine except for the stumble now.