c.bayens

iTrader: (2)

I just finished a head/cam swap on my 93 LT1. The car fired right up and after a few minutes appeared to run and idle fine. The car idles perfect but when I test drove it it seems to be misfiring under any load. The car is still accellerating fairly quickly(feels about the same as before the swap), it is just "choppy" while doing so. I know I obviously need a tune and am planning on getting it dynotuned I am just wondering if anyone has had a similar experience or can think of any other issues it may be BEFORE I take the car to get tuned. I checked all the wires, it has new plugs, grounds are all good. I was wondering if maybe a valve hasnt seated properly or rockers are adjusted wrong? Any input would be very appritiated as I want to eliminate any problems before I get my tune.

Thanks

RamAir95TA

iTrader: (2)

Before you can rule out any mechanical problems you need to at least get a mail-order baseline tune. You're kind of working backwards.

You also need to STOP DRIVING THE CAR before you do serious damage by running it untuned.

96capricemgr

iTrader: (1)

With a heads/cam swap a 93 that came with 22lbs injectors REALLY is going to need larger injectors 30lbs would probably be fine, then again 30lbs would be enough to destroy the engine if not tuned for.

get a custom mailorder chip immediately or trailer the car to the dyno.

It is entirely possible there is a mechanical issue too, be it valvetrain adjustment or plug wire problem or something but untuned it wont run well enough for you to even diagnose.

c.bayens

iTrader: (2)

Thanks for the advice. I didnt really think it would do serious damage driving it untuned but since it might I should probably get a mail order tune for now since the dynotune shop is about a 2 hour drive. Looks like my car will be sitting a while while I wait lol. Any suggestions on mail order tune? I was thinking PCMforless although I have heard some bad things about some of their tunes. Have also heard they are good from quite a few people so just wondering if there is anywhere better?

c.bayens

iTrader: (2)

I do also have some 34# injectors going in when I get it dynotuned!

c.bayens

iTrader: (2)

Okay so here is an update... I got a PCMforless tune to see if it helps. I put the new prom in and it started up great, still had stock injectors in(tune set for my bigger injectors) took it for a test drive just to see if it was any better and it would barely run as soon as I touched the throttle.... The next day my injectors came so I threw them in and took it for a test drive again. It ran much better althought it is still misfiring under load. It still has lots of power and it seems to misfire worse under light load(about 1/2 throttle). I checked all of my connections to sensors, plug wires, plugs, fuel pressure is good. ect another strange thing is that the fan comes on after it runs for about 10 seconds and wont turn off.(was working properly before my tune) Any idea what this could mean? What else should I be checking??? Any ideas would be helpful!

lt1-xjs

I've had the light load misfires on a couple of vehicles after doing tune ups. It was always a cracked plug, just a hairline in the porcelain.

c.bayens

iTrader: (2)

Thanks, I'll have a look at them tonight!

c.bayens

iTrader: (2)

I checked my plugs and they all looked fine.. however they are brand new TR55gp plugs(.055 gap) I checked and all the gaps were consistant but could the slightly large gap contribute to my problem? Should only affect higher rpms where as most of my problem is just under light acelleration right?