Biz383

hello all, I am new to the site, any advice and help would be much appreciated.

94 z28, mildly modded, auto trans. last october was driving and started sputtering, brought it to a buddy that is a mechanic he cleaned a few plugs and said to replace the plugs when i got it out this year. so i parked it(ran great when parked) started it a few times this winter. put new plugs in it this week (what an unbelievable pain.) drove perfect breaking tires loos in every gear. (10 minute ride)
drove again next day cel came on. (10 minute ride again)
drove next day after a few miles started sputtering, went to go back and when i got back it started running fine.

here is what it does now, cold start, drive ~5miles runs fine. then sputters shakes pops like a misfire about 5 miles. then will suddenly run fine and cel comes on, and will keep going back and forth between running fine for a few minutes and running rough a few minutes. if while it is sputtering i put it in nuetral, shut off the engine and immediately restart it will run fine. (for a little bit)

i havent ruled anything out but i have checked,
plugs/wires, all tight, look good. misted water over them and didnt see arcing,
optispark was replaced last year.
starts perfectly every time, no extra cranking.
scanned it, not able to pull codes.

anxious to be killing mustangs soon this summer. thanks again

Injuneer

Since the SES light and the stuttering seem to go hand-in-hand, scan it again for codes. They have to be there. What tool did you use to scan it? If you don't have access to the correct OBD-1 scan tool, use the free download 94/95 scan software in this thread:

https://www.camaroz28.com/forums/com...95-lt1-874306/

There is info in the thread on the cable requirement, which you can buy, or build for as little as $20.

Since it runs better when you restart it, there's a possibility the problem is being caused by a faulty O2 sensor, when the PCM enters closed loop. But why guess - if the SES light comes on, the code is stored, unless you are somehow losing power to the PCM.

Biz383

thanks for the reply

I bought some generic autozone scan tool that said it was for a 94 camaro as well as others. according to the directions when plugging it in the engine light is supposed to flash the codes. when i plug in the tool the engine light goes off and does not blink or anything. the fans kick on when i plug the thing in so i assume its working, minor kicker here, the motor was transplanted from a vette, unsure what year. but looks the same as my other LT1's ive owned... i assume that could be why scan tool not working.

if this all sounds impossible to diagnose via the net think i should take it in? ill try the scan tool again tomorrow, thanks again for the link and the help.

4586

If you are up north and parked it for the Winter...could have some moisture in the tank especially if the tank wasn't full. ie misfires, SES lights and fouled plugs.

Gas line anti freeze won't correct the problem...you need something with a "water displacer" that breaks the water down...anti freeze only prevents the water from freezing.

Injuneer

The "scan tool" you have simply shorts the pins in the ALDL connector, to flash the codes on the SES light. The last year that will work is 1993. I bet its an Actron and cost about $30. Says on the box it will work on a 1994, but it will not. You need a real OBD-1 scanner, or free scanning software and a cable. There is a thread "stickied" at the top of the "Computer Diagnostic...... " forum that has a link to a free download of software written specifically for the 94/95 LT1.

Biz383

aha! yes it is a Actron and yes it did cost $30. I will find a way to get it scanned sometime in the next few days. will keep you posted, thanks

Biz383

so got out of work early today, have a mechanic friend with a scanner that will read my car, unfortunately he wont have time till the weekend.
so i figured i would look at the 02 sensors, drivers side was black, passenger side was blackish around the bottom and gray black on top. is this bad or normal?
replaced both with Bosch sensors (good brand? idk) car seems to run perfect now. no lights, no sputtering. i was advised to look at the 02 sensors again after some miles were put on the car. which i will be doing soon.

one other thing. after installing the new sensors car ran rough and smelled like gas for 30 seconds or so after first started up. after a few minutes of driving, ran perfectly since. is this normal?