lathens

Hi guys,

Had a miss develop a couple weeks ago. Under WOT, the miss goes away until RPM's get around 5.5k. Worst miss is cruising in any gear in the 1200-2000 rpm range. Could this be opti? Car sat for two years and was only started a few times during that period. Just started driving it again a few weeks ago. Miss started about a week after putting her back on the road. Appreciate any suggestions for troubleshooting.

Thanks,

1996 LT4, GM 847 cam, ported heads, longtubes...etc.

Chimera96

it could be several things...opti being one of them. Storing a car for 2 years with occasional starts can take its toll. I assume you had gas stabilizer in the tank but if you didn't, best get rid of the old gas from the system

check for any plug/wire arc in a dark condition. misting wires with water can help bring out a arc condition

you have a OBD2 so a cheap code reader can show any codes thrown which will help narrow down the problem

generally opti issues get worse at higher RPM but it still could be a part of the problem. Poor functioning EGR can result on low rpm, throttle tip in stumble

from this side of the internet we can only suggest what problem it "may" be.

data scan would help but just scanning for codes would be a start

shoebox

You'll always feel a miss more at low RPMs and high load. Plugs and wires are where I would start.

Injuneer

Does the SES light flash when it misfires? Do you have access to an OBD-2 scanner with "GM Enhanced Parameters" capability? That would allow you to access the misfire count by individual cylinder. Given the fact that you have an aftermarket cam, the misfire count could be somewhat meaningless, though.

lathens

Hi guys,

Thanks for all the responses. Yep, got rid of old gas. Can't see any arcing in dark conditions even with misting water. SES stays on, but does not flash with misfires. SES light has been on since big cam and new tune for years anyhow. No access to OBDII. Will the scanner they use at Autozone or O'Reilly work? I use to have Autotap and LT1 Edit but all was lost in divorce and while I was in prison...which is why car was stored. What good software is presently available for LT1's? I don't mind purchasing software as I bought the car new in 1996 and will likely never sell it.

Beat up wife's boyfriend = 22 months in prison + divorce + lose almost everything . Seemed like a good idea at the time, but not so much now

Thanks,

moparman

Autozone can do OBDII.

Injuneer

You can get a basic OBD-2 scanner for very low $$$$$. Isn't going to do enhanced parameters, but it will tell you what code turned on the light. Not sure why you would drive it for years without getting it scanned. Yes, auto parts store routinely scan OBD-2 for free. There are even phone apps that can read codes and display sensors and computer parameters.

lathens

Thanks again guys,

New symptom - Engine idles very high 1700-2500 rpm. If i coast in gear until i lug the engine down to 1200rpm and then press in the clutch and stop, the idle will remain around 1200. If I press in the clutch at highway speed with rpm up, engine will stay at high idle for a minute or so after coming to a stop.

The SES has been on ever since I had Ed Wright here in Tulsa revise the tune (on the dyno) back in 2006 with the 847 cam but the car ran great until I put it in storage in 2013. Since the car ran great, I never checked into the SES light; just thought is was triggered by a false misfire due to the large cam.

One more thing: the low coolant light stays on constantly, but there is plenty of coolant. This light has been on for years too. I figure its just a sensor or something.

I'm finally gainfully employed and can start spending money on the car and getting it back in ship-shape. For now, I can take it to AZone or such and get it scanned. But, in the long run, I want to purchase my own scan software similar to the AutoTap I once owned. Is Autotap still a good diagnostic tool or do you recommend something else. I appreciate all the help. As mentioned in a previous post, I've been out of the loop on things for a couple years.

Thank you,

Injuneer

The low coolant light is an extremely common problem. You can try cleaning the sensor, but it usually won't help. The coolant appears to seep into the guts of the sensor and corrodes the printed circuit board. The light being on does no affect anything. If you just want the light out, and routinely check the coolant level, just unplug the sensor.

Auto Tap is no longer available.

http://www.aldlcable.com/diagnosticsoftware.asp