Changed the plugs, still skipping.

**Zapper2003** · 10-30-2008, 05:14 PM

Alright. Changed the plugs and wires hoping to correct the issue I had with a low RPM miss. Car would start right up no problem at first, idled fine, and ran great after 2500RPM's, however, between 1k and 2500, it would miss/skip. I changed the plugs and wires, hoping this would solve the problem, and it didn't. However, since the change, I have noticed lifter tap on the drivers side. Its not horribly loud, but its evidently there. So I have a few questions. 1. Would the lifters cause my miss at this low rpm but clear up the faster it revs? 2. Could it be my opti causing this miss, and the lifter tap just be coincidence?

I did not notice the tap before the plug/wire change, however, the car has been sitting for approximately 5 monts undriven. The skip was noticed about 3 months ago and has been sitting unstarted since.

I am looking for a place to start. Obviously throwing a timing light on this engine is going to be a huge pain in the ass, but possibly do-able. And throwing parts at this would be a costly process, as the cheapest Opti I can find (GM or MSD) is 475$ online.

I will also be cross-posting this in General Help area as well.

**96slow6** · 10-31-2008, 10:18 AM

Ok I am lost. What did you try before the plugs and wires? fuel filter, and o2's would have been a lot less work and a more likely cause. Also the tick is more likely an exhaust leak or a loose plug then a lifter. Any mods on to your motor?

**bigrondownhiller** · 10-31-2008, 11:20 AM

The lifter tap could be causing the computer to pull timing down low thinking it is detonation. I have a lifter that sticks a little when warm and I can feel the same thing. The driver side is easy to get the valve cover off. I had a rubber gasket so I didnt need a new one. Check to see if it is just a rocker arm. GMpartsdirect has it for $317. How many miles are on the car? You could also just replace the cap and rotor on it.

**Zapper2003** · 10-31-2008, 04:24 PM

I did not try anything else before the plugs/wires. The car has 105k miles on it, 5k of which I put on. I changed the fuel filter after I got the car, so it has around 5k miles on it. I didn't touch the O2's, however, the engine light has not come on, at all, ever. I'm going to see if I can borrow an OBD2 scanner and see if there's anything in there, but I'm doubting it. There are no mods, just a dynomax muffler. Exhaust leak is a negative, its coming from up high. I was listening to it again tonight and I'm wondering if I may have pulled a wire too tight when i was strapping them up, and maybe pulled it off the plug a bit and its the spark i'm hearing, but it doesn't seem that way because it still runs the same it did before the plugs/wires. I am going to change the oil and filter because of the car sitting for such a while now.

**chuckie669** · 10-31-2008, 04:43 PM

It's probably hard with our small engine bays, but put your hand on top of the wire boot while the car is running. If you feel a tap then your spark plug wasn't tightened all the way. If it's good, you won't notice anything when touching the boot.

I had a similar tap on my silverado after putting in new plugs and wires. Apparently I didn't tighten down one as much as I thought I did (I'm sure the antiseize had a small hand in loosening the plug too since it wasn't snugged up enough).

Just a thought

**JoshieDoom** · 10-31-2008, 09:42 PM

Sounds like another case of the opti-shit. Stock opti?

**Zapper2003** · 11-01-2008, 10:22 AM

Yeah, stock opti with 105k on it (as far as i know, again, ive only had the car 5k miles)

Another new development though:

Car is running (what smells like) rich as hell, and idling way fast, anywhere from 1400 to 1900 RPM's. As soon as I start the car it runs great, no bumbling idle, no missing, etc. However, soon after startup, within probably 30 to 60 seconds, it starts acting up.

**JoshieDoom** · 11-01-2008, 01:26 PM

Hmm, dont know much about lt's but my 88 sbc blazer did the same thing when the 02 sensor went out. Sounds like when it runs the diagnostics its putting it in limp mode

**Zapper2003** · 11-01-2008, 05:36 PM

I'm going to try and borrow the OBD2 scanner from the autozone, its retarded you have to pay a deposit (refunded of course) but its like 180 bucks lol, oh well.

**Zapper2003** · 11-03-2008, 04:35 PM

Help? Anyone?

LS1FirehawkWS6 led me to this thread, and I've found lots of useful information on there, but nobody has the running rich issue that I've got.

**Chad97SS** · 11-04-2008, 07:37 PM

often misfires are more pronounced at low rpms. So you say you dont feel it at higher rpm's but what if it is really there and you just can't tell.. hmm

And all a scanner will do is read SES codes or real time data but can you interpret real time data and what if there are no codes?

This does sound opti-spark related. But don't listen to me. I'm just a squirrel..

heck you might even have a spark plug wire not seated on a plug properly.

**Zapper2003** · 11-05-2008, 01:33 PM

The battle continues.

I still have to check the plug wires, currently the car sits out under its little carport right now.

As for the skip down low in RPM range, I think you're right about it being pronounced down low and non existant up high, and seeing as how its not a CONSTANT skip, and it fires some of the time, up in the higher revs its smoothing out when it does misfire.

I rented the code scanner, and just as i had felt would happen, since theres no SES light, there are no codes, nor any stored.

I started it today, it runs OKAY until the motor gets a bit of heat into it, once warm (170-180ish), the idle picks up speed (1400 rpm today) and the throttle gets very touchy. Touchy as in, you blip the throttle, and it stalls. It wouldn't restart until i held the throttle to the floor and cranked and cranked, once restarted, it ran like crap (as usual) and another blip of the throttle stalled it.

So at this point I'm ready to start throwing parts at it. What controls the idle on these engines? Is it an idle control solenoid, or is it an electric motor on the throttlebody butterflies?

**bigrondownhiller** · 11-05-2008, 01:43 PM

It would probably be cheaper to bring it to someone who can do a driveability test on it. They can run it with a scanner in real time to help located the problem.

**Zapper2003** · 11-05-2008, 01:45 PM

The local GM garage is 25 miles away and I don't have the cash to spend on the labor, otherwise i'd really consider it.

**Red on Red WS6** · 11-10-2008, 11:02 PM

I tend to agree on the data logging. Any local garage should be able to do a datalog but it will cost you around 65 dollars. But that alone may save you hundreds. Check the free easy stuff first though. Plug wires, look for any arcing while dark outside.

**lemons12** · 11-11-2008, 01:34 AM

skipped a lot.. but 100 bucks its the o2s.. EXACTLY the same thing mine was doing... the missing in lower rpms and stuff...

replace them, i would almost promise it will stop..

**lemons12** · 11-11-2008, 01:34 AM

you got LT's?

**Zapper2003** · 11-11-2008, 12:58 PM

Nope, Everything is stock save for a dynomax muffler. Stock manifolds. I picked up the air temp sensor (or 'air charge sensor' as they call it) cuz it was the cheapest part I could throw at it, and because i've had it in and out a few times monkeying around in the past. I may have to save my beans over winter to try and get this thing into a shop, or something.

**Red on Red WS6** · 11-11-2008, 05:19 PM

Try disconnecting the Mas Air Flow sensor and see if it helps. Like mentioned above the O2 sensors if bad could be causing most of your problems. Un plugging your MAF will put you in speed density mode and not use your front O2's.
What were the actual Codes you got when you scanned it? I am curious if it is showing front or rear O2 codes.