pghjeeper

I have an 02 with 58k on its mostly original. Last week I took it for a long drive and at one point I was coming up a ramp at low load and it developed a shudder. I gave it more throttle and it was fine. Drove it to Canfield,Oh and back and when I got home it started to shake badly, motor related, periodically when sitting at idle in drive. No check engine lights and no codes that relate to this in the computer.
It has the original plugs and wires so I plan to start there. I got GM red wires and NGK iridium IX plugs. Any chance it could be the TPS? Any other ideas?

JR-01

I would start with the gasoline before you start throwing money at it. Could be bad gas. Does it sit for long periods?

pghjeeper

Brand new Sucocco 93 octane with a bottle of Lucas FI cleaner. But it literally happened within 30 mins of filling it.

JR-01

Does it miss at wide open throttle? Did you fill at a gas station that gets a lot of traffic?

pghjeeper

No not at all, only at idle in drive or under heavy load light throttle

JR-01

Can you hear any vacuum leaks?
The problem starting right after fill up might be a clue.

pghjeeper

Not that I can hear, where would they be leaking from? I was convinced it was the plugs and wires being original

JR-01

Should get 100K miles on plugs and wires. My '01 has 80K with originals and does not skip a beat. I would think if it was wires or plugs it would miss when pulling hard. Could be wrong.
Dirty Mass Air Flow sensor could cause rough idling.

pghjeeper

I'll check the MAF tomorrow when I change the air cleaner. Wish it had a damn code so it would be easier to diagnose

Choreo

I was having a similar problem a few years ago, turned out to be a dirty butterfly valve in the throttle body sticking. Especially worth checking if you have an oiled air filter.

pghjeeper

Thank you guys!! I'll clean the MAF and TB tomorrow when I swap the airfilter. It has a standard paper filter

~Josh

I'd look towards an ignition misfire or possibly a broken valve spring.

pghjeeper

Man I hope it's not a valve spring, I have a non z06 and I was told they didn't have the valvesping issues.
If it was a valve spring wouldn't it happen all the time? This is only at idle if I'm WOT it runs like a champ

Deneb

I know little but can't a bad spark plugs wire especially #5 n 7 cause this problem?

pghjeeper

I looked at my wires and they look very dry and brittle, I'm hoping that's my problem. I didn't think it was the plugs but I figure I might as well change them while I'm in there

OleStraightStick

Doesn’t sound at all like a valve spring issue to me.. I had a slight misfire recently and it turned out to be a couple bad plugs (were not original, I installed them 5 yrs ago or so, with the high performance red wires), and a faulty IAT sensor

Allieboy

you always say the worst scenario? lol

JR-01

Yes. There are a variety of things that can cause rough idle. Best to address the cheapest things to fix first. Would kinda suck to replace a bunch of parts only to find out it was a batch of bad gas, vacuum leak or dirty thottle body or MAF sensor.

pghjeeper

So I pulled the airfilter, cleaned the MAF sensor and cleaned the TB. The airfilter was isnane!! It was so clogged it actually had hard corn kernels in it. MAF wasn't to bad and neither was the TB.
Sadly the miss is still there, I'm convinced its plugs and wires but I could be wrong. Gonna try and do them tomorrow.
At least I got the nasty airfilter out, I wanted to post a picture but Photobucket sucks now

JR-01

Keep us posted.