HELP! Car runs rough...(Scan Data included)

GN138

New Member
Joined
Jun 28, 2002
Ok, car has been running RICH for the past few months. Finally got around to working on it today. I did the following:

Replaced plugs (AC CR43TS gapped at .035")
Cleaned, dried and reoiled K&N Air filter and both valve cover breathers
Oil change

Now, my oil smelled of gas PRETTY BAD! Plugs didn't look too bad but they didn't look good. The car has been running fine in the morning going to work, on way home (about half way home; 10 min) sitting in stop and go, it started cutting out. Almost the same feeling as a bad MAF. Ran fine on NO boost but once boost hit it just sputtered. Again, this was only on the way home. In the morning I can run 18lbs of boost just fine.

After working on the car it idles rough and seems to break up as I rev it and acts the same while driving. I checked spark plug wires and they are on in correct order. When I first start the car it starts to idle at 2000 rpm and slowly backs down to 700-800 rpm.

Scan Data:

O2 Volts - 300-800 at idle

O2 Cross Counts - Starts at 8 and slowly works up to 200 and the falls back to 8?

TPS - .39 at idle; 4.59 at WOT

MAF - 5 at idle

INT - 123-135

BLM - 120

Knock - 0

Idle Air Meter - 56 to 57 steps

Temp - 169.2 f

Idle - 700-700 rpm


Any ideads? I'm thinking my O2 may be shot. Usually it jumps around at idle but seems to have lesser of a range to jump around in. Car does not run well enough for me to get any WOT #'s. Any help will be appreciated!!
 
Need more info.....

What chip?

If it is an aftermarket chip.....Do you know if it idles in open or closed loop? Your cross counts should start at 0.... progress to 255 and start back at 0...... the faster it makes it back around to 0.... the better the O2 is working.....a very slow progression (or not hardly at all) could indicate a lazy or about to fail o2... if it is in fact in closed loop...... I would imagine... the scanmaster's update rate is too slow for you to see the 255..... or 0 ..... that is why you see 8-200 ......

You idle IAC's are a little high..... the computer is trying to raise the idle some..... might look up the "how to" on gnttype and reset the IAC/TPS..... shoot for around 30 idling.....

That is a start.....
 
Thanks, am replacing the O2 tomorrow. Will also raise the TPS a bit and reset the IAC while doing so.

Car is stock besides: Walbro 340, blue tops, chip for blue tops, Accufab AFPR, THDP, K&N, hotwire, 160 degree thermo and 3" single shot exhaust

I just re-scanned the car. O2 is staying steady pretty much at idle, 470-500. My good O2's usually jump around a bit at idle but this one seems shot....probably from how rich the car was running.

Thanks!
 
Problem found: Rear driver's side plug was broken internally. No visable cracks on the outside but I noticed it rattled when I took it out and had it in my hand. Replaced with new plug and all is well.

BUT...


The original issue I had still exists. This is what I was trying to fix by cleaning the K&N filters and changing spark plugs:

Going to work, car runs fine. Can get into boost and do whatever I like. After the car has been sitting in the sun all day and then driving home (about 20 min) I hit a bit of stop and go traffice for about 5-10 min. Car is warm but not overheating and it stunmbles any time I get into boost. It doesn't break up like it was doing with the bad plug yesterday but coming home from my parent's garage just now it was doing the same thing it was doing before....after it gets warm/ hot you can't get into boost, it just cuts out.

I am still waiting for an O2 sensor and a fuel rail fitting that will let me hook my fuel pressure gauge back up, so I can tune a bit better. Car ran fine til last week and we've had hotter weather in the past month than we've had this past week.
 
Nope! Wires are all routed away from headers.

After I got the car together today, I took it for a test drive. It was running awesome. After it got warm it started cutting in and out again. After installing my FP gauge I took it out again. Ran fine. Parked it. Ran fine on the way home again.

When it cuts out it is similar to MAF issues and also similar to when my cat was plugged (car would run fine til the engine got hot, then would cut out and slowly die, in that case). It doesn't die on me now though.

I'm waiting til Tuesday when my O2 comes in. Hopefully that is it....
 
I have a spare coil....could test the one on the car when it starts acting up.
 
You most likely have something that is getting heat soak and not working properly when hot. The stock coil/module really stinks for working under heated conditions..... so much so.... that I have read thread after thread suggesting.....that don't ever buy an aftermarket (read parts house brand) coilpack/ignition module...... I have seen threads suggesting failure rates of non-GM stuff like 1 out of 3 actually work.... and that is only initially.... not after years of use/abuse...... My point is..... if there ever was a product prone to be tempermental/troublesome..... the coilpack/ignition module has to be near the top of the list.

Just my 0.02.

FWIW.... when mine went out... I converted to the type II coilpack/module..... no horsepower advantage.... but the concensus is that they are much less tempermantal than the magnivox unit.

HTH
 
GN138 said:
I have a spare coil....could test the one on the car when it starts acting up.
Had same problem here. I found it to be a bad coil. It ohmed OK when cool but I put it in an oven and the problem showed up. Sure sounds heat related.
 
It definately is heat related...

The coil/ module I have I bought from GM about 6-7 years ago. I still have the stock coil/ module. I bought a new coil/ module because I had just bought the GN and was chasing an issue and thought it was the coil or module.

What's this Type-II conversion consist of? Is it cheaper or more readily available?

Last night I noticed my O2 was only scanning between 600-700 at idle. New O2 should be in today, hopefully.
 
So, now that my car is nice and hot....it's missing. Can I measure the resistance across the coil packs to test if the coil pack/ module is shot without taking it off the car? It seems to be doing it less today. It was only missing at slightly off idle but after getting up to speed I could get into boost.

NOTE* I noticed when it starts missing/ hesitating I smell a kind of catalytic converter smell, just not as much of a strong egg/ sulfer/ fart smell. Does this mean anything? The cat that I have is only 2-3 years old, got it with my THDP.
 
Ok, I went to try and test the resistance and found TONS of corrosion on the back coil towers (driver's side cylinders) but not any on the front (passenger side cylinders). After cleaning them and the spark plug boots, the car runs the same. Any thoughts on why only the rear 3 towers on the coil pack would be corroded but the front 3 look brand new?

I went to get new spark plug wires but NO ONE stocks them. I had to order them.

Now, I hooked up an old fashioned timing light to each spark plug wire and I'd say 4 out of the 6 seem to be missing. Cylinder #1 seems to be missing a ton more than the others.

Tomorrow I will put on the working stock coil pack that I still have and will also use the new spark plug wires. Hopefull my O2 comes in so I can tune the car a bit more.

I'd like to thank everyone who chimed in on this thread as it may be helping me get my car fixed. So, thanks! And keep it coming. :biggrin:
 
Put new spark plug wires on (8mm), used dielectric grease. Took it out for a spin and it's better, but still just a bit of a miss or hesitation. Waiting for O2 to come in still. Still looking for my spare coil pack too.

Going to adjust the IAC and TPS further right now.

Any thoughts on the corrosion on the back 3 posts on the coil pack?
 
sometimes when coil pack is weak the corresponding terminals will corrode...
 
Thanks man! Still trying to find my other coil pack. It's been so long since I last saw it. Could be at my house or my parent's.

I just noticed that it only misses at or around 2000 rpm. Before and after that it runs fine, at WOT or partial throttle.

I have fixed the issue where, when the car is warm and I restart it, it idles up to 2000 rpm. Seems like it was the IAC.
 
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