Vinscully50

I have a 1986 Camaro IROC Z LB9. For the last few weeks now when my car is warm it gives me hard starts. It will give me a very sporadic where it revs up to 1200 RPM and down to 400 RPM several times. Sometimes it does that for a good 30 seconds and levels out with a high idle at 1000 RPM and after 60 more seconds drops to 700 or so. Or it just stalls out.Also when warm my engine has a burn smell too. Not quite exhaust not quite rich. It's hard to describe. It only happens when it starts when warm and it goes away after the problems kind of fix themselves.

When it does this and I do managed to get it started, the car has low power and stalls out at stop lights or when braking. I cannot figured this out.

I checked my injectors they are all at 16.5 oms even when warm. Fuel pressure stays around 35 PSI when the car is off.
Plugs, wires, cap, rotor and coil were replaced in the fall. IAC, MAF, MAF Rely, MAF Burnoff, TPS, EGR and have all been replaced at different times over the last few years. All AC Delco save for the MAF which is Bosch. Starter was also recently replaced with O'Reilly's brand.

Here are videos for example:

Long Drive (Near the end this one does have some of the engine bogging when braking. Really just watch the first 30 seconds)

Hard Start At Night

I'm beyond frustrated at this point. If anyone has any ideas. Any at all let me know.

Komet

Datalog might help. Assuming everything replaced is good and there's no vacuum leaks, I might be suspicious of the CTS and o2 sensor. Is fuel pressure good when it's acting up?

M G Brewer

Here's a link to my thread back when I was fighting idle issues.

https://www.thirdgen.org/forums/tech...ng-issues.html

Vinscully50

I know the CTS is only 3 years old and when the original went bad it give very different symptoms then this. I've read on other Chevy forums that the sporadic idle going from 1200 RPM down to 400 and doing several times is a symptom of a bad 02 sensor. Problem is, I can't find mine for the life of me! I had a shop install a full hooker exhaust system (headers, y-pipe and muffler) 5 years ago. I cannot find my 02 sensor though. On the exhaust, I found a bung. But it had a bolt in it. I removed the bolt and inside is a chunk of metal that looks like it has been welded in place.

I also found a pigtail with a purple wire near my brake booster. I tried asking if that pigtail is the 02 sensor pigtail or if people can take a picture of their 02 sensor pigtail/wire on the exhaust forum. But no one would confirm it or they just kept giving me pictures of the 02 sensor...




Could this be my 02 sensor pigtail?

It's hard to see due to lack of light. There is a big "wall" of metal inside the hole. It basically blocks an 02 sensor from being screwed in. This is on the driver's y-pipe near the header.

Could a missing "deleted 02 sensor" cause my symptoms?

Komet

Well, I'm pretty sure you need an o2 sensor, otherwise the ecm isn't going to know what it needs to do. I would prioritize finding it, or finding the wires that went to it.

Reddragon88gta

IIRC that sure looks like the oxygen sensor pigtail. It sounds like the shop never installed the O2 sensor and just put a bolt in after blocking the hole? Why they would do that is beyond me but it looks like you found your problem. When was the exhaust installed?

Vinscully50

The kicker is the exhaust was done close to 6 years ago. These symptoms only started 2 or so months ago.

My only other theory is that I got a nail in my tire about 4 months ago. I took it to a local mom and pop tire shop with good reviews (they have been open for over 20+ years and have great 4.8 stars after hundreds of reviews on Google). My only theory is that they removed my 02 sensor and plugged up the hole.
I'm starting to think that has to be the cause. But I'm not sure how to unblock the hole...

Vinscully50

Here is a Tunerpro Scan I did a few weeks ago. It's a replay of the scan. Can anyone tell me what this means?

Komet

Looks like you've got an o2 sensor attached somewhere. Zero cross counts isn't great.

Crazy idea but I've heard of it; sediment in the tank shifts forward under braking and clogs the pickup, starving the engine for fuel. What does fuel pressure look like when it's acting up?

Vinscully50

I cannot find an 02 sensor for the life of me then. I've checked every inch of my exhaust piping and looked under the hood for any wire that looks like an 02 sensor wire. Not a single one. The only evidence I found is what I posted in my earlier pictures. Any idea of where it could be?

Also what does zero cross counts imply? That the 02 sensor is dead?

As for the sediment thing. The gas tank was replaced 3 years ago. But I'll put the fuel pressure gauge on tomorrow and see.

Vinscully50

Updates. So I did a fuel pressure test. Good news, I was able to test at idle with no problem. Bad news, my fuel pressure gauge isn't long enough to reach my windshield...

Anyway, with the car set to run the fuel pressure climbs to just under 50 psi and hovers around 47 or so. After 10 minutes it's around 45. With the car running. When started it drops to 40 even and after about 2 to 3 minutes, it drops to 37-38 psi. It remained there for 15 minutes until I shut off the car. I let the car sit for 10 minutes and fired it up the second time. The car did the sporadic idle thing. I ran to go look at the gauge. It only moved slightly with the rev jumps. Basically jumping between 33 psi and 40 psi. After the car settled it hit 38ish and remained there.

Injectors again tested at 16.5 ohms.

I'm guessing it has something to do with the 02 sensor then. That's my only remaining guess. Any thoughts?

Vinscully50

I want to bump this. Can anyone tell me what 0 cross counts for the 02 sensor means? Does that mean it's shot or missing? Is that the answer to my problem?

3rdgenzroc

Try searching "cross counts on a car data log" (not on here, use the internet). It will give you the info your asking, along with possible solutions for your issue at hand, it has been discussed quite extensively on this site and related others. Lots of info.

Vinscully50

I've tried that and even found another thread about Zero Cross Counts but no one could give a straight answer on to what it actually means. I tried reading threads on CorvetteOnline and samething. No one gives a straight answer.

3rdgenzroc

The oxygen sensor output varies between about 200 mV and 800mV, so a middle number, say 650 is OK (as long as it doesn't stay there). It should bounce back and forth between about 200 and about 800 without staying in between. The O2 cross counts increase when it's switching. The count increments by one every time the O2 sensor switches between the extremes. When the count reaches 255 it resets to zero and starts over. The main thing to watch for is that it is increasing. It should increment by one about every second or two. Did not look at your logs, (I'm not logger or reader), but I think if the numbers are not increasing (or at all) he was implying that the O2 sensor is not doing its job (or anything). That sensor is going tell the ECM if your "rich", "lean", or running ok. The ECM is going to adjust from that input. Soooo, track down and find that sensor, make sure it's working, and then go from there. Until that step is done, you will not be to be sure if anything, IAC, whatever, is correct on the other sensors (whether they were just bought or not) as long as the ECM doesn't have the information it needs. EX: this could be from carbon build up on that sensor causing it to stay open, or ECM making adjustments according to wrong info. So what I was trying to imply is that the "cross counts" was not really the issue, but finding that missing O2 sensor was.

Vinscully50

Ok so the cross counts don't move at all. This stay permanently at zero. Does that mean it's shot or missing?

I've combed up and down my entire exhaust, looked all over my engine bay. The only evidence I can find of an 02 sensor is that pigtail in the picture above with nothing attached to it and a the bung on the driver's side y-pipe that has been sealed up with a chunk of metal. I'm leaning towards that shop, I took my car to for a tire repair removed my 02 sensor to create more problems. Do the permanent zero cross counts basically imply that it's shot or missing?

Komet

I'm wondering if it busted in half, and the plug that you're seeing is what's left of the o2 sensor that stayed in the header, and the other side is dangling around somewhere.

Vinscully50

That could be true. Likely more than half though. Because the metal part that's lodged in there , is deep in the hole. Parts of the threads aren't covered by anything. The pig tail has nothing plugged into it, so I'm assuming the rest feel out on the highway somewhere.