Cruising lean/o2 giving negative voltage
I had an idea. Are you running a purge control valve? I'm wondering if it's leaking. Start your car and pull the large vac line off(probably easier to disconnect from the other end). Vacuum should not be felt below 2000rpm.
Also check the check valve close to AFM and be sure it's functioning correctly(one way only). Make sure it isn't in backwards either.
These are two possible leaks that would be hard to find.
Having a girlfriend who will put up with it is half the battle haha.
Also check the check valve close to AFM and be sure it's functioning correctly(one way only). Make sure it isn't in backwards either.
These are two possible leaks that would be hard to find.
Having a girlfriend who will put up with it is half the battle haha.
So I woke up and had a coffee and wondered "what if both valves test fine"?
If they do test fine this is what might be going on. I think I remembered you saying you have an exhaust leak. This could be giving you a false positive and your bucking could be totally unrelated.
The bucking could be because and an improperly adjusted throttle body. Your main might not be open enough. This is common when TPS is adjusted. Maybe your adjust screw isn't even touching. Your primary might be too closed. This will cause bucking.
Solution
Open up the primary a bit then readjust the TPS(obviously).
If they do test fine this is what might be going on. I think I remembered you saying you have an exhaust leak. This could be giving you a false positive and your bucking could be totally unrelated.
The bucking could be because and an improperly adjusted throttle body. Your main might not be open enough. This is common when TPS is adjusted. Maybe your adjust screw isn't even touching. Your primary might be too closed. This will cause bucking.
Solution
Open up the primary a bit then readjust the TPS(obviously).
Senior Member
Joined: Sep 2009
Posts: 735
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From: Independence Mo
Hey bud,
you have a pretty good sized vac leak there. You have positive pressure at the air filter, feeding into the filler neck through the catch can, then through the check valve into the intake. I don't see a means of actuation to stop that off, or regulate the airflow.
The stock pcv valve works based on a pressure differential between pre- and post-throttle plate vacuum sources. That means sometimes it doesn't flow based on throttle position. The stock valve can function improperly if the vacuum sources are mixed up.
There are a couple options you have.
1. Get rid of PCV system, block vacuum ports and just use the catch can.
2a. Put stock PCV valve in, eliminate air filter on catch can, and run that vent line with a check valve to a port in between your MAF and turbo inlet like the stock system would have been.
2b. Same as 2a, but get rid of the catch can and use stock vent system.
Once that is done, check for vacuum leaks, re-adjust throttle, and re-tune.
you have a pretty good sized vac leak there. You have positive pressure at the air filter, feeding into the filler neck through the catch can, then through the check valve into the intake. I don't see a means of actuation to stop that off, or regulate the airflow.
The stock pcv valve works based on a pressure differential between pre- and post-throttle plate vacuum sources. That means sometimes it doesn't flow based on throttle position. The stock valve can function improperly if the vacuum sources are mixed up.
There are a couple options you have.
1. Get rid of PCV system, block vacuum ports and just use the catch can.
2a. Put stock PCV valve in, eliminate air filter on catch can, and run that vent line with a check valve to a port in between your MAF and turbo inlet like the stock system would have been.
2b. Same as 2a, but get rid of the catch can and use stock vent system.
Once that is done, check for vacuum leaks, re-adjust throttle, and re-tune.
Hey bud,
you have a pretty good sized vac leak there. You have positive pressure at the air filter, feeding into the filler neck through the catch can, then through the check valve into the intake. I don't see a means of actuation to stop that off, or regulate the airflow.
The stock pcv valve works based on a pressure differential between pre- and post-throttle plate vacuum sources. That means sometimes it doesn't flow based on throttle position. The stock valve can function improperly if the vacuum sources are mixed up.
There are a couple options you have.
1. Get rid of PCV system, block vacuum ports and just use the catch can.
2a. Put stock PCV valve in, eliminate air filter on catch can, and run that vent line with a check valve to a port in between your MAF and turbo inlet like the stock system would have been.
2b. Same as 2a, but get rid of the catch can and use stock vent system.
Once that is done, check for vacuum leaks, re-adjust throttle, and re-tune.
you have a pretty good sized vac leak there. You have positive pressure at the air filter, feeding into the filler neck through the catch can, then through the check valve into the intake. I don't see a means of actuation to stop that off, or regulate the airflow.
The stock pcv valve works based on a pressure differential between pre- and post-throttle plate vacuum sources. That means sometimes it doesn't flow based on throttle position. The stock valve can function improperly if the vacuum sources are mixed up.
There are a couple options you have.
1. Get rid of PCV system, block vacuum ports and just use the catch can.
2a. Put stock PCV valve in, eliminate air filter on catch can, and run that vent line with a check valve to a port in between your MAF and turbo inlet like the stock system would have been.
2b. Same as 2a, but get rid of the catch can and use stock vent system.
Once that is done, check for vacuum leaks, re-adjust throttle, and re-tune.
Edit: After a bit of research I think I get it. Literally just run both the middle iron nipple and oil filler neck nipple to the vented catch can.
Last edited by tetsu50; Sep 8, 2019 at 09:27 AM.
Alright I went ahead and removed the catch can from the throttle body. Its now as discussed with the catch can just run to the filler neck and middle iron nipple and the old port it used to be hooked up to plugged. AFRs got quite a bit richer at idle however it still struggles to idle and it still leans out at the same spots. I will say the lean spot did get a bit better. AFRs now range from low 16s to low 17s but keep in mind thats with me still adding 10% with the SAFC.
So I'd say it still has the issue but its getting better. Any other suggestions? I'm personally still thinking it could be the MAF.
So I'd say it still has the issue but its getting better. Any other suggestions? I'm personally still thinking it could be the MAF.
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