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Hey guys. So 8n continuing with the difficult smog pass situation I have been checking the EGR system.
I originally wrote this in my build thread but there is much more exposure here I think. So. Pasting. As always, thanks in advance for your help!
At the moment I am testing the EGR system. I am going through the FSM. And I am getting the following results as per steps in fsm.
1. When vacuum applied directly to EGR, engine dies. EGR valve is good.
2. Modulator. Cold test: no vacuum at EGR (one would think this means vsv works as intended). Hot test: no vacuum at EGR at idle, some vacuum at 3500 rpm.
Next test is disconnect ports P, Q and R, plug P amd R, apply pressure in port Q and at idle air should flow freely out of filter. Check. Works. Next check at 3500 rpm should be lots resistance to above teat. Check. Buuuut, I noticed that at idle there is also a LOT of resistance, almost as much as at 3500 rpm. The FSM seems to suggest to do first part with engine off and second part at 3500 rpm. Does not mention what it should be at idle. To me this seems nothing to worry about as the function at idle doesnt maTter.. correct?
VSV tested and works. However....
Next test not in the FSM. I figure that the vsv is supposed to close at idle in all conditions. The very first steps makesbit seem this is happening. Once the engine warmed up though, I tested the vsv passage at 3500 rpm and idle and they were both open. Now this is a ecu to vsv signal issue. Since my engine is not dieing at idle that means that even if the vsv is open the modulator is doing its job. And when im at high rpm vsv should be open anyway.
So, now I need to understand the engine temp senser for this circuit, which one is it? Unfortunately we have several sensors... I should test that next. Right? My thinking is if the ecu is using this information for other parameters it may be using bad information and causing other aspects of the combustion to be out of balance. What do you guys think?
So I tested the ECT sensor. The ECT manifold was at 147 degrees and I got a resistance of 450 Ohms. This seems to be in the correct range on the graph from the FSM. I will check again when cold and confirm that reading as well.
Sound like you have a last gen 22re, sorry on mobile and don't see Sig lines if it's there.
It seems from here your modulator is dirty or otherwise sticking. Did you start with the first step which in the manual I'm looking at us cleaning the filter media on the modulator?
Hey Co 94 PU, I have a 1991 3vze. It was rebuilt about 40k miles ago. Yes, I cleaned the filter and the test that it's connected with passes.
The only uncertainty with the modulator should not affect emissions, I think. So at this point I have moved on from the modulator.
According to my last smog check my HC and CO was too high. This is why I got the AFR meter to check how rich the mix is.
At this point I have leaned out the mix a little bit, retarded timing to 10. I want to retard timing further to 7 or so and take it in for a test to see what my readings are. If it passes, great, if not, I will have new set of numbers to go off.
I passed smog. But, just by a tiny tiny margin. Which means next time in two years I probably won't pass.
It took me and the mechanic some tuning on the spot to get it to work. I made a deal with him that I would pay a few bucks more if he let me tune the AFM and timing to find a balance that works for all of the parameters. It was interesting to say the least. We did all this during a pretest.
The EGR and Modulator were working fine. I had already tested the ECT sensor with various other temperatures and it was right on.
Anyway, simply put it seems everything is working well but passing smog was still a struggle. The Engine only has about 40k miles after the rebuild, and I had tested compression some time ago and they were all good.
I did take a minute to control the vacuum of the EGR and see the effects of it within a few seconds on the screen. Anytime I go any of the three, HC, CO and NOX to change the others would too. I'm just glad we found a setting for it to pass. He wouldn't let me put the timing below 8 degrees, he said the rules are now +-2 degrees not 3. Wouldn't matter though, just to test it I moved the timing around during the test and it would cause one to go up the others to go down.
My spark plugs and wires are pretty new. Plugs are cheap and easy to change so I change them much more often then actually needed. Same with cap and rotor.
I have one question left.... My igniter and coil are just within spec. But could it be still that they are 'weakened' through the years of usage and are not providing enough energy in the spark?
"Adjustable Ignition Spark Tester" Google that, you want to find something with a good readable user friendly scale.
I don't recall with any great detail the KV number you're looking for off hand. I want to say between 150-200kv is the right number, but hopefully someone with a documented number can provide some details.
It's too late and I'm too lazy to do the research and math. Sorry
You know what, why the heck didn't i think to check the voltage going to the spark plugs??? I will look into how that can be done due to the short duration of the current.
I wish I could spend a whole day using the emissions tester. I'd like to try out different plugs and wires to see what actually makes a difference. Among other things of course
You can actually spent time on the sniffer, in Denver it costs about $100/hr for a dyno (which includes the sniffer data), and that's really cheap in lots of ways since the shop hourly rate average is close to that. Of course it depends where you are.
So I rushed the response, the spark analyzer I am talking about has and adjusting gap and a scale next to it that corresponds 1 2 3 etc to kilovolts. You set the gap distance and judge the color (I'm colorblind and not qualified to tell the difference) from light blue to dark, you want a nice steady dark blue to violet (?) In the 150-200kv range out put from the coil..
You need to be mindful of the spark gap in the plugs and the resistance of the high tension (spark plug wires) as it effects the wear on the coil. There are some specs in the FSM.. If you have to much gap or wire resistance you have what's called coil breakdown, which is its when it is easier for the current to jump the shielding in the coil. This also has an effect on the heat the coil retains which will degrade it's power out put.
I hope I made sense of that since its way past bed time.
I guess the bottom line is you're not just checking for spark but trying to quantify it's energy and there are different tools for each.
You can actually spent time on the sniffer, in Denver it costs about $100/hr for a dyno (which includes the sniffer data), and that's really cheap in lots of ways since the shop hourly rate average is close to that. Of course it depends where you are.
So I rushed the response, the spark analyzer I am talking about has and adjusting gap and a scale next to it that corresponds 1 2 3 etc to kilovolts. You set the gap distance and judge the color (I'm colorblind and not qualified to tell the difference) from light blue to dark, you want a nice steady dark blue to violet (?) In the 150-200kv range out put from the coil..
You need to be mindful of the spark gap in the plugs and the resistance of the high tension (spark plug wires) as it effects the wear on the coil. There are some specs in the FSM.. If you have to much gap or wire resistance you have what's called coil breakdown, which is its when it is easier for the current to jump the shielding in the coil. This also has an effect on the heat the coil retains which will degrade it's power out put.
I hope I made sense of that since its way past bed time.
I guess the bottom line is you're not just checking for spark but trying to quantify it's energy and there are different tools for each.
$100/hr is not bad at all actually.
I see, I do not have one of those spark analyzers. I don't mind myself a good new tool though Won't really need it for a while now.
I think I may as well do another leak down test.Burning more oil than normal probably doesn't help the numbers. I lose some oil through the valve covers so I can't be sure if any is going through the rings. I am on a relatively fresh re-built engine though, about 40k miles.
I was hoping for this thread to be more helpful to others with similar smog issues, but I didn't really get to the bottom of it... :/
If I find anything else related to this I will try update this thread.
Thanks for your time Co_94_PU, I will definitely get around to checking the spark and ignition system for optimal performance.
Generally the EGR system is there to deal with NOx. If you have high HC and CO, the EGR is probably not the issue.
How old is your O2 sensor. My vehicle was starting to creep up toward the emissions limits in the past several years, although still passing. I changed out the O2 sensor and the emissions dropped back to 10 year ago levels.
The other suspect might be your cat. Is it a good (OEM?) one. Passing emissions depends on the O2 sensor providing good information to the ECU so that the mixture is running right at stochiometric, and that then allows a working cat to clean up what's left.
My O2 sensor is about 2 years old. The CAT is 4.5 years old with about 40k miles on it. I cant be sure what the condition of the CAT is, but it probably isn't great. I believe I had been running rich (according to the numbers from my AFR trials above) and as I understand this doesnt go well with CATs.
I used the AFR meter to lean out the mixture to where I am slightly rich under hard throttle. The tan? Flowmaster injectors are higher flow and I believe well outside of the ECUs ability to adjust for with stock AFM setup.
Alas, I was hoping by next smog check in two years I would have a 3.4 in their, but I am a bit cautious now with the whole smogging the 3.4 now.
The high HC and CO can indeed be a result of running rich. Too little oxygen to completely burn the fuel. The cat then tries to finish the combustion and gets hotter than normal in the process, leading to early failure.
There's probably a limit to how short a duty cycle the ECU can use to fire the injectors, so with the high flow injectors you may not be able to avoid running rich at low power settings regardless of AFM tweaks and the health of the O2 sensor.
Check the VF1 port on the diag connector with a voltmeter when the engine is warmed up and running at 2000 rpm or so. Ideally it should be running at 2.5 volts. 1.25 or 3.75 volts is OK as well. If the voltage is stuck near 0 V, it means the ECU is trying hard to lean out the mixture but has run into its hard-coded limits. (If it's near 5.0V, the ECU is trying to enrich the mixture but has hit its limits - probably not your issue.)
If you can run some wires from the diag port into the cabin, you can measure that same voltage while at steady cruise to see what is happening under load. That voltage is invalid at fully open or fully closed throttle.
The attached picture (courtesy of @scope103) may be of some help.
This article told me a lot about emission analysis, and as RJR says, high HC and CO combined points (initially) to running rich. Probably not the EGR.
One frequent cause of high CO is "missing." Every time a cylinder fails to fire all the unburned fuel allocated to that cylinder gets dumped into the exhaust, and reads as HC. (Paradoxically, running too lean can be a cause of missing, but the result is excess HC.)
Does your engine run smoothly at the rpms used in a smog check?
The high HC and CO can indeed be a result of running rich. Too little oxygen to completely burn the fuel. The cat then tries to finish the combustion and gets hotter than normal in the process, leading to early failure.
There's probably a limit to how short a duty cycle the ECU can use to fire the injectors, so with the high flow injectors you may not be able to avoid running rich at low power settings regardless of AFM tweaks and the health of the O2 sensor.
Check the VF1 port on the diag connector with a voltmeter when the engine is warmed up and running at 2000 rpm or so. Ideally it should be running at 2.5 volts. 1.25 or 3.75 volts is OK as well. If the voltage is stuck near 0 V, it means the ECU is trying hard to lean out the mixture but has run into its hard-coded limits. (If it's near 5.0V, the ECU is trying to enrich the mixture but has hit its limits - probably not your issue.)
If you can run some wires from the diag port into the cabin, you can measure that same voltage while at steady cruise to see what is happening under load. That voltage is invalid at fully open or fully closed throttle.
The attached picture (courtesy of @scope103) may be of some help.
I can and have previously run wires to my analog meter for this reason. But since then I installed the current injectors. May as well do it with the voltage method from the 02 sensor as I returned the AFR meter I had been using for a few days, it stopped connecting with my phone.
I will check the voltages and post back here. My buddies and I scheduled a ride later this month so I would like the engine to be in the best condition it can be. RJR, I was previously excited about your little setup to connect to the OBD1 port, but if you remember it turned out the 1991 August and earlier ECU's didn't have one of the connectors, e2? So, bummer!
If this were true it would throw a code when the learned trim hit its limit.
I have been wondering about this... But my test results from the AFR meter did show that the range of the AFR changed with every click of the AFM adjustments. So, this tells me that the ECU is not able to keep the 14.7 ratio. This was mostly apparent under medium to heavy acceleration. What would be the explanation to this? I definitely didn't get a code, and if I didn't that means the ECU is detecting the fuel mixture and adjusting it to stoic. Now, if it can't adjust it and keep it at stoic it knows that yet isn't throwing a code? This is interesting
This article told me a lot about emission analysis, and as RJR says, high HC and CO combined points (initially) to running rich. Probably not the EGR.
One frequent cause of high CO is "missing." Every time a cylinder fails to fire all the unburned fuel allocated to that cylinder gets dumped into the exhaust, and reads as HC. (Paradoxically, running too lean can be a cause of missing, but the result is excess HC.)
Does your engine run smoothly at the rpms used in a smog check?
THanks for the article reference Scope, I will read it soon.
What you are saying about the missing spark/combustion is very interesting. When I check the timing with the timing gun I have I have to further insulate the spark plug wire induction clip with some aluminum foil. I came to this conclusion because I would get a very erratic light from the gun and it took me some time to realize it is some noise the induction clip is picking up. I figured it's a bit cheap perhaps? SO, for a few years I have been wrapping the clip with aluminum foil and that definitely makes a drastic difference in the behavior of the light. However, it has never been perfect. It still regularly does not light up as one would expect. It seems to miss a few beats regularly. I took this to be additional residual noise from the proximity of the grounding wires and other spark plug wires. Then this year when the smog tech was checking my timing I was looking over his shoulder and I saw the light gun represent roughly the same light pattern as I would get with my light gun with the aluminum foil. I assumed then that all of these tools have some noise interference. Fair to note that all of this is at idle or close to idle RPMs, as the rpm increases it is hard to tell if there are missing light pulses.
With that in mind, what you are saying about a missing spark makes a lot of sense and it would definitely lead into the symptoms I am seeing. Perhaps I should accelerate the investment in a spark analyzer tool...? The spark plugs are always news, I change them frequently as they are cheap and easy. The wires are fairly new. The igniter and coil are stock but have been consistently passing the FSM tests. The distributor is off of a 1995 with 150k miles and passes all inspections.
09-22-2019, 11:41 AM
