Another Emissions Thread

[Audio Man]

After searching many times through the forums I haven't found a solid answer.
I have Ty #0032. It has passed emissions prior to my owning the truck. This is in the state of GA by the way. Truck runs great, new plugs, wires, cap, rotor, silicone vacuum hose kit, cleaned out the throttle body to get rid of carbon build up, ran a can of Seafoam through it, etc. Has a little bit of rough idle but as I have read these trucks do that normally anyway so that to me was not a concern.
The truck only has to do a 2 speed idle test since it has full time all wheel drive and there are no 4 wheel rollers for the emissions test. Here were my test results after putting some denatured alcohol in with the fuel, the smaller can at Home Depot.

2500 RPM TEST:
HC ppm: 103 tested, allowed: 220 : PASS
CO%: ,01 tested, allowed: 1.2 : PASS
RPM: 2447 tested, 2500+/- 300 : PASS
CO+CO2%: 14.9 tested, 6.0min. : PASS

Idle RPM TEST:
HC ppm: 507 tested, allowed: 220 : FAIL
CO%: 0.00 tested allowed: 1.2 : PASS
RPM: 1068, 1250 allowed : PASS
CO+CO2%: 14.9 tested, 6.0 allowed : PASS

I did the denatured alcohol out of a desperate attempt to see if it would help get it to pass as I read that it would. I do have an adjustable fuel pressure regulator that does not have a gauge on it though so I cannot tell what the fuel pressure is. I do have DM but cannot save the readings anymore on it. All I can do with it is real time readings on my laptop.
Any thoughts would be appreciated, it has been very frustrating as the 2500 test passes no problem but the idle test fails miserably...more then double the HC allowed.
Thanks for any help guys!!

 

[JSM]

Re: Another Emissions Thread

HC is unburnt fuel at idle. Got any E85 stations around?

you could try a new O2 sensor, what chip are you running.

 

[dgoodhue]

Re: Another Emissions Thread

What plugs are you running? Thermostat?

 

[SY2455]

Re: Another Emissions Thread

Are the plugs new after the Seafoam ? How old is your catalytic converter and your oxygen sensor ? IF they are both new since the Seafoam, Then it sounds like the testing place you used, let the truck return to idle real fast by just taking their foot off the gas pedal. Almost everyone of these truck will fail if you just take your foot off the gas pedal. Alot of shops use this to bring in more work at the shop. You need to buy a fuel pressure gage so you know what your fuel pressure is set at. On my truck with a 160* thermostat, I have to set the fuel pressure at 35lbs for smog testing. There are some really good postings on here about smog testing, but you will need to seach for them.

 

[It's just a six]

Re: Another Emissions Thread

I like to raise the idle up to 1000 RPM, don't go higher than that. Adjustment on the TB w/a Torx screwdriver.

As suggested, if you let off the throttle too fast, it starts to run a bit rough & the idle hunts for a bit before it smooths out. Need to let off throttle slowly down to idle.

You could disconnect the tan wire under the pass side carpet, it will through a CEL (check engine light) , just put a business card to cover up the light.

You need to set the idle to 1000 RPM after the tan wire is disconnected (if you are going that route)

If not wanting to disconnect the tan wire, you could retard the timing about 10 degrees set the idle to 1000.

Don't go hot rodding it around like this,it will be real lazy & the EGT's will be high. Just take it easy on it.

Before testing, tell the guy to put some heat into the cat, 2500 RPM for 5 minutes.Then procede to the testing.

Hope this helps.

 

[The Bronze]

Re: Another Emissions Thread

2500 RPM TEST:
HC ppm: 103 tested, allowed: 220 : PASS
CO%: ,01 tested, allowed: 1.2 : PASS
RPM: 2447 tested, 2500+/- 300 : PASS
CO+CO2%: 14.9 tested, 6.0min. : PASS

Idle RPM TEST:
HC ppm: 507 tested, allowed: 220 : FAIL
CO%: 0.00 tested allowed: 1.2 : PASS
RPM: 1068, 1250 allowed : PASS
CO+CO2%: 14.9 tested, 6.0 allowed : PASS

It's pretty lame they don't provide the O2 readings. With that I can calculate A/F ratios.

CO is rich/lean indicator. Partially burned fuel. No cat ~.5% With a cat ~0-.2
HC is a misfire indicator. Pure fuel that never was ignited. Can be too much fuel, not enough fuel to support combustion or a mechanical or spark issue that prevents combustion from taking place.
CO2 is an efficiency indicator. Any good running engine (Honda or GMC) can reach 14.5% without a cat. A cat can typically take the CO2 up to ~15.5%
O2 would indicate whether the mixture was rich or lean. Not present here.


2500 test. Catalyst is working reasonably or your CO2 would be under 14.5, even with good fuel control. It is also controlling your CO, as it would be ~.5 to .8%. HC are still a bit high, considering a catalyst and good fuel control (need some DM info)

Idle test. Your buddy the inspector already was running the test close to the upper limit. If he pushed it right to 1250rpm then he would likely start generating attention from the I/M program officials (It would for me). Adding a few more rpm isn't going to miracle-drop the HC's by over 50% anyways. You will notice that the 2500 rpm test occurred first so that the catalyst would light off. Most programs have a precondition program that allows for a couple of minutes at high rpm to light off the catalyst if it fails the first 2500 rpm test. It would then run the 2500 rpm test over. At idle, as it was at the 2500 rpm test, the catalyst is still working. Running this vehicle around the block would likely not do much more in my opinion. Once the catalyst is actually lit off, there isn't significant reductions to be found with the catalyst.

The HC isn't due to too much fuel, or the CO would be higher. The HC could be from a lean condition, but we would need to know what the O2 sensor and fuel trims are reading (assuming it is correct, but O2 sensors typically fail with low output, creating a rich condition, not lean). The stuff to check:

1) Engine vacuum. Connect the gauge to manifold vacuum and observe the needle. Looking for a steady needle. Document vacuum level and fluxuations (min/max) if present.
2) Compression: Even cylinders. Leak check if one or more are too low.
3) Fuel Pressure: If the O2 (fuel trim) indicate it is lean.
4) Cylinder balance test. Assuming it is one or a few cylinders misfiring, then you could put some junk plug wires on it, ground a test light and then start stabbing the top of the wires where it attaches to the cap. When the probe hits the conductor of the wire, it will send the spark to ground. Note if the engine speeds up, slows down or there is no change (misfiring cylinder). I do this a few times. It is best with the idle motor bypassed and throttle mechanically holding rpms just off idle, but not necessary.
5) Cylinder balance test by injectors. Pull the injector harness individually. Note changes as described above.
6) Artifically richen mixture. You don't want to add fuel pressure to the injector rail, if the injector flow is the issue, then the other cylinders will just be richer. You want to add fuel (ie. propane) into the inlet and see if it helps richen up an otherwise lean (vacuum leak or dirty injector) cylinder. You can also do a injector cleaning (not with the gas tank additive) to see if it helps, but up here it is around $100 bucks.
7) EGR needs to be OFF. Removing the EGR and applying a cardboard gasket temporarily will go a long ways to VERIFYING no EGR is flowing.
8) I didn't mean to leave this for last, but ignition timing will definitely cause a higher HC at idle. I occasionally do this on purpose for technician diagnostic training. As noted in other threads about timing, we are talking timing using ACTUAL TDC, not what is indicated on the dampner.

Note: The CO limit they allow would allow this rig to pass without a catalyst as long as it was running even remotely close A/Fs.

I do have DM but cannot save the readings anymore on it. All I can do with it is real time readings on my laptop.

Run your vehicle to a nice, warm idle. Note coolant temp, BARO, MAP, O2 readings (high low and cycle time), Crosscounts, RPM and IAC position. Add the other thing that I am likely forgetting as well. Where things are changing dynamically, note the range and where it typically falls. Of course, you could always pay for DM...The diagnostics we are discussing are saving you enough to pay for that. :2cents:

 

[midnightbluS10]

Re: Another Emissions Thread

It's pretty lame they don't provide the O2 readings. With that I can calculate A/F ratios.

CO is rich/lean indicator. Partially burned fuel. No cat ~.5% With a cat ~0-.2
HC is a misfire indicator. Pure fuel that never was ignited. Can be too much fuel, not enough fuel to support combustion or a mechanical or spark issue that prevents combustion from taking place.
CO2 is an efficiency indicator. Any good running engine (Honda or GMC) can reach 14.5% without a cat. A cat can typically take the CO2 up to ~15.5%
O2 would indicate whether the mixture was rich or lean. Not present here.


2500 test. Catalyst is working reasonably or your CO2 would be under 14.5, even with good fuel control. It is also controlling your CO, as it would be ~.5 to .8%. HC are still a bit high, considering a catalyst and good fuel control (need some DM info)

Idle test. Your buddy the inspector already was running the test close to the upper limit. If he pushed it right to 1250rpm then he would likely start generating attention from the I/M program officials (It would for me). Adding a few more rpm isn't going to miracle-drop the HC's by over 50% anyways. You will notice that the 2500 rpm test occurred first so that the catalyst would light off. Most programs have a precondition program that allows for a couple of minutes at high rpm to light off the catalyst if it fails the first 2500 rpm test. It would then run the 2500 rpm test over. At idle, as it was at the 2500 rpm test, the catalyst is still working. Running this vehicle around the block would likely not do much more in my opinion. Once the catalyst is actually lit off, there isn't significant reductions to be found with the catalyst.

The HC isn't due to too much fuel, or the CO would be higher. The HC could be from a lean condition, but we would need to know what the O2 sensor and fuel trims are reading (assuming it is correct, but O2 sensors typically fail with low output, creating a rich condition, not lean). The stuff to check:

1) Engine vacuum. Connect the gauge to manifold vacuum and observe the needle. Looking for a steady needle. Document vacuum level and fluxuations (min/max) if present.
2) Compression: Even cylinders. Leak check if one or more are too low.
3) Fuel Pressure: If the O2 (fuel trim) indicate it is lean.
4) Cylinder balance test. Assuming it is one or a few cylinders misfiring, then you could put some junk plug wires on it, ground a test light and then start stabbing the top of the wires where it attaches to the cap. When the probe hits the conductor of the wire, it will send the spark to ground. Note if the engine speeds up, slows down or there is no change (misfiring cylinder). I do this a few times. It is best with the idle motor bypassed and throttle mechanically holding rpms just off idle, but not necessary.
5) Cylinder balance test by injectors. Pull the injector harness individually. Note changes as described above.
6) Artifically richen mixture. You don't want to add fuel pressure to the injector rail, if the injector flow is the issue, then the other cylinders will just be richer. You want to add fuel (ie. propane) into the inlet and see if it helps richen up an otherwise lean (vacuum leak or dirty injector) cylinder. You can also do a injector cleaning (not with the gas tank additive) to see if it helps, but up here it is around $100 bucks.
7) EGR needs to be OFF. Removing the EGR and applying a cardboard gasket temporarily will go a long ways to VERIFYING no EGR is flowing.
8) I didn't mean to leave this for last, but ignition timing will definitely cause a higher HC at idle. I occasionally do this on purpose for technician diagnostic training. As noted in other threads about timing, we are talking timing using ACTUAL TDC, not what is indicated on the dampner.

Note: The CO limit they allow would allow this rig to pass without a catalyst as long as it was running even remotely close A/Fs.



Run your vehicle to a nice, warm idle. Note coolant temp, BARO, MAP, O2 readings (high low and cycle time), Crosscounts, RPM and IAC position. Add the other thing that I am likely forgetting as well. Where things are changing dynamically, note the range and where it typically falls. Of course, you could always pay for DM...The diagnostics we are discussing are saving you enough to pay for that. :2cents:

wow. Awesome post. Wish I was that good lol

 

[Audio Man]

Re: Another Emissions Thread

Bronze and others, thank you for your help!!
I do have a new Bosch O2 sensor in place. Vacuum on my boost gauge comes from the manifold and is dead steady with no fluctuations...it is aftermarket, not the stock one just to clarify. I had a guy do a compression test and everything tested good, he also verified the vacuum level was good and steady using my gauge.
He said number 4 cylinder was misfiring due to a possible intake manifold leak since everything else was good and this was causing the misfire at idle. Could this be the culprit? From everything Bronze said a manifold leak might be causing the lean condition possibly I would think.
Which one is number 4 on the firing order? I can spray some carb cleaner around the intake and maybe find the leak if it is present...this was not verified by the mechanic. Anyone know a good quick way to check for a manifold leak other then what I mentioned with the carb cleaner for these trucks? If it was a manifold leak would the vacuum be steady like it is?
My EGR has a block off plate already in place...no one noticed it so far.

 

[The Bronze]

Re: Another Emissions Thread

. We used to adjust carbs to "lean best Idle", something you've never heard of, right? Do you even know what a carburetor is?
Dave

I think it's the thing that you adjust after the points?

 

[JSM]

Re: Another Emissions Thread

I wonder what would happen if you were to just unhook inj #4 injector. That cylinder would not get air, sure truck wouldn't run right, but the air coming in/out of that cylinder would dillute the rest of the air.

Not the way to fix it, just wonder if we could cheat the system that way

 

[Audio Man]

Re: Another Emissions Thread

I wonder what would happen if you were to just unhook inj #4 injector. That cylinder would not get air, sure truck wouldn't run right, but the air coming in/out of that cylinder would dillute the rest of the air.

Not the way to fix it, just wonder if we could cheat the system that way

I see what your saying and the logic is sound. If that cylinder is not getting fuel and it is the problem then it should pass. Interesting thought.

 

[dgoodhue]

Re: Another Emissions Thread

I can tell you from experience that if you have an intake gasket leak it will show up on the vacuum gauge.

 

[The Bronze]

Re: Another Emissions Thread

Many vacuum / boost gauges that are intended for in-cab monitoring are dampened. They will not "bounce" and show the leak. You have to use a test gauge. These are very sensitive, and will show the dip of the cyl that has the blown intake gasket. An Autometer-type most likely will not be sensitive enough to show this.

Long runs of small diameter tubing will also certainly reduce the sensitivity of the reading. As indicated in my post, I believe it connecting to the brake booster port (although a few vehicles run the booster off of one intake runner- don't do that!) to provide the best reading. Some of this attention to detail won't matter for the $15 craftsman gauge, but when putting a scope on it, you better believe it matters.

 

[The Bronze]

Re: Another Emissions Thread

I wonder what would happen if you were to just unhook inj #4 injector. That cylinder would not get air, sure truck wouldn't run right, but the air coming in/out of that cylinder would dillute the rest of the air.

Not the way to fix it, just wonder if we could cheat the system that way

I bet you meant that it wouldn't get fuel. This usually doesn't work, as the extra air that is not burned passes by the O2 sensor which reads a lean mixture and richens it up. The other cylinders then overfuel and you are back to square one. Remove the O2 sensor and it doesn't pass the visual and the PCM will add fuel anyways.

This will have to be fixed. The misfire, while rather unlikely at idle and low load, can overheat the catalyst which can increase backpressure.

 

[The Bronze]

Re: Another Emissions Thread

I see what your saying and the logic is sound. .

Negative ghost rider.

 

[Audio Man]

Re: Another Emissions Thread

Negative ghost rider.

I understand. I will go get a real vacuum gauge as the mechanic that was doing the check at the time used the one from my gauge. Obviously that is not accurate for this type of diagnostics. I actually think I have a friend of mine that has a vacuum gauge but I think I may just buy one myself.

 

[Audio Man]

Re: Another Emissions Thread

Just thought I would post what the real issue was and what solved the problem on 2 of my trucks. Replaced the damn catalytic converter. Solved all of the emissions issue and I am driving my truck again.
Let me say this though...
My 1994 K1500 Blazer (full size) did not pass on the rollers. High NOx reading. Immediately was told that was due to a EGR malfunction of some sort...clogged, dirty, maybe needs to be cleaned or replaced. So I replace the EGR with a new one, clean the intake where it bolts on all the way inside the orifice, replace the EGR solenoid, and noticed a few vacuum lines going to these items were old and some were cracked...replaced them all with fresh new vacuum lines. Truck tests exactly the same...no difference. Read on the internet that NOx is due to EGR or high temperatures in the combustion chambers. Which can be attributed to carbon deposits..etc. Also read could be from bad or lazy O2 sensor. So I run 2 cans of Seafoam though the engine. Clean it out completely smoked like crazy but got it all burned out. Then I replace the O2 sensor and have a look at the plugs. Nice brownish color on the plug, no burnt spots...they look nice. Go for another retest...tests the same...no difference at all. Talk to another friend..he says a crappy running car/truck with a new cat or functioning cat will pass emissions regardless of all the other problems the car may be having. Spend $250.00 for a new cat and it passes without even burning the thing in properly...only had 26 miles on it when I took it for retest. Almost no emissions were coming out of that thing.
So....with that behind me and new knowledge in hand, I take my 92 Typhoon to the muffler shop and have a new cat put on. Come to find out that the cat on there was original to the truck from 92. Drive from the muffler shop to the emissions place and passes the test easily.
Cat for that truck was $207.00 installed. So 2 trucks 2 new converters ($200.00 each truck), pass your emissions with no issue at all. Just wanted to share so others may benefit and not have to spend the money I did to find out that it was something else.