Emissions Test Failure - 88 Red Coupe

[WTS]

Took the Vette in today for Emissions test. It failed curb idle, CO% and
HC ppm.

Drive Test ASM2525
HC ppm - Limit 58 Car was 117
CO% - Limt 0.32 Car was 0.55
NO - Limit 652 Car was 37 ?

CO% Curb Idle - Limit 1.00 Car was 1.02

Appears to be running rich.
I'm thinking O2 Sensor or Cannister Purging

Has any body seen this before ? If so any suggestions would be appreciated.

Thanks in advance !


WTS

 

[Schrade]

Took the Vette in today for Emissions test. It failed curb idle, CO% and
HC ppm.

Drive Test ASM2525
HC ppm - Limit 58 Car was 117
CO% - Limt 0.32 Car was 0.55
NO - Limit 652 Car was 37 ?

CO% Curb Idle - Limit 1.00 Car was 1.02

Appears to be running rich.
I'm thinking O2 Sensor or Cannister Purging

Has any body seen this before ? If so any suggestions would be appreciated.

Thanks in advance !


WTS

Pick up a fifth bottle of Everclear ethyl alcohol at the liquor store. 15% gasoline and 85 % ethyl alcohol (aka E85) will reduce CO output to 1/10 current level. You don't have to go all the way to 85% alcohol tho'...

Alcohol will increase burn temps, which will increase NOx, and you have plenty of room for that too, with 37 current, 652 allowable.

HC's will come down with alcohol/gas mix, which increases burn temps, and reduces HC count.

Get some alcohol, or get tuning...

 

[WTS]

Thanks for the information !

WTS

 

[Paul Higg]

I just failed for the same thing, I have a 94 and I don't know if you have one but I replaced the EGR and it fixed it.

Good luck.

Ignore Halverson.

 

[Schrade]

I just failed for the same thing, I have a 94 and I don't know if you have one but I replaced the EGR and it fixed it.

Good luck.

Why did you replace the EGR? 32 code? Did you replace the valve, or the solenoid itself? Many folks don't realize they're 2 different animals...

Do you happen to have before and after emissions readouts? This could be interesting to see the differences.

 

[Paul Higg]

I posted them in great detail, all the readouts. You'll have to do a search. I can't right now. Just look under my name. It was very recent. It explains all that I did and what the readings were. I had four tests. Failed first, retest, failed second, failed retest. So there should be four sets of readings and what I did between them.

 

[Paul Higg]

Sorry I didn't answer the rest. I replaced the whole EGR. It was covered in soot.

It had 98K on it, time for a change. Soon as I replaced it, BAM, passed with flying colors and no more unburned fuel smell either.

 

[Hib Halverson]

(snip)

Ignore Halverson.

I can always count on Mr. Higg for a laugh.

As for the 88 which blows the smog check, all the suggestions about EGR really can't amount to much because clearly, with the car making 37 PPM oxides of nitrogen against a limit of 652 PPM, it's unlikely EGR (which has a big part in the engine's oxides of nitrogen emissions) is a problem.

Being that the HC is so high at idle and low speeds and considering the age of the engine, the first thing I'd do is go looking for leaking injectors. You can find them by running the fuel pressure tests listed in the factory service manual. You'll also need a fuel pressure gauge designed for use with port injected engines.

Once you determine the injectors are not an issue, then I'd look at the 02. if it's never been replaced, considering it's over 20 years old, I'd just replace it on GP and that may or may not fix the problem.

Lastly, there was no mention of the MIL in first post so is the check engine light on in this car? If so, what codes are set? If not, does it come on during bulb check? If yes, then don't worry about codes. If it doesn't bulb check, you may have codes set. The FSM will explain how to read the codes and it will explain what to do if the MIL does not come on briefly during bulb check.

As for canister purging, that's certainly possible but, if it was, I suspect by now you've checked that and been back for a retest.

One tip for emissions tests which require running on a chassis dyno, get the cats good and hot before you test. The cats work better when very hot. I'll drive around the block the smog station is in three times in first gear at 20 mph to get those babies hot, hot, ad. If the smog station is near a freeway, I'll drive the last 5 miles of the freeway in third gear in an automatic and fourth gear in a stick, rather than the higher gears. That also gets the cats hot. Sometimes a car that's flunking due to HC can be made to pass by getting the cats hot.

 

[WTS]

Thanks for the reply !

I changed the O2 sensor yesterday and subsequent to a brief test drive the car is acting vertually the same with respect to the flag alarms indicating a rich condition.

No codes are being set.

Prior to the last emissions test I ran the car for approximately 30 minutes up and down the local highway. The car sat for approximately 30 minutes before they got around to the test.

The Fuel injectors are next on my list. I must review the requirements in the service manual and see if I have the required test equipment. I do have a fuel rail pressure guage.

The one thing I did notice is that the MAF output at idle is reporting 9.0 grams as opposed to 4.0 to 7.0 as the service manual stipulates. I don't know what the typical vehicle yields. If the MAF is outputting a higher than normal flow I can imagine that this might affect fuel delivery on the rich side of normal.

Regards

WTS

 

[Hib Halverson]

You have the gauge so just follow the fuel pressure tests in the FSM.

Now, that will only tell you that you have leaky injectors but it won't tell you which ones are leaky. I don't have my 88 manual handy but I think there is a subsequent test that helps you ID which injectors are leaking.

But, considering the car is over 20 years old, you might be better off, if you can afford it, to just replace all eight if you find one or more leaky ones.

 

[WTS]

Thanks for the reply!

A subsequent review of the service manual indicated that an indivdual injector test is possible.

With respect to the Emissions Failure I noticed something intersting today. With the engine running I noticed that the diagnostics BLM line was showing 116. When I disconnected the PVC valve the BLM went to 128. I then reconnected the PVC valve and disconnected and plugged the vacuum port that connects to the cannister purge solenoid and saw roughly the same thing.

The PVC valve seems to be OK with no plugged lines.

If block learn is above 128 the ECM is supposed to change fuel injection to add fuel for a lean condition. If the block learn is below 128 the ECM is supposed to subtract fuel to compensate for a rich condition.

Do you think this could be the main source of my emissions problem ?

Previously with all vacuum lines and the PVC connected properly the ECM would report as low as 114 for the BLM on a continuous basis.

Regards

WTS

 

[vetteboy86]

What is your fuel pressure? Bone stock motor?

 

[Hib Halverson]

116 BLM, as you know means the system is subtracting fuel. When you remove the PCV and its restriction, more air flows into the engine leaning out the air fuel ratios. The 02 senses that and the ECM begins to add fuel or, more exactly, leans the air fuel ratio less than before.

Do the fuel pressure test.

If you key-up and the pressure rises quickly to spec but drops soon after the pump goes off, it's possible you have leaking injectors.

Leaking injectors will cause the engine controls to skew the fuel delivery lean to compensate.

 

[Schrade]

Thanks for the reply!

A subsequent review of the service manual indicated that an indivdual injector test is possible.

With respect to the Emissions Failure I noticed something intersting today. With the engine running I noticed that the diagnostics BLM line was showing 116. When I disconnected the PVC valve the BLM went to 128. I then reconnected the PVC valve and disconnected and plugged the vacuum port that connects to the cannister purge solenoid and saw roughly the same thing.

The PVC valve seems to be OK with no plugged lines.

If block learn is above 128 the ECM is supposed to change fuel injection to add fuel for a lean condition. If the block learn is below 128 the ECM is supposed to subtract fuel to compensate for a rich condition.

Do you think this could be the main source of my emissions problem ?

Previously with all vacuum lines and the PVC connected properly the ECM would report as low as 114 for the BLM on a continuous basis.

Regards

WTS

116 means it has been running out of tune for a LONG time.

Think of it as a '0' average in school. After it has been at 0 for a long time, it takes lots of 100's to raise it. 10 0's, and 10 100's only gets you to 50. It ran at 128 for years. Then an error here, an error there, and the average moved slowly away from 128, to 127, 126, ... all the way to 116, which is really low.

I think your O2 was workin' fine, which was reading too much HC (gas) (HC ppm - Limit 58 Car was 117), and it was telling the computer to decrease injector pulsewidth. Whether or not less fuel was going in, we don't know. But if you still have the old O2 sensor, it IS working - keep it. This is one reason I get so disappointed when I see parts bought blindly.

Do a TIMED pressure bleed-down, and write down results as fast as it drops, like at 5 or 10 or 30 second intervals, depending on how fast it drops. Then measure each injector for impedance cold AND hot. Post the results...

That's a NON-executive, know-nuthin' wrench monkey summary yup uh HUH!

 

[Hib Halverson]

I was wondering, what were the results of the fuel pressure tests?

 

[WTS]

Thanks for the reply.

Sorry for the late response !

When I pulled the plugs several tips were saturated with fuel. At least 3 cylinders indicated leaking injectors.

Pressure did drop also indicating injector bleed down.

I have decided to replace all 8 injectors with new as I don't believe the remanufactured units are the way to go.

WTS

 

[WTS]

Pressure was approximately 43 Lbs on static power up.
Operating pressure, (engine running) was approximately 36 to 38 Lbs

WTS

 

[Hib Halverson]

Took the Vette in today for Emissions test. It failed curb idle, CO% and
HC ppm.
(snip)
Has any body seen this before ? If so any suggestions would be appreciated.
Thanks in advance !
WTS

I just failed for the same thing, I have a 94 and I don't know if you have one but I replaced the EGR and it fixed it.

Good luck.

Ignore Halverson.

(snip)As for the 88 which blows the smog check, all the suggestions about EGR really can't amount to much because clearly, with the car making 37 PPM oxides of nitrogen against a limit of 652 PPM, it's unlikely EGR (which has a big part in the engine's oxides of nitrogen emissions) is a problem.

Being that the HC is so high at idle and low speeds and considering the age of the engine, the first thing I'd do is go looking for leaking injectors. You can find them by running the fuel pressure tests listed in the factory service manual. You'll also need a fuel pressure gauge designed for use with port injected engines.
(snip)

Thanks for the reply.

Sorry for the late response !

When I pulled the plugs several tips were saturated with fuel. At least 3 cylinders indicated leaking injectors.

Pressure did drop also indicating injector bleed down.

I have decided to replace all 8 injectors with new as I don't believe the remanufactured units are the way to go.

WTS

I was wondering...does Paul Higg have a final comment on this thread?
Paul...Paul?
Are you still there...?

Darn. And he was so active at the beginning of this thread. I wonder where he went?

Oh, yeah, the injectors...

The best in the market IMO (based on use of them in a couple of different engines) are from RC Engineering. Admittedly, RCs, being a premium high-performance and racing product with all stainless internals and less than 1.5% flow variance, are expensive. I've also heard that the new-design Bosch injector (I forget the name of them) has acceptable quality and performance and has a lower price. Also, I had a clutch put in my C5 at Corvette Mike's in L.A. a couple weeks ago. They also had a C4 L98 in there for injectors and they were using Accels.

After you get the new injectors and go back to the emissions test, please, let us know how you did.

 

[Schrade]

Pressure was approximately 43 Lbs on static power up.
Operating pressure, (engine running) was approximately 36 to 38 Lbs

WTS

These are good numbers, but we need MORE. Vette is high-strung, speaking from a tuning standpoint, with 8 injectors in the intake ports - not 2 in the throttle body. You can replace 8 injectors if you want, but without bleed-down times - EXACT times - we can't really gauge what's going on with the fuel (other than too much is gettin' to the inspector's sniffer).

 

[Hib Halverson]

With fuel pressure checks you want no bleed-down at all.

Fuel pressure "Bleed-down times" have nothing at all to do with tuning. If there is any bleed down time, it's a maintenance problem, that is: if the fuel pressure drops after the pump goes off, then the injectors may be leaking.