Thomas6614

Thought I would post a thread before running off to a dealer or local shop to assist in passing the Harris County (Houston, TX) emissions test.

I have an ’89 coupe that passed with flying colors about 18 months ago (roughly 3K miles ago). Obviously, I don’t drive the car much and rarely get on the highway for any extended periods of time. I have noticed the car does have a rich exhaust smell while idling at a stop light lately. Also, the idle is a bit rough the longer I wait and the car does surge a bit under low steady speeds. Otherwise, my mileage is pretty steady at just under 20 mpg and the performance is great.

The shop that performed the test from a quick visual thought it might be a leaking fuel injector (which is a culprit from my research on this site). They also were in a big hurry as the place was packed on a weekend, so the car sat for a long time before the test and it may not have reached operating temperature.

The sad facts (High Speed 2007 actual/2008 actual//standard); (Low Speed “”)
• HC (PPM): 61/115//152; 90/139//157 – (Pass)
• CO (%): 0.58/2.12//0.97; 0.65/2.08//0.88 – (Failure)
• CO2 (%): 13.7/12.9//NA; 13.4/12.8//NA
• O2 (%): 1.0/0.6//NA; 1.3/0.8//NA
• NOx (PPM): 216/200//1082; 229/232//1184 (Pass)
• Dilution (%): 14.3/15.0//>6; 14.1/14.9//>6

Over the past year I installed new spark plugs (RapidFire #5), spark plug wires, distributor cap and rotor, new pcv valve and a new EGR temperature sensor.

Recently, the passenger side pre-cat has started to rattle under acceleration when the car reaches operating temperature. I mentioned this to the shop, but they stated this was not the issue for the failure of high CO readings.

Any suggestions on my next steps?
• Run a can of RXP Gas Kicker and make sure the shop is not busy and leave the vehicle running before the test?
• Any clues in the #’s as to whether this is an air pump, leaking injector or vacuum leak issue?

Thanks for your time!

Thomas

1Harley 1Vette

Hey Thomas, I had a 1995 Bonneville that failed emmisions testing in Dallas several years ago. I don't know what the numbers were but the mechanic told me to run a bottle of RXP through a full tank of gas. Then change the engine oil and fill up with fresh gas. That fixed me up and ever since I have always ran a bottle of RXP through my vehicles a week or so before emmission testing and changed the engine oil. I hope this helps.

zr1fred

Bad cats WILL cause high CO. However, I think you just have a clogged/dirty/sticking injectors. Try injector cleaner first.

Thomas6614

Thanks for the ideas. Any injector cleaner brand/product in particular?

My plan is to run one tank with the cleaner followed up with the RXP. I will run one tank in-between with no additives. Hopefully, I will not have any plug fouling issues.

donmye

Hey Thomas 6614 ,where in Spring are you, I am 3 miles west of the freeway,and fixin to put the Bosch 111 injectors in my 90 in about a week or so. If you want to watch {or help} Don

Firevette

If you still have the stock Multec injectors I would just swap them out. They will continue to give you problems in the future.

If you want to get rid of that rattling pre-cat Ive got the stock y with precats off of my car, 69k miles on it. You can have it for next to nothing. Its just taking up space in my garage.

Don, if you run into any snags with your injectors, shoot me a PM. I live right off of Louetta road.

Thomas6614

Don/Firevette - I am about 5 miles south of Kuykendahl and Woodlands Pkwy off Kuykendahl.

Don - Let me know when you plan to do it...I'd like to help and take notes for what appears to be an upcoming project.

Firevette - How much? I was planning on upgrading the exhaust, but it looks like that will be put on the back-burner for now.

Can I do a visual to verify presence of stock injectors?

GIMMESOME

Bad cat,probibly not pre cats.Run some Techron through it,and get that baby nice and hot before you have it tested.Good luck.

Firevette

Ive tried to sell it before, nobody wants one that has cats.

Its not really worth anything. If you can pick it up, its yours. Otherwise $5 delivery charge.

As for the injectors, I cant remember any markings on them that you could see when they are "in use". You can tell if their the multechs by looking at them, if you know what they look like.

Thomas6614

An update with my situation trying to pass emissions test in the Houston area.

I decided to run some Lucas Fuel Treatment. The idle after about a 1/4 tank into it went from bad to worse.

I thought I would have the dealer take a look at it to let me know what is causing the rich condition. So far all they have told me is that "yes, it is running rich and that is why you failed the emissions test".

They have spent the last few days trying to track down a Tech1 scanner. Today (after I hadn't heard from them in over 24 hours and left a vm) they returned my call stating the Tech1 and the car were not communicating. They then went on to say how the Tech1 was not used for who knows how long and could be bad or the ECM was bad. I suggested they find another Tech1 before deciding the path forward, to which they reluctantly agreed. They Ohm'ed the injectors, and they all came back to within specification.

I took the car there to get a quick opinion on the reason why it is running rich and 48 hours later all I have is frustration.

Thoughts?

At this point I'm ready to pay the $98 and start pulling parts myself.

In your collective expertise, other than the injectors or ECM...what is your best guess as to the problem?

zr1fred

Have you checked the fuel pressure? A bad/dis-connected fuel pressure regulator will cause a rich problem. Ohming the injectors merely tells you if the coils in the injectors are good. It says nothing about sticking or leaking injectors. A bad O2 sensor can cause you problems too. Make sure your cats are getting hot (should be noticeably hot after running if they are working.

Firevette

I have to agree. Check the FP. The injectors could be bad and still Ohm out just fine, especially if the car sat for any prolonged period of time. Have you pulled the spark plugs and given them a look?

djxib

I might be off base, however I have helped fix 3 (friends) cars in the last 6 months, all exhibiting hunting idle and low speed problems, every single one caused by a vacuum leak, diagnosed by spraying throttle body cleaner around the intake with the engine running, and fixed with either new gaskets or vacuum hose.

Might be a cheap way to eliminate vacuum leak before laying out $$$ on injectors.

Good luck with your problem!

Benny42

My '89 Formula 350 failed last year. Ohm the injectors in place, change them all if any are bad. Mine had 3 bad ones. It sailed thru very clean
after the swap. benny

89er

I have a 1990 that passed the first year I had it. It failed the second year and I took it to the dealer. After paying the dealer $400 they got it to pass but the next year it failed again. The dealer told me my 1990 C4 engine was a piece of junk.

I then paid $100 for a catalytic converter on ebay and a local shop installed it for another $100. It turned out that the cat that was on it had been gutted. How it passed the first year I had it and how the dealer got it to pass is a mystery to me.

I believe high CO was one of the failures. After the new cat the car passed like a new car.

89er

And they probably said the pre-cats were not the problem since their operation is for when the engine is cold. During the test it's the big cat that does all the work.

Corvette505

PASSING EMISSIONS
Bring it in on a low tank of gas (1-2 gallons) and add a quart or two or rubbing alcohol (at least 80% alcohol, the greater the concentrate the better) right before the test. This should lower your emissions by 20-40%. Since rubbing alcohol has water in it (hence the reason to go with the strongest alcohol content) immediately drive your baby to a gas station afterwards and fill-er up.

Thomas6614

Thought I would give an update to my situation.

I paid the $98 fee to Parkway Chevrolet and started ordering parts as they suggested it was the ECM. I replaced both the ECM and the O2 sensor. Neither change helped as the idle continued to bounce around 600-700.

Today I tested the fuel pressure and resistance as you guys suggested (even though the dealer claimed to have checked both and I was told they were within specs).

Well, the dealer either didn't bother to check or gave me bogus information as the resistance is way out of spec (based on my research on the forum spec should be 16-17).

Fuel Pressure Readings (Time/PSI):
*Initial/40; 1 min/40; 5 min/39; 10 min/38; 30 min/38

Car idled at 34 PSI and held pressure above 30 (32) even after 2 hours. I ran this test first and figured maybe my injectors were OK.

Visually I can tell 2 injectors are not original (#4 and #6).

Ohm Check: (cold)
#1: 7.8
#2: 11.9
#3: 8.9
#4: 16.2 (appears new)
#5: 11.8
#6: 16.2 (appears new)
#7: 11.9
#8: 16.3 (only original in spec)

I ran the car and checked the resistance hot. Those out of spec went lower, with the in-spec injectors increasing in resistance.

Is it safe to say my injectors are shot? Good thing I contacted FIC while they were on sale in good faith of my fellow forum members...thanks guys!

shadowman1

A vacuum leak will generaly make an engine run lean

Thomas6614

After a few weekends of fun I now have all new Bosch III injectors. Thanks to the excellent customer service and communication by Jon at FIC Injectors! Also, Sam Lam's write-up...couldn't have done it without it!

I took a detour and went ahead and repaired a leaking valve cover gasket (pass side) and properly replaced anything questionable along the way (vac lines, heater hose...gaskets).

She now idles better than ever and no longer stinks up the garage. I'm pretty confident in passing the test over the next few weeks.

This forum made this job possible all the way around.

Thanks!