Help - car failed emissions test!


Old 12-04-02, 07:30 AM
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Help - car failed emissions test!

My 95 G20 failed the low speed HC portion of the emissions test. Allowable HC is ~130 mine was 260 (I can't remember the units...ppm?) The inspector recommended that I get the injectors cleaned since the car has 105K miles and the injectors have never been cleaned. I have always been skeptical about injector cleaning so I've never had it done. Could this be causing the problem?

I tuned the car up a few months back:

new NGK plugs
new air filter
cleaned throttle body
new pcv valve

need to set timing, could this be problem? (105K, original timing chain)


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Old 12-04-02, 10:37 AM
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You missed the distributor cap, rotor, and wires if so equipped. They will contribute to high HC.
Old 12-04-02, 10:50 AM
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Is this an infinity G20?

If so, you can't set the timing, it's computer controlled. If you have a timing BELT as opposed to a chain, better get the belt replaced. If it breaks, you're in for mucho $.

If your injectors have never been purged/cleaned, would be a good idea to have it done. -not dumping a can of STP into the gas tank but actually feeding cleaner under pressure directly to the fuel rail.
Old 12-04-02, 10:53 AM
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Be careful about that...

Many OEM's do not recommend cleaning fuel injectors as the seals can be damaged and there is usually little benefit in doing so. GM is one company that does not recommend injector cleaning....Multec injectors by design (ball and seat) do not require cleaning.

The problem is likely elsewhere. If the injectors were that gummed up, the thing would probably run noticeably bad.
Old 12-04-02, 08:44 PM
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GM TSB #913126E (dated 1991) advised against injector cleaning for Multec injectors that were introduced in 1991, based on the theory that their design resisted being clogged by varnish on short trip, hot soak situations. Also strong solvents could damage certain fuel injector components according to the General. GM also stated that no real benefit would be realized by purging the injectors (I'd say that too if I could sell new injectors at a $100 a copy, rather than cleaning them)

Newsflash, varnish still builds up on injectors - multec or otherwise, GM now has Multec 2 injectors as of 1999 and guess what? They clog too.

When varnish builds up and clogs the injector tip, the spray pattern degrades and the end result is an inefficient engine with high HC emissions.

We've been offering and performing injection purges for our clients for years successfully. In some cases it means the difference between a pass and fail on an emissions test.

further reference:
Old 12-05-02, 06:43 AM
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Nah, not needed. Ball and seat design injectors rarely clog. Bosch pintle style injectors which are virtually obsolete as far as current applications (EV1, EV3) do clog due to design.

If you need to clean them, the RIGHT way to do them is ultrasonically and that is removing them from the car and doing them on an ASNU machine.

We have taken injectors out of junked cars and flowed them on our equipment here at work. Most flow perfectly.

Injector clogging is typically a fallacy which points to other root causes (bad maintenance or quality of fuel)

Bad aid solution at best.
Old 12-05-02, 08:13 AM
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The labour to purge a full bank of injectors is a lot less than removal and bench cleaning individually. I for one prefer to keep my money in my pocket.

My .02: If someone says that injector tips don't suffer from varnish build up or contamination from the odd bad tank of gas, they're dreaming. That's like saying carbon doesn't build up in combustion chambers over a period of time.

An injector can flow just fine on an internal basis, but you can still end up with a bad pattern at the tip if contamination / varnish is present. My take on it can be biased as we have pretty crummy/dirty fuel up here. In fact, certain additives/detergents that major brand gas retailers can actually contribute to tip fouling over time.

Interestingly enough, a TSB from 1991 recommends against the practice, but in CERTAIN circumstances (that I won't get into lest everyone here runs to their neighbourhood dealer for their free purge ), GM will pay us warranty to purge injectors ONCE during the base warranty period as a courtesty to the client.

I don't want to turn this into a pi***ng contest, therefore I won't argue the issue any further. The original poster can make their own mind up for themselves based on the above.
Old 12-05-02, 08:18 AM
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True .

I can tell you from actual testing of junked parts on the same equipment that the OEM uses (which we use here at work), that most injectors do not clog and go bad.

It's mostly all marketing on injector cleaning. And, as noted, if you have to clean the injectors, you have problems elsewhere---poor fuel, dirty filters, contamination of the system.

We do teardown analysis on returned parts and 9 times out of ten it is due to bad fuel.

I can tell you I have never had to service any GM Multec injectors on anything I own and they pass all the dyno emission tests with flying colors.

Maintenance is key. Marketing is well---marketing .
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