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92 GMC Fails Emmissions

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Farmer Paul in

07-06-2005 05:57:01

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My old truck has failed emmissions twice now and is giving me fits. The truck is 1/2 ton 5 litre ( 305 ) with TBI. It passed at idle; but at speed the HC is over the limit of 79ppm my reading is 110 ppm. I have changed plugs, wires,cap ,rotor, coil, 02 sensor, and the egr solenoid,air cleaner ,fuel filter,and the timing is bang on.

The truck will surge when travelling at low speed, it will also do this at highway speed from time to time. But it is itermitent. My dealer tells me if i have done all these thing it should pass, well it doesn't.

I tested the EGR valve by pulling the vac line an it runs smooth, apply vac to the valve and I can stall the engine. The only other things I can think of are injectors and fuel pump ( dealer say if the pump is weak it would not even run ). A friend says it could even be caused by a faulty ECM.

Any help would be appeciated.

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devildawg(tx)

07-07-2005 21:15:24

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Re: 92 GMC Fails Emmissions in reply to Farmer Paul in Ontario, 07-06-2005 05:57:01

Even though it's been changed it still sounds like the egr solenoid. A bad solenoid can send screwy signals to the ECM. Had this happen on an Accord. I know this is made in a different country and all but it was sending bad signals to the ecm and the ecm was adjusting all the settings to the bad signals. It can make your truck lean out or run too rich.

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Redmud

07-07-2005 12:41:37

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Re: 92 GMC Fails Emmissions in reply to Farmer Paul in Ontario, 07-06-2005 05:57:01

Replace the gasket between the throttle body and intake.

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NC Wayne

07-06-2005 21:37:06

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Re: 92 GMC Fails Emmissions in reply to Farmer Paul in Ontario, 07-06-2005 05:57:01

Man those emissions checks are a real pain in the a--. I had a 55 Chevy years back, 283, high lift cam, Holley carb, all the goodies, and I had it checked just for kicks one day when I went in for the safety inspection. My buddy said it checked cleaner than a brand new car. My 78 J10 Jeep had a 360 AMC with a smog pump, no converter, nothing. The last year I had to have it emissions checked I got told the same thing about it, it ran cleaner than a new car... Guy at the Jeep dealership told me once that the new emissions contol crap was creating dirtier cars than any previously on the road. Basically in the past people could affordably tune up and maintain their car before a major problem arose. With the new stuff it was so expensive to have anything done they waited til it absolutely wouldn't run, and was polluting massivly, before they took it in for repair...at least that was what he was seeing and he'd been at that dealership for alot of years....Now onto your problem, I'm not that familiar with the engine you've got but I had a F150 with the 5.0 V8 and it developed a small leak where the intake manifold and the head meet. I don't know what it did to the emissions at the time because it had been inspected not too long before but I seem to remember the way it acted sounds like what your talking about. In my case it didn't start out leaking all the time, it depended on how far I drove, how hot the engine got, etc etc. I guess it took enough heat to cause the intake to warp slightly, or whatever, in the beginning to cause it to leak, but eventually it eroded enough off the gasket that it did it full time. I know it's a little deeper into things than you've gone so far but it might be worth checking out. Good luck...

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504

07-06-2005 19:48:39

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Re: 92 GMC Fails Emmissions in reply to Farmer Paul in Ontario, 07-06-2005 05:57:01

Paul,Check to see if the gasket between the T.B.I halfs is leaking. If you take off the air filter and grab the tbi and see if you can twist it,if it moves you have found the problem.

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buickanddeere

07-06-2005 20:42:26

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Re: 92 GMC Fails Emmissions in reply to Seth_ia, 07-06-2005 18:30:25

You must be a dumb redneck. No pass, no license or pay a bunch to repair a few things then re-test. If it fails you get a waiver but have to re-test in another couple of years again.

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Seth_ia

07-07-2005 20:18:30

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Re: 92 GMC Fails Emmissions in reply to buickanddeere, 07-06-2005 20:42:26

I"m assuming this is just in canada. I have never even heard of such a thing. Atleast in Iowa there are no real laws except that the vehicle is supposed to have all the emision control and exhaust equipment on it that it came with from the factory. However the only thing that is ever inforced is that you have muffler. On rare occations if a cop sees you with out a muffler he might look for a cat converter. That why A lot of us just gut them and reweld.

Let me impress this upon you in another way. Iowa is just know going to require farmers" strait trucks(ie. grain trucks) to pass a safety inspection. We all are guessing that if 25% of them pass that would be amazing. Most of grain trucks around here will not pass safety inspection, so the farmers are just planning on not having them inspected, and just paying the fine if ever caught. I just found out about a mechanic today that will pass just about any truck that hits his shop. Seeing how most of these truck won"t pass a practical safety inspection I can garantee that none would pass some dumb emmissions test.

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07-08-2005 17:26:07

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Re: 92 GMC Fails Emmissions in reply to Seth_ia, 07-07-2005 20:18:30

Iowa not testing yet- wait for DesMoines to start soon. Eastern Wisconsin and chicago area in Illinois have been testing for years. No pass = no license plate= no drive. Few years back got a vehicle in Wisconsin from a guy that was living in eastern Wi. He had just been inspected and failed multiple violations including a bit of exhaust work. Officer told him if he got caught on road vehicle would be impounded, he would go to jail for contempt, -I got the call to pickup man, wife and vehicle. Took vehicle to Iowa after fixing lights, horn- quick inspection and got Iowa registration. Brother in Iowa had to pull plates and not drive on road a couple that didn't pass safety inspection- 1939 chevy needs some body work and stop engine leaks and smoke, maybe in couple years. Iowa exhaust checks are in response to a car that ended up killing people in 2 seperate incidents from poor exhaust not fixed, bad publicity, law got changed to require tight exhaust system. Iowa inspections coming closer.

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Seth_ia

07-08-2005 20:52:51

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Re: 92 GMC Fails Emmissions in reply to RN, 07-08-2005 17:26:07

Thanks for explaiming all these crazy laws. My friends and I had never heard of any of these emisions test. I would note that Iowa did away with the safety inspection for personal vehicles. most of the mechanics that did the inspections passed anything, and it was just too hard to inforce, I guess. The pickup I just bought would not pass even the easiest safety inspection. All I had to do to get plates and licence was take in the signed title, sign another form, and pay sales tax and registration($65/year). I sure hope you are wrong about this testing crap coming to iowa. I guess I have another criteria for selecting politians now!

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thejdman01

07-06-2005 17:13:00

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Re: 92 GMC Fails Emmissions in reply to Farmer Paul in Ontario, 07-06-2005 05:57:01

unfortunately i have had the very painful experience of emissions and tryign to get them to pass. one huge thing is the air cleaner. you want all the fresh air you can get to burn all that fuel your injecting. we have gone to the extent of removing the air cleaner for the test. no rules against that. also 110 octane fuel helps the motor doesnt have enough squeeze to burn it wont giv eyou carbon emissions. another thing thatyou must check is your pcv valve. put some straight 40 weight oil in your motor so you wont be burning oil. make sure your engine is hot. also if your truck is rather quiet i have removed exhaust manifold gaskets as a last resort if it leaks around the headers/exhaust manifold w/o being noticed by the inspector and doesnt get to the wand at the edge of the exhaust pipe that helps as well let me know if that sdoesnt work there are a few more tricks

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James2

07-06-2005 10:45:11

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Re: 92 GMC Fails Emmissions in reply to Farmer Paul in Ontario, 07-06-2005 05:57:01

What do they measure? CO and hydrocarbons? If they don't measure NOX (which is expensive to do), then advancing the timing will reduce both CO and hydrocarbons, but will increase NOX. We don't have these emission checks yet, but I'm still interested what may come.

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Mike M

07-06-2005 09:23:15

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Re: 92 GMC Fails Emmissions in reply to Farmer Paul in Ontario, 07-06-2005 05:57:01

If all else fails sell it here in Ohio in Wayne and Ashland Co. for sure, no e-check,no rust out laws makes a good dumping ground for those that don't pass.

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supergrumpy

07-06-2005 09:16:46

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Re: 92 GMC Fails Emmissions in reply to Farmer Paul in Ontario, 07-06-2005 05:57:01

not trying to give you a hard time but you hit a nerve, I used to work on my "old junker classics" but not anymore

EPA doesn"t care about passing your old vehicle, they want it off the road and in the junk yard

as they insist on more of this "testing" the only economical path is new car every 4-5 years

ask anybody who works on cars in CA about "gross polluter" and you will get an education

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buickanddeere

07-06-2005 09:02:49

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Re: 92 GMC Fails Emmissions in reply to Farmer Paul in Ontario, 07-06-2005 05:57:01

If it's wearing the origional 12 yr old Cat Convertor. You should be pleased she's doing this well. It's getting about time to scrap the vehicle anyways. High Octane fuel just means the fuel has to be heated higher before it ignities. That's why it's used in high compression engines to prevent auto ignition from heat during the compression stroke. I added a stiff mix of alcohol to the tank just before dropping the vehicle off at Canadain Tire for the E-Test at noon. Came back that afternoon and it wasn't tested. By the time the test was run late the following day the truck was hard to start. The fuel pump failed the next week due to the strong alcohol mix ruining the plastic,rubber & nylon etc. Some people claim retarding the timing will cut the cruise hydrocarbons some? The new oil change is vital as previously stated. Running a 195F thermostat helps to.

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ChrisLSD

07-06-2005 08:43:07

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Re: 92 GMC Fails Emmissions in reply to Farmer Paul in Ontario, 07-06-2005 05:57:01

try the magnet on the gas line and the opposing magnet on the air intake line - I have experimented with them quite a little - might give u a tad more power - can't get my car to increase any in MPG - but they say emissions go way down

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Midwest redneck

07-06-2005 08:09:56

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Re: 92 GMC Fails Emmissions in reply to Farmer Paul in Ontario, 07-06-2005 05:57:01

Try an alcohol mixture, may work--dont know but it cant hurt to try. Also years ago in Mich. we had to have a $10 AET done here and my old boss had a car that didnt pass and the service tech at a garage stuck the pipe sensor in another car because his would not pass, I guess you could call that tricks of the trade. What about drilling a hole sideways in the tailpipe and injecting oxygen into the pickup sensor, this might help too. Those emission tests are a PITA. Good Luck.

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RB/CT

07-06-2005 07:54:27

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Re: 92 GMC Fails Emmissions in reply to Farmer Paul in Ontario, 07-06-2005 05:57:01

Just two tips from much info on this subject. One: Change your engine oil, just before the test, then if oil passes the rings its clean oil notdirty. Two: Do not keep your gas tank full during the test vapors may bypass if full and reburn, screwing it up. Thankfully you do not live in CT. 96 and up they check the codes with a computer, any service engine light on fails you. (an example, someone I know had a bad transmission and a service engine soon light on, 3K later a new transmission just to pass) Prior to 96, you go on the rollers. Now if you reset the light, and erase the codes, you get an alternate test, which is the rollers. After Nov 1, there is no alternate test in this condition and you fail The threshold for repairs and getting a waiver is $660 spent which gets you a two year waiver. Good luck. I know others who completely removed the air cleaner, but this doesnt probably work.

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Martini

07-06-2005 07:50:08

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Re: 92 GMC Fails Emmissions in reply to Farmer Paul in Ontario, 07-06-2005 05:57:01

The best way I have got cars to pass is to
purchase " Guarantied to Pass" fluid at CTC. Add high octane gas drive at highway speed for 2-3 hours before the test. Go to a Emissions Centre who only do the tests and are always on time for
the appointments. Merivale Road in Ottawa is the best I've seen and they will often do a re-test
free if you are close the first time.
The burnout fluid is usually the key if you have a dirty converter!

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tortmort

07-06-2005 07:30:30

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Re: 92 GMC Fails Emmissions in reply to Farmer Paul in Ontario, 07-06-2005 05:57:01

I had 89 GMC 350 with TBI and I failed, then replaced catalytic converter and it passed.

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Davidj

07-06-2005 07:12:14

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Re: 92 GMC Fails Emmissions in reply to Farmer Paul in Ontario, 07-06-2005 05:57:01

Put farm plates on it. No E-test needed. David from Ontario

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Allan in NE

07-06-2005 06:32:25

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Re: 92 GMC Fails Emmissions in reply to Farmer Paul in Ontario, 07-06-2005 05:57:01

Paul,

Whatever is causing your surging is causing your high readings.

In addition to other items mentioned, wobbled out injectors, pressure regulator, PROM or ECM could be suspect too, as the fuel strategy is controlled electronically.

Your check engine light is on, right? If it isn�t, something is wrong in that area because if the system isn�t clamping as it should, the O2 readings should trigger that light on.

The converter "might" be adding to your woes, but it will not normally cause surging, I wouldn't think. Fix the surge and you've fixed your emmisions.

Allan

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Revredneck

07-06-2005 06:15:30

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Re: 92 GMC Fails Emmissions in reply to Farmer Paul in Ontario, 07-06-2005 05:57:01

Farmer Paul,
If you've changed all the filters and made sure she's all tuned up, then your problem is most likely the catalytic converter. I assume the truck has a lot of miles on it (my '92 has 380,000). Catalytic converters do wear out over time, so you'll probably have to replace it. Pretty much the only way to tell is when everything else doesn't bring the numbers down. Good Luck and God Bless, Tommy

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T_Bone

07-06-2005 12:05:31

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Re: 92 GMC Fails Emmissions in reply to Revredneck, 07-06-2005 06:15:30

Hi Tommy & Paul,

My daughter got pulled over one night by the Serrif and said her muffler was glowing red. He could see this as he followed her, now that's plugged. Plugged up cat.

Alcohol in the gas, veggie oil in diesel, and 50wt motor oil in the engine has passed many emission tests.

T_Bone

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wdtom

07-06-2005 17:27:35

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Re: 92 GMC Fails Emmissions in reply to T_Bone, 07-06-2005 12:05:31

How much (percent) alchol?

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