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Just rebuilt engine. How to pass inspection??
Topic Started: Jun 1 2010, 03:06 PM (1,576 Views)
alivedw
New Member
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My dear Metro Forum friends,

With your guidance, I successfully completed my first-ever engine rebuild on my 1990 Geo metro (1.0 L, ,3 cyl). I got it running smooth, set the timing to 8 degrees BTDC, and took it for a couple of nice long drives - runs better than ever. But I took it to get inspected today and I failed the tail pipe test. This is my daily driver and I really need to pass ASAP so I can get tags! So, any advice would be really appreciated.

Here’s the diagnosis from the inspection tailpipe test (IM240 result):

IM240 RESULT:
HC: Reading: 12.2339 GPM, Limit: 2.0000 GPM FAIL
CO: Reading: 66.0522 GPM, Limit 30.000 GPM FAIL
NOX: Reading: .4967 GPM, Limit 3.0000 GPM PASS


What do you think is going on here? Here’s the info on my car:

--Just rebuilt the engine with professionally rebuilt head, all new exhaust valves, new rings, new bearings. New gaskets all around.
--Replaced exhaust manifold, and put in a new/used cat from a 1990 Geo w/ 80,000 miles on it. Don’t think this cat is plugged/fouled but can’t say for sure.
--New spark plugs (not certain they are gapped correctly).
--Cleaned the PCV valve – no obstruction as far as I can tell.
--Set the timing to 8 degrees BTDC.
--Engine running smooth, good performance, and no visible smoke in the exhaust.


Two questions:

1) Can retarding the timing help me pass emissions?
2) Could spark plus gap size affect this? If so I’ll pull the plugs and re-gap them to make sure I got it right.

I’m grateful for any advice on how to pass this test!
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Memphis metro


A freshly rebuilt engine should have no trouble with inspection. Not sure whats in a 90 model myself but if it is fuel injected check to see if your map sensor vaccum and wires are hooked up. If its running the spark plugs arent going to make that much differance, of course they do need to be gapped right though. Advise to pass inspection. Go on rainy day. Before I rebuilt my geo during the winter I could not hardly get mine thru inspection but after I rebuilt it the numbers were barely on the paper, nice and tight and right.
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starscream5000
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Got 70 MPG?

Back the timing off to the factor recommend setting, that should lower the NOX some, but you may need to drive the motor hard some more to seat the rings. You're cat may be clogged, that would be the only thing I can think of besides what enginedoc alread said.
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alivedw
New Member
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Wow, guys, thanks a lot for the quick response. You've left me with a couple questions, I hope I can ask and maybe take another minute of your time:

1. Fuel injection is throttle-body injection. I unfortunately don't know what a map sensor vacuum is or where it is on the car, could you shed a little light?

2. Is there a test for a clogged cat?

3. I'll definitely back the timing off to factory spec (5 degrees BTDC).

4. One more thing, I have no idea if it's relevant: The engine idles a little funny--not really rough, per se, but it sounds almost like it's on a cycle and changes idle speeds when a "switch" catches (i'm speaking metaphorically, i don't know how to describe it)--it idles smooth, then "catches" at a certain point and comes down in idle speed and comes up, then "catches" itself again and comes up. Sometimes it idles staright and smooth for two or three minutes but sometimes it does this "catching" thing fifteen or twenty times in a minute. Normal?
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alivedw
New Member
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Oh, one last thing, I don't have an EGR valve on this engine (I know that b/c I spent half an hour looking for it when I first got the car!). Would I still have a MAP sensor?
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Spock
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Live Long and Prosper.

are you getting it inspected in Virginia or Maryland? I lived in Virginia for 27 years and every year I had to get my car inspected , it was an ordeal. I actually had one place tell me I needed brake pads, when my pads weren't even an hour old....still had the receipt in my pocket. On the surface a state inspection is a good idea, but every one I ever had was a total rip off. I am ashamed to admit this, but in my youth I got to be pretty savvy with a paint program (can't remember which) and I used to make my own inspection stickers. Fortunately I never got caught. Heaven only knows what prison sentence I would have got for that!!

Good luck to you man!
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alivedw
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luckily they're not testing for any of the safety stuff - i live in dc, so it's just emissions. and emissions is where i'm failing, with my CO reading two times the limit and my HC reading six times the limit (!). any ideas out there for what's wrong with my engine or how i can fix this?
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Spock
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Live Long and Prosper.

Wild guess....Oxygen sensor? Maybe?
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mcmancuso
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Did you get the engine hot before testing (at least 30 minutes driving, not idle) the engine must be HOT for the car to not add extra fuel and for the catalytic to work properly. Advancing timing further will decrease HC's and CO, but increase NOx, retarding the timing is for when your car has too much NOx to pass. I'd advance it to 10 degrees myself (that's what mine is at). Also 3oz acetone to a tank of gas will help with fuel vaporization and may decrease those numbers.

Clogged cat, loosen the manifold to first exhaust section bolts (the ones with springs) and see if it runs better, if the cat is clogged it should make a big difference.

The idling up and down sounds like a vacuum leak, mine did that till I found a disconnected vacuum hose on the back of the TB. If you haven't, it wouldn't hurt to replace all the vacuum lines, they're 20 years old and may have cracks and such in them. If you have a vacuum gauge, T it into the MAP sensor line (see pic below) it should read rock steady -20 if its fluttering or much below 20 then you've got a leak somewhere.

here's some advice from over at teamswift:
(get the car hot before doing this)
1. run the fuel down to E

2. Add 1/2 gal %91 isopropyl alcohol, 1/2 gal camp stove fuel (white gas), 1/2 gal 87 octane

3. drive a mile or two

4. set timing to highest idle, then back it off a hair or two

5. Take emissions test

both white gas and alcohol burn very clean and should reduce HC's
it dropped his values as follows:
HC's 225 to 180
CO 3.64 to 0.06
(this is in canada (metric units) so don't look at the values look at the ratio of change)

when you're done, add water remover to the tank and fill it up with regular gas (the water remover is important, without it the water in the isopropanol will come out of solution when you fill the tank, and you'll have water sitting in the bottom of the gas tank.

MAP sensor is on the passenger side firewall by the wiper motor:
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Edited by mcmancuso, Jun 1 2010, 06:44 PM.
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Woodie
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alivedw
Jun 1 2010, 03:06 PM


Two questions:

1) Can retarding the timing help me pass emissions?
2) Could spark plus gap size affect this? If so I’ll pull the plugs and re-gap them to make sure I got it right.

I’m grateful for any advice on how to pass this test!
Spark plug gap is meaningless, if the car runs, it's fine. In your case, advancing the timing would help, retarded timing reduces NOx, that's the only thing you're passing. I'd put an O2 sensor and cat on it. There's very little chance that a twenty year old catalytic converter is any good, that's why it's illegal for junkyards to sell them. Also, make sure your throttle body is getting good water flow to it, that's where the temperature sensor is. If the computer thinks the engine is cold, it's going to run it rich and have exactly the emissions you list.

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mcmancuso
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:+1 on the cat replacement, if it hasn't been replaced before its probably due. the O2 sensor wouldn't hurt either, though you could test it first (you need a fancy meter to get the data from it tho) But they're only $10 for a generic that fits these cars, probably easier to just replace it. If your idle is not dropping to 850RPM or so, you may have a clogged water line into the throttle body, cleaning these out is a good idea, and they are frequently clogged, as said above, it will run rich if it thinks the engine is cold and will have high CO and HC
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crankcase


It sounds like you may have a vacuum line that is leaking or not hooked up . Take off the air filter assembly for better access, and spend some time looking for any breaks or hoses that are not hooked up. Start car and carefully listen for any sucking sounds from all sides. I had a similar problem that ended up being the MAP not hooked up.

An alternate test for cloged exhaust is to hook up a vacuum gauge to the intake (there are several places to T into the engine vacuum such as the brake booster etc.) Look for normal vacuum at start up that quickly decreases. You will find many examples of how to read a vacuum gauge if you Google it.
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