1975 Fuel Injection Emissions

[manta73wi]

Hello,
I have a question about emissions for my "new" 1975 fuel injected Manta. In some areas of Wisconsin, our cars have to pass an emission test equal to the standards in effect at the time of the car's manufacture. This is done periodically for newer cars, but for those of us registering older cars for collector plates (pay for it once and no renewals as long as you own the car) it only has to pass once and we're legal. My '73 Manta did fine when I registerred that one.

My '75 passed the NOx portion, but didn't pass the Hydrocarbons and Carbon Monoxide parts. As tested, it ran 5.06 grams per mile of HC with a limit of 3.0 gpm, and 100.4 gmp of CO with a limit of 65 gmp.

I've read through the forums and replaced two cracked vacuum hoses, checked spark plug gaps, and adjusted the screw on the FI unit to burn leaner (Thanks for the FI instructions posted, Otto!). I've also heard that adding a bottle of isopropyl alchohol (gas line antifreeze) will lower emissions. Anything else I should try before bringing it back in for the second test?

THANKS!
-Jeff W
'75 FI Manta
'73 Manta

[GTJIM]

With both HC and CO up it sounds like you are already burning rich, especially with NOX low too - have you checked oxygen levels in the exhaust?

Bob, I should do more posting with my brain engaged! Sleep depravation is the pits!

[RallyBob]

Jim, CO percentage is strictly an air-fuel ratio issue. High CO means rich, low CO means lean....this is the method often used to dial-in cars on a dyno rather than via air-fuel ratios. High HC's can be a LOT of things, but is usually ignition/spark or engine efficiency related. Weak rings will show higher HC I've found.

Bob

[tekenaar]

Originally Posted by manta73wi Hello, I have a question about emissions for my "new" 1975 fuel injected Manta. In some areas of Wisconsin, our cars have to pass an emission test equal to the standards in effect at the time of the car's manufacture. This is done periodically for newer cars, but for those of us registering older cars for collector plates (pay for it once and no renewals as long as you own the car) it only has to pass once and we're legal. My '73 Manta did fine when I registerred that one. My '75 passed the NOx portion, but didn't pass the Hydrocarbons and Carbon Monoxide parts. As tested, it ran 5.06 grams per mile of HC with a limit of 3.0 gpm, and 100.4 gmp of CO with a limit of 65 gmp. I've read through the forums and replaced two cracked vacuum hoses, checked spark plug gaps, and adjusted the screw on the FI unit to burn leaner (Thanks for the FI instructions posted, Otto!). I've also heard that adding a bottle of isopropyl alchohol (gas line antifreeze) will lower emissions. Anything else I should try before bringing it back in for the second test? THANKS! -Jeff W '75 FI Manta '73 Manta

Some more things to check for smog test . . . I'm amazed that they require it at all for a 30 year old car!

Do you still have the EGR valve and piping connected between the tailpipe and the bottom of the throttle body? Is the vacuum hose to it intact? Have you separated the valve from the pipe and cleaned the carbon from the valve so it seats properly?

Do you have "CA" car with catalytic converter? Is it plugged? If cat equipped, did you fully warm up engine (to light off cat) BEFORE taking it for smog check? Checked your air filter?

[namba209]

Now that's interesting Bob. Makes me wonder what do the O2 sensors in the exhaust measure and give input to the computers, like on my V-6. I was under the impression, maybe erroneously, that they measured air/fuel ratio and adjusted the injector timing/duration and ignition timing to maintain 14.7:1 mixture under almost all conditions of throttle settings. I guess I'm gonna have to go back to the books again.

[tekenaar]

Originally Posted by namba209 Now that's interesting Bob. Makes me wonder what do the O2 sensors in the exhaust measure and give input to the computers, like on my V-6. I was under the impression, maybe erroneously, that they measured air/fuel ratio and adjusted the injector timing/duration and ignition timing to maintain 14.7:1 mixture under almost all conditions of throttle settings. I guess I'm gonna have to go back to the books again.

The '75 Opel FI doesn't use an O2 sensor . . . L-Jetronic open loop system.

[namba209]

Yeah, I know Otto. I was just curious about what the O2 sensors actually measured, specifically on my Sequential Fuel Injected 3.4 V-6. Everything I read on it, was the computer controlled the duration and timing of the injectors as well as adjusted the ignition timing to maintain a 14.7:1 fuel ratio, with the O2 sensors providing the major feedback to the computer after the inlet sensors did their input to the computer and after actual firing in the combustion chamber. Modern technology is a wonderful? thing.

[manta73wi]

Originally Posted by tekenaar Some more things to check for smog test . . . I'm amazed that they require it at all for a 30 year old car! Do you still have the EGR valve and piping connected between the tailpipe and the bottom of the throttle body? Is the vacuum hose to it intact? Have you separated the valve from the pipe and cleaned the carbon from the valve so it seats properly? Do you have "CA" car with catalytic converter? Is it plugged? If cat equipped, did you fully warm up engine (to light off cat) BEFORE taking it for smog check? Checked your air filter?

I do not see any fitting, EGR valve, or piping connecting the exhaust manifold to the throttle body as far as I can tell. The exhaust manifold splits into two pipes down the side of the engine which join into one tailpipe near the back end of the transmission. From there, the exhaust system is very new, but from the engine to that point it looks original (I'm hoping/assuming this is the "sprint" manifold?).

Car is a 49 state Michigan car, so no catalytic converter there now. Engine was warmed up when I brought it to get emissions checked. Air filter was new when I got car 2 months ago.

THANKS for the help!
-Jeff W

[manta73wi]

I'm glad to say the '75 Manta passed emissions today , so I'm good for as long as I own the car. A combination of the new vacuum hose & air hoses, a leaner air/fuel ratio, a check of air filter & plugs, and regular gas seemed to work. THANKS again!
-Jeff W
'75 FI Manta
'74 Manta parts car
'73 Manta

[yellaopelgt]

Glad to hear you passed! I hate it when you have to let some putz drive your baby thru emissions, when I took the Gt in, I threw a fit when some young kid tried to hop in the drivers seat! I said "OH NO,I DONT THINK SO!!!!" I had the guy in charge drive it with me in the passengers seat giving him the evil eye the whole time!
On another note, you do know that if the car doesnt pass you could always do the "other county" trick!
Congrats!
Joe