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Car running too rich


scotts77z

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I need advice. My 77 runs very rich. the gas smell is very noticable when standing near car with it running. So far I have replaced all of the z-pole connectors for the injectors, thermotine switch, cold start valve, Water temp and air regulator. They were very loose and brittle. Have done a continuity test per the shop manual with every switch testing good.I have also corrected any vacume leaks, replcing all vacume lines. I am wondering if it could be the mixture setting on the airflow meter. My shop manual says to use a CO meter during adjust it. Does anyone know if you can damage the engine by adjusting the mixture without it. I am thinking of just adjusting it counter clockwise a 1/4 turn at a time and test drive it to determine if mixture improves. Any advice on this or on what else to look for would be greatly appreciated.

Thanks

Scott

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When you say that the gas smell is very noticable when standing near the car, where do you mean? Are we talking engine bay area or exhaust?

How are your plugs? Fouled?

Reason I ask is this-Recently I had an issue where there was a definate smell of gas eminating from the engine bay. I had replaced all the vacuum lines, cleaned connections, checked for various leaks, etc. What my problem turned out to be was a faulty fuel pressure regulator.

The FPR was leaking gasoline directly into the engine manifold (kind of like having the cold start valve on full time), so the car seemed to run well, but with poor gas mileage.

Raw gas was dousing the PCV valve, and was leaking out through it, hence the smell, and the wet valve was the final clue to the mystery.

After the car has been running for a bit, pull off the vacuum line that connects to your pressure regulator (on the fuel rail somewhere), and see if there is any gas in there.

Be prepared for this by A-turning off the engine, and B-have a clean, dry rag in hand when you disconnect the line.

I would check this out before fiddling with the airflow meter.

FWIW

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David - Thanks - I had not thought about the fuel regulator. The smell is coming fromthe exhaust. I did pull hte plugs and confirmed that there is unburned fuel. The plugs are wet and smell of unburned fuel. I will test the regulator this afternoon.

thanks for the advice.

Scott

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  • 1 month later...

The FPR can also get stuck and keep your psi to high. Bought a 77 with this problem, the local shop it was at sold the guy a new AFM, head temp and a bunch of other parts for about $700. We bought it for $250 and fixed it with an old FPR in about an hour. You can check it by pinching the return line off the fuel rail. If there is no change, try pinching the supply line. If the FPR is bad, it should start to clear up then die.

Jim

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The FPR was leaking gasoline directly into the engine manifold (kind of like having the cold start valve on full time), so the car seemed to run well, but with poor gas mileage.

Raw gas was dousing the PCV valve, and was leaking out through it, hence the smell, and the wet valve was the final clue to the mystery.

Geez! Sounds like what mine's doing!

My PCV valve is crazy wet (can't tell if it's oil or gas or both) ...

I'm gonna look into this FPR business too, thanks for the tip!

(Sorry for the brief hijacking) I hope you're getting this issue resolved on your 77 Scott! My '76 and I are feelin' your pain! (BTW, if you're really serious about playing with the AFM, I don't recommend it, counter clockwise would enrichen the mixture further, to lean it out turn it clockwise.)

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Still have not figured it out. The FPR seems fine. I checked to make sure it was not leaking fuel into the intake through the vacumme side of the regulator. I also tested the cold start valve and air regulator. After looking at other posts on this site and some other z site tech bullitens, I decided to look at th AFM. I found it had been messed with before do to the silicone glue being missing on the adjustment screw. Now the problem is that while trying to adjust it to leaner misture, I let the spring unwind. For now I am taking a break and will try to fix it. I found a trick from one z site on how to adjust it using water as a weight on the flapper. The site is http://atlanticz.ca/zclub/techtips/ in case anyone is interested. It also has many other tips for z car problems.

Scott

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Doesnt that mixture screw on the AFM just adjust the mix at idle?

The one that he is reffering to is the mixture screw inside the afm (cover must be off). But there is also a seperate screw for mixture at idle down below on the right that you can access without the cover off.

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When you say you changed the "water temp sensor" do you mean the one wire sensor or the two wire sensor that uses a fuel injector plug? The one wire is for the gauge only, not the EFI. Try removing the head temp sensor (with the fuel injector style plug in.) The engine should go rich. If you have no change, then the head temp is bad. Nissan part number 22630-N4200. I seriously doubt the AFM is bad, it's just is a bandaid to try to compensate for another problem.

Jim

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Thanks _ I have tested the two wire temp switch. I have already gone through the entire EFI system using my factory service manual. I Replaced all the connectors for injectors, water temp, cold start valve,AAR. I also have replaced all of the vaccume lines, new PCV valve. I did test the FPR as Jim had suggested. The weird part is that the problem only exists when the car is warm. If you engage the clutch and come to a stop the motor revs to about 2200 RPM. You can get the car down by draggin the clutch and then it returns to 800. I opened the AFM cover and marked where the wiper sits when idling at 800 RPM. I then took it for spin down the street, engaged the clutch to get it to stick at 2200 or so RPM and looked at the wiper on the AFM. It was still at the same position. So the flap on the AFM or the throttle linkage is not stuck open. If I move the counter weight with my thumb, the car will stumble and then return to 800 RPM. I am thinking the AFM is just bad and is sending incorrect voltage to ECM causing it to open the injectors. At this point its all just a guess. I could be totally off base here. I have not had a chance to look into further but if I find out what it is I will post for anyone else who has this issue. If all else fails, I may take to a shop here in Atlanta called E Raditz. I understand they deal in Z specifically. I just hate to be outdone by friggin car!

i appreciate all the responses.

Scott

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