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AFM or TPS?


innerware

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O.k. so I have been having problems in the morning when it is cold getting the car to start. I thought it might be fuel but I pulled a spark plug after trying to start it and there was fuel pressent. I just replaced my plugs, cap, rotor, and wires thinking there was a problem there. When it is warmer out (over 50) it will start up. Under and pretty much no go. So I think that it is my AFM or TPS. My thinking is that either when it is cold my TPS is sticking shut or I am getting a wrong reading to my computer from the air temp sensor or the AFM is giving me too much fuel compared to air flow. I really think that it is an air issue. Once it starts up for the next minute or two if I give it gas it will rev low, choke up , and sometimes back fire in the intake. This seems to me that I am not getting enough air and when I gas it it starves for air and then chokes up.

 

That said how do I check those things to see if that is the problem. I'm hoping that someone has had a similiar problem and it saves me a trip to the shop.

 

Thanks as always

Kyle

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I had the exact problem recently in my '77. When it was cold out it was a bear to get started. Taking several minutes of pumping the gas pedal while trying to start it before it would finally choke itself to life. Do you also have a "boost" spot in the gas pedal. Upon excellerating you can push the pedal down further and further until you hit this one spot and it seems to suddenly take off quicker?

This is what I did to resolve it just this last new years day. This may not be the proper way to adjust the afm, but it worked great for me.

Pull the cover off the afm. Crank the car and let it get warm. Reach into the afm and turn the "wheel" alittle bit at a time CCW. Then try it CW. I'll bet the engine revs higher going CCW, but only for alittle bit of a turn. Once you turn it to much it will drop the rpms down and alittle further it will die(or try to). If it does rev higher going CCW shut off the motor. You need to take the little screw loose(the one in the very middle section, with silicone on it) and turn the arms CCW by just a little bit. The out side edge of the arm should only move CCW about 1/8, probably less. Tighten things back up and bend the thicker arm back CW to get it to open the lead when the afm is at rest with the car off. Crank the car again and do the turning test of the afm again. If you can still get higher revs by turning it CCW, you may need to adjust it more. If you get higher revs CW you need to back it off more. Get it set right and it only drops revs turning in either direction. With all that done go for a ride.

You've basically fooled the ECU into giving it more gas throughout the range of motion of the afm.

Hopefully, you can thank me later. I know my neighbors have been thanking me ever since I did this. Hearing someone cranking their car up for 10 minutes at 5:30 in the morning would annoy me more then actually being the one cranking the car for 10 minutes at 5:30 in the morning.

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It appears this has not solved my problem after all. I cranked my '77 until the battery was dead this morning trying to get it started. This was the first high 20* day we have had since this problem arose. I got home this afternoon and jumped it off without a problem, in low 40* weather. I'm almost at my wits end with this. Cold start valve and cold temp work properly. TPS and AFM is adjusted. I can only think of one other thing that could possible cause this. Cold temp sensor, but I have replaced it with 2 other known good ones. Anyone help us on this?

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It appears this has not solved my problem after all. I cranked my '77 until the battery was dead this morning trying to get it started. This was the first high 20* day we have had since this problem arose. I got home this afternoon and jumped it off without a problem, in low 40* weather. I'm almost at my wits end with this. Cold start valve and cold temp work properly. TPS and AFM is adjusted. I can only think of one other thing that could possible cause this. Cold temp sensor, but I have replaced it with 2 other known good ones. Anyone help us on this?

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It appears this has not solved my problem after all. I cranked my '77 until the battery was dead this morning trying to get it started. This was the first high 20* day we have had since this problem arose. I got home this afternoon and jumped it off without a problem, in low 40* weather. I'm almost at my wits end with this. Cold start valve and cold temp work properly. TPS and AFM is adjusted. I can only think of one other thing that could possible cause this. Cold temp sensor, but I have replaced it with 2 other known good ones. Anyone help us on this?

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Glad I didn't mess with it yet. Sorry to hear that it didn't solve your problem though. As I standd on the issue now it is in the shop. I hate having to do that. Money being an issue and all. Plus all the money that is spent there is less money for mods to the car. But, hopefully they will be able to get down to it. It is at the Z doctors up in Richmond CA and I know most of you think they are over priced I have had nothing but wonderful service and find that they are fair. Anytime I have a question I can call them and ask. They have spent probably a total of hours walking me through things on the phone. So all that said I have faith they will find out what it is and I will pass on this new knowledge to you. In the mean time good luck and let me know if you fix it too.

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I'll hopefully post tomorrow with a confirmed fix but here it is so far. About a year or so ago I replaced my thermotime switch and the harness that goes to it and the water temp sender. Apparently when I hooked it all back up I switched the two wires and hooked them up backward. So this said we will find out in the morning if the car starts in the cold. Untill then..........

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