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[Brian L.]

Had my car running like a top! This past week I had fixed my vacuum advance on my distributor, reset the timing, and fuel mixture because it had been running a little rich but now its running great, well until a couple o days ago. Monday on the way home from work I picked up a new distributor cap and rotor and when I got home I pulled the rubber intake boots that go from the air meter to the throttle body also pulled the throttle body and adjusted the micro switches and did some clean up on the intake and the head. When I tried to restart the car it was a little hard to start but had to keep it at 2,000 rpm or else it would want to die and when I would rev it up it could go past 5,000 RPM but it would be cutting out the whole time. I decided to undo what I had recently done. Put my old cap and rotor back on and went over all the boots and vacuum lines. I don't know what I did but spent the last day and a half trying to get it started again. Nothing but popping and jerking.

Well I finally got it running but now it will idle okay but when you rev. it over 1500 RPM it pops and backfires and will die, go over 1,500 rpm it will die right out!

While checking the fuel pumps I can disconnect the in tank pump and it doesn't seem to make any difference but now its noticeably louder. I think tomorrow I will pull the in tank pump and the in line filter and look for blockages. Anybody have any ideas?
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1980 924 N.A. Monaco Blue owned since 1987
"Remember, sitting on your ass won't finish your project" -Puddins fab shop.

[ThomasJoseph315]

Any chance of crossing wires?

[Brian L.]

I would never be dumb as to do that! You know that was exactly what it was acting just like. I would turn the key and it would crank over but only occasionally fire and pop out of the intake. I would then go over the intake boots and hoses to make sure nothing became disconnected. Now that I at least have it running it will idle no problem but as soon as you give it more throttle it get to about 1.500 rpm and it will just cut right off and back fire, get off the throttle and it will recover and once again idle nicely. I'm thinking its just getting enough fuel for a fast idle and anything more than that and it starves out.
Tonight after work I think I will do a fuel pump volume test and if that checks out then try a injector volume/spray test.
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1980 924 N.A. Monaco Blue owned since 1987
"Remember, sitting on your ass won't finish your project" -Puddins fab shop.

[dpw928]

Backfiring though the intake can also be caused by an extremely lean A/F ratio. A medium to large vacuum leak could be causing this. When you replaced the boot off the air sensor plate were all the correct and tight? Also, was the crank breather hose checked for leaks and a good connection on the boot?

Dennis
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81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black

[Brian L.]

Figured out my mystery problem. My super duper genius vacuum advance diaphragm that I made was over advancing my timing. Funny because I didn't think it was going to advance enough. When I would crack the throttle it would pop and backfire. It took me all day again just to get it started, changed the cap and rotor again and just happened to forget to plug in the vacuum hose to the advance and there you have it, it fired right up! To find out what was wrong I should have looked in the mirror first! Cheers!
Brian.
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1980 924 N.A. Monaco Blue owned since 1987
"Remember, sitting on your ass won't finish your project" -Puddins fab shop.