Sc Backfire...timing?

B.Lane · 08-26-2003, 09:58 PM

JUST GOT DONE WITH REBUILD. HAVE POP OFF VALVE THANK GOD. ANYHOW, SHE IS BACKFIRING AND SPUTTERING A BIT AS WELL AS RUNNING ROUGH. WILL THE ENGINE RUN AND REV IF I'M 180 DEG OUT ON THE DISTRIBUTOR? MAYBE I PUT THE DISTRIBUTOR IN 180 OFF? COULD I HAVE BEEN ON TDC EX. AND STILL GET THE ENGINE TO RUN? I HAVE REVED IT UP TO 5000 SO FAR AND SOMETHING IS JUST NOT RIGHT. HELP IF YOU CAN. SOUND IS LIKE...WELL...A POP. AND IS NOT CONSTANT...IT'S RANDOM AND VARIES WITH RPM. COULD IT BE THE VALVE LASH OUT OF WHAK? TO TIGHT? GRR..

3.0 SC <---

Jdub · 08-27-2003, 06:43 AM

I believe your engine could not possibly run with a distributor out by as much as 180degrees. If you have any questions about that you ought to TDC the engine and note where your rotor points (ought to point to the slot in the dist.).

There are so many variables and so little I know that I couldn't possibly begin to diagnose. However, I'd look for air leaks across the rubber plenum and other hoses as a start. Be sure also that your plug wires are all 100% resistance-wise.

But for certain I would take some time to adjust your CO. That could change things quickly. JohnW recommends a 3.5% CO.

Best of luck,
John

Superman · 08-27-2003, 06:50 AM

Yes, a lean mixture will cause intake popping. A quick check is to remove the air cleaner and press upward on the air flow sensor plate. If that causes the engine to idle smoother, you may simply have a lean mixture.

But a lean mixture can also be caused by vacuum leaks. I'd say that after a rebuild, if you did not mess with the mixture screw, the chances of assembling the engine with something like a vacuum leak are greater than your chances that the engine somehow needs a different mixture. Probably, the mixture setting is still correct, or very close.

stlrj · 08-27-2003, 07:08 AM

Check your ignition cables for firing order, too easy to cross wires.

Cheers,

Joe

B.Lane · 08-27-2003, 04:30 PM

OK ALL...EVERYONE HAD GOOD IDEAS HERE. I did have #5 wire in #6 slot so that is one problem solved. i cant get the thing to start when its cold now so i dont know if i have the main issue solved yet. I think it is either a cold start valve problem or fuel presure (warm up) regulator. I have a vaccume hose off the regulator that i cant find a place to plug into. My engine is in so i can't see the back. i have been using a mirror and feeling but still no success.

UTKarmann_Ghia · 08-27-2003, 06:58 PM

B.Lane, I have pics of the back of my '82 SC engine when I took it out last week. Pretty high-res stuff if you need some snapshots. PM me and I'll email em to you if you'd like.

stlrj · 08-28-2003, 08:21 AM

Still may have some wires crossed.

Joe

MotoSook · 08-28-2003, 08:46 AM

The vacuum hose to your distributor is supposed to plug into one of the vacuum ports on your throttle body. You are likely leaking from that port. Plug the port or plug your vacuum advance (what yr engine again?) into it. You can feel for the port one the backside (toward firwall) of the the throttle body. Next to the larger port that connects to the decal valve, there are two small ports (common). I don’t know what equipment you have on your engine, but one of the smaller ports may be plugged already. There are ports on the front (toward rear of car) two, once is vacuum one is “atmospheric.” Those should be plugged or used by an ancillary device on your engine. A little more information about your motor would help us HELP YOU.

MotoSook · 08-28-2003, 08:48 AM

Double, tripple check your ignition. Checking the wires and firing order is easy and you don't have to run the engine. If you can't start the car, try lifting up the air sensor plate to prime the cylinders. Once started, give us a report.

B.Lane · 08-31-2003, 09:06 PM

Its a 1982 SC 3.0 CIS. I got the thing running. It ran pretty good untill it got warm then it started to backfire a bit somewhat random. I first thought maybe it was timing. Then i thought it was a rocker to tight or even maybe my cam timing was off. But it only did it once it was warm and was hard to start after it was shut off and still warm. i realised it was my Auxillary air valve. I fixed the shorted wire there but have been unable to start the engine since. It has been cold here so i checked the cold start valve and i think its the problem. There is TO much fuel geting in when i go to start it. It might also be the WUR. I have just purchased a new cold start valve, WUR, oxygen sensor, and air sensor rubber boot. When these part arrive i am going to replace them all. I want a trouble free engine so this should eliminate most potential fuel problems. I also have a new fuel filter and fuel pump. Once all fuel problem are eliminated i hope to be able to start then engine then time it. I have tripple check my fire order and wires as well as spark to all plugs. I have check to see if my distributo was off a tooth and all looks to be good. I am sure i am lined up at TDC because i pluged a preasure gauge into the #1 plug hole and set roto to comresion stroke. All lines up as i marked it before dissasembly. Ill post when i get all my new parts on and we will see how things look at that point. Thanks all for all your help. Pelican is great and all you people have been a super big help through this whole process. BTW, if anyone has questions on how to paint your P-car, let me know. Mine came out perfect and i did it all myself. I will be posting a "HOW TO PAINT YOUR PORSCHE" post once everything is 100%.

MotoSook · 08-31-2003, 09:46 PM

If you had a bad component and started to adjust the CIS to compensate for that bad component, now you have to adjust back. The reason you are too rich now, may be that you were adjusted for extra air into the intake via the AAV which was not closing.

Your cold start and then lean running when warm was indicative of an air leak, which you found with an AAR that was not closing. If your CSV is leaking you can pull it to verify. With just the fuel pump running you should not get any fuel out of it.

If your fuel pressures are correct and your mixture screw is close to spec, then it should start (if all throttle by-passes are not out of wack). Even with the new parts, you may still have problems. SO I guess, what I'm suggesting is to verify that the current parts are really bad and that nothing is just out of adjustment.

Don't give up. I spent months chasing my problems, but I kept at it and I "bonded" with my CIS and engine. Learn/understand how the components work and how they should work together. CIS is not that complicated...fuel, air, spark...fuel and air is CIS' job..where are all the possible air sources and where are the fuel sources....then how much and when...

Good luck. YES! Please post Painting Info...my next DYI job.

B.Lane · 09-01-2003, 12:48 AM

i will post it and you will all be quite impressed i am sure. Everyone that has seen my car has been taken back by how good the paint turned out. they all think i spent 10k or more for it. Anyhow....one of my biggest problems has been finding this DAMN place to plug in the WUR's vaccume line...i cant find it for the life of me!!!

MotoSook · 09-01-2003, 01:53 AM

I'll send some pictures if you need it. I have a 78 CIS on my car (plenty of pictures on the hard drive), and an 81+ CIS on the garage floor.

The vaccum port is easy.

E-mail me if you'd like as it might be awhile before I have TIME! to format pix for the BBS.