flummoxed by CIS - help
 

So I decided to do a valve job on my 83 sc.

Changed the spark plugs, wires, cap, rotor, oil.

started the car and it ran fine except it had a clicking sound (probably a valve that was too loose). My Porsche enthusiast friend and perfectionist said I should do it over. I did. I double checked the work.

I started the car and it ran for a minute at 2500 RPM, then sputtered a died.

restarted . . . backfire, sputter, missfire. Sounds like a leak! I do a smoke test with a cigar but find no leaks. I do a fuel pressure test and all is good (warm and cold).

Fuel pump works.

I take out all the injectors and sleeves and replace the seals and sleeves. still sputter, backfire, dies.

It wants to start but I have no idea what I should do next. Any advice would be welcome.

Thanks in advance

BM

Was one or some of the valves WAY out? THe reason I ask this is you may have done the wrong cam at the wrong time (right cam at the wrong time - oh never mind) and adjusted it right out of spec. In 25 years of 911SC ownership, and checking each year, I've only ever had maybe half a dozen valves that have needed adjusting.

Am going to pull the valve covers off again and check.

Thanks Bill

I’ve only done a couple of valve adjustments but I am just across the river in Potomac and I’d be happy to lend a hand if you are in need.

Here's a thought...

What tends to happen over time is CIS gets gradually leaner with small vac leaks that get worse and worse. Owner or mechanic gradually enriches mixture over time to compensate.

Now you replaced a bunch of stuff fixing vac leaks and creating better spark energy. Your mixture is likely off.

I like Bill's idea too.

No worries you'll get it. Try again.

Get to TDC on 1, have the cap off the dizzy and make sure you are pointed at one. Grab hold of the rocker with your hand and wiggle it, you'll hear and feel the gap. Now you are ready to adjust. If the rocker doesn't move, double check your mark. Doesn't hurt to rotate the engine over again and watch the rotor go 'round till you get to one again.

Once you have re adjusted everything, double check your wires. (Actually I might do this first) One wire off the plug or in the wrong spot can cause the problems you described. When putting the plugs back on the spark plug wires, a little twisting action can make them snap right on. Give a slight tug to make sure it's really on there. The rubber dust shield sits nice and flush closing the hole. If it's not, the wire may not be seated on the spark plug.

I assume the dizzy was not changed timing wise.

What wires did you buy? Did you get the right parts on there for your 83?

I bet it's the plug wires either the wrong order or one of them is not quite connected something like that.

Why would his engine run at 2,500 rpm for a minute, then sputter and die?

Question for BM (OP) is how smooth was the running in that minute?

A thought, when you lift your front hood does the courtesy light come on? That is in the Lambda system fuse circuit. If that fuse has blown, you will have the sputtering, backfiring, misfiring. Also, not wanting to climb in rpm's worth a snot.

Check your distributor rotor. I had one crack and bust on me a while back, not sure if replacement quality is as good as new/OEM.

It was just after a valve job so I was mighty confused. Just check it.

Thank you for all of the responses. Garment, I greatly appreciate the offer to help. I may send you a PM if I get stuck.

Spent the afternoon in the engine bay and under the car. Redid all the valves. some were a little off. I need to get the covers back on and the spark plugs in, etc.

The plug wires I purchased are Clewett. Good quality. When I get it all back together. I will crank her up and report.

Many thanks to all of you

Cheers
BM

I have the Clewett ones too. You know when they are seated on the plug because they give a nice "click" when they mate with the plug.

You're probably right Bob. It's just a WAG from me.

No criticism, whatsoever.

Interested to hear the outcome.

One dude about two years ago was talking about how his car ran like crap-o-la. Fifty hundred members said check your plug wires. He went silent for two days. Like 40 posts with complex thoughts subsequent.

Plug wires were on wrong per OP.

I beat him to death for the time lag given the effort of the members.

He has not been back. My bad.

I have no friends. :D

Edit: Clewett wires for me as well.

Hi Bob,
Checked the courtesy light. That's the one on the passenger side of the front hood (just checking). It comes on - working. slowly eliminating problems. Got home from work and did cylinder three valves. Top side was more of a pain than before. But the valve was shut when it should be open. Could be a sign of progress. I'll do cylinder five tomorrow, put it back together, and report.

Bob, I will definitely have people double check my ignition wires.

thank you
BM

No worries. I have been taking my medicine.:D

Oh no worries. None taken!

after my last valve job when I replaced wires, cap, and rotor, I accidentally put the dist cap on 180 degrees out - it wasn't aligned with the locking tab. It started and ran, but it ran like crap.

I would also had to recheck where you grounded the spark wires.

NikosF, what do you mean about grounding the spark wires?

thanks
BN

No grounds on Clewett wires. Beru or OEM only.

Wouldn't it be great if the original thread title could be edited?

I bet your valve job got out of wack. Too coincidental.

This is why I do valves (and oil), test drive the car, next thing such as spark plugs leads, test drive, and so on.