3.6 engine misfiring.. help..

[rattlsnak]

Yea!! I finally got my '95 993 3.6 installed in my project car,
Boo!! its not running right!

The engine has been sitting for @ 2 years and is now installed in a '72 with the Timmins kit.

It seems to be running on 4 cylinders. With the engine runing, I can:
1. disconnect the fuel injector connectors (one at a time) on cylinders #4 and 5 and it makes no difference in the way the car runs. All the other ones do.

2.Have taken a compression test on 4,5 and 6, being 150, 145, 155 on each.

3.Swapped #5 and 6 fuel injectors around, no difference.

4. 'noid' light shows a correct pulse.

5.Swapped plugs around, all to no difference.

6.Checked for spark at wires (plug end) both are good.

7.When its running every so often it will backfire.

8.Havent pulled the valve covers yet, but am thinking its the next step.

Help..!
Anyone???

[rattlsnak]

OK, for those who want to know.. I pulled the valve covers off and 4 of the 6 lifters on the right side are collapsed. I can literally easily squeeze them with my fingers over 1/4". So apparantly, they are opening enough to get compression, but under pressure, not enough to make it run properly. After I put the new ones in, Ill let you know waht happenes.

[mede8er]

Good detective work, dude.....

[Kevin Stewart]

who sold you the motor, Kevin

[rattlsnak]

I got it from the same place where ive got my last 4 motors. German Auto Dismantlers. I already talked to him, and he said he would be more than happy to give me another set, but of course used, and its not worth it, they are only @ $35.00 new, so i'm just going to get new ones. No gripes at all. And I checked my time line, it sat for over 4 years! The two worst ones were probably in the loaded position, or open, for that entire time. Besides from what ive been hearing it is a common problem and there is even a Porsche TSB addressing this issue.

[Bill Verburg]

I wouldn't think that lifters would cause your symptoms, when they collapse they make noise. Since the valves w/ collapsed lifters have less lift and duration they are less prone to backfire(a little anyway)

You're sure that the dist. belt is still there and hasn't jumped a cog?

all grounds are solid? plug wires and ends are all nominal?

[ischmitz]

I would check vacuum leaks on the intake. There are several ports that need to be plugged to make sure you don't get unmetered air which would make for rough idle and backfiring.

The rockers being bad is a clear sign of abuse/overreving, valve springs are cracked. That needs to get fixed no matter what.

Regading the scondary dizzy/belt a 964/993 idles perfectly fine with only one coil hooked up. I use that as a quick test once in a while to check the dizzy belt. With one coil only the engine will ping under load though. Ask me how I know....

[Bill Verburg]

Yes, if either set is disconnected it will idle fine but if one dist. has jumped a cog, or the belt is broken there is no telling where or which the plug will fire.

I agree that vaccuum leaks should be checked.

[beamonk]

plug wire crossed at distributor, backfiring?

[rattlsnak]

OK got the new HLAs in, problem fixed.. It seems there was two problems. In the first picture you can see that the o-rings were basically dry rotted and destroyed so they couldnt get any oil pressure behind them. The new design uses a teflon seal. (on right). In the second picture you can see that they were truly collapsed. You shouldnt be able the compress these at all (maybe 1~2mm). But as you can see they squeezed down all the way, or about 10mm. Im using pliers in the photo, but using no force. They squeeze with my fingers with no effort at all. I couldnt really tell if there was much noise or not because I dont have a muffler on the car yet, and its uh.... quite loud.
But anyway, its fixed, so now I can hook up the rest of everything.

[Sunroof]

Hey Marc..
Bummer man, but your the guy to get it all together. I bet its a great installation. What's left to do?

Bob
73.5T

[rattlsnak]

Bob, not to much ( in the grand scheme of things). Just the seats, lights, alignment, corner balance, muffler, foot pedals, axles, some wiring,.
Hmm, well, maybe a lot more!

[Sunroof]

Let me know if you need a hand............would love to learn somethings along the way.

Bob

[ghnat]

I would like to come by and check it out...