Rebuilt top end with blow by and pinging...Help!

[Rob Timmons]

Hi I have a 79 FI beetle that might drive me crazy. I just rebuilt the top end with new pistons/rings(87mm), and heads. Dwell is at 48 and timing is right on at 5ATDC. I decided to rebuild this motor after having an episode with it late summer of having some pinging and then no idle after a long trip to a show during 95 degree temps. When OI pulled the engine apart I found the good old number 3 cylinder with the outer rings stuck to piston and part of the bottom of piston top burned away. I have all new cloth vacume hoses, new injector seals. The EGR tube going to the exhaust had been cut and pinched off before I bought it. I have left it that way, I have also blocked the small vacume hose coming off of the egr valve itself. The car was running great around town the few times I have taken it out but once I got about 6 miles down the interstate at 65 mph I noticed a pinging when stepping on throttle and then a loss of power and smoke out of exhaust. I pulled off the next off ramp and into parking lot to check it out. The motor was not hot at all, I could hold on the dip stick for as long as I wanted, but it didn't have a smooth idle anymore. Had oil in engine compartment on lid and other spots and it seems that by pulling the 3 wire it doesn't seem to cause any stumble like the other three. Any ideas? I'm thinking I might pull the egr valve and make a plate to plug the tube going to plenum. I'm going to pull and replace plugs today and see what they look like.

[mark tucker]

sounds like it burnt #3 again.just changing parts dont always fix things.I know nothing about the vw FI.it might have a cloged injector.or something else wrong

[spencerfvee]

hi rob FI bug motors can be a pain in the butt. when you put the 87 s in you raised the CR . allso the 87s have a thin cyl. wall . there bored out 85.5 s they trend to have blow by some times . allso i feal you need to run high test gas 93 . allso i feal your timming is way off i allway rev. the motor up till i get 32 degs full adv. allso your distributor could be wore out and giveing to much adv. you might have to buy a deg. pulley so you can find out how your distributor is working allso when you did the top end did you have the heads cut for a clean up if you did you raised your CR . i am not a big fan of FI . when they work there great when they dont they dont and no one knows much about them . if i was you i would think about taking the FI off and going to a carb motor just my two cents maybe others can help you on this forum .spencerfvee

[SRP1]

^^^ what he said

I would opt for a good dial back timing light in lou
of the degree pulley however, aftermarket parts arw a crap
shoot.
Also I recommend you take your injectors and have them
serviced and flow test, along with pressure testing your fuel
system in the car.
Last ditch those 87's not a good choice particularly on
an FI car.

[Rob Timmons]

I had a gut feeling that changing piston size with the FI wasn't a good choice. I did check my CR with the on line calculator and it all was within stock numbers as well as deck height. The new heads were left alone no cutting. The car ran great at the around town and rural roads at 55. It wasn't until I got on the freeway that I had problems. I checked with carb cleaner today and wasn't able to find even a slight gain anywhere. Last year when I first had the same problem I check valves and notices a rusted off bail end and a valve cover leaking air. I thought maybe this was the problem and decided to rebuild the top end this winter. It didn't want to idle when cold, first mile, after that the rest of the summer it ran good. I even ran it over an hour each way at 65 with no problems. The odd thing is if it was the CR wouldn't it ping all the time when you wot the gas? It's like it would only start doing it after a 7-10 minute run on the freeway. That is why I was thinking something with the EGR. Like maybe it takes a while before this starts to open and when it did it gave me the air leak. I had a couple hours today so I have it pulled out and I'm going to pull the head tomorrow and see what I cooked. Checked compression and had nothing, dam!

[alex77]

do you have a temp gauge in it?
sounds like it's overheating.
_________________
91 mexibeetle

[Rob Timmons]

I don't have a temp gauge and thought the same. I was almost at the off ramp when it started to smoke so got off and pulled into a parking lot. I got out and touched the dip stick thinking it was going to be crazy hot and was surprised that I could have stood there and held on to it all day. I didn't have the injectors cleaned maybe I will now. Thanks.

[spencerfvee]

hi rob some thing is making your bug run lean . on the free way . when you have a car that is 32 years old . and its has FI . that realy did not work that great from day one . and when there are very few people that understand how it works and can repair FI . it leaves you out in the cold . as to what to do . from what i understand about FI on bugs . haveing worked in a vw repair shop . and talking to others who have had FI on there bugs .and have been where your at . they allways say best thing you can do .is chang over to a carb. your just going to put more money into this motor. you cant keep burnning holes in pistons . there are no new parts for this FI motor . you have to use used parts .if you can even find used parts for your FI motor . over the years i have changed over 25 FI motors to a carb . and after doing so . all were very happy about doing it . i know you dont want to hear this but i am just trying to save you . time and money . something for you to think about good luck spencerfvee

[Rob Timmons]

Hi Spencer,
Trust me the carb idea has gone through my head several times. If it was a 78 I would have all ready changed it, and I might still. Is there anyway a bad connection on the throttle switch do this? I had unplugged the wire harness from the computer instead of taking all the wires off the components, after realizing that you have to take most of thewm off any ways and how hard it is to get the plug through the hole I just unplugged it from the engine. I noticed that the two back spades had green corrosion on them, any chance that this could do it.

If it is a CR problem wouldn't I notice it when starting as well? It doesn't turn over any harder than before with the 85.5's? I'll know in a few hours what it did, now what to do! Thanks for the help.

[Rob Timmons]

Well It did burn the bottom of the piston again. I'm close to going carb but not willing o commit yet.It was the number 3 cylinder the last time too. Does this mean that it ha something only to do with that cylinder? I know typically it's 3 because of heat from the oil cooler but am I looking at it being and injector that I should have had cleaned.

[Steve Arndt]

When our shop rebuilds those engines they receive new injectors. No deal otherwise.
Steve

[bugracr]

sounds to me like a failing injector!

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[nsracing]

[Rob Timmons]

Thanks,
I replaced all the o rings, intake block/gasket and vac lines. Before I pulled it yesterday I went over everything with carb cleaner and found no leaks. Seams how it is the same cylider again I'm going with the injector and having them flow tested and cleaned. If it was the pump or regulator wouldn't it be all the cylinders having a problem? I'll do a pump pressure test before I run it again. Now I have to find a new forged 87.93 piston a cylinder made by mahle. Does anyone know why they don't offer one piston only sets?

[Steve Arndt]

aircooled.net sells singles.

[spencerfvee]

hi rob . the green corrosion is one of the things that i would think would mess a computer up . if i was you i would clean up the two black spades and try it and see if it helps and check all the other plug ends and clean them up too. i know the ground wires can mess things up big time so clean them too . . i hate to say this but i allways cut the plug off because i was allways scraping the FI and did not care . because i was changing the motor over to a carb motor .. green corrosion was a big problem on plug ends .and is one of the things that vw did a poor job on. when they made the plug ends and made the connecters for the FI motor...what happens over the years is because the air intake on the engine lid lets water in on the motor when it rains .. and we all know what water does to electrical componets .it breaks them down the only thing i can think of . is when you took the motor out to do the cyls and head work a wire must have broke on the inside of the wire from corrosion where you cant see it with your eyes . it happens a lot on vws with older wire . even on my carb motor vw i have to replace the wires because of corrosion from the air intakes on the engine lid. letting rain water on the motor . (GOD I CANT SPELL LOL ) i am sorry i cant be much help to you . i hope some of the samba guys can help you more than i can good luck spencerfvee ................................................................................................

[Matthew]

Now that you have burned up two top ends and the history of the bottom end is probably unknown, I would go all the way through it this time if you want any longevity from it. Much of that metal from the bad pistons ends up in the bottom end and the oil carries it to all the bearings.
_________________
1965 Beetle sedan
Click to view image

[raygreenwood]

[spencerfvee]

when i worked at a vw dealer from 1973 to 1978 the FI motors were a pain in the butt .you eather got a good one that run great or a bad one that would allways be in the shop .lol the big thing here in ohio was salt on the roads salt would raise hell with every thing. from starters to FI motors . 1973 was the big year for vw they installed in all the dealer ships in the USA a computer that would print out every thing that should be fixed on a vw and tell you if every thing was working wright on the motor. it could read the timming on the motor . and tell you if the brakes needed work and a lot more.. well the salt did its job you can guess why . needless to say the computer was a pile of junk did not work right from the start lol lol as you can tell i am not a big fan of the FI bugs allso if the FI motors were so great why do you do see so many FI bugs with carbs on them now adays just my two cents spencerfvee .....................