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240 My 400k mile B23 rings are probably trashed

S

smncutler

Member
Joined
Feb 5, 2012
400k mile B23 shows it's age, issues keep changing

My VX cammed N/A 83 245 has always run like crap when cold, even after I had the head rebuilt. It runs pretty well when it gets hot but that takes half an hour. This afternoon I was pushing 80 in third gear over in Guadalajara. When I'd settled down (at maybe 3k) I heard a brief but godawful crackling, and the sewing machine head sounds seemed worse. I hoped it was something with the head, but my fears were confirmed, dear reader, when I did a compression test. Five months ago 190, now all are at 90 PSI. It runs and drives just fine, but I'm afraid to rev it. I certainly can't thrash it without a rebuild first. Who knows how rapidly it will worsen?
EDIT: compression tested with throttle closed, will report back with WOT retest
 
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Did you reuse the old coolant temperature sensor for the LH-Jetronic system when you had the headwork done? That can cause the car to run like crud when cold.

Compression is low. Should be at least 128 psi hot with throttle blocked open. Timing gears set correctly when crank is at TDC for #1? That could cause valvetrain noise, poor running, and low compression.

-J
 
Coolant temp sensor is original. Retested compression at WOT and I have 120, barely, after 45 seconds of cranking. There was some oil in one cylinder the first time, not good. The car doesn't smoke at all - it only did briefly at the one moment of engine crunch.
Car runs super lumpy after compression test, sputters a bit. Running so rich I can smell it. Made sure of ignition connections. Could my oxygen sensor be oil fouled?
(Yeah I have a Bentley manual but I can't get it right now)
Will check cam timing tomorrow, it's possible it jumped a tooth? Cam gear and timing belt are new...
 
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OP a real answer for what has happened with your high miles engine does not happen via the TB poll.

Inspect... Test... Verify.

Basics first. Cam timing. Leak down test for the engine. You 'know' that compression is low or is that tester accurate? I've seen many cheesy testers condemn healthy engines... Though the number of miles on yours implies that she may just be dead Jim.
 
Intake hose from AMM filled with nice fresh oil. Cleaned it and the AMM with Brakleen and the CRC stuff. I should get the Yoshifab catch can! Maybe if I get it running I'll find another tester. I don't see how my compression could drop so rapidly, it was excellent pretty recently... gimme a sec to check cam timing.
 
Compression is good until it isn't. At 400k it did good. Probably was holding on by a thread. Thread broke. It's tired. Hopefully will need a hone and new rings.
 
Cleaned up some wiring and cleaned the cap and rotor metal bits. Runs and revs okay, no unusual noise or smoke, but an occasional exhaust popping is present at idle. Planning on bottom end build with new rings bearings and some balancing.
 
it's very unlikely that all 4 cilinders drop down to low compression all of a sudden due to ring wear.
I'm with JohnLane on this one, check cam timing.
And because you are running a VX-cam the valves might have kissed the pistons. which would explain the 'sewing machine sounds'
 
Really? I called iPd before I bought the cam and they swore up and down it wouldn't make the engine interference. Once again experiencing rich running, lumpy, sputters and has no power when driven.
 
some cams make the block non-interference like the T-cam, other higher lift cams make the block interference.
just start by checking cam timing and go from there. Fix that faulty cam timing, make sure the tensioner has done the tensioning and after that was bolted down and then do another compression test. Maybe you got lucky.
Even if the cambelt jumped 1 tooth it will have an effect on compression reading. To know for sure what's up you have to investigate.
 
Found one of the causes - the end of the coolant temp sensor broke off in my hand. I installed a new one and it's better but still breaks up over half throttle (only under load). Will investigate timing.
 
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Timing marks on cam and intermediate shaft are aligned. Bottom piece of my timing cover broke off long ago and I don't have a place to leave the car if I break something while pulling the fan out (water pump studs are the worst). I can't get under the car right now to remove crank pulley. New distributor cap, no change. Ignition coil resistance between 1 and 15 should be about 1.3, it tested around 8. It was also out of spec between 1 and center tower. New plug wires on the way, continuing electrical testing. The strange thing is that I only noticed the sputtering/etc once I had reassembled after a compression test. How easy is it to create a hairline crack in a spark plug? Could I have a leaking injector?
 
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