83' 3AC with low compression (~140 PSI)

[2yota]

Just wanted some advice from the experienced. Just got a 1983 Tercel with tha 3AC motor. Runs uneven (up and down rpm in cycles), probably a vacuum leak?. Has almost no exhaust system remaining too.

I tested compression and got results around 140 PSI, but all cylinders were within a few PSI. I gapped the valves and tried again....no effect.

So, I live in Colorado and have to pass emissions. Is there any way this car could do that with this low of compression (the car was peppy driving it home through the mountains).

Trying to decide if I should keep and fix or sell to someone (perhaps living in a county w/o emmisions testing).

[splatterdog]

Vacuum leaks can be a big problem. Give a close visual for condition and routing. Then run it while giving it controlled shots of carb clean anywhere vacuum would be present. Observe any change.

If you trust the gauge, that compression is low. A cylinder leakdown test would be the next step. Then verify cam timing. This can be checked by pulling the upper belt cover(after belts and water pump pulley). Put the balancer on TDC and check cam sprocket position. You might have to turn the crankshaft 2 turns to get the correct TDC.

Also, when testing compression did you have a warm engine,all the plugs out, and throttle blocked wide open?

Good luck!

[xirdneh]

[quote="2yota

I tested compression and got results around 140 PSI, but all cylinders were quote]


i have three tercels
recently tested compression on all three
engine was half warm on all
two were around 150 average
one was around 125 average
the two at 150 get around 29 mpg highway
the one around 125 gets around 38 mpg highway
make of it what you will
if all cylinders are within 7 psi i would not worry about it
its when one is way off the others that problems begin

[Typrus]

Before Larimer County killed emissions, mine passed no problem. 146PSI or so on average.
Just make sure your cat is in good shape.

BTW, a lot of exhaust leaks will make you fail emissions.

[ARCHINSTL]

Welcome to the Club !
What is the range of your RPM cycling? Do a Search for that term - lots of info on it.
Tom M.

[splatterdog]

I guess I have the odd one here. I checked my 200k engine in the 86 before its recent transplant and was just shy of 210psi. Just figured this was typical. No known history of any major repairs(head gasket/shaved head) but the engine was in outstanding condition internally. 0% sludge.

Don't know how thorough your emission testing is. Before they gave it up here a common trick was to raise the idle and put a bunch of HEET(isopropyl)in the tank. Maybe we had looser standards. Seen several 70's cars pass the visual and the sniff with only converter heat shields welded over the straight pipe too. Pre-80 had higher ppm's allowed.

The other typical trick was registering the car outside the testing area.

Good luck!

[Typrus]

If you commute into Denver, you will be expected to pass the rolling sniffer tests there. They will keep track of if you commute to Denver for work or the likes.
I have no idea if any other big cities are that way.

Yes, Denver has vans that do your emissions tests while you roll on the onramp to I-25.

[2yota]

Thanks for the info. When I first got the low compression numbers I tried an older tester, but got the same results.

All of the cylinders are reading very close, probably within about ~4 PSI. So, maybe it will be worth fixing this car....some of you seem to offer some hope that it might pass emissions with compression this low?

Another question about those compression numbers: the odometer says car has about 140K miles. Could the original engine be reading those low numbers with only 140K miles? Or, you think the engine is a replacement?

[shogun]

with the weber i have the same issue, but is when the nuts on the adapter come loose, hace to tighten them up every once in a while