Bought a car for FE but im having trouble need Mech help!!!
 

I posted this exact question on other sites with mixed answers, so i would like to try it here. The car got 36mpg on the first 1/2 tank. Now im driving more efficiently but my mpg is dropping.

Please take a gander and tell me what you think.

My question is my 1989 Civic HB D15b2 that is smoking when i rev it or excellerate hard. Its burning about 1/2 Qt every 200 miles. It's leaking from the dist the normal amount.

Here is some engine info.

I just purchased it for a commuter, it was a one owner daily driver, it has 217k. i bought it with a seized cam. i replaced the head with a head off of a 1993 DX with between 100-150K, and had it milled and torqued to the TSB specs and all new gaskets, the cylinders still had cross hatch marks on them. ( i didnt talk to the owner so i dont know the full history of the engine)

New timing belt, water pump, plugs, PCV valve.

Starts and runs great and as strong as i would think a 1.5 could be.

Dry compression check showed, from dist. to timing belt:

180 185 170 180

Leak Down

4% 4% 5% 4%

The car appeared to be running for quite some time with a leaking head gasket. When i replaced the PCV valve i noticed a build up of carboned oil on the hose connecting the PCV valve, although air flowed through the line fairly easily.

I hate posts that lack info so i hope i listed enough.

Please let me know what else i could check or what else it may be.

Thanks,
Tim

hmmm my minivan gets 30mpg on the "first half" of the tank, and 10mpg on the bottom half.... are we expecting the gas gauge to be accurate here?

I think he means the first fillup was a 1/2 tank. not everyone runs the tank empty.

the smoke is textbook symptom of bad rings, i'd vote for cyl 2 (as engine cylidners are always numbered from the timing belt end) do a wet compression test and get back to us.

I would try cleaning out your entire intake, as it sounds like your PCV system was causing some problems, it sounds like you either have a blockage or a leak allowing your crank case to build up some pressure and let oil leak past your rings, so I would clean out all the passages and hoses, and check for leaks, this will hopefully reduce the smoking, and improve your gas mileage.

Compression tests should be done with a fully warmed engine, the throttle should be open (gas pedal pressed) and the engine should be cranked 3-4 revs (the needle will jump each rev), disconnecting the wire going to the coil will keep the engine from starting while doing this, you can also pull the fuel pump fuse to keep fuel from being dumped, or the engine from firing, but with a warm engine your compression should be around 195psi, so 180psi with a cold engine is good!

Exactly, i just filled it up after i used a half tank after the first fill.

Thats how i did it, the engine was warm, all plugs removed, fuel pump disconnected, gas pedal to the floor. The shop manual says 185 max and 135 min. So i think I'm OK with the compression readings.

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Is there a way to check how much crank case pressure i should have, or a good way to check if my PCV system is working properly? When i squeez the PCV hose the valve doesnt rattle, but when i take it out, the engine revs up and there is a lot of suction in the hole where the PCV goes. When i have the PCV in my hand it rattles as its supposed to.

Yea your right, cylinder 2 is suspect being the lowest in compression and leak down. Ill do a wet comp test as well as a leak down test while the piston is lowered down the cylinder. I heard that the wall could be damaged further down and can be detected that way.

Thanks for all the info, keep it coming and ill update my results.

Are you using the PCV valve for the original block or the new head? PCV valves are metered according to expected blowby of the piston/block combination, so if you're using a different/later one that fits that head, you might need to figure out how to get the '89 PCV valve to fit it. Not familiar enough with Honda motors to know whether they changed the ring package between those years or whether capacity was different.

Edit: why I ask is because if it it is oversized, then it may be pulling too much vacuum in the crankcase and messing things up, (not allowing compression to seat rings properly) or leaking too much vacuum and messing things up (like a vacuum leak would) or if it's undersized, it could be allowing crankcase pressure to build too high, which could force oil past valve seals and out of other places where it's not meant to go.

Good info, the PCV valve mounts into the intake manifold so im using the one for th 89. This should be correct buy what you are saying?

But this is the exact type of thing that i think may be hapening, something little that is just throwing things off.

Thanks i should be able to get that wet comp test and additional #2 power stroke leak down this week.

Back to your original description of the smoke. Is the smoke blue and does it have that strong burned oil smell? I would make a PCV filter for it just for the heck of it. It wouldn't hurt no matter what, and could possibly stop the oil burning if indeed its being caused by the pcv system. I made a pcv filter for my truck for about $15 out of an air tool water seperator. It catches about a shot glass worth of oil every two weeks- oil that normally would have been sucked into the intake.

Also, the next thought of mine is your o2 sensor is not working properly anymore- due to the oil.

One other thought I have is your fuel system. If you have an injector staying open or if they're spraying horribly then it could be washing the oil off the cylinder walls and at the same time causing horrible gas mileage, and smoke. You may want to have an injector service done, or have them removed and tested, or better yet just replace them depending on how easy/expensive it is.

Pull the oil pan and check your oil pick-up screen to see if it is partially clogged. I lost an engine because of that. It smoked for a couple days then ran good for a few. Then I parked it for 3 days and then the net time I drove it, it smoked bad and threw a rod.