lazylama

i have 98 ek3 1.5ls civic with d15z6 engine, 2 inch exhaust everything else pretty much stock. Driven 320 000km, head was rebuilt 60000 km ago. i cant just figure out this problem..
everything began when i was driving on a rough country road and hit a few bumbs. Suddenly engine noise changed a little and felt major power loss expecially on lower rpms(i´d say about 30hp or more). It still run just fine,
but it was really hesitant and laggy until about 4500 rpm and then starts pulling real good. basically like vtec kicks in but d15z6 only has vtec-e?
At first it definetly sounded like skipped timing belt but no.. i have double, triple and propably overchecked it..

It has been running like that for a long time now. Also noticed that fuel consumption has gone up to about 8-9l/100km, used to run less than 7l/100km. Also it failed smog test. On idle Hc is too high:about 300/ 100 ppm and also co was high. On higher rpm HC drops to under 100 but too much o2 and lambda value is wrong. So its running rich down low and bit lean high? The higher the revs the better it runs.

So the symptoms i have noticed:
-really low torque on low rpm, after 4500 starts pulling lot better
-On idle if you press gas pedal fast it first bogs a little, then starts reving.
It sounds like it chokes of too much air? same thing when accelerating under heavy load.
-random misfires and sputtering on idle, sputtering intesifies at about 2500 rpm
-exhaust has gotten a black coating
-emissions and bad fuel economy
-idle is just little high, cant be adjusted further
-also i noticed today there was some water in my exhaust and muffler but i guess thats normal?
-consumes some oil but not much smoke, just little thin white smoke
-no cel codes


what i have tried so far:
-checked timing too many times. when crank at tdc, cam gear marks line with gasket surface( or maybe few degrees off but cant line it better) also have tried to advance and retard it one teeth, but then it just runs worse.
-new timing belt and tensioner
-ignition timing set with timing gun, alternator set about in the middle
-changed o2 sensor, crank fluctuation sensor
-changed fuel filter and air filter
-injectors cleaned
-checked exhaust, new gaskets etc.
-valve clearance set
-compression test, 190 psi on all four
-flushed piston rings with diesel
-measured voltage on map sensor
-ecu reset many times
thats all i remember..
Also it was in a repair shop where they just cleaned injectors and said its running ok.. clearly it isnt..
Only thing that comes to my mind is ecu.. could it be the cause allthough everything else is fine?
Can send pictures/videos if that could help


i´m getting so frustrated.. i just dont want to give up
Any help would be GREATLY appreciated! Thanks!
turned out to be really long writeup.. and sorry for grammar mistakes

TS2008

If I were you, I would buy a tune up kit and I start from there. I had similar problem with other car ( random misfire, jerking while accelerating and etc ) but no cel. Finally, the culprit was was the rotor from the distributor.


I changed lot of stuff before I found the culprit (wires, spark plugs, cap, fuel filter, ignition coil). If the same problem happened to me again, I will buy a tune up kit and I will start from there.


my two cents.

lazylama

Thank you for reply!
Forgot to mention, i have also changed dizzy cap and rotor, tried different ignition coil and icm and changed spark plugs. Only thing i havent done is spark plug wires so i could try that next!

The thing that bugs me is that sudden power loss after hitting a bump..
what i can think of it could have cracked something, broken a wire/sensor, skipped belt.. or something like that

Wankenstein

From the symptoms you've described it sounds like another head gasket or cracked cylinder head issue that's leaking into the a cylinder. Losing coolant at all? Rough idle at startup then smooths out when engine warms up?

Other possibilitities: maybe a clogged cat or weak (but not failed) o2 sensor that's not throwing a CEL. Have you check spark plugs? notice any signs of black oil, soot or other abnormal apperance on them?

Have you performed a:
Dry and Wet compression test
Block test for hydrocarbons

lazylama

Got new spark plugs and wires but no difference.
could be a head gasket issue but i doubt it. Not loosing coolant from what i have noticed, no coolant in oil and no overheating issues. idle is pretty smooth right from starting, although some random misfires. idle is little high (about 900rpm)and it cant be adjusted any lower.

Cat or exhaust is not clogged. o2 sensor is also replaced. spark plugs were black and had little burned oil in them.
Have done a dry compression test, 190 psi on all four

thanks for ideas turd_ferguson!

Wankenstein

Are you monitoring both the overflow tank and the radiator for coolant loss? An HG breach would most likely cause coolant loss in radiotor and coolant gain in overflow tank. Generally, these engines won't show many other signs such as the others you mentioned. Do a block test on it.

On all of them? Read this: http://www.aa1car.com/library/spark_plug_fouling.htm

lazylama

Rechecked coolant, it has not lost any coolant or gained any in overflow tank. Will do a block test when i find a shop that does them.

All spark plugs were almost black before. Then i flushed piston rings and advanced timing a little to correct mark. It helped and run smoother. Now after 500 kms on highway all of them had a white tip and black ring. Similar like in the picture (not my picture though).

Wankenstein

Do your own block test.. very easy to do and shown on Youtubes. Rent the block tester from O'reilly's or Autozone for free adn purchase a bottle of $10 test fluid at either parts store.

What did the repair shop do to clean the injectors? The proper way is through use of an ultrasonic cleaner:

Did you first crank the engine a few times with the spark plugs removed after the piston soak or did you just install plugs and crank/ run engine immediately after soak? If you did the latter then the deisel fuel most likely cleaned the spark plugs during combustion.

Have you checked for vacuum leaks or had a smoke test for vacuum leaks done? Find the vacuum hose that connects to the cruise control bladder to the intake manifold.. make sure it's connected and that there isn't any cracks or splits.

lazylama

We dont have those kinds of shops in my country. And and i have never seen block tester sold in any of autoshops here.. but i will try to look for it

Not sure how they cleaned injectors but i belive they did that with ultrasonic.

after flush and sucking the diesel out i turned engine manually several times.
well now i put the new spark plugs in, have to check them again after driving for some time

intake manifold and all the hoses have been checked multiple times. I did a spray test for intake manifold. could remove and check the whole intake manifold but its a bitch to remove in a civic

thanks for helping out man!

lazylama

Also did a smog test today.
At idle
Hc 350-400ppm
co2 15 %
co 0.18
lambda around 1.0

At 2500 rpm
hc 20 ppm
co2 15%
co 0.02
lambda 1.015

Higher than 3000 rpm it started to rise hc again to about 250ppm and lambda value 1.03 and higher (limit here 1.03)

this doesnt seem right at all?