Hello. I have a 93 Civic DX that recently started stumbling on a drive over a 6000 foot pass. I've done it in the past without a problem but this time it started with a single stumble...then another...they got closer together. You get the story. It was definitely worse when I accelerated up the hill. I ended up puling over and I could hear out the exhaust a stumble every 5-10 seconds. That has now progressed to a point where it stumbles on any slight increase in gas and is very boggy when driving. I am not sure it can even drive over 35 mph.

I did a compression test and got numbers that in comparison to others I've seen online are quite low...but the thing is they are all consistent. Here they are:

1) 101psi
2) 99psi
3) 100psi
4) 101psi

The car has always been pretty pathetic on power but I never thought much of it. While these numbers might explain the poor performance do they really explain the stumbling? It feels almost as if one plugged was pulled...but as can be seen there is no irregularity in the readings so I would not think this would be the case.

Just to mention I have also replaced the distributor, coil, cap, and rotor at one point and there was not improvement. On the electrical side I am down to plugs and wires. On the fuel side all I can think of is fuel injectors.

One other side note. Just before I went on this drive I filled up my tank (about 6 gallons). My first concern when this was all happening is that I maybe got bad gas. The next day after getting back I removed all the fuel and put in fresh fuel from another station. It ran with no hesitation or stumbling. I even ran up the same pass fairly hard for about 10 minutes. It ran fine. I was so confident that I drove straight to the gas station to make a complaint. Here is the thing though. When I got back in the car after my discussion with the gas station attendant (about 5 minutes) the car slightly stumbled. I got home and by the next day it had gotten worse to the point is now.

I have no clue whether this could possibly still be fuel related, but I guess at the least I would like to know whether anyone else sees these compression readings as a possible cause.

Thanks

 

check the Catalytic convertor

 

You didn't mention the CEL at all. Is it on? Does it work?

 

135 is minimum for a healthy engine. Time for a rebuild/replacement.

 

Before rushing off on a rebuild or replacement I'd have a cylinder leak-down test performed. Such a test will be able to identify whether you have a problem at all, and if you do, where the problem exists.

For my part I don't believe there is a mechanical issue with your engine at all; the compression numbers are just too consistent.

 

Thanks for the fast replies.

Solster: How would the catalytic convertor cause the stumbling? I ask because there is actually an exhaust leak sound I can hear. I am now curious about seeing exactly where.

jbpnoman: I didn't receive an error code. I have a 93 DX. Does this have CEL. If so, how would one go about turning it on or off? Having a CEL error code would make this easier.

grumblemarc: I agree that the engine is not a it's best performance and probably ripe for having a cylinder finally go, but at this point isn't more of a weak engine as opposed to a dead engine?

shipo: Considering the numbers are consistent, would I expect to see any signs of leakage?

 

A clogged cat won't let the engine breathe, even with a small exhaust leak. This can make the engine stumble. You also said that it's taking some time before it starts stumbling, which makes sense.

Yes. The CEL is the Check Engine Light, on your gauge cluster. It should turn on when you first turn the key, and stay on for about 3-5 seconds.

Old engines wear out. That can create even leaking.

 

Any thoughts on why I haven't had any error codes pop up despite the way the engine is running. Is there a possible cause of stumbling that would more likely not initiate a error code?

To confirm, the CEL comes on briefly during startup but then turns off within a few seconds. If it stays on the there is an error code to read.

 

crappy gas
clogged fuel filter
time for a tune up
faling ICM
oil in the spark plug tubes
oil in the dissy
clogged air filter
clogged cat
any combo of the above could do this and not throw a code.
it's a 93 not alot of sensors are used.

 

How did the spark plugs look? Reading the plugs provides insight into how the engine is running. Test the plug wires with an ohm meter. How long since the wires were replaced? How long since the plugs were replaced? Maybe go one heat range cooler if the plugs look worn/melted especially if you are climbing mountain passes frequently.

Compression should be:

new - 184
min - 135
max variation - 28

Ignition coil primary winding - .6 - .8 ohms @ 77 degrees F
Ignition coil secondary winding - 12900 - 19300 ohms @ 77 degrees F

Plug wires - Replace if greater than 25000 ohms @ 70 degrees F

 

Does this go for any motor? Or just his motor specifically?

 

I'd go with his motor assuming 1993 USDM D15 DX.

 

Solster - Thanks for the list. I actually have or are in the process of checking many of those things. Here is what I have done so far.

Replaced dizzy as well as coil, cap and rotor (all included).
Checked Compression - Low but all consistent
Replaced Fuel Filter
Check resistance on my injectors - 12.2's and 12.3's - good there.
Checked the fuel pressure in the system - 37psi - good there
Ran SeaFoam through injections system
Right now I am the process of cleaning the fuel rail.
Checked Air Filter
Waiting for it to dry up a bit to check my cat convertor.
I did have oil in 2 of my spark plug wells but I thoroughly cleaned the well, plugs, and wires.

I can't get over feeling like just one cylinder, or plug, or wire, or injector is not working properly. I was thinking of buying 1 new plug wire and 1 new plug and try them at each of the four positions. Any thoughts on that idea?

Does anyone else believe that while consistent readings of 100psi are low, that perhaps this engine has been running this way for some time and that the issue is most likely not related to my engine itself (cylinders, valves, head gasket, etc)?

 

If your doing the test correctly, 100psi is too low, and will be in need of reboring/resealing.

Is the engine misfiring? What do the spark plugs look like? It will probably be hard to tell if there is oil in the holes, it will just coat them.

Check crankcase pressure, and does your engine oil smell rich of fuel?