1998 CR-V sudden erratic idle

[mjsloter]

1998 Honda CR-V running great on the way to school. During the trip home sudden erratic idle and loss of power.
MIL Codes P0303, P0302, P0304, P1399.
New distributor cap, rotor, (plug wires tested within specs), fuel filter and plugs.
Compression test (psi): cly. 1 - 115, 2 - 110, 3 - 115, 4 - 95 .
Valves adjusted. A few tight exhaust valves, intakes were a little loose
IAC valve cleaned.
Still have an erratic idle that varies from 500 to 1,100 rpms. There is about 6 seconds between the rough idle and the "normal" running and feeling (1,100 rpm) idle.
The new plugs are fouled (rather black) but not burnt or oily.
Thinking burnt valves?
Also thinking of having a leak down test performed to check the rings.
I read that this can sometimes be the result of air in the cooling system?
Engine Control Module?
Running out of ideas and patience.
Thoughts anyone?

[Buffalo4]

Definitely a rich fuel-air indication (black fouled plugs).
Doesn't sound like serious burnt valves with those comp readings.
Are you still getting MIL codes?
The P1399 indicates a random misfire, I believe. Those codes could just be from the plugs getting fouled.
Do an ohm reading check on your ignition coil.
Do not turn the engine over (using the starter) with the coil connected (distributor connector) and the cap off or the sparkplug wires disconnect and not grounded because it can cause the coil to arc and internally short itself out.
Any possibility of bad gas? (water in gas).

I would think that air in the cooling system could send a low coolant temp reading to the ecu and produce a richer mixture, but I'm just guessing.
Google for a way to check the engine coolant temp sensor or look it up in a factory service manual.

Perhaps the timing belt slipped a tooth. That could cause a sudden problem also in engine power.

A failing ecu could account for it also. (If you have a junk yard nearby, perhaps you could pick up a used one for a small amt of money, but don't just start replacing parts as it can be very expensive.

Some have had problems with a bad distributor (worn bearing) and erratic idling.

A leakdown test, as you suggested, would be a good idea.

Buffalo4

PS: Driving a vehicle that is running way too rich can destroy the catalytic converter.

PPS: Please post back when you figure it out as it could help others.

[mjsloter]

Thanks so much for the Reply.
I took it in to a local shop last night.
Compression 150 across the board, good news.
I did notice while adjusting the valves that the timing belt seemed a bit loose.
After some diagnostic work (1/2 hr.) the local guy thought that the belt might have skipped a tooth as you suggested (hence explaining the "sudden" nature of the problem).
Told him to proceed as he thought he would have another hour of work. Money well spent if the belt is the culprit.
Will post the final outcome.

[mjsloter]

Final Answer:
Vacuum leak from a blown intake manifold gasket.
I heard a whistle but wasn't smart enough to go down that road.
Runs fantastic after paying for 2.5 hrs. of labor. $264 "all-in", parts and labor.
By the way, 138,000 miles.

[Buffalo4]

Well, you have a newly tuned up vehicle now, adj valves and a clean IAC.
Thanks for posting what the actual cause was.
BTW, did the mechanic change the timing belt also?
Very happy to hear that it is now running GREAT!
Buffalo4

[mjsloter]

The timing belt and water pump were new @ 109K so I didn't think it necessary.

I was referred to a new, good, honest mechanic by a colleague. He very easily could have dug in further and checked and/or replaced the timing belt and soaked me for a few more hundred dollars.

Instead, he heard a whistle, sprayed carb cleaner around the source of the noise (which changed the idle speed) and deduced that the gasket was blown. He said it wasn't necessary to mess with the timing belt.

Nice to find a few good men. They will get more of my business.

[Buffalo4]

Thanks.
Timing belt was new at 109k miles: sounds good unless your present mileage is now 200k miles.
Sounds like an honest mechanic.

Buffalo4

[glm_crv]

2001, 161,000 miles. I adjusted the valves about 30k ago.

On 1st start after a highway trip, I notice very rough idle, and CEL came on flashing after about 15sec. P1399 multicyl misfire.

Replaced cap and rotor (scorched contacts on both) no change.

Comp test 1: 160, 2: 150, 3: 132, 4:160. Is this burned valve territory for #3, possibly just valve adjustment territory, or even significant? I'd say it's significant. I plan to check the valve clearances this weekend.

FWIW, I pulled a plug wire on each while idling, no rpm drop on #4! Swapped plugs #1<->#4, still no RPM. Fiddled with the wires some more and now it's beautifully smooth, with RPM drop on #4, and no CEL.

Resistance on the wires was 12k, 8k, 8k and 6k (roughly in line with their length, but should they all be the same?).


Grateful for any hints or comments.

Thanks.