'99 Honda Headscratcher

Our '99 CRV (108K miles) continues to vex. Here’s what’s been done so far…

At the dealer:

-Replaced the burned spark plugs

-Replaced ignition wires

-Replaced distributor cap & rotor

-Replaced air filter

-Replaced the PCV valve

-Removed IAC and cleaned “a lot” of carbon out of system

-Compression test was normal

The independent shop:

-Checked electronic components

-Cleaned idle speed solenoid

-Replaced timing belt (it was visibly loose & out of sync)

-Replaced worn tensioner

-Replaced Water pump

After all this was done, the Check Engine Light went on as I was backing the car out of the shop. The codes were P0170 and P0172 (rich mixture). The car is running smoother, but it still stalls at idle. It’s a manual transmission, so I’m thinking of growning a 3rd foot to help juggle downshifting, braking, AND trying to keep the RPMs up…

Any ideas? This problem has so far stumped 3 different garages.

To clarify the problem: we brought it in 6 weeks ago for rough idle/stalling at idle. The shop did a complete tune-up. 6 weeks later, more stalling and hesitation on acceleration. The CEL went on, and the car computer reported multiple misfires. That’s when we brought it to the dealer, and had the work done that’s listed above.

There is a service bulletin for your car, for these symptoms, which the dealer should certainly be aware of. It concerns the exhaust valves receding into the cylinder head, and the fix is a new cylinder head.

The bulletin, 03-038 Nov 05 2004, mentions Honda dealer ‘goodwill’ repairs on vehicles out of warranty. The problem can be verified (and sometimes even rectified) with a valve adjustment. A compression test would also be a good step. Once again, the dealer should know about this and have already tested it. Why were the plug wires burnt?

Thanks - none of the shops we’ve brought it to so far thought that was the problem. We do have a printout of the bulletin & have shown it to each shop, including the dealer. A compression test resulted in a reading of 148 135 psi, which the dealer said was normal.

Even if it was the valve lash problem, the dealer doubted that Honda would extend a goodwill warranty on a car this age with a history of independent shop (not dealer) service. I did some poking around on the internet and what I found seemed to confirm that conclusion.

If replacing the head doesn’t fix the problem. I would guess to change the engine computer or fuel injector(s). Remember it’s guesswork.

Also, we’re not sure why new plugs would be black, but the new mechanic said it’s because of the “running rich” issue. He also looked at the valves/head & thought they were okay. I actually suspect that some unnecessary work was done at the dealer, since some of the parts they gave us back looked fine.

yes, guesswork, sigh. & every guess is costing more and more $… it’s really adding up! although the timing belt and tensioner definitely needed to be replaced; the new guy took photos, which showed the teeth in the belt totally out of whack, and the little marks on the gears out of alignment (I gather they are supposed to match up).

The ODB-II diagnostic system is great, but not perfect. For instance, it does not monitor the fuel delivery system. The code P0170 is for fuel trim malfunction, which sounds like th computer has trimmed back the fuel pulse as far as it will go. Code P0172 is for system too rich. It sounds like the injectors are simply pumping out too much fuel. One reason could be the fuel pressure is too high, due to a bad regulator. This is easy to check with a fuel pressure check. I’ve seen this on a few vehicles, including a Ford SUV last year. When I hooked up the fuel pressure gauge, it was fluctuating between 20 psi to 100 psi! The idle fluctuated with the pressure, and every time it went to 20psi, the idle smoothed out, then almost stalled every time it spiked to 100 psi, spitting black smoke. A new regulator fixed it.

I don’t know the specs for your car, but 148 135 sounds kind of low to me.

100psi,and black smoke. hmmmmm! very interesting, please tell me more about fuel trims,I don’t get the term.

I wondered about that… but the dealer said for this model it was okay.

YOU BETTER RE-CHECK, Hondas run very high compression, same as the bikes.

I strongly disagree with your dealer about the compression readings. Both the 135 and 148 are comparatively low for a Honda.
Most modern cars with good compression run in the 175 PSI and up category.

Tight valve lash can cause this and if that is the problem it’s also possible that adjusting them may not help much. Tight valves, especially when it comes to the exhaust valves, will burn very quickly.
This also affects the manifold vacuum which in turn affects the idle, fuel mix, and everything else.

The valve lash should be inspected and the compression rechecked. These guys should know this and a “complete tune-up” means a valve lash check and adjustment IMHO.
Adjusting tight valves is similar to closing the barn door after the horses got loose; it can be an exercise in futility.

Thanks! I’ll run this idea by our new mechanic.

The new guy said he “visually” checked to see if the valves had receded into the cylinder head, but they looked fine. Is that enough of a check, or is there more that should be done? I don’t know why everyone so far has been reluctant to consider the likelihood that valve lash is the problem. I don’t suppose there is some way I can easily check for it myself…?

I also don’t buy that bit about “visually” checking to see if the velves had receded into the head but they “looked” fine.
This statement is nothing more than utter nonsense and not possible anyway.

As to why everyone is reluctant to consider valve lash I have no answer for that. The compression readings you were given are not normal and when this occurs on a solid valve lifter engine (any engine) the valve lash is something that should be considered right off the bat.

Inspecting and adjusting valve lash is a bit technical for a novice and without knowing how deep any mechanical inclination you have goes, it’s difficult for me to advise you whether you should attempt this yourself or not.

IMHO, the bottom line is that these people are overlooking the obvious and choosing to throw parts at a problem. Granted, you probably need some of those parts but those parts probably failed due to poor engine performance caused by low compression. Low compression eventually leads to plug misfire which then leads to failed plug wires which then leads to… See where this is going?

What should be done right now is inspect/adjust the valve lash and then recheck compression. If the compression remains lowered then a leak-down test will determine if the problem is caused by burned valves or something even more serious (piston ring problem). Hope some of that helps anyway.

Re: not monitoring the fuel delivery system…are you sure about that? I’ve been looking at some diagnostic scanners for OBDII and they list the following items (and more) that can be monitored in real time:

? Engine RPM
? Calculated Load Value
? Coolant Temperature
? Fuel System Status
? Vehicle Speed
? Short Term Fuel Trim
? Long Term Fuel Trim
? Intake Manifold Pressure
? Timing Advance
? Intake Air Temperature
? Air Flow Rate
? Absolute Throttle Position
? Oxygen sensor voltages/associated short term fuel trims
? Fuel System status
? Fuel Pressure

I may be wrong, but…