I have a 1998 Odyssey purchased new. The car has been absolutely stellar. The only actual “repair” was a thermostat replacement at 83,000. The car now has 133,000 miles.
Last fall (2008), at 122,000 miles, I detected a slight stumble - like the engine was misfiring for a split second. It happened rarely, and only at 40-43 mph under very light acceleration. I checked the plugs and found black residue, instead of the normal light gray/brown. The plugs were new with only 12,000 miles on them.
I replaced them, but the problem remained - the same occasional hesitation, within a very narrow speed range, only under the slightest acceleration, and black plugs. I checked around on the internet and found many articles describing the symptoms. Most of them said the problem was most likely in the EGR system.
I took the car to the local Honda dealer. The mechanic drove the car and verifed the problem. They diagnosed the problem as a dirty or faulty EGR valve/system. The repair estimate was over $400 for an EGR “kit”, consisting of a new valve and cleaning the system. That seemed like an awful lot of money, since I already knew that replacement valves were $130-150. Even if Honda charged $250 for the same thing, that left about two hours labor. I asked what exactly they cleaned and got a vague “all the lines and tubes”.
All my research evidence points to a problem with the EGR system, notably carbon buildup and clogging in many makes and model cars. I found numerous Honda articles, advice columns, service bulletins, extended warranties, etc. I have step-by-step pictures of cleaning procedures for some 4 cyl Accords and V6 engines, including the “pipe kit” replacement for the 1999 Odyssey V6. But found nothing for the 1998 Odyssey 4-cyl engine. My intake manifold seems to have but one EGR vacuum port, and no other “lines and tubes”.
Following common advice for other engines, I removed and cleaned the EGR valve with carburetor cleaner. I blocked off the exhaust side port to the valve, started the engine, and sprayed carburetor/throttle body cleaner into the vacuum side port, and replaced the valve. Then I replaced the EGR valve and repeated the cleaning. The symptoms remain. and are getting worse. Now the stumble can happen 38-45 mph, and it’s harsher. Last fall, the hesitation would randomly appear, then disappear in a fraction of a second or with any change in throttle position - up or down. Now it occurs routinely and can last a second or two.
I’ve read the EGR system description and troubleshooting in the service manual. I don’t know if the Honda mechanic did any PCM diagnostics. The service rep did not mention any P0401 or P1491 error codes, and the “check engine” light (which does work) has never come on.
1. What precisely is the problem? What am I missing? What exactly needs to be done?
2. The factory service manual says the EGR valve is controlled by the PCM (computer), which gathers data from from he many sensors. Is it possible that one of the sensors needs replacing, even thought no “check engine” (MIL) light has come on? Maybe just an O2, TP, or MAP sensor?
Although I’m not a mechanic, I do my own maintenance, brakes, valve adjustments, plug changes, etc. The car has never been “tuned up” per se. I still get the same mileage as the day I bought it: 29/30 mpg in city and mixed driving, dropping to about 27-28 on Interstate trips, cruising at 75 mph. I’m convinced there’s one specific thing that’s causing the problem, and a $400 shotgun “kit” solution really isn’t necessary.
“The only actual “repair” was a thermostat replacement at 83,000. The car now has 133,000 miles.”
If that’s true you’re riding on borrowed time.
Has the timing belt been replaced? If not, I’d worry much more about that than the hesitation. If that eleven-year-old belt breaks the engine will suffer significant internal damage, and the $400 EGR kit will look like pocket change.
I’m VERY easy on the car, and maintain it religiously.For example, I first replaced the front brakes at 122,000.
But back to the topic at hand: What about the EGR?
Carb cleaner might not remove the hard gunk that collects in EGR passages.
Have you looked into the ports etc.?
You might have to take off the inkate manifold and other parts and go at them with a coat hanger or other stiff wire.
Did the plugs all have equal blackening?
Does this engine have a distributor? It might be worn out.
Weak ignition can blacken plugs too.
The logic with which you do your troubleshooting is outstanding. It certainly has all the earmarks of an EGR malfunction.
It’s unlikely to be a sensor. The sensors used in the logic that the ECU uses to open the EGR valve are used for other functions. They’re the same sensors used to determine the engine’s demand needs. A defective sensor would not only likely trip its own code, but would cause other problems.
Let me suggest in addition to the hard gunk that Circuitsmith suggested that you look at the EGR solenoid. That’s the pieces that the ECU directs to open the EGR valve when the engine is under heavy load.
Post back.
Bqbama
If you do your own maintenance to include valve adjustments, I think you can start calling yourself a “mechanic” at this point. I know several others who call themselves mechanics who have never adjusted a set of valves. Just for fun, since I’m not familar with your motor, does your system include a EGR sensor as well as the egr valve? If so, have you considered checking the sensor in case it went south? Instead of putting all your eggs in the EGR basket, have you considered any other problem? If the engine was actually missing, you should have gotten a CEL for misfire. So let’s assume for a minute it wasn’t the EGR. Does the stumble feel like it could be in the transmission? Like the TCC locking up or unlocking then suddenly locking up? Is there any RPM indication when it stumbles? I’m thinking it happens so fast there isn’t much of an instrument indication to go by. What about a fuel delivery problem? I’m just trying to think outside the box since you replaced the egr valve and the problem didn’t change for the better. Are air air and fuel filters clean? Have you cleaned the MAF sensor? I would find out if your car has a timing belt vs chain, and like mcparadise suggests, I’d be changing that baby asap if it is original. Keep looking around, you’ll crack this nut.
Carb cleaner might not remove the hard gunk that collects in EGR passages.
Yes, that appears to be the case. As I said in the original posting, I’ve already tried that.
Have you looked into the ports etc.? Yes. I found one exhaust port and one intake port under the EGR valve. But you can’t really see into either. I poked wire up into the intake side as far as it would go.
You might have to take off the inkate manifold and other parts and go at them with a coat hanger or other stiff wire.
Yes. I’m aware of that, having spent two days researching the issue. Can you tell me how to determine if that is necessary? Is manifold carbon build up, in fact, the cause, given so many other possibilities? Removing the intake is beyone my tools, expertise, and time. If it comes to that, I would have take it to a Honda dealer, and that would be expensive repair (to me). Are there easier, faster diagnostics?
Did the plugs all have equal blackening? Does this engine have a distributor? It might be worn out. Weak ignition can blacken plugs too.
Yes, yes, yes, and yes. My guess is that the black plugs are also a result of whatever is causing the stumbling, not the cause of it. Are you suggesting that the problem may not be EGR related at all, but exhibits the identical symptoms? That’s a possibility, but is contrary to what the Honda mechanic said.
The logic with which you do your troubleshooting is outstanding. It certainly has all the earmarks of an EGR malfunction.
Thank you. Everything I’ve learned on my own says it’s related to the EGR system. As you already know, that was corroborated by a Certified Honda Engine Mechanic. However, I don’t like throwing money at a problem without knowing the specific root cause. Honda’s $400 “kit” appears to address various possibilities that all went bad simultaneiously.
It’s unlikely to be a sensor. The sensors used in the logic that the ECU uses to open the EGR valve are used for other functions. They’re the same sensors used to determine the engine’s demand needs. A defective sensor would not only likely trip its own code, but would cause other problems.
Yes, although this very website makes it clear that a bad MAF can cause problems without generating an error code. Do you know if a bad MAF is a known cause of stumbling under the conditions I described?
Let me suggest in addition to the hard gunk that Circuitsmith suggested that you look at the EGR solenoid. That’s the pieces that the ECU directs to open the EGR valve when the engine is under heavy load.
Uh? isn’t the solenoid part of the EGR valve assembly that I already replaced? Remember, we are not looking for generic EGR fixes. We need to be focused on only the 1998 Honda Odyssey engine, the symptoms of the hesitation, and an effective way to diagnose the specific cause…
Thanx for your efforts.
Thanx, Benny. I really need to hear from somebody who IS familar with the symptoms and causes for my specific year, make, and model. Known EGR fixes, often established through manufacturers’ service bulletins and extended warranties, vary with each of those three factors.
After more thought I think it would take excessive EGR to cause hesitation.
First thought is a sticky EGR valve not closing properly, but you’ve changed the valve.
Other possibility is cylinders getting unequal amounts of EGR flow due to a clog in the intake manifold, but the equal appearance of the plugs rules it out.
I no longer think it could be a clog anywhere else in the EGR path.
“Are you suggesting that the problem may not be EGR related at all”
Yes, a weak spark could cause hesitation and soot on the plugs.
Years ago my '88 Accord developed a midrange stumble. At the suggestion of a friend )who was a top mechanic at a Honda dealership at the time) I replaced the distributor. Problem solved.
I’m just saying it’s possible the mechanic you went to was wrong.
At any rate the engine is just not misfiring enough to set off the check engine light.
You are right in your responses to me, and kind in your responses to me. I tip my hat to you out of respect.
While I would expect a bad mass airflow sensor to present additional symptoms, it is a possibility.
At this point I’ll gracefully exit and leave the actual Honda experts to help. But I wish you the best.
Interesting. I’ll check the distributor, but I’m wondering why the weak spark would occur only under the very narrow operating range and throttle position I described. And why a new set of plugs wouldn’t change the symptoms, at least temporarily?
Can you explain what “excessive EGR” means?
Is it likely that the cylinders are equally affected by an EGR restriction in a single vacuum port that is subsequently split and diverted to individual cylinders? If so, I would expect the plugs to appear the same. I can’t find a picture of the intake manifold internal passages for my engine.
I truly appreciate your thoughtful help. By any chance are you an experienced Honda engine mechanic?
“Can you explain what “excessive EGR” means?”
Too much exhaust gas being fed back into the intake, which can cause hesitation and misfiring.
The EGR path in the intake manifold branches into 4 passages. If they get unequally clogged the total amount of EGR could be OK, but one or more cylinder could get too much gas.
“By any chance are you an experienced Honda engine mechanic?”
No, but I’ve known one for over 20 years.
First, thanks to everybody who offered good leads and suggestions. I sincerely appreciate it.
As it turns out, the “stumbling and hesitation” was in fact the torque converter lockup - quickly engaging & disengaging.
I changed the transmission fluid, and the problem disappeared. Amazed the hell outa me.
Again, thank you all.
That was an excellent call by bennyandthejets. It DID answer the question, "Why isn’t the stumbling lighting up the engine sensors, like “misfire P0300” or something? Answer (as you discovered), it WASN’T a problem in the engine.
NOW, you can concentrate on changing that overdue timing belt. Good luck.
You have become fixated on the EGR system. Big Mistake. A plugged EGR will not make an engine stumble or misfire. When you request acceleration, (step on the gas) the EGR should close instantly. The ONLY time it should be open is at constant throttle, high manifold vacuum, cruising speed. At idle and under acceleration, it should be closed. Disconnect the egr valve and see if that makes any difference in the misfire. I think not.
Now that we have eliminated the EGR as the cause, we can move on to other suspects, like a mal-adjusted throttle position sensor or a dirty airflow sensor or dirty injectors or low fuel pressure…
How does it run when at WOT, right up to the redline??
Remember everyone: a tech at a Honda dealer diagnosed it as an EGR problem.
That’s justification for the average person to get “fixated on the EGR system.”
You’re exactly correct. The “fixation” barely qualifies as an oversight, much less a mistake. Many people still don’t distinguish between a good decision and good outcome.
All the information I found pointed to a faulty EGR system causing the symptoms I described. There are scores of such articles, blogs, advice websites, etc., for anybody who looks. Now, add to that the same conclusion reached independently by a Honda certified mechanic.
FYI, I also posted the problem here:
http://www.2carpros.com/forum/1998-honda-odyssey--1998-honda-odyssey-egr-problem-vt361752.html . Clearly, the Certified 2CarPros Technician implicitly agreed with the EGR theory.
(Be sure and read his last posting on Thu Oct 29, 2009 2:46 pm.)
So… if you’re standing in the middle of Texas and hear hoofbeats, what comes to mind? A zebra? Or a horse?
Finally, I’m not sure why I should pursue “other suspects” when the problem has already been fixed. The car is smoothly and quietly purring along like the day I bought it - 11 years ago.
HIndsight is always 20/20.
Again, thanx to all.
bgbama
Agreed. Benny planted the possibility, which I honestly dismissed in light of most information pointing to the EGR. Likewise, I didn’t pursue Benny’s suggestions either - that the hesitation arose from the air filter, fuel filter, or MAF sensor. While admittedly “possible”, they seemed like long shots, too.
There have been numerous Honda TSBs on EGR-related “hesitation and surge”, resulting in repair procedures and extended warranties for precisely that problem.
And, as Benny observed, there were no transmission codes or tach fluctuations, perhaps because of electronic “dampening” to prevent false positives.
So it’s true that Benny called it, embedded with other “calls”. But when looking at the many responses i received (and on http://www…61752.html as well), a person has to weigh the evidence, so to speak. Benny asked if my car had an EGR sensor (it effectively has a dozen EGR sensors), and candidly admitted he was unfamiliar with the engine. That’s a good thing, as it allowed me to use his input in perspective with several others I received.
In a fantasy world there’d be a score card for each responder, which had their batting average for specific single diagnoses. Such track records would help people who are floundering (like me) to weigh the inputs, but it’s just wishful thinking… 
I’m grateful for ALL input!