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CB5000
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Roughish running engine once warmed up

Tue May 31, 2016 11:48 am

I got a weird car problem (1990 Honda Accord) that started suddenly a few weeks ago where the car runs completely fine when the engine is cold, but as soon as the engine warms up, it hesitates/jerks during acceleration, and has rough idling. Also the car has reduce gas mileage as well. Once the car gets to a higher RPM >3000 or so, it also runs fine… but seems like there is a bit of reduced power. There is also no check engine light coming on, but I think with a car this old, only a few things like ignition issues trigger the error codes. So since it does run fine cold, I think ignition issues, fuel delivery issues can probably be assumed to be okay. The only thing that comes to mind is air/fuel mixture ratio just seems off once the engine warms up.

Initially I thought it was the MAP sensor since it isn’t needed too much when the engine is cold, but I did a Vacuum voltage test and the voltage scales smoothly with vacuum and pressure.

Next I looked at the EGR valve which on this car doesn’t open until the engine warms up. Supposedly it only opens a little during idle and up to about 3000 RPM once the engine is warm, and is supposed to recirculate exhaust gas that contains unburned fuel back into the intake manifold. I think because perhaps the valve never opens and the engine never gets the extra amount of fuel into the manifold, it hesitates and stumbles until the engine RPM reaches above 3000. The valve itself seems fine, and after cleaning it with carburetor cleaner it seemed like to runs a little better but still pretty bad.

So now I’m looking at the EGR vacuum solenoid which doesn’t seem to ever engage, which prevents vacuum from reaching the EGR valve and open the valve. I’m not quite sure how to check if the solenoid is defective or not. The car is having some weird electrical problems, and it could be some issues with wiring that is not connected properly/worn out, but so far all the wires I checked have good continuity.

I think the solenoid can also be checked to see if it is shorted out or if the coil burned out, and I could check with an ohm meter, but I’m not sure how much resistance is normal… I’m guessing somewhere around 50 ohms?
 
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Re: Roughish running engine once warmed up

Tue May 31, 2016 11:56 am

Get a cheap ODB II interface for your phone. It will save you hours of hunt and peck if you can read the codes. For $20 it is a worthwhile investment.
 
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Re: Roughish running engine once warmed up

Tue May 31, 2016 12:00 pm

Deanjo wrote:
Get a cheap ODB II interface for your phone. It will save you hours of hunt and peck if you can read the codes. For $20 it is a worthwhile investment.

If the 1990 model year is correct OBD II is useless as it came in for MY 1996. He'll need an OBD I tool and those were mfg-specific as to pin-outs. Best thing to do is to follow these instructions:

http://www.smogtips.com/smog-question/1 ... ble-Codes-
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CB5000
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Re: Roughish running engine once warmed up

Tue May 31, 2016 12:19 pm

As far as I can tell, there are no codes to even read. The check engine light has never lit up.
I could just go ahead and check for error codes though and see if there is anything stored in memory.

So it seems like the problem is something other than the possible errors listed on the error codes for the 1990 Honda accord?
It's also possible that the electronics are defective and the check engine light won't even come on. I can try disconnecting the MAP sensor or the EGR valve position sensor and see if the check engine light will come on.
 
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Re: Roughish running engine once warmed up

Tue May 31, 2016 12:26 pm

CB5000 wrote:
So since it does run fine cold, I think ignition issues, fuel delivery issues can probably be assumed to be okay.


Wrong.
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Re: Roughish running engine once warmed up

Tue May 31, 2016 12:28 pm

CB5000 wrote:
As far as I can tell, there are no codes to even read. The check engine light has never lit up.
I could just go ahead and check for error codes though and see if there is anything stored in memory.

So it seems like the problem is something other than the possible errors listed on the error codes for the 1990 Honda accord?
It's also possible that the electronics are defective and the check engine light won't even come on. I can try disconnecting the MAP sensor or the EGR valve position sensor and see if the check engine light will come on.


The check engine light should come on during start up.
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Re: Roughish running engine once warmed up

Tue May 31, 2016 12:28 pm

Captain Ned wrote:
Deanjo wrote:
Get a cheap ODB II interface for your phone. It will save you hours of hunt and peck if you can read the codes. For $20 it is a worthwhile investment.

If the 1990 model year is correct OBD II is useless as it came in for MY 1996. He'll need an OBD I tool and those were mfg-specific as to pin-outs. Best thing to do is to follow these instructions:

http://www.smogtips.com/smog-question/1 ... ble-Codes-


Good point. Forgot that it wasn't finalized until 1996 and Honda was late to the ODB-II party.
 
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Re: Roughish running engine once warmed up

Tue May 31, 2016 12:41 pm

spiritwalker2222 wrote:
CB5000 wrote:
So since it does run fine cold, I think ignition issues, fuel delivery issues can probably be assumed to be okay.


Wrong.


Another thing it could be is the ignition module.
The ignition module+coil was replaced about 13 years ago. The replacement coil was replaced again a few years ago because it went bad but the module wasn't replaced at the same time. It could be that as the module heats up, it starts to behave erratically, like solder loosening or some other problem.
But again when I had these ignition issues a few years back the check engine light came on and the symptoms were different... where the engine won't rise above a certain RPM ~4000. Right now the engine can easily reach redline once it crosses 3000 RPM. Going from idle to 3000 rpm is the struggle.

Also since the problem started suddenly rather than gradually, seems like some component just died?
 
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Re: Roughish running engine once warmed up

Tue May 31, 2016 12:43 pm

Does this car have fuel injection and oxygen sensors?

If so I would check fuel rail pressure and make sure you are getting the right voltage from sensors.
Poor fuel injector performance (poor atomization) might explain it, but I'm leaning towards oxygen sensor or the cat.

Sensors may be off making the car run really rich which would explain rough idle, poor takeoff power, and reduced fuel economy.

Lastly check your catalytic converter. If you have not gone a straight pipe it may be clogged which would also explain your symptoms.
I would go to straight pipe if the muffler is providing enough back pressure for the oxygen sensor.
Clogged cat sometimes will not throw a code.

Not a car mechanic but I've seen some things.
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Re: Roughish running engine once warmed up

Tue May 31, 2016 1:02 pm

Aranarth wrote:
Does this car have fuel injection and oxygen sensors?


It can be the O2 sensor.
They are cheap so I might as well replace it since as far as I know, it has never been replaced.
At higher RPM, the engine has great power, so the fuel pressure is likely okay?
 
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Re: Roughish running engine once warmed up

Tue May 31, 2016 1:09 pm

I vote O2 sensor. At startup the engine typically uses pre-programmed map. I had a Jeep 4.0L that also went to a pre-programmed mapping at ~80% throttle. If you have an engine code/light it can often be an O2 sensor. My ford '91 300ci inline 6 had an "EGR insufficient flow" code. The EGR valve was replaced and it didn't go away. Turns out the O2 sensor was sending bad info to the ECU, making it think the engine needed more/less EGR.
 
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Re: Roughish running engine once warmed up

Tue May 31, 2016 1:32 pm

The car is 26 years old - have you ever replaced the spark plug leads? I had a Lexus SC400 that started running rough at 90k miles, so I went through the ignition from cheap-->expensive. Rotor and cap first, then plugs, then ingition/coil lead. Finally hit bingo on the leads. It was stumbling and complaining on acceleration, but after the change it idled like a champ and pulled away willingly.

Usually you'll see these problems after a rain or just a spell of humid weather, but these cable were just worn out. It happens, and you can't always tell by looking at the jackets.
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Re: Roughish running engine once warmed up

Tue May 31, 2016 1:39 pm

My 1990 Accord EX was prone to plugging up the EGR valve every 80-100k miles. You might be able to clean it up to unstick it or it could need replacement.
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CB5000
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Re: Roughish running engine once warmed up

Tue May 31, 2016 1:58 pm

sluggo wrote:
The car is 26 years old - have you ever replaced the spark plug leads? I had a Lexus SC400 that started running rough at 90k miles, so I went through the ignition from cheap-->expensive. Rotor and cap first, then plugs, then ingition/coil lead. Finally hit bingo on the leads. It was stumbling and complaining on acceleration, but after the change it idled like a champ and pulled away willingly.

Usually you'll see these problems after a rain or just a spell of humid weather, but these cable were just worn out. It happens, and you can't always tell by looking at the jackets.

Yeah I got a new set of leads only a few years ago when I had some engine problems related to rain and humidity, and the leads were the problem. Probably not the problem this time since weather has no effect on it. Replaced the rotor and cap since the cap was semi-cracked and but no change.
JustAnEngineer wrote:
My 1990 Accord EX was prone to plugging up the EGR valve every 80-100k miles. You might be able to clean it up to unstick it or it could need replacement.

Yeah I cleaned out the EGR valve pretty thoroughly, and still the same problem. The valve it self moves up and down pretty smoothly with manual manipulation. The valve diaphragm seems to be undamaged, and doesn't seem to leak.
Losergamer04 wrote:
I vote O2 sensor. At startup the engine typically uses pre-programmed map. I had a Jeep 4.0L that also went to a pre-programmed mapping at ~80% throttle. If you have an engine code/light it can often be an O2 sensor. My ford '91 300ci inline 6 had an "EGR insufficient flow" code. The EGR valve was replaced and it didn't go away. Turns out the O2 sensor was sending bad info to the ECU, making it think the engine needed more/less EGR.

Yeah I'm starting to think it could be that. MAP sensor and EGR valve seems to be functioning properly and the EGR solenoid appears to be okay but needs more through testing to make sure. According to the service manual, MAP sensor or EGR problems would light up the check engine light, and a O2 sensor that is only partially functioning won't trigger a engine code according to other "online" sources. Once I get home I can take a look at it and see if it is fouled up with carbon deposits or not... ebay has them for only 15$, so I might just go ahead and order one once I'm off work.
 
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Re: Roughish running engine once warmed up

Tue May 31, 2016 1:58 pm

Could be old spark plugs, when was the last time you changed those? Maybe fuel filter, check that. Some heavy duty fuel system cleaning additive might be worth a shot. Could be EGR. Could also be you ICM.

https://www.youtube.com/watch?v=hM7wfyikVEg
 
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Re: Roughish running engine once warmed up

Tue May 31, 2016 2:03 pm

TwoEars wrote:
Could be old spark plugs, when was the last time you changed those? Maybe fuel filter, check that. Some heavy duty fuel system cleaning additive might be worth a shot. Could be EGR. Could also be you ICM.

https://www.youtube.com/watch?v=hM7wfyikVEg


Spark plugs and fuel filter was changed only a few years ago. Tried several kinds of fuel system cleaners to no avail. ICM was replaced about 13 years ago... probably could use a new one.
 
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Re: Roughish running engine once warmed up

Tue May 31, 2016 2:27 pm

On the spark plug front, I was most disappointed when I installed a set of the then just introduced expensive Bosch platinum plugs. The 90 Accord hated them. It ran great on the cheap NGK plugs.
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Re: Roughish running engine once warmed up

Tue May 31, 2016 4:02 pm

Come to think of it, I had an older Acura V6 that started to run horribly when warm. The O2 sensor was mounted on a little flat metal stem off the intake manifold, and some oil from an iffy valve cover gasket had seeped down the underside of the stem and found its way into the O2 sensor, fouling it. It was still sending out readings, but the readings were so far off the engine would sometimes just stall at 20 mph.

I remember it being a rather expensive replacement part, but cleaning the bad one was apparently (according to the Honda guy I spoke to) not an option. YMMV.
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Re: Roughish running engine once warmed up

Tue May 31, 2016 4:05 pm

Another vote for O2 sensor here. If the engine was carburetted I'd immediately have said choke problems but with EFI it's going to be an electonic gremlin and I've had this exact issue from a dead O2 sensor on one of my own cars (a Mazda MX6).

It's possible you have a bad connection somewhere in the fuel injection system and that one of your cylinders isn't squirting fuel properly, but I think then you'd get rough idle when cold too. Honestly, if it's running well cold but not when hot you have one of two problems; electronic air/fuel mix error or a leaky gasket that only fails when the engine expands slightly. You'd know about gasket problems just by checking the oil, so I'm assuming you know enough about cars to already have done that.
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Re: Roughish running engine once warmed up

Wed Jun 01, 2016 9:36 am

Another vote for Losergamer04's idea of the O2 sensor.

The behvaiuor you are describing fits with something wrong with the closed loop running and OK on open loop, so the O2 sensor is a big possibility. They can be a major nightmare to get out of the exhaust, especially if this is the first time it has been replaced in a car that old! Note that they need to be clean on the outside as well as the inside - they work by having oxygen seep through from the outside to the inside - modern ones actually breathe through the wires. When installing it check that any grease you put on the threads is O2 sensor safe, some lubricants can give off gases that will contaminate the O2 sensor.
 
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Re: Roughish running engine once warmed up

Sun Jun 05, 2016 9:05 pm

Here is an update:

Ordered and replaced the O2 sensor and it seemed to have resolved the issue.
I think it was the stock sensor that was originally installed on the vehicle as I had to get a 22 mm impact socket to get it free after multiple rounds of PB blaster to get it loose.... yeah like notfred said, it was a bit of a struggle to get that thing off.

I also replaced the oldish sparkplugs with new a set of NGK ones.

Thanks for the help and tips guys!! :)
 
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Re: Roughish running engine once warmed up

Sun Jun 05, 2016 10:19 pm

Interesting! My 1992 Accord developed very similar symptoms three days ago. I discovered this thread just now.

Symptoms:
Idle and very light throttle are fine. I can cruise around town on ~40 MPH roads and ~1500 RPM just fine so long as I don't exceed a critical throttle application.
Any significant throttle below ~2400 RPM (varies somewhat with temp) produces mild to moderate misfire. Possible smell of rich mix.
Above ~2400, it runs perfectly. The transition from misfiring pig to Honda Powah! is immediate.

Attempted remedies:
Disconnect battery for soft reset of possible corrupted ECU parameters.
Check O2 sensor wiring for wear through or popped connector. All OK.
Pull distributor cap and inspect. M-Ohm plug wires. All OK.
Pull plugs. Check gaps. Drain oil from plug tubes. Clean connectors.
Check fast idle valve. (Pop cover, check for backed out annular ring.)
Block air boost line, presumably deactivating the thing.
Block EGR vacuum line so EGR valve cannot be opened, disabling the entire damn thing.
Pull distributor (the one thing on this car that is dirt simple to access!) No broken or shorted wires found.
Swapped igniter with known good. No help.
Measure coil resistances. Primary uncertain - my meter shows 0.7 ohms (OK), but then slowly drops to ~0.3.
Secondary OK, but since problem occurs when hot I wonder about HV breakdown at temp.
Bought $15 OEM coil at junkyard. No joy. Symptoms unchanged. :(
(Was gonna buy the O2 off the same wrecker for $10 but left appropriate wrench in car. 11AM + Tucson = 105F+ and I just wanted to get out alive!)

To Do:
Check coolant temp sensor R and/or output voltage.
Will return to junkyard for O2 sensor. Sensor was changed about 4 years ago. After a terrific tussle getting it out, I was careful to apply very light torque on the new one. Hopefully, this swap will go more smoothly.

Your O2 solution gives me great hope! :)
Last edited by Geonerd on Sun Jun 05, 2016 10:25 pm, edited 1 time in total.
 
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Re: Roughish running engine once warmed up

Sun Jun 05, 2016 10:21 pm

JustAnEngineer wrote:
On the spark plug front, I was most disappointed when I installed a set of the then just introduced expensive Bosch platinum plugs. The 90 Accord hated them. It ran great on the cheap NGK plugs.


Yep. I think that's true of most Hondas of that era.
 
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Re: Roughish running engine once warmed up

Sun Jun 05, 2016 10:23 pm

spiritwalker2222 wrote:

The check engine light should come on during start up.


LOL! I'll be sure to forward your Imperial Directive to my ECU.

Thanks for all the help... :roll:
 
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Re: Roughish running engine once warmed up

Mon Jun 06, 2016 12:51 am

Geonerd wrote:
Interesting! My 1992 Accord developed very similar symptoms three days ago. I discovered this thread just now.

Symptoms:
Idle and very light throttle are fine. I can cruise around town on ~40 MPH roads and ~1500 RPM just fine so long as I don't exceed a critical throttle application.
Any significant throttle below ~2400 RPM (varies somewhat with temp) produces mild to moderate misfire. Possible smell of rich mix.
Above ~2400, it runs perfectly. The transition from misfiring pig to Honda Powah! is immediate.


Yeah that's the same exact symptoms. Exactly the transitions at 2400 RPM and only when the engine is cold. It was also doing the "critical throttle application" thing too. It's somewhat fine as long it was a idle level of throttle application, but as soon as the throttle was pressed further it started jerking at low speeds, and sputter at higher speeds.
After the O2 sensor replacement, the car is basically back to its normal running performance.
I guess the other problem could be the MAP sensor if your O2 sensor is okay.
 
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Re: Roughish running engine once warmed up

Mon Jun 06, 2016 12:06 pm

Just to throw this one in for people who may find this thread and still have an older car with an air flow meter instead of a MAP sensor: a break or leak in the intake section between the AFM and the manifold can also produce this behavior because the AFM will sometimes read lower than what the manifold is drawing, leading to lean mixture and starve-out. Had that happen on an early Toyota 'A' engine back when.
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Re: Roughish running engine once warmed up

Tue Jun 07, 2016 12:08 am

Little question for you guys with these old Accords - what refrigerant is your AC using? I thought those shipped with R12, which is banned nowadays.
 
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Re: Roughish running engine once warmed up

Mon Jul 18, 2016 6:12 pm

localhostrulez wrote:
Little question for you guys with these old Accords - what refrigerant is your AC using? I thought those shipped with R12, which is banned nowadays.


Yup. While the unit will 'run' with modern refrigerant, it win't be terribly happy or efficient. I think (?) a proper conversion kit replaces the pressure regulating equipment to better tune the system to the new refrigerant's characteristics. If nothing else, do a complete purge when swapping R12 for R134 - the old and new oils don't always play well together.
 
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Re: Roughish running engine once warmed up

Wed Aug 03, 2016 1:22 pm

Quick update on this:
The car developed a new problem where it felt like it was misfiring a lot no matter what the RPM. Turns out the spark plug wires are bad even though they are only a few years old. They were Bosch MAG wires which were pretty expensive so I expected them to last longer than just 2 years. Replaced them with NGK OEM equivalent MAG wires and the engine runs like it used to with a lot of power.

Now there is yet another problem. The car suddenly dies or fails to start up. A jiggle in the main relay switch area under the driver-side dash and the car starts up just fine so I think the main relay switch is going bad again. Before one of the solder joints failed in the relay switch when its hot, and I think it's developing the same problem.... or the solder I used before isn't tolerant of heat cycling, So I'll have to take it apart and resolder the joints with a better solder I think.

Geonerd wrote:
localhostrulez wrote:
Little question for you guys with these old Accords - what refrigerant is your AC using? I thought those shipped with R12, which is banned nowadays.


Yup. While the unit will 'run' with modern refrigerant, it win't be terribly happy or efficient. I think (?) a proper conversion kit replaces the pressure regulating equipment to better tune the system to the new refrigerant's characteristics. If nothing else, do a complete purge when swapping R12 for R134 - the old and new oils don't always play well together.


My car is filled with R134 right now and still has some residual mineral oil in the system. The problem with R134a and mineral oil is that they are not miscible so the mineral oil doesn't circulate with R134a in the system. PAG oil is not miscible with mineral oil either so the residual oil just sits and might clog things in the long run. The next best thing is Ester oil which is miscible with mineral oil and R134a, which is that in in my system right now. It's not as cold as R12 but gets cold enough that it's not miserable in 100F heat.
 
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Re: Roughish running engine once warmed up

Wed Aug 03, 2016 5:23 pm

Yeah, in terms of older Hondas (even my 2005 Civic, early 2000's design), you generally want to stick with the stock NGK stuff for spark.

I will also point out that some of those (ex. 6th gen Civics, 96-2000, probably others) are known for having the main relay fail due to cold solder joints/poor connection. Usually means that the car intermittently won't start, but usually runs fine once started (granted, if that relay goes out, it will stall the car regardless). May be a good idea to replace the relay entirely, assuming you can find an OEM one for that older car.

Even on my 2005 Civic, I had one of those relays act up super intermittently (at least, I think that's what it is - can never be sure with an intermittent issue).

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