Engine stumbles at 3000 rpm

[bkcorso]

Using the search I found a few references to this but no solution. when revving the engine slowly, at 3k the engine stumbles, the check engine light comes on. If I push it past 3400 rpm it's fine and the light goes out. If I snap the throttle to 5500 rpm it briefly stumbles(like a hiccup) at 3k and the light comes on briefly then goes out, and on the way back down to idle, same thing at 3k. No codes either. any ideas ?

88 accord lxi 2.0 fi Auto.
plugs, cap, rotor, wires, filters are new. I will clean out the intake with some cleaner this evening.

[danronian]

I have basically the same problem with a real bad stumble from 3-3500RPM. I replaced everything tune-up wise except for the 02 sensors just b/c I didn't want one to break when I needed to drive the car multiple times per week. That is probably also your problem. I'll let you know if it helps in about 2 weeks when I plan to replace them. I replaced the coil, plug wires, cap, rotor, plugs, fuel filter, air filter and I still have this problem. Other than the 02 sensors I have no idea what could be causing it? I have posted about this many times and no-one else on here seems to have the problem or know how to fix it other than the sensors, which probably is the problem. Also my mileage has gone from 29 to 24 since I had this stumble start, you probably have had something similar happen.

[bkcorso]

There is a way to test the O2 sensors with a voltage meter, I worked at a shop in the early 90's and I do remember that. I just hate throwing parts at the car hoping it will fix it. I'll do some research to see what I can find. I remember one of the sensors was responsible for transition from low to high rpm. It's seems to be too specific to be an O2, but with electronics ya never know. I'll keep diggin, and mabye we can figure it out.

[Jareds 89 LX-i]

Almost sounds like a throttle position sensor with a dead spot. I can't remember offhand but I believe the service manual has a procedure for checking the resistance of the sensor to make sure it changes smoothly without dead spots from closed to fully open. May want to give that a look

[bkcorso]

I was looking into that, but it not really related to the throttle position. It happens when you slowly creep up to 3k, or wide open throttle. Whenever 3k is hit it happens.
Almost makes me wonder about the distributor. I'm not sure of the internals though.
I got to start somewhere, I'll put in some old plugs and clean out the intake, and check the tps. I'll keep updating with what I try.

[FyreDaug]

If its only at a certain rpm range I wouldnt consider internals to be a factor

[mouchyn]

if the CEL light comes on, there should be a code in the ECU. did you physically look at the ECU to see if there are any codes blinking? maybe get someone to rev the car to 3k rpm while you look at the ECU?

that code would help out a whole lot.

[bkcorso]

FyreDaug , I didn't think there was anything internal that would cause this, I was referring to the internals of the distributor, when I put the rotor button on , It felt like something was putting tension on it. I am going to dig into it today.

mouchyn, I'll see what I can do with getting a code, it flickers while it stumbles. makes me think a sensor is picking up the effect of the stumble, not the cause, but if I can pull that damn code it may point me in the right direction. ( have to get a midget to work the throttle with the seat all the way forward ) :)

[mouchyn]

short women are good for that ;) unfortunately, my fiancee is almost 6 feet tall, so she doesn't help me much.

as for the flicker... the CEL isn't suppoed to flicker. It's supposed to come on or stay off. If it's flickering... man, i don't know. I don't think the ECU is telling the dash light to do that. That might be happening because of a freak electrical problem.

have you noticed any other weird problems with the car that seem unrelated to the stumble? dimmed lights? broken indicators? weird sound from the "dingers?" poor gas milage? smelly exhaust? black stuff building up on your muffler tip and bumper?

[mouchyn]

oh, i was thinking about the distributor, too. I've had one go bad before. The vacuum advance diapghragm was bent of creased or something and wouldn't work at certain engine speeds. It would get stuck or something and the increased vacuum sort of jerked it along to the next "stuck" spot.

does that make sense?

do you have another dizzy to try?

[bkcorso]

mouchyn, That is exactly what came to mind with the distributor, but I think I eliminated the dizzy for now. after about 2 cans of carb cleaner the 3k stumble is gone. it will still stumble, but it is random now. my guess is a sensor in the manifold.
I have to put the good plugs back in to see what changes are made, but the idle was up quite a bit, aprox 1250, but very smooth.

Now the bad news, I got the light to stay on, and went to check for codes, and the light was steady red !!! I may have an ecu issue, or a ground problem, I remember reading through pauls manual and seeing this , I'll have to find it again and see what to do, but doesn't sound good.

I haven't been driving it because I just put in a new engine, and I don't like to drive them until all the bugs are fixed. I did take it around the block, but that is it. I'll keep it updated, one thing I found searching is a lot of threads that the poster never came back to tell what fixed the problem.

[mouchyn]

gotta love when the thread author just disappears when he fixes his problem. really helps the rest of us out.

have you tried resetting the ECU since you dumped 8 gallons of carb cleaner in there? try setting the idle speed once everything gets warmed up, too.

[bkcorso]

Well, I put the new plugs back in, and the stumble was erratic, as was the idle. The good news, the ecu threw a code at me, #5 the map sensor(thanks to Shep's sticky) which is $175 from autozone, please tell me there is a way to clean this ? I'll reset the ecu and see if it comes back......till next time, as the 3geez spins. :rofl:

[mouchyn]

just about all honda map sensors are interchangable. just go you the junk yard and grab a handful. i had a rather large collection of them when i was driving my preludes. those 3G preludes would chew through map sensors for some reason.

[bkcorso]

Well, I reset the ecu, and it wouldn't throw the code again, yet the cel would still flicker/stumble erratically throughout the rpm band. it is sounding like an electrical problem, I grabbed a piece of pvc so I could mash the throttle while watching the red light, and it flickers as well, when ever the engine stumbles it flickers. I'll go through and check the connections in the bay. My thinking is it can't throw the code because whichever connection is loose/bad isn't allowing the ecu to catch it. :dunno: I've also read that a funked up coil will do these things too. Back to work !!!

[mouchyn]

if the red LED on the ecu is flickering, then there is definitely something wrong. Call around to some local junk yards and see how much they'll charge you for an ECU. I can get 'em around here for about $20. I would much rather spend $20 to eliminate the ECU as the problem before i spend hours and hours getting friendly with a multimeter trying to track down a ghostly electrical issue.

[bkcorso]

mouchyn, where do you live ?? they are 75-250 out here, and at least a 2 hour drive to get one !!! I'm gonna check a couple of other things first, but I may be running out of options. I replaced the throttlebody, and the thermal thingy behind it, no dice.
Swapped the dizzy, not a bit of difference. I'll go to the O2 sensors next, since it is very erratic now. The idle also jumps around a bit. If this doesn't work I'll have to get a map sensor and an ecu. yeah for me. :ugh:

[shepherd79]

If the light on ECU stay on all the time, it is time to get a new ECU. i may have one somewhere but i am not sure.
if you get #5, map sensor, it is located inside the black plastic box. it is a small rectangular black thing with one vacuum hose and electrical wires attached to it.
You can get them cheap at junkyards. You can get them from any honda, but you will have splice the wires with a plug, so your best bet is to get one from 3G. Less problems in the future.

[bkcorso]

Shep, the light will go off, and the code hasn't come back yet. When I do get the cel to stay on the red led on the ecu is steady as well, if I goose the throttle a few times they both go out.

Swapped the O2's no change. I'm gonna call it a day. Do some research and hit in the am again. I'll try to figure out if it's fuel or fire getting cut. I'll be back !!!

[shepherd79]

get the shop manual and check the Throttle position sensor.
if that checks out OK, try new ECU.

[w261w261]

FWIW, I had the stumble problem at about 3000-3500 rpm, but not real bad. I let it go and finally it got hard to start. It was the TW sensor, about $18, it's mounted near the thermostat. That was the only thing I changed, and it cured the problem.

[bkcorso]

I checked the tps and it's in range 5.08 kohms, I had replaced the whole throttlebody unit, so I checked both, and they are within range. I'll check the tw sensor next, and when the yards open I'll go get an ecu. How would one go about finding what is triggering the light ? I don't have many sensors left, what's the chance of a funky relay ?

[whowasdat]

quick question, if your engine idles at like 2500 rpms and you pull back on the gas pedal is it suppuse to drop it? if not can someone please tell me wats goin on wit my f'n car?

[bkcorso]

whowasdat, it should drop, fast idle should only be 1800 rpm, then after warm up around 850 rpm, what other symptoms are you having ?

[mouchyn]

quick question, if your engine idles at like 2500 rpms and you pull back on the gas pedal is it suppuse to drop it? if not can someone please tell me wats goin on wit my f'n car?


you might want to search a little. there is tons of info on idle problems around here. if you can't find what you're lookin for, start your own thread. don't jack this one.

[bkcorso]

mouchyn, thanks , I should have mentioned that to him.

Update, so far I have replaced the following with no change,

plugs,cap,rotor,wires & filters
throttlebody w/tps & fast idle valve
dizzy
both 02 sensors
ecu
vaccum control box (map sensor)
ignition coil and resistor
The resistor on the drivers side fender (metal box)

I've tested the following,
tps, and tw sensor, both in spec

I'm running out of options, what would be the best way to isolate if fuel or fire is being cut ?
I will also test voltage from the alt, back to basics.

[bkcorso]

Can you see what's wrong? :uh:
http://myweb.cableone.net/bkcorso//Pics/honda/pict0812.jpg

Gotta love it !!!

http://myweb.cableone.net/bkcorso//Pics/honda/pict0813.jpg


I was wanting a hand grenade at this point, but I kept on it. I figured it had to be electrical,( I posted this thought earlier ) only because it was so random with the symptoms, and the cel light flickering, and not giving a code. With the engine running I started tapping all the sensors..no change, then went around and lightly tugged and pushed on the connections, then the harness.

That is when I hit gold, tugging on the big bundle of wires that comes of the drivers side fire wall caused it to stall. I had never stalled before. Then went to the injector harness, (I went there because I had earlier put a screwdriver on them to listen, and when the engine would stumble, they sounded like they would flutter) it stall again, I looked around and saw a spark, and that was the ground wire sparking on the manifold. I had meant to look for loose wires the night before, but was pretty wore out.( No light makes it easy to spot a ground issue, or a spark plug wire arcing )

3days of getting intimate with my Honda....Priceless

I gotta give big thanks to all that help, it kept me focused on tracking down the culprit, and not giving up. Turns out It was me !!! Good news is that now I know where just about every part is under the hood, now I just have to figure out where the valve cover is ??? :rofl: jk

[w261w261]

well, at least you got all that nice new stuff replaced in. :)

[mouchyn]

you know what's funny? I just had the same problem with that ground wire bundle.

when i swapped in my freshly rebuilt engine, i couldn't get it to start. The ECU wouldn't even come on. I tested and replaced damn near everything. I was testing wires at the ecu and found the ground wires had continuity to each other, but not to ground.

I looked and looked and looked and couldn't find anything wrong. I finally gave up and grounded those wires myself and the car started right up. Two minutes after getting the car started, i noticed that same bundle wasn't bolted down. i bolted it down, removed my ghetto wire-tapped grounding at the ECU and everything worked fine.

it's always the simple stuff, huh?

glad you found it.

[bkcorso]

w261w261
well, at least you got all that nice new stuff replaced in.
Great, Now I have no money to put gas in it !!jk


mouchyn, I had a feeling it would be something simple. I also got a crash course on how my Honda doesn't work !!! Thanks again. I've only got one more issue, then it's road worthy. It will be worth it :)

[Oldblueaccord]

quick question, if your engine idles at like 2500 rpms and you pull back on the gas pedal is it suppuse to drop it? if not can someone please tell me wats goin on wit my f'n car?

loosen your throttle cable slightly its to0 tight. Lube the linkage and the shaft.


wp