Honda misfiring on bank 1, vtec issue?
Honda has 198,500 miles on it and the owner had never performed any maintenance on it other than oil changes. No misfires at idle or power braking. Only misses at light cruise around 40 mph. I thought it was torque converter shudder until I saw the misfire counters. AFR on bank 1 will indicate lean as misfires are felt. All 3 cylinders will count misfires but 2 and 3 show more than 1. I changed the spark plugs and swapped coils front to rear. Thought I heard valvetrain noise and checked valve clearance. Swapped AFR sensors. Cleaned throttle body and MAF. Air intake tube was broken after MAF and replaced it. Also checked for restricted exhaust. So far nothing has fixed it. I am changing the timing belt now because way over due but not expecting that to cure issue since all the marks appear to be lined up. Can vtec operating at low RPM cause this issue? I have no prior experience testing Honda’s Vtec systems. There is no variable valve timing or cylinder management on this engine.
Have you checked for correct EGR operation and clear passageways? I've had that cause misfires on that rear bank during light accel only. You should also be able to watch VTEC operation on your scan tool. That's typically only activated at higher RPM or WOT conditions on Hondas though. Very commonly accompanied by dirty engine oil and a P1259 if I remember the code right.
I have monitored both. No commanded Vtech and egr flows as commanded. The misfires don’t seem to occur in sync with egr flow.
Try in cylinder testing- I've seen a lot of misfires on these engine related to tight valves,
I will do that. I did check relative compression and it was very uniform. I checked and adjusted valves. Some were a little loose but none were too tight.
I would say disconnect the egr valve and road test it . valve lash adjustment is big deal on this honda . keep that in mine
Make sure when doing the timing belt that you change everything. Timing belt tensioners are a huge failure on those engines and this can cause a misfire on one bank due to cam timing being off. The other indicator of tensioner issues is a "flapping" noise when the engine is cold due to the belt slapping around.
I will, thanks. I was thinking timing too because I believe bank 1 would be most effected.
Maybe an injector issue with the lean mixture . You could also try disconnecting the egr valve and road test to see if the misfire is gone. Just a few things I’ve seen that were a little different than your normal cases
Thanks, I added some fuel system cleaner to the tank and have been driving the vehicle for a week. No improvement. I am considering trying some swaptronics and moving injectors between banks. It does not appear to run lean when not misfiring. ST and FT are in Lamda usually see 1.04 and 1.02. I believe that’s adding 6% total?? Not sure
You would not even have to do that. Graph out lambda for both banks and put the pedal to the metal… In Open Loop, O2 sensor feedback will be minimal however, you can see the actual air fuel ratio in the exhaust through the AF sensors. That will tell you right there, if the injectors Are lean on one bank. Grab the low-hanging fruit first, my brother
Am I interpreting the trims on this Honda correctly? 1.04 adding 4%?
Just for my own knowledge would that still work if only one injector was at fault?
Yes, the under fueled cylinder would have excess oxygen to pump downstream. When contacting the air fuel ratio sensor, PCM will See it as lean. The best part is, you have the other, non good bank to compare it to, simultaneously. Be sure to put it in draft format so you can share with us 😬👍
A missing combustion event flows excess air (oxygen) regardless of whether fuel or spark is missing. ps, Go Yankees
Yes, but the AF sensor ms and Rear HO2 sensor data will tell you if the misfire is due to lack of fuel or due to ignition fault
If you hooked a first look sensor to this and check for tight valves this would eliminate tight valves right ??.so many post here to check tight valves . Explain this test.
Randy, valve adjustment was verified
So if you had first look sensor hooked up under test drive could you not see low vacuum to those effective cylinders if egr was the problem ???
Unlikely, FLS only shows “change-in-Pressure” (DELTA)
i will check on monday but i think i have run this test before . with evidence . so if not A VALVE problem and not a egr problem what does that leave . fuel delverary problem ?? current ramp pump or injector flow test ??
I don’t think you can get anything useful from an FLS while driving the vehicle. Especially on a 6 cylinder. Idle is difficult, at least for me. Cranking the engine is the most useful pattern, and then you need lots of practice.
a vacuum gauge is far better in this scenario as you want to confirm HIGH vacuum at idle . honda wants to see 21 inches . one of , if not the highest in the industry . it's more than "important" .
Ok, with the P.S. we can’t be friends any longer.... at least for this 3 game series anyway!
LOL. These black and white uniforms are stupid. Thanks for snapping our losing streak. ;-)
I did this and both AF sensors read around .8 about 12 to 1. No need to worry about those.
I was hoping you’d post the graphed data for everyone to see. It’s good learning-info that can be applied to any vehicle .👍. fad -different from iATN, “Everyone” is here to grow. Would you be so kind, Robert ?😬
Yes I will, sorry Verus battery died. Will do that when I get a chance
Thank you, Robert. That will be very helpful
Graph out misfire data and EGR pintoe position to see if they correlate. That will that Will tell you if the misfires occur during EGR operation. If the PCM cuts fuel for anticipated EGR but, the inert gas never arrives, a lean-condition will be present
Ok I will, but would that effect bank 1 only. thanks
If only bank 1 ports are clogged, sure
What are the fuel trims doing during the event? Do you have any scan data graphs you can post up?
I will record some data after I get it back together. Fuel trims are usually 1.05 ST and 1.02 LT
Check TSB #09-090, have you inspect the spark plugs? Correct oil weight and level?. If valve adjustment is need it inspect the cams and rocker arms very close with magnified glass if need it
When I am looking at a misfire on a Honda, I always connect my low amp probe to the coil fuse with a loop. It's real easy and will tell you if your misfire is a primary ignition miss, or if you should be looking at fuel delivery type misfires.
Were the valves too tight on that bank, especially exhaust? If they were tight for too long there tends to be a ton of carbon buildup on intake and exhaust valves. Also you mentioned noise, we have seen multiple camshaft 'delamination' issues on the J35 motors, especially high mileage or any that have not had regular oil changes. You will be able to see heavy pitting and gouges on the cam lobes…
None of the valves were too tight. I will check for delamination, thanks. Fuel trims seem to hover around 1.04st and 1.02Lt. Have you seen the vtec rockers stick either on a bank or individual cylinder? There are no vtec codes. Vtec is not commanded at the time. Thanks
Here's a thought. Watch bank to bank fuel trims during the misfire (closed loop). If one bank is going positive and one going negative the negative one is the bad guy. From there look for clogged cat on that side, cam timing etc. basically anything that would reduce airflow through that bank only.
.........Misfires can be caused by ignition or fuel delivery issues. Fuel trims may help point you in the right direction. What if the engine has an exhaust that incorporates catalytic converters for each bank and one side is restricted? But also verify egr valve operation you can actuate it, and it might have gotten stock close or open....... Check.
Disconnect egr valve and drive. Got to believe egr ports are restricted. If so, pull intake and clean.
If not, simply leave disconnected until issue is resolved. Certainly won’t hurt anything.
Disconnected egr can cause a piston failure do to much heat
Short term for testing? Not a chance.
I don’t think this is likely, Randy. I’m not saying it’s impossible but I’m quite sure if it was bad enough to don”that”, PING would be very evident prior to any sustained damage
Not always . I have seen shops disconnect egr for testing and miss fire goes away . And leave it unpluged and tell the customer that it is another problem not to worry in tell smog is do . Egr flow changes cylinder cubic inc . On fords if egr is not working properly you can burn a piston . Butt just my observation . Shops who disconnect stuff to get ride of original com plate is not un common …
Wow! Good to know, thanks Randy
Check the condition of the spark plugs and replace if necessary.
I installed a new timing belt, water pump and related components. I checked EGR passages and all were clear. Still has misfire on bank 1. I previously checked both banks for restricted exhaust with back pressure gauge. But I did unplug the EGR and test drive the truck and didn’t appear to misfire anymore. Misfire counters stayed at 0. I wonder if the misfire monitor runs with the EGR unplugged?
Forget the misfire monitor, how did the trims behave before vs after the EGR was disabled? And did it remain in closed loop? you said you “checked” the passages...do you mean each individual pencil-lead sized hole at each intake runner?
Please don't take this the wrong way, but this is getting to be amusing watching you and others flounder around, running around like a wild man with your hair on fire trying to fix this problem. Many years ago, Snap on, along with other scan tool manufacturers came out with a wonderful feature. This sort of magic feature was the ability to graph scan data. Many years ago, back in the iATN days…
I have to agree with Albin. Considering he has been using data like this to derive a diagnostic direction, right from the driver’s seat. What we have been offering to you to give you a direction (without disassembly) will save you lots of frustration , wasted time/money. Robert, please Don’t take Albin wrong. He is doing his best to not only help you to provide a direction with this vehicle …
Do you remember snap on scan graphics . For the brick great tool
I have To say , “ that was before my time” but the ability to graph changed my career
Ha ha ha . I now im showing my age .
Ya I now . But thanks for what you do with these new tecks . You to will get old
Not yet, will post some data though. Thanks
It does run fine with the egr unplugged. I checked and the egr passages were clear. Back pressure gauge showed almost no pressure at idle and around 1 psi at 2500rpm on both exhaust manifolds.
Here is a screen shot during a bank 1 misfire and it occurs just after egr is commanded. The spike at the end on both banks is the fuel cut. This Honda fuel cuts hard. As soon as you lift the throttle, it feels like a miss.
Perfect! see how easy that was....always grab the “low-hanging” fruit first. This diagnosis , using scan data (instead of running-around crazy) will take you less than 10 minutes (with practice). NOW YOU HAVE JUSTIFICATION to remove the plenum and go clear those clogged ports on the rear bank 👍
nice capture. See how much time that saved? Oh, and you didn't even have to get your hands dirty either!!
Beat ya , Albin! (Our minds think alike 😬)
A screenshot at wot showing both banks rich
It is normal for both banks to be rich at WOT, the system is running in open loop, and in the fuel enrichment mode.
Yep, exactly what you want when you are pulling-out into traffic (especially with Albin approaching fast ,in a log-truck)👍
Just a shot of the misfire counters. Cylinder 1 is always has fewer than 2 and 3. Bank 2 counts a few misfires but never sets a code.
Robert, not a pic of your particular engine but this shows how the EGR ports can get clogged. I believe on your engine you may also have a small diverter part on the open section behind the throttle body with a couple nuts holding it down.
Yes, this is what I meant. The ports can get clogged individually
Thanks for the pics. I get the vehicle back on Thursday. I’ll post some pics and hopefully some good data. Thanks for everyones help and advice. I didn’t realize the pcm cuts fuel for EGR flow.
think about it... EGR fills the cylinder (to basically make the effective-area smaller) when the EGR fills the cylinder, fresh-air (O2) is displaced. if the fuel was delivered as if EGR was not introduced, the cylinder would be very rich. The PCM cuts the fuel to match the cut-O2. This is why pintle-position is necessary does this make sense, Robert?
Yes makes absolute sense, thanks again.
Bob, since this engine is using a MAF sensor to measure the airflow into the engine, the PCM uses this data to calculate the fuel needed to be injected. When the EGR valve is open, inert flows into the cylinders and displaces air/fuel mixture. Since the EGR is displacing air, the airflow into the engine is lowered. The PCM will only inject fuel, calculated from the input of the MAF sensor. The…
Very true . So egr does what to vacuum reading ? High vacuum or low.
So if egr drives it high . Is the vacuum reading low or high . Explain to young tecks
With the EGR VALVE opened, the exhaust stream is connnectes To the intake manifold. This creates an internal vacuum-leak. The MAP sensor voltage is “low” during periods of string-vacuum. When the EGR valve opens, this “vacuum-leak” lessens the strength of the manifold-vacuum Ana the MAP signal will begin to rise as a result.
there is no such thing as vacuum. In this world we only work with pressure. Learn what MAP (manifold absolute pressure) is and how it works. 14.6 PSI is atmosphere. anything lower than that is a negative pressure. Anything higher is from a boosted engine.
What I mentioned above was regarding speed-density systems, Robert. A lack of EGR dilution will make the cylinders (with restriction) lean. As Albin mentioned, on an MAF-strategy vehicle, a lack of EGR “equally” to the cylinders will cause no change in trim. However, the MAF is input for fueling both banks equally. If only one bank has restricted ports, that bank will indeed be “lean” and fuel…
So if egr flows to 3 out of 6 cylinders . What would excessive egr flow to three cylinders be . Blow the flame out . But this is just my observation. Over the years
Depends on severity of dilution. Here is a taster ignition pat displaying dilution on a cyl(s). Can you find the over-diluted ones?
Excessive EGR results in a density misfire. Basically the density of the air fuel mixture in the cylinder is diluted by exhaust gas to the point of either poor combustion or no combustion at all.
Robert, did you come up with a fix for this vehicle?
… I wondered the same, Brandon
No, I did not. I removed the intake and EGR passages are clear. The misfires go away with the EGR unplugged. It sets a code for bank 2 inefficiency and the egr tube originates from the base of that cat. Could a slightly restricted converter cause this on the opposite bank? I did check with a back pressure gauge on both banks and they were in good. It doesn’t feel restricted.
Ok fuel delivery problem . Do fuel pressure drop at each cylinder
I would current ramp injectors first