random buck/surge between 20-40mph
 

Hi all hope you can help me, been scratching my head on this one. Overall b16a2 engine health for its age is great, apart from this issue it runs well, pulls well in VTEC, no smoke, services are done every year and mostly with genuine Honda parts. Car has done 117k miles original engine and is stock apart from a aftermarket exhaust manifold.

1 month ago it started to develop a minor (best described) buck or surge during accelerating between 20 and 40mph, mainly in 2nd and 3rd gear. Happens when you floor it or gradually getting up through the revs. It idles perfect both cold start and when running, this issue doesn't happen any other time.

about 1 month ago it threw a CEL which diagnosed as primary o2 sensor failure. This has since been fixed with a Denso O2 sensor which was recommended by Honda and now light has gone off and hasn't re appeared. In pursuit of narrowing the potential fault here is what has been changed recently:

* changed spark plugs with NGK plugs part code specific for this engine

* oil drained and new oil

* new genuine Honda oil filter

* new fuel filter (NOT genuine Honda, parts store gave me a cheap brand, after some difficulties with fitment and sealing the top banjo bolt from fuel seep with correct washers) I have a genuine Honda fuel filter on standby if it needs swapping out

* coil plugs renewed 1 1/2 years ago

* Bosch battery about 2 year ago (has a 5 year warranty and volt readings are perfect)

* new air filter

New CAT converter as exhaust manifold and cat back were new 1 year ago and custom designed by a custom exhaust garage.



That's were I am. I have tested the TPS sensor as it is the original one never been changed as its still riveted in from factory. Video below shows results from testing the TPS sensor wire. I've also confirmed the TPS sensor is receiving 5V and a good ground. I've disconnected the plug to the sensor and drove around to rule out TPS sensor issue and although the surge and buck isn't as often it still happens.

I've also checked over the condition of the Dizzy cap and distributer itself and visual inspection looks good, no cracks leaks, rust etc.

What's your suggestions?

Thanks for reading through all this!






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Re: random buck/surge between 20-40mph
 

Check the alternator and belt. Make sure both battery connectors and ground cable connection are clean and tight.

Re: random buck/surge between 20-40mph
 

:popcorn:

Re: random buck/surge between 20-40mph
 

Also clean the heavily corroded points or just replace the cap.

Re: random buck/surge between 20-40mph
 

Thanks battery connections and altinator belts are running true no slipping. How do you clean the contacts as you can't use brake/parts cleaner in the cap with risk of combustion

Re: random buck/surge between 20-40mph
 

Misfiring at low rpm and heavy throttle is usually weak sparks.

I would try a set of spark wires on it. What is up with that wire that is about a foot too long? That is not a hallmark of a quality set.

The cap actually looks serviceable. Use a knife or screwdriver to scrape off most of the corrosion and get down to bare metal. It's a common misconception that those "contact points" need to be squeaky clean. Actually, the rotor never touches them. A spark jumps from the rotor to the contact every time. Look for a cap with brass "contacts" instead of aluminum, they last longer.

Re: random buck/surge between 20-40mph
 

Try this test at night with the headlights on.

When the engine is surging/bucking at 20-40 mph, watch for dimming or flickering of the cluster dash lights and the charging system warning light. If you see this, the problem is likely electrical.

Are any pending CEL codes stored in the ECU after surging/bucking events?

Re: random buck/surge between 20-40mph
 

Tried it tonight and no dimming or flickering. no CEL lights show during or after buck/serge and when trying to pull codes nothing appears. it doesn't have a obd2 port so have to do it the old fashion was and no live data.

Re: random buck/surge between 20-40mph
 

Yeah so the spark plug wires will be my bad doing. I replaced them over a year ago. And looking at the different lengths when the arrived in the box and measuring the distance from the dizzy cap point to the corresponding cylinder this was the best way. However one wire has to stretch over the dizzy cap to fit which I don't link but their was no other way of arranging them and been working fine like this up until a month ago. since this reply I have ordered a new genuine Honda cap and rotor replacement. However to get the rotor off the screw has to be lined up with the hole to disconnect. If it isn't how do I re align the rotor so that I can get access to the screw to take it off and fit the new? Thanks

Re: random buck/surge between 20-40mph
 

Update today: yet another issue just started. The past two mornings it's been raining. And the car fails to start like the batter is dead. Manage to jump start it up both times and throughout the day after some driving it's fine. But once left overnight its dead again. Tested the battery when switched off after running and reads over 12v. When testing it while engine is running its 14.7v so can't image its a charging issue but a power drain? Could this be any thing linked to the 20-40mph surge?

Re: random buck/surge between 20-40mph
 

Sounds like the plug wires are bad and allowing spark to jump to ground in the engine bay. Replace them.

I find the easiest way to work on the distributor is to remove it entirely. You can draw a mark across the top of the distributor to the head to preserve ignition timing after reinstallation, but check the ignition timing with the timing gun anyway because I will assume that you are not absolutely sure the timing is currently correct.

Re: random buck/surge between 20-40mph
 

BTW it's easy to get access to the rotor screw, just disconnect the distributor or the ECU or something so it doesn't start, then bump the engine over by turning the key until the screw is showing.

Re: random buck/surge between 20-40mph
 

Thanks I'll look into that. As for the flat battery issue on the morning. What could cause that? Faulty altinator?

Re: random buck/surge between 20-40mph
 

Details, gauge cluster lit? When you tried to crank what did you hear? When this occur did you check battery lvl?

Re: random buck/surge between 20-40mph
 

Sorry, when trying to crank sounded like a very flat battery tries to crank but doesn't complete a full crank, lights on dash do appear but are dim. Battery after failed crank shows over 12v but can't test running voltage until I jump start it. Strange thing is after you jump start and drive around during the day every time you stop for a hour then try again starts OK. It's only when left for a lot of hours e.g over night that I get this issue

Re: random buck/surge between 20-40mph
 

How are your battery cables? I've seen them corroded inside the insulation and cause problems.

Re: random buck/surge between 20-40mph
 

The earth lead is original and looks old, the terminals seem ok though.

I manage to capture a video (youtube link below) of it failing to start so you can see or hear for symptoms. There is also a relay clicking but think its just doing that when it tries to crank?