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Engine bucking under load

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So we squared away the previous tps issue and got her on the dyno.. after attempting to tune through a language barrier, he finally brought in a superbike tuner who slid right into the hondata program. We experienced a few anomalies like what appeared to be a malfunctioning ECT sensor, then some engine bucking under load..

I had an issue where the engine started bucking while on the throttle, not at WOT. The lambda sensor that the tuner had would be running around 12 and then all of a sudden hit 16 and it started bucking. I didn't see the RPMs from my angle but I would say it was happening between 2500-3500. It definitely happened in 5th gear, but I'm pretty sure it happened in other gears as well. It stopped at one point and we pressed ahead with adjusting the fuel tables.., but then it started back again.

Initial thoughts lean me toward an electrical problem. That would explain why the problem was intermittent. So.. maybe a bad dizzy, bad wiring going into the ECU, or bad ECU..? I looked through the wires and couldn't see anything that popped out at me as bad. I taped anything that even remotely had a potential to ground or arch, and checked ECU and wiring diagrams.. The ECU is used but I had the shop look at it when they installed the Hondata for me.. And the dizzy, well, we're probably gonna swap it out tomorrow.

We've gone through the S300 repeatedly and verified all of the settings. The only oddity that happens is that when the bucking occurs, we get a rev limiter "on" indicator, even though we turned it off. The tuner thinks that we may be seeing a spike of some sort or having a grounding issue somewhere.

I don't have a map/cal to post, left my laptop at the shop so they could continue working it. I've been reading everything from a bad ECT sensor to a boost leak and even spark plugs grounding through the rubber boot.. The tps is new and wires are good, new map sensor, ignitor cleaned.. idk.. I have an oem narrowband.. was trying to install the aem uego gauge but they said it would tune fine and I could install it after the fact myself.

Any ideas or thoughts? Below is my setup, minus all the stuff that I don't think would be an issue..

'91 EDM EE8

Factory B16a1 w/GT2871R

OBD-0 to OBD-1 conversion

P28 ECU w/Hondata S300

Bored over to 82mm

Wiseco Forged Pistons @ 10:5:1CR

Eagle ESP forged rods

Cometic Head Gasket

ARP Head Studs

Supertech over-sized Black Nitrade Domed Valves

Supertech Springs

Supertech Retainers

Skunk2 Pro 1 Camshafts

NGK Iridium Spark Plugs (7's)

NGK Plug Wires

Injector Dynamics 1000cc

AEM Fuel Rail

AEM Fuel Pressure Regulator

Edelbrock Performer X Intake Manifold

Omni-Power 68mm Throttle Body

Speed Factory 4 Bar MAP sensor

Walbro 255lph Fuel Pump

Does your speed sensor work? First when you tune hondata or a Honda ecu, disable the vtec and tune the non vtec map first, once you get that dialed in move onto the vtec map. If the speed sensor is not working and you have a two step enabled in setup maybe its activating the two step. If you can post your calibration I can try to help you. Most of the time the Honda distributor is not what fails, if it fails then you would get a crank or cam sensor code. What goes bad is the ignition coil, if its old then its time to get a NEW QUALITY part. The cheap ones go bad quick. Good thing is that its a 5 min job to swap one out.

Now that I think of it 3000 rpm is when your turbo is starting to make some boost, which would explain the lean AFRs and bucking. Best tip is to add some fuel and then lean it out as needed instead of running lean and then adding fuel.

If you have a datalog or a calibration then that would help.

Definitely good info.. I will get with them and see about the vtec and two step bit. Unfortunately I'm in one of those predicaments where I don't have quick or ready access to my car due to my work location and theirs.., not many options in this entire region. In regards to the speed sensor, we had a code for the cylinder sensor, code 9 if I recall correctly, and we removed and reinstalled and no more issues with that sensor. The car was going into boost fine and not leaning out.. it was more like a spike event with fuel cut. We were definitely working the fuel prior to spool up. I'll check on the vtec and two-step and see if I can get ahold of the cal and any datalogs we may have on it.

All of the launch control is disabled. VTEC was enabled but the oil pressure sensor was not. We'll disable it altogether and try again. One thing I noticed though.. on the VTEC tab is an option for an additional VTEC output, which was enabled and was using A15 Air Conditioning Clutch.. might this be the problem? I can't think of why I would need an additional output for a VTEC engine with VTEC p28 ECU.. Says it should be used for non-VTEC ECUs..

The additonal output is not needed, you should always tune the low cam (vtec off) cam first then when that part is done tune the high cam (vtec) map, this way you can then find the best crossover point on the dyno and not have to retune the maps. Code 9 is a code from bad wiring or bad cps sensor in the distributor. Good thing you got that fixed.

The VTEC pressure switch is not needed. JDM motors dont come with them. VTEC system uses a lot of oil and oil pressure, its purpose is to check that you have enough oil pressure in the head to engage vtec, most likely cause for lack of oil pressure during vtec is being low on oil. If you have the Injector Offset data then input that in the SManager. Also first things first did you do set the base ignition timing?

Calibration attached.. VTEC already disabled. We were just getting into the fuel tables when we came to this impasse. There is no datalog from the session....... I have no idea what happened, and can only assume he didn't save when it asked him to. I watched him turn it on at least once, so that's all I can figure happened. Again, the help is definitely appreciated. I'm learning as I go, and this has been a great learning experience for sure!

Attached Files

I believe your issue might be the Protection limits set up in your Calibration. Disable them and try again but be cautious and watch your AFRs.

Also the injector dead times are off from what ID specs are, not sure for the reason why the supplied specs were not used. Without a log i cant really see anything else that jumps out to me.

The dead times were auto-generated by the s300 when I selected the ID1000's in the drop down. I verified the dead times per hondatas recommended adjustments for the ID1000's, this being based on their knowledge of the ID dead times not matching and requiring adjustment. There's info in several threads on their forums relating to the reason. I can't find the dead times from ID, if you know where I can find them I would like to get ahold of a list. Everyone says they're on their site but I searched all through it..

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