Hondata

I'm having a problem with my car surging while I drive. Its very noticeable on the highway. It gets better when in closed loop but is still there. I have tried advancing timing, a little at a time with no success and adjusting fuel tables makes no difference.

the engine is a b18cr recently rebuilt
je 9:1pistons
eagle h beams
t3/t4 turbo on log manifold
hondata I/m gasket
r/c 750 injectors
fuel pressure 45psi

I have attached 2 datalogs of the surging while revving the engine and the current calibration

It looks like you have a vacuum leak. Find and correct that and it should get better.

Thanks for your help! I tried to find a vacuum leak today, using propane and cant find any leaks.
Do you have any more ideas?

Have you talked to your tuner about this issue?

I have not talked to the tuner about it because i dont think the problem is his problem. Maybe im wrong but especially if its something like a vacuum leak it has nothing to do with him.

Im still having the same problem weeks later. I have check thoroughly and there are no vac leaks. I thought my fuel pressure looked suspect so i replaced the fpr and the pressure looks good now but the problem still exists. I have checked for ignition problems but cant find anything wrong.

Have you had your tuner take a look yet?

I'm still having the same problem, ive tried replacing different ignition and fuel system parts and sent my injectors back to rc to be cleaned, nothing is helping. I first noticed the problem on the way to the tuner, i figured the problem was because it wasnt properly tuned yet. The tuner could not figure out what was going on while i was there so talking to my tuner about the problem would be a waste of time. That is why im posting here, its been months now that ive had this problem and not been able to drive the car. I really need more eyes on the datalogs to help me figure this out. Thanks for your help.

Why are you refusing to discuss this problem with your tuner?

Because he couldnt figure out what was going on when the car was in front of him, why would he have any idea over the phone?

You suggested it may be a vacuum leak which has nothing to do with the tune or tuner. If there is an engine related or hardware related problem it has nothing to do with the tuner. I first noticed the problem on my way to the tuner and when ive tried other basemaps the problem still occurs. I just cant see the connection or the logic in talking to him anymore about the problem.

I had hoped to get some help from someone on this forum who had maybe run into this sort of problem before. The tuner must have never had the same problem because he had no idea what was going on.

I would much rather have just a little bit of help diagnosing the problem but if thats not possible could you tell me why you insist i should contact the tuner

Sticky FPR?
Has harness been cut for VAFC before etc (VSS/MAP)?

Good thinking, thank you. I never had a vafc but i have replaced the connector so i did a test of the map sensor reading. I hooked up a vacuum gauge to the manifold and watched smanager display and at varying vacuum and throttle both the gauge and smanager read the same. I think that rules the map sensor and connection to the ecu out as a problem.

The vss seems to be working fine i took it for a short drive to confirm.

The fpr seem good as well the pressure changes with the vacuum

Ive been chaging the fuel map and ignition map and the engine doesnt seem to run any differently, better or worse. That and the absence of cel has me wondering if the ecu or s300 are bad. I just dont have or know anyone with another ecu to try.

Try retarding timing at low load col 1-4 and retune AFRs

Im still having this issue and havent been able to drive the car for months. I have tried retarding and advancing the timing but it doesnt change the surging issue for better or worse.

Spunkster, i talked to the tuner a few times about this issue and he thought it looked like a vac leak and suggested i fix the fitv but i dont have one. He has since stopped replying.

I have recently checked again for a vac leak using smoke, carb clean, propane and pressurizing the manifold to 15 psi. There are no leaks.

What would make the engine act as if there is a vac leak without there actually being one?
Thanks everyone for the help

I would recommend taking this to a different tuner so they can take a look and see if they can help you resolve the issue. This is something that needs to be looked at in person by someone knowledgeable to help you find and resolve the issue.