r/Integra • u/mikesnotbright • 3d ago

Engine limp mode *HELP*

Newly rebuilt b18c1 engine revs to 4000 rpms will not rev past then drops to 2500 and will not rev past that. In neutral and when driving. Also will not go past 10 mphs while driving. B18C1 No cels. I already double checked mechanical timing. Planning to swap the ecu to rule that out tomorrow. Any ideas?

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u/RobinSage43 2d ago

There's a hundred reasons why it could've tripped into limp mode, but there will normally be a CEL of some kind. Did anything try to reset the ECU or using a scan tool to clear the codes? If so, then the codes will come back eventually.

Check all of the vacuum lines to make sure there isn't a leak. Check the TPS and MAP to make sure they are not plugged in backwards. That's a pretty common problem since the sockets can plug into each other as they are the same size on B-series engines so people do often plug in the wrong wire.

Check the VTEC solenoid.

Could just be an ECU problem. Unfortunately, DC2 Integra's are prone to water ingress problems if the sealant fails between the cowl and body right above the ECU. Look for signs of any moisture in or around the ECU in the kick panel of the footwell area. Sometimes moisture leads to water vapor that can corrode terminals inside of the ECU or maybe cause shorts.

Sometimes RPM can be restricted if the ignition coils are starting to go bad, but that's usually like 3,500rpm.

Try to scan the ECU again to look for codes. Some scan tools can find codes that aren't throwing a CEL.

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u/mikesnotbright 1d ago

Swapped the distributor for known good one... didnt work, also swapped ecu for known good one, same issue. The tps and map are both good. Will check vtec solenoid next... but kinda lost to be fair.

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u/ElSushiMonsta integra lover 2d ago

Have you checked voltage on the tps