Sorry to threadjack but I'm having similar issues with my 86 S5 swap. The car will rev past 3500rpm under load but not at heavy throttle I can go all the way to redline but only slowly under light throttle. Should I pursue grounds first or try to mess with the tps? Btw EVERY vacuum line was checked/replaced and unused ports capped and sealed so don't believe that is the issue also car revs fine at full throttle when clutch is in or out of gear.

make your own thread but a s5 into s4 takes a bit more work then a s4 to s4 there should be a thread somewhere in the swap section of this forum that has your question if you cant find it start posting in relative sections

the unfortunate part is I didn't do the swap, the car was purchased like this as a project

how much of the s5 stuff is gonna be ran? how much s4 is gonna be used? but again start your own thread do a relative search in other sections and also when you make your own thread list whats being used from each series and you should get the answers you need

ok so i got a new/used eomp in good working condition. that has been replaced now im just waiting for a ecu to come in and we will be on the road in no time!!.... i hope

good luck

thanks man, but i just realized the ecu in my car is a N351 and i ordered a N350, does anyone know if there are going to be problems with this being that the N350 is california emissions???

Do you have a check engine light? if you do use the onboard diagnostics system to find out what circuit the problem is in...



Also checking the OMP is easy if you access it from below, and it DOES NOT require removal. Just have to reach over the undercover past the swaybar up to the connector. I will say it is easier with the undercover removed though.

Check it with a multimeter per the FSM.

If everything is good at the OMP (or MOP as the FSM calls it), follow the wiring up the front of the engine, there will be a connector right next to the TPS connector that connects the OMP wiring to the engine harness. verify everything is reading right right from that connector as well. I found my problem was the wiring that goes to the OMP. The lower connector was bad, breaking the circuit. It tiggered a check engine light and limp-home mode. In limp home mode you cannot apply much throttle or she'll lose power. I have two threads on that very topic.



I found after ordering a new ECU that mine was fine...



Do a search for your ecu code, there is a thread that goes through what ECU goes to what application.

well the ecu arrived today and i installed it and the car is still in limp mode. so far i have learned that the only thing that can cause a s5 to go into limp mode is a bad eomp or a fried ecu due to bad eomp. i have replaced the eomp and ecu and the car is still in limp mode. this is sooooo frustrating. idk what to do im about to sell it... any feedback will be appriciated. now i really feel left in the dust.

the issue may be that either eomp, either ECU,, or the common wiring loom is still faulty



go the rtek chip, from here it is the easiest cheapest solution to limp mode



if you still have issues after that,, then you ave a voltage issue at the injector,, or an earth issue in the device earths

both issues are usually fixed when you strip back the wiring loom up to two feet out from the cu plug

there is two earth bundles,, tied with a brass crimp,,, that require resolder,, and maybe adding a decent earth wire to and earth on the ecu case



there is also a power hub ( with its own crimp ) that could also possibly do with a reheat and resolder



there is reams of info about these common faults online ,, and if you havent tried this then you havent really tried yet