Hello, I am primarily an E34 guy but I am posting here because there are probably more experts on this forum that have done the S52 OBD1 swap. I have just swapped an S52 from 98 M3 into my 95 E34 wagon and done the OBD1 conversion. It starts right up and has a stable idle but stumbles with any acceleration. Blipping the throttle while under the hood also results in a stumble. It may be a misfire but I am not certain. There are no codes being set on the DME. When I drive it, it is way down on power and shakes under load as if not running on all cylinders. It smooths out if I lift throttle and cruise at steady speed.
I was pretty meticulous while prepping the engine and replaced all rubber hoses associated with the intake manifold and ICV. All gaskets are new. I cleaned the ICV and believe it is working properly because the idle quality is good. I checked compression and all cylinders are between 185-200 psi. I am running a red label DME with TRM OBD1 chip. I bought it used from a Bfc E34 forum member that had used it in his S52 swap before going to forced induction. Fuel injectors were all cleaned and flow tested prior to installation. Knock sensors are new. Spark plugs are NGK Iridiums. Coil packs are the ones that came with the S52. I am using the M50 PCV and plumbing it to a port on the throttle body where the stock M50 engine was plumbed. The only thing I have not measured is vacuum at idle and under load because my gauge is broken.
This really has me stumped. It has less power under 3000 rpm than the M50 engine I pulled from this car. The way it stumbles and shakes as soon as I try to accelerate led me to look for vacuum leaks but I am not finding any. Do these symptoms sound like anything experienced by forum members here? Is there something that I am not thinking of in my troubleshooting approach? My next step is probably to pull the manifold off and recheck all hoses and gaskets. Not looking forward to it but I can't think of anything else to try. I thought about the VANOS being the culprit but the power loss and shaking is so severe, it is hard for me to believe it is all due to worn VANOS seals. Any suggestions will be appreciated.
I was pretty meticulous while prepping the engine and replaced all rubber hoses associated with the intake manifold and ICV. All gaskets are new. I cleaned the ICV and believe it is working properly because the idle quality is good. I checked compression and all cylinders are between 185-200 psi. I am running a red label DME with TRM OBD1 chip. I bought it used from a Bfc E34 forum member that had used it in his S52 swap before going to forced induction. Fuel injectors were all cleaned and flow tested prior to installation. Knock sensors are new. Spark plugs are NGK Iridiums. Coil packs are the ones that came with the S52. I am using the M50 PCV and plumbing it to a port on the throttle body where the stock M50 engine was plumbed. The only thing I have not measured is vacuum at idle and under load because my gauge is broken.
This really has me stumped. It has less power under 3000 rpm than the M50 engine I pulled from this car. The way it stumbles and shakes as soon as I try to accelerate led me to look for vacuum leaks but I am not finding any. Do these symptoms sound like anything experienced by forum members here? Is there something that I am not thinking of in my troubleshooting approach? My next step is probably to pull the manifold off and recheck all hoses and gaskets. Not looking forward to it but I can't think of anything else to try. I thought about the VANOS being the culprit but the power loss and shaking is so severe, it is hard for me to believe it is all due to worn VANOS seals. Any suggestions will be appreciated.
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