318is Engine swap results Tachometer failures

Hi!

Recently i changed my 318is (1995) engine for 525i (1992) one. Almost everything seems to work properly. One of the major issues at the moment is that after driving for a while with warm (temp. gauge in middle) engine tachometer and fuel gauge start jumping and die/drop to 0. When turning on additional electrical devices (for example blow to max, fog lights or using power windows) then these gauges wake up and work a bit more or until i turn those additional devices off. Has anyone any idea about this weird problem?

Second issue is that my full OBC show very funny fuel consumption about 4-7L/100km on highroad but when fuel gauge is working it shows about 10L/100km.


I would really appreciate if anyone has opinions or possible solutions..
Regards,
RaunoV

You didn't swap in an instrument cluster for a 6 at the same time you replaced your 4 with a 6, did you? The 4 cylinder cluster will work, but it won't read correctly. You need a 6 cylinder cluster. Also, it sounds like your connections on the IC are loose.

Originally Posted by hornhospital

You didn't swap in an instrument cluster for a 6 at the same time you replaced your 4 with a 6, did you? The 4 cylinder cluster will work, but it won't read correctly. You need a 6 cylinder cluster. Also, it sounds like your connections on the IC are loose.

Difference in 4cyl and 6cyl cluster is just how right rpm-s are, and I changed them also. This problem occurred on both clusters. Probably not connections cause both clusters had same issue and this is somethings to do with engine temerature?! Or somethings with electrical system...

Electrical system. And why do you think it can't be connections since it does it on both clusters? If the connector plugs are bad, that's exactly how it would react, showing the same symptoms on both clusters.

Originally Posted by hornhospital

Electrical system. And why do you think it can't be connections since it does it on both clusters? If the connector plugs are bad, that's exactly how it would react, showing the same symptoms on both clusters.

And how could you explain that engine swap caused it? As before there wasn't any issues.

Did you make sure all of the ground wires are connected securely?

Originally Posted by B1MM3R

Did you make sure all of the ground wires are connected securely?

I think so. Weird is that it always happens after some time of driving, about 20-30km..If ground is bad, sould it affect all the time?

Not all the time. My dads 318 cluster would randomly act nuts and then he found the ground was loose, tightened it and voila it was fixed.

Mhh, okay. Need to find some diagram to check all grounds and not miss any of them.

Any ideas about the second issue? About second issue I noticed that Range is also acting very weird. Today started driving with 98km and after arriving destination (15km) it showed 30km to go..

Are you sure you have a 6 cylinder cluster in the car now? B/c range will be off if not.

Originally Posted by B1MM3R

Are you sure you have a 6 cylinder cluster in the car now? B/c range will be off if not.

Yes, old 318is cluster showed way higher rpm-s. With this cluster rpm-s are normal.

But does that matter that i have 525 ECU? As new engine is older and they don't match with OBC?

No, all of the dme's are the same with (6 cylinders) electrical but just the chip is different in the dme per which engine you have. Im not sure then.

Can it be something related to engine temperature sensors?

AS how this ground always fails after some time of driving?! Really confused..

Not sure, any CEL on?

Originally Posted by B1MM3R

Not sure, any CEL on?

Not in cluster, OBC's Check function fails and turns OBC off..

I know what they do...I was saying for the first issue where you asked about temp sensors causing rought idle.