1985 325e - possible fueling issue - loss of power

[acarpenter86]

I picked up a very well maintained 1985 325e for cheap because it has some mild hail damage. Working those dents out and painting soon. The engine (the whole car, really) are in great shape considering it has definitely been driven some miles. I even found documentation of recent timing belt replacement. Idle is pretty solid and doesn't sound tick-y, though I do plan to perform valve adjustment soon just to confirm. The only weird thing, and I don't think it is just me coming from a 335xi and 35d X5 (those are some torque monsters in comparison) is that it seems to very slightly hesitate between 2/2.5k and 3.5k. It's like it wants to go but kind of sputters or just loses power. My gut is telling me something fueling related? Any ideas where I should start? I've done quite a lot of mechanic work, but it's all unplug/unbolt/swap king of stuff and I kind of suck at troubleshooting on my own. Still learning though.

[acarpenter86]

[ZeKahr]

I picked up a very well maintained 1985 325e for cheap because it has some mild hail damage. Working those dents out and painting soon. The engine (the whole car, really) are in great shape considering it has definitely been driven some miles. I even found documentation of recent timing belt replacement. Idle is pretty solid and doesn't sound tick-y, though I do plan to perform valve adjustment soon just to confirm. The only weird thing, and I don't think it is just me coming from a 335xi and 35d X5 (those are some torque monsters in comparison) is that it seems to very slightly hesitate between 2/2.5k and 3.5k. It's like it wants to go but kind of sputters or just loses power. My gut is telling me something fueling related? Any ideas where I should start? I've done quite a lot of mechanic work, but it's all unplug/unbolt/swap king of stuff and I kind of suck at troubleshooting on my own. Still learning though.

I had an 86 Eta and it felt the same way. I think it’s just a characteristic of the choked intake manifold, head, exhaust design. BMW built these Eta engines specifically NOT to rev and focused the torque band below 4000RPM. As soon as you hit 2500RPM, the engine just feels like it doesn’t want to rev any higher unless you give it considerably more gas. The low-end torque is very nice though, makes the car go up hills much easier without a lot of gas

[acarpenter86]

I had an 86 Eta and it felt the same way. I think it’s just a characteristic of the choked intake manifold, head, exhaust design. BMW built these Eta engines specifically NOT to rev and focused the torque band below 4000RPM. As soon as you hit 2500RPM, the engine just feels like it doesn’t want to rev any higher unless you give it considerably more gas. The low-end torque is very nice though, makes the car go up hills much easier without a lot of gas

Appreciate the reply. That thought crossed my mind as well.
I’ve started shifting this thing waaay earlier than I initially was and honestly it takes off faster. Drive less like a race car driver and more like a human auto transmission I guess…

[ZeKahr]

Appreciate the reply. That thought crossed my mind as well.
I’ve started shifting this thing waaay earlier than I initially was and honestly it takes off faster. Drive less like a race car driver and more like a human auto transmission I guess…

Well yeah, you’re supposed to drive it at low RPMs with wide throttle openings - that’s the whole idea behind maxing out your fuel economy and torque output. That’s basically the Eta concept in a nutshell; it’s a posh economy car with old American V8 like torque vs a race car. The Eta engine is designed to be paired with an auto tranny given its torqueband and lazy character.

[82eye]

i wanna drive a 5spd e now lol

[jbontke]

I have an 86 eta and it feels like its surging when its floored. It's much better in the winter, but hot days it surges more. I have gone over speed/cranks sensors, TPS settings, coolant temp sensor readings, etc. I had an 87 eta that sort of did this, but it cleared up after an injector cleaning. The 87 ran well after that, pulled till the redline. I still have not figured it out, but I am not trying to spend a lot of money on this motor either.

[acarpenter86]

i wanna drive a 5spd e now lol

They're pretty fun, even if not the fastest. I like driving it different ways. The open throttle way ZeKahr mentioned, but also revving it out a bit more. Exhaust has a slight mod on mine so it sounds cool with the windows down.

[acarpenter86]

I have an 86 eta and it feels like its surging when its floored. It's much better in the winter, but hot days it surges more. I have gone over speed/cranks sensors, TPS settings, coolant temp sensor readings, etc. I had an 87 eta that sort of did this, but it cleared up after an injector cleaning. The 87 ran well after that, pulled till the redline. I still have not figured it out, but I am not trying to spend a lot of money on this motor either.

Interesting. This one does seem a bit dependent on weather as well. It also likes to warm up for a few minutes (just driving very moderately as I usually do anyway).

[jbontke]

Interesting. This one does seem a bit dependent on weather as well. It also likes to warm up for a few minutes (just driving very moderately as I usually do anyway).

When I use 89 octane gas, the surging is less. I filled up with 86/87 octane earlier this week and forgot how much a difference 89 octane makes.

[acarpenter86]

When I use 89 octane gas, the surging is less. I filled up with 86/87 octane earlier this week and forgot how much a difference 89 octane makes.

I’ll try that- thanks! I’ve only been running 85. (We get 85-87-91 here

[packratbimmer]

Remember that the eta was a fairly high compression engine (higher than the 325i) and that at least some early eta cars had higher compression than the later pre-super eta cars. It does not surprise me that you see a difference after switching from 85 octane. I would put some 91 in there and go run the piss out of it for a few hours if its up to it. Good luck!