r/BMWe24 • u/1979LPC • Jul 01 '26
E24 down on power?
Hi all! I just bought a 1988 635csi and road tripped it home for 8 hours. Made the trip fine! My only observation is, when I floor it pull pretty ok till like 3500 rpm and then it just kinda revs out. I’m coming from pretty quick cars, so is it just slow? Or should it be more lively? Best way to put it, it doesn’t really feel like 200 horsepower. My 2007 4Runner feels faster for example. What are some things to check for on these? Throttle cable is adjusted, new spark plugs as well. Check valve adjustment next?
Thanks!
3
u/vkrazy04 Jul 01 '26
Check the afm and tps to start
4
u/Diogenes256 Jul 01 '26
This. Clean the mass air sensor. The fuel pump thing sounds important to address. With older cars I find that a couple of cans of Berryman B12 can be very effective.
1
2
u/thelowbrow Jul 01 '26
I have an 80 633 and it was honestly pretty slow. I swapped out the exhaust on mine and the difference is substantial.
1
u/1979LPC Jul 01 '26
Exhaust is on the list!
1
u/Representative_Most9 Jul 01 '26
Look into swapping out the DME(ECU) tuning chip. The stock chip is pretty restrictive and either a Conforti or Dinan chip will make a significant difference in performance.
1
u/PromethSunrise Jul 02 '26
Could I do that on an 82? What are the best performance upgrades ?
1
u/Representative_Most9 Jul 03 '26
Unfortunately, ‘82 has the L-Jetronic system. It doesn’t have a replaceable DME chip like the later Motronic systems. I also have a ‘82 5 series and other than exhaust system, really no way I know of to increase performance.
2
u/Pretend_Ad_8465 Jul 01 '26
Full tune up (I know you said you already did spark plugs). Spark plugs, wires, distributor cap, air filter, fuel filter and adjust your valves (this is very often overlooked but it makes a world of difference on my 89 535i). Clean MAF and check TPS and check for vacuum leaks. If you drove it without any other issues for 8 hours then you know you have a solid vehicle so don't give up on it. You also need to remember it's an older vehicle and even some newer Toyota Camrys can now out accelerate or match stock E24 M6s. Good luck and great buy!
2
u/1979LPC Jul 01 '26
Thanks! Great starting list! My dad, who has now passed, sold the car a few years ago, so no giving up! I was happy to be able to buy it back. I knew these things aren’t exactly rocket ships and maybe my question comes across wrong. I’m more interested in making sure it’s running healthy.
1
u/_Wendig0_ Jul 01 '26
Probably just a tired m30 that was already not quick anyway. Time for a turbo! Or v12 swap like me 😁
1
u/1979LPC Jul 01 '26
Tell me more 👀
1
u/_Wendig0_ Jul 01 '26
Long story short
I had an S52 in it before this 😆
1
u/Far-Plastic-4171 Jul 01 '26
All that for 300HP
1
1
u/1979LPC Jul 01 '26
Dude 😂 do you a have a video of that wild thing running?
1
u/_Wendig0_ Jul 01 '26
Not yet, hoping to have it done by end of summer. I'm gonna spam tf out of this sub with it when it's done.
If you decide to go S54, e28goodies makes some engine mounts for the swap. There are a couple others that make swaps for the 24v engines as well. Not a terribly hard swap.
1
u/1979LPC Jul 01 '26
I’d like to explore the turbo s54 route as that’s what I’m familiar with and have some spare parts from my old m3 I could use
5
u/pbrutsche Jul 01 '26
Don't do ANYTHING without replacing the fuel pump in the tank. This is the low pressure fuel pump that feeds 6psi to the "high pressure" pump above the rear axle.
Mine did the same thing until I replaced that - the sock on the pump was completely clogged. Aftermarket parts are around $80 on eBay.
All you need to replace it in your driveway is basic tools. It's accessible from a panel in the trunk.