OBD-I m60/m62 driveability (long, looking for input from others with experience)

[JGood]

I'm looking for some input from those of you who have put some miles on your m6x swaps running the 404 DME (OBD-I).

I originally had an m60, first with a stock chip, then with a Mark D chip. Then I built an m60b44, and ran the stock and Mark D chip in that as well. I've also tried both the m60 and m62 throttle body, and various m60 intake manifolds. I have a total of about 30k miles with m6x's in my e30 now over the past 4 years. I've replaced every single sensor and gasket, some multiples times. MAF's, CTS, ICV, IAT, CPS, Cam position, knock sensors, O2's, the whole engine wiring harness, etc... I've had it on a data scanner in graph mode looking for abnormalities. I've tested the entire harness from the DME to every sensor. I've run all new power and ground cables. I've done smoke tests, vacuum tests, compression tests, and leak down tests. Safe to say, this thing is running as best as it possibly could. Literally everything is new and tested.

On to the issue:

I've found going on/off throttle to be very touchy, and it's very hard to drive smoothly. If I'm driving along, lets say 4th gear, and just coasting, and it's engine braking, when I get on the throttle, the first few degrees of throttle body movement have no effect on anything. Then, as a push just a hair further, it feels like it's opening to maybe 10%, and I suddenly am accelerating instead of just maintaining a steady speed. I try to leave off just a little, so I can just maintain like 5% throttle position and drive at that constant load and not accelerate or decelerate, but it's either 0 or 10%. I'm either going into engine braking if I don't give enough throttle, or accelerating with more throttle then I want to. There is no in between, and it's not a smooth transition between the two.

In addition, I get one loud crack out of the exhaust when getting on the throttle after engine braking. Every single time. It has never, in 30k miles, not done that one loud crack when getting on the throttle after engine braking. In addition to that, it also hesitates a split second when getting back on the throttle after engine braking, which is more noticeable the harder I get back on the throttle. If I just stand slam it to WOT while engine braking, it just doesn't respond for a second, does the loud pop/crack during that time, then takes off like normal.

I can't imagine e34 540i's are like this. I've never driven one though. Does anyone else have similar experiences with these engines?

[delamaize]

I've found going on/off throttle to be very touchy, and it's very hard to drive smoothly. If I'm driving along, lets say 4th gear, and just coasting, and it's engine braking, when I get on the throttle, the first few degrees of throttle body movement have no effect on anything. Then, as a push just a hair further, it feels like it's opening to maybe 10%, and I suddenly am accelerating instead of just maintaining a steady speed. I try to leave off just a little, so I can just maintain like 5% throttle position and drive at that constant load and not accelerate or decelerate, but it's either 0 or 10%. I'm either going into engine braking if I don't give enough throttle, or accelerating with more throttle then I want to. There is no in between, and it's not a smooth transition between the two.

I'm running a bone stock M60B40, with 2.5" pipes, with a cross over, and a Flowmaster 40 out back. I don't have any issue with weird throttle response, Although mine doesn't seem to be linear. the amount of power that comes on over 50% throttle seems to be more than the bottom 50%, if that makes sense. I'm running an auto harness from the donor, (mid year 94 540i) that I removed all the auto crap from. I'm running all the original sensors, except the temp sensor for the gauge, the knock sensors, and the O2 sensors. one thing I have noticed, when it drops into "engine braking" it's obvious, almost like flipping a switch. But when I bring it out, and back to being under power, it's pretty smooth, and takes about 5% throttle to get the power back. The only issue I am having these days is a oil pressure light that fades on, and fades off, sporadically, for no reason, and doesn't change with RPM, Pressure seems to be good still. And I'm throwing a 1263 code, Which is a "tank purge valve" I didn't think I needed it, and I removed the wiring for it. I'm trying to figure out how to bypass that right now, with no luck. Something else to keep in mind, I'm not using a E30 accelerator pedal, I'm using a modified IS300 one.

Another thought, My idle "bounces" between 400 and 1000 after hard braking, after it cycles up and down about 3 times, it settles into a normal idle again. Someone told me this is a sign that the ICV is weak. The same person told me the ICV assists with throttle response below a certain throttle. I don't know how creditable that information is.

In addition, I get one loud crack out of the exhaust when getting on the throttle after engine braking. Every single time. It has never, in 30k miles, not done that one loud crack when getting on the throttle after engine braking. In addition to that, it also hesitates a split second when getting back on the throttle after engine braking, which is more noticeable the harder I get back on the throttle. If I just stand slam it to WOT while engine braking, it just doesn't respond for a second, does the loud pop/crack during that time, then takes off like normal.

I can't imagine e34 540i's are like this. I've never driven one though. Does anyone else have similar experiences with these engines?

I though I was the only one that was having this problem. Mine was REALLY bad when I first got the swap on the road. Like sounded like a backfire. This was also when the o2 sensors were not hooked up right. Lately, Now that the O2 sensors are functioning right, It's better, but I still get that crack when I get back on the power, just not nearly as bad or loud.

[beggs]

I had a similar problem for a little while with the poor throttle response. My problem was that the MAF wasn't tuned for the 3" pipe I had put it in. But after I added a restrictor it fixed it right up. Hope this helps.