Fjergus
New member
- Joined
- Dec 5, 2014
- Location
- Seattle-ish
1985 240DL with a freshly rebuilt NA B230 and a K cam (about 10k miles on the rebuild). The engine is out of a later 240 (a 1993, if I recall correctly). LH2.2 ECU, Chrysler ignition, and an M46.
I swapped my tired old engine out for a freshly rebuilt one last year, and the damn thing has never really run properly. It seems to behave itself at higher RPM, but it runs very rough at idle. It behaves a bit like a really bad vacuum leak, but I have spent many, many hours searching for one in vain. No leaks around the intake manifold gasket, no leaks in the intake boot or any of the hoses, and the air fuel mixture stays pretty steady at 14.7 (I installed a wide band sensor a while back for diagnostic purposes). It just sputters and shakes like a dog ****ting a peach pit anywhere below about 2000 RPM. It also runs slightly better for the 30 seconds or so when I start it cold, but it starts to run like **** almost immediately.
I'm fairly confident the IAC is working correctly: turning the AC knob causes the idle to increase by a few hundred RPM, and unplugging the IAC at idle causes the idle speed to drop slightly.
The ignition timing is set correctly according to the book. It is worth noting that the timing wanders around a ton at idle, but that's pretty normal for the Chrysler ignition systems from what I understand.
Valve timing was set correctly when I put it together, and it hasn't changed since then.
I recently got a vacuum gauge:
Any ideas? According to various sources on the intertubes, the jiggly idle vacuum business may be caused by worn valve guides (or maybe just the wrong ones, since this engine only has about 10k miles on it), or some other valve train issue. I'd be pretty damn irritated if that were the case (again, only 10k miles), but that's kinda the direction I'm leaning. Thoughts?
I swapped my tired old engine out for a freshly rebuilt one last year, and the damn thing has never really run properly. It seems to behave itself at higher RPM, but it runs very rough at idle. It behaves a bit like a really bad vacuum leak, but I have spent many, many hours searching for one in vain. No leaks around the intake manifold gasket, no leaks in the intake boot or any of the hoses, and the air fuel mixture stays pretty steady at 14.7 (I installed a wide band sensor a while back for diagnostic purposes). It just sputters and shakes like a dog ****ting a peach pit anywhere below about 2000 RPM. It also runs slightly better for the 30 seconds or so when I start it cold, but it starts to run like **** almost immediately.
I'm fairly confident the IAC is working correctly: turning the AC knob causes the idle to increase by a few hundred RPM, and unplugging the IAC at idle causes the idle speed to drop slightly.
The ignition timing is set correctly according to the book. It is worth noting that the timing wanders around a ton at idle, but that's pretty normal for the Chrysler ignition systems from what I understand.
Valve timing was set correctly when I put it together, and it hasn't changed since then.
I recently got a vacuum gauge:
- At idle, the reading rapidly oscillates between roughly 10in-Hg and 15in-Hg. The oscillation appears to match the engine RPM.
- At roughly 1700RPM, the vacuum bounces from around 16in-Hg to 20in-H and back again, completing a cycle roughly once per second. The needle stays steady between cycles (it doesn't jiggle like it does at idle).
- At steady state throttle anywhere else in the rev range, the vacuum stays steady around 20in-Hg.
Any ideas? According to various sources on the intertubes, the jiggly idle vacuum business may be caused by worn valve guides (or maybe just the wrong ones, since this engine only has about 10k miles on it), or some other valve train issue. I'd be pretty damn irritated if that were the case (again, only 10k miles), but that's kinda the direction I'm leaning. Thoughts?