Very Rough, Low Idle and Missing - Help!, 73 D-Jet - SOLVED! Options

[ThinAir]

RRC is only a couple of weeks away and I'm beginning to get desperate that I'm not going to be able to drive my 914.

When I posted this, my problem was just that the idle would hunt, but otherwise it drove well. After reading the responses and reviewing Brad Anders' stuff again it made sense that my hunting problem was probably that I was just running lean. I turned the ECU 3 clicks clockwise to see if that would improve things, but it didn't seem to.

Well, things have gone from poor to bad. Right now I've got a car that barely idles at all, and when I'm accelerating or driving on the highway it often bucks/misfires. I haven't run it long enough to get it warmed up. I've tested the AAR by pulling the supply hose and it seems to be working. If I remove the AAR output hose the RPMs go up to 1000 so perhaps the AAR isn't opening fully.

I've measured the ohms on the CHT at 124 so that's within range, and I've got a brand new 270 ohm resistor inline. I have 3 MPS units that all pass on resistance and vacuum and changing them makes no difference in the behavior. I've also recently replaced the spark plug wires (not to solve this problem, but just because) and I've made sure that they are as far away as possible from the MPS unit. I've also checked every electrical connection that I can find.

Sorry that all that is so long - any clue what I should be looking at? I'm beginning to panic (IMG:style_emoticons/default/blink.gif)

[ThinAir]

Well the news is that I keep eliminating things so I've got to be getting closer to the answer (IMG:style_emoticons/default/smile.gif)

The 012 CHT arrived on Saturday. I tested the R values at different temperatures to match up with Brad Anders' tests. It tested pretty close to 017 with the 270 ohm resistor added. 39F - 10.2K, 61F - 2.02K, 210F - 280 ohms. It seems to run pretty much like the 017 as well (no checking with instruments, just the feel of how it drives). I'm running the 012 without an added resistor, so that eliminates the CHT.

I found that my 043 MPS (that has the best vacuum holding time) doesn't like the 012 CHT - idles smooth for a bit, then dies. I switched back to my original 037 and it seemed to run better than my spare 037 at idle, but all I think I can say for sure is that the problem persists no matter what MPS I run so I don't think it's the MPS.

The TPS has been disconnected and it made no impact on the behavior.

Tonight the battery was removed and all the cables and posts cleaned, including the post on the body. I also double checked every electrical connection that I could find anywhere on the engine (except the injector wiring for the injector points - left this alone on purpose to see if the rest of it affected the behavior.) Still no change in the behavior.

So I figure I'm down to 2 things, distributor/Pertronix/injector triggers or ECU. There is also the possibility of a fuel filter. I run 2 filters, but since one of them is under the fuel tank where I really can't get to it, I'm not going there yet. There's also a sticking injector, but checking injector flow/spray is more work than I want to do yet (and they've been working fine for so long that I doubt they are involved in this).

Since I have a spare distributor all ready to go, I'm going to try swapping that tomorrow night. That will give me a different Pertronix, injector triggers, and vacuum canister in one shot. It will also give me a chance to examine the injector trigger wiring more closely. I know one of the connector tabs is broken off, but I've also been unable to get the boot down into proper position on the connector. I'm hoping that I'll have a better angle on that as part of putting in the different distributor.

Anybody got a spare 037 (021E) ECU they want to loan? How about a '74 ECU? Since I have an 043 MPS and the 012 CHT, one of the '74 ECUs would give me Brad Anders' preferred setup for a '73 2.0L.

The thing that bugs me most about this is that the problem is intermittent. It will seem like things are going well, only to have the bucking & low idle come right back sometime during the next test drive.