I spent Saturday swapping out my hood - pin mounts broke last Thursday - and the MAF. Took it for a 240 mile drive in the Rockies and did a bunch more tuning. I've made improvements but now I have another issue. I think.
So, after reworking the timing map and shaving off another degree or two, it mostly runs great. So, I'd say about 90% good. I think with a bunch more tuning I could get that up to 93%. However, the current other 10% sucks.
Assuming this is not being caused by a bad MAF or MAP - and I'll know shortly 'cause I have a new MAF showing up this week and a new MAP in the front seat - I think I've hit the wall with the stock ECM. I think the problem I'm seeing is from pulling too much timing. I don't know for sure and I'll do some testing tonight on the way home. However, if that's the case then this idea is dead. <img src="/forums/images/graemlins/frown.gif" alt="" />
While I can get the AEM to work pretty dang well in Denver and pretty dang well at Eisenhower Tunnel @11K ft, I'm having a hell of a time getting both. And, I haven't even started on the off-road tuning. <img src="/forums/images/graemlins/frown.gif" alt="" />
So, I'm keeping my fingers crossed its the MAF/MAP that's causing the problems. At this point, it's undrivable until the vehicle warms up to operating temps. Bucks and seems to cut out like crazy and there a wierd 'miss' sometimes at really light cruise. Sigh. <img src="/forums/images/graemlins/frown.gif" alt="" />
At this point, though, I've pretty much come to the realization that there is NO WAY that this solution will work at sea level. The lower you go in altitude the less timing is needed and there's just way too much. The only feasible solution is really to go with a MegaSquirt, take the timing completely out of the ECM's hands, and let the MS do all the timing. At which point you are in for a ton of tuning and dyno time to build a custom timing map. The MS could still fill the piggy-back function for reducing fuel, but timing would be solely on the MS.
Anyway, I'm re-approaching the ECM swap idea. Danny's thread got me thinking so I did some research into the Montero. I THOUGHT they did a Montero with the 3.5L and 5-speed manual but I was wrong. '96 was in fact the last year apparently and those ECMs are not OBD-II - which means I can't pass emissions.
As I understand things, '99 is when they transitioned to PCM - integrated ECM/TCU - which just puts me right back to the problems I had with using the '99 Sport PCM. Can't get past all of the TCU stuff that the ECM actively interfaces with.
So, I did some research on the '97 3.5L SOHC Montero ECM (MD338137) and it LOOKS like its virtually identical in functionality to the '97 Sport ECM. Time frame matches, too. Late '96 to early '97.
I would have liked to go with a '98 ECM for possibly better OBD-II, but I can't tell which ones have anti-lock or which don't or if they all do. No way am I going to try to fake out ABS in an ECM. <img src="/forums/images/graemlins/frown.gif" alt="" /> And, I don't know if they expanded integration with the TCU in '98 - and I don't want to find out. As far as I'm able to tell so far, the extent of the '97 ECM/TCU integration consists of one wire which is a 'bus' line that the ECM uses to make sure the TCU is still 'there' periodically. Same as the '97 Sport. Tech doesn't think if that's disconnected the ECM even triggers any type of code. That'd be perfect - just leave it unplugged and ignore.
I have a set of '97 Montero FSMs on the way and an ECM. Once I get the manuals I'll start cross referencing the ECMs and see where I end up. I suspect that at the very least I'll need another Boomslang harness because all the pin locations are not identical to the Sport ECM but at this point, after talking to the tech, I don't expect too much more. Hah. Famous last words. <img src="/forums/images/graemlins/frown.gif" alt="" /> At least it uses the same 'green' plugs as the '97 Sport so cross-referencing will be cake. I also got an ECM with the four plugs still attached so I can see which are populated and which aren't very easily.
The only part I really don't like, provided this approach works, is that the timing will STILL be for an automatic, not a manual. And, I do know that there are small differences between the maps. However, at least they won't be enough to cause more than slightly degraded gas mileage. And 'slightly degraded' is probably relative. With 240 miles of nasty storming windy mountain driving, I ended up getting 17.9 Mpg. In an almost 6000lb vehicle with solid axles and 35" M/Ts and the profile of a block house. Not my normal 19-20 back-and-forth from Moab, but not horrible.
Sucks to have to start looking at going almost back to square one, but I'm fast loosing confidence in the current solution. I MIGHT be able to get away with an off-road map and a street map, but I'm not even sure that'll work now. Sigh.
One thing I've absolutely for sure settled - there is NO WAY you can just run a 3.5L on a 3.0L ECM/PCM. Not even with knock sensors. There's more timing than the knock sensor circuit will be able to deal with and the ECM is going to start dumping gas to try and suppress knock and what you'll end up with is a pig that gets 14 Mpg - maybe, if you're lucky. Sucks. I didn't think it'd be quite this bad. Can't believe I'm pushing 8 degrees in parts of the map now. <img src="/forums/images/graemlins/rolleyes.gif" alt="" /> <img src="/forums/images/graemlins/frown.gif" alt="" />
And if you put a 3.0L on a 3.5L ECM, you're going to wish to God you'd never been born 'cause it'll be such a pig you'll never get it moving. Unless you turbo or super charge it. That might work out pretty well.
Edward
