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1990 with 1994 engine, small turbo setup with DIYPNP2, built by me. Been running fine with a shitty street tune that I've been meaning to improve, but it was running fine. Would start, idle after a block or two, and run well. Used VEAL to get a decent fuel table.
Driving down the street the other day and the car just cut out. Turned the key and got whirring from the starter but no catch. Popped the hood and a plug wire was loose. Re-seated it, car started briefly then died again. Would not be coaxed back to life. Started chasing things, ending up replace starter, coils, plug wires. Then I came to my senses and checked the timing belt. The belt was intact, but the cams were way out of alignment. Looks like the belt had gotten loose and skipped teeth somehow. I re-installed the timing belt per factory specs, with cams correctly aligned. I just installed this timing belt, with new pulleys, less than 2000 miles ago.
Started the car up and it immediately idled reaaaaaaaal high. I had always had a hard time getting idle set on this car after the megasquirt install, and I figured re-setting the timing belt had impacted the timing on the megasquirt somehow, impacting the idle? Either way, the engine was revving up to 5k by itself, with no throttle, putting a fair amount of black-ish smoke out of the valve cover breather tube, which on my car just vents to atmosphere. Then the car died. I started it back up, and now it's sluggish, takes a ton of throttle to start up, won't idle at all without at least 7% throttle, sounds like it's missing. I checked the timing belt again - everything good at TDC, cams aligned - and put in a new set of spark plugs for good measure. Same deal, hard starting, sluggish, requires tons of throttle to stay alive, sounds terrible. Pulled the plugs and several of them had high levels of soot or carbon coating the electrodes. Replaced the PCV valve (why not, it's cheap, ) and attempted to set the timing per brain's write-up but with a rock holding the throttle down to keep the car alive, RPMs fluctuate and the timing marks jump all over the place. While this is all happening, my vacuum is around zero, so I don't think it's a vacuum leak.
Here's a datalog of me starting the car and keeping it alive with throttle for a while. Any ideas?
MAP sensor readings look dickered. Check the hose running to the MAP sensor on your megasquirt.
Thank you, I'll check that when I get home. Something to note is I'm using the 4-bar MAP sensor: https://www.diyautotune.com/product/...ic-correction/ since this car will eventually be driven in mountains and I wanted the fueling to stay consistent. Not sure if that would account for the weird readings you noticed? I'm going to check all the connections either way and report back.
Are you sure you haven't been running around(shitty tune) on a skipped belt this whole time? Maybe that's why it felt shitty. Are all your grounds connected and the threads not full of rust?
I'm running the same MAP sensor setup. Did you follow the setup instructions on that page?
Post your tune.
I thought I had, but checking again, it's not quite the same. DIY's instructions show screenshots from their older software and maybe I didn't translate it all over. Still weird though because it was running ok before the timing belt slip, on the tune that I'm including here. This tune ran the car fine before the timing belt slip. The car made 8 PSI and was plenty quick, the biggest issue is that if you revved it past 6k it wouldn't want to idle after that, unless you gave it throttle for a while. As in, if I gunned it to make a light, and then had to slow down and come to a stop at another light soon after that, it wouldn't idle at that light. Felt kind of like a limp mode. Been meaning to track that down. Anyways, this is the tune that ran the car, minus perhaps some mucking about with the ignition trigger setting.
I checked the MAP hose connection in the engine compartment and all seems well. I'll check it at the ECU and boost gauge next. Ground strap on the rear driver side of the engine is good and tight. I guess I can clean the threads too just to be sure.
You missed a setting to allow real-time baro correction. This isn't your primary problem though.
The sensor calibration that you are using is correct. You have a hardware issue some place. The MAP signal is oscillating all over the place and no where near the expected range. If the MAP sensor line is connected to any other vacuum lines you need to check them for leaks as well. Best practice is to run a tee off of the fuel pressure vacuum line for your MAP sensor, and not share it with anything else.
Your VE table also doesn't make sense. Once you fix your MAP issue double check your injector settings and import a VE table from a base map.
You missed a setting to allow real-time baro correction. This isn't your primary problem though.
The sensor calibration that you are using is correct. You have a hardware issue some place. The MAP signal is oscillating all over the place and no where near the expected range. If the MAP sensor line is connected to any other vacuum lines you need to check them for leaks as well. Best practice is to run a tee off of the fuel pressure vacuum line for your MAP sensor, and not share it with anything else.
Your VE table also doesn't make sense. Once you fix your MAP issue double check your injector settings and import a VE table from a base map.
Could the MAP signal problems also come from a leak in the IC piping? I have the MAP hose tee'd off the fuel pressure line like FM and everyone else seems to recommend. Anyways I'll follow your steps and get back to you. I suspect the MAP hose has split at the ECU or the tee I have near the ECU to connect to the boost gauge. Thanks!
When I started up the engine again after resetting the timing belt, it immediately revved pretty high and foolishly I let it do so while I monkeyed with other things. I'm guessing the oil passage under that part of the cam wasn't flowing enough oil right after startup to provide sufficient lubrication at the high rpms it was running. Live and learn. I'll get a new head, run some compression checks, and hope it all works out.
You'll want to rebuild your entire engine at this point. If any of that debris (and I'm talking about the tiny pieces) made it's way down any of the 8 giant drain holes back to the pan and into the oil pump, your bearings will be wiped, or they will be soon. You may already see some sparkles in the oil still sitting up in the head. I'd pull it, strip it, replace the oil/water cooler and any other oil cooler you use, the oil pump, and clean the engine with a couple hundred dollars worth of brake clean before reassembling with new parts.
Sadly I've lost my garage space and I'm moving across the country in a month. I will have to rebuild the engine while it's still in the car. I had already planned on pulling the head and I have a good used one on its way to me. Man, this is going to ******* suck. But I'm running out of options.
08-05-2018, 09:51 PM
here's one to stump you.
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