1993 KA24DE - Poor Idle, Dies Randomly, Bogging

[Gokussj5okazu]

Hey guys, got a big head scratcher here. A few days ago I started working on my 240 again after letting it sit for several months after I rebuilt the engine. Couldn't get it to start, just spit and sputter. New dizzy cap, rotor, coil, plugs, wires, MAF. Finally got it running with some starting fluid, turns out the dizzy was off 1 tooth.

So now I've got it to where it will start albeit difficultly, but the idle is very poor. It's hunting for RPM a lot, and dies randomly. If I give it throttle slowly, it will rev to the moon, no problem. But if I goose it suddenly is bogs down BAD, and typically dies if I don't let off.

So tonight I went and bought a timing light to make sure the timing is 100% right. I started out checking it WITH the TPS plugged in. #2- #4 were dead on 20* BTDC. #1 was WAY off to the point that I had no clue where it was.

Then I read the the guide to setting timing, pulled the TPS, and this time I was able to set #1 to 20* BTDC perfectly! While I was doing this the idle was smooth but around 1500 and it started overheating. I figured I would try setting the idle next. Turned the idle screw both clockwise and counter-clockwise and nothing! No matter what the idle stayed more or less the same though it was still hunting.

Suggestions? I'll be doing a fuel pressure check tomorrow. Also, I pulled all the plugs and they look identical.



SO to sum it up, the timing is set at 20* but that's around 1000 rpm. And the idle is all over the place, randomly dieing. Unplugging the IACV does drop the idle to the point of nearly dieing. It's also difficult to get started.

[PapaSmurf2k3]

Almost sounds like a vacuum leak. Check all your hoses all over the engine bay, as well as your intake manifold gaskets, and intake tube.

[Gokussj5okazu]

Thanks, I managed to find a decent leak at my EGR block off plate.

So I pulled the intake, and tapped/drilled then plugged every hole on the damn thing except for the IAC, the brake booster, and the small vacuum line above it for FPR.

Put it all back together and couldn't get it to start, just crank and crank. Turned the IAC idle screw all the way in, and cranked some more. This time it stumbled a bit like it was trying to start. Backed it all the way out, and nothing, no stumble.

So I'm instantly thinking not enough fuel?? Shot some ether down the IAC tube and it fired right up! For about 3 seconds and then it's like the ECU is shutting off the injectors, it just dies instantly. I can hit the throttle and rev it way up all I want, but at exactly 3 seconds it dies.

Ideas? This thing is ridiculous!

[PapaSmurf2k3]

Is your fuel pump kicking on? Can you hear it when you key-on (without starting)? I'd start be verifying its delivering fuel to your injectors.

[Gokussj5okazu]

Yeah it's definitely kicking on. I can hear it hum, then hear the relay under the hood kick off after a few seconds. So it's priming properly. I'm thinking either the ECU is turning the pump off or it's just not firing the injectors after a few seconds. I'll pull the rail and see if they all squirt properly tonight. I'm also going to go ahead and relay the fuel pump directly to ignition to eliminate that as an issue.

[Gokussj5okazu]

Alright, so fuel is NOT the issue. I went ahead and hot wired the pump. Tried to start it, and nada. Used a bit of starting fluid and it started again but died after 3 seconds.

So I decided to try it without the MAF plugged in. Started with a bit of ether again, and it runs! The idle was super low, but adjusting the IAC screw fixed that. Then I checked the timing. It was at about 5* retarded, and that was with the dizzy fully advanced. So I advanced it 1 tooth, and was able to set the timing back to 20* advanced at about 700 rpm.

So timing is perfect, idle is great and smooth, and I have absolutely no vacuum leaks - tested it to 20psi. BUT obviously at this point it's in limp mode. Now if I plug in the MAF it stumbles for a second then dies in the exact same way that it was dieing before.

My first thought would be a bad MAF, but this is the second one that I've had on this car since I've rebuilt it. The first one gave these EXACT same symptoms. And now this one too? Definitely not a bad MAF.

Now here's the interesting part. When I had it running it sounded like there was a damn jet engine inside the air filter! I swear this thing is pulling a HUGE amount of vacuum, which would explain why it wont run with the MAF plugged in. Too much air! So what could cause a rediculously high vacuum?

[Gokussj5okazu]

Well made a bit of progress this morning. Got it started without the MAF plugged in. Plugged it in, and it almost died so I unplugged it. Decided to pull my air filter and plug it back in and it actually stayed running! It was super rough and the idle dropped down very low, but it ran. Also touching the throttle AT ALL kills it.

So no filter and it runs. MAF problem. Yet I know the MAF is good. Jumpered the MAF ground to the body and the RPMs increased. So looks like I had a small ground issue. But still runs like crap. So I measured the voltage at the MAF. 12.10v from REF to GND. With the engine running that should be closer to 14, right? So I checked at the battery, only 12.20v. So damn, my alternator isn't charging.

Took a look at my fuse block, which is a custom setup, alt post to fuse block to batt. Alternator was putting out 35v!! But the fuse was blown. So now I've got a charging issue to deal with as well. But back to the MAF.

So with KOEO, the MAF signal voltage was 0.22v. With engine running it was between 1.0v and 1.15v.

[PapaSmurf2k3]

That sounds about right.
I wouldn't have set the timing while in MAF limp mode though. I'm not sure if that's the same as disconnecting the TPS to do it or not, but you might want to double check it.
I wonder if you got some voltage spikes somewhere and that cooked either some of your sensors, or certain fuses.

[Gokussj5okazu]

Good news! I ran a new 8 gauge alternator ground wire, replaced my 80 amp fuse and the alternator is charging! Nice 14.2v! So that problem's solved.

Rechecked voltage at the MAF, getting 11.8v in, good ground. 0.3v KOEO, 1.3v KOER idle. So all good there.

So I decided to go through all of the sensors, and found a loose pin at the TPS. Got it fixed up and that seems to have solved most of the problem.

It now runs and idles pretty well around 700 with the MAF, TPS, etc all plugged in! BUT, now I've got a good bit of a hesitation if I goose it. It will eventually catch up, but it pops and shakes. Also it still will NOT start on it's own, I still have to give it some starter fluid to turn over the first time.

I'll be rechecking the timing, adjusting the TPS, and setting idle speed again tomorrow. Any other suggestions though? ECU is just giving me 55.

Also any suggestion on fixing a tachometer stuck completely clockwise?

Here's a video of the current state.