vredniykot

Hi guys
Boy, do I have a good question for you

92 sc400 - starts poorly, idle rpm not steady when both cold and warm, when started cold exaust smells of rich gasoline, when I step on the pedal it spits and sputters with ocasional bang into air intake, to get it to rev up I have to just tap the pedal and kinda dance on it at the very top pos., in gear is even worse . . ..

Fuel is there, pump works, plugs, wires, caps, rotors,solenoids check out (it really hurt zzzzz)

Is it fuel or timing that's messing with me I can't figure out, I wanna blame both
Fuel pressure regulator and trottle sensors or is it just a tooth off on timing belt? Timing marks and TDC check out ok. Fan seems to be on all the time

Before I go and give an arm and a leg to a good cause, maybe someone could help me out?

I've read on planetsoarer.com about OBD codes but where am I supposed to read them? They are not talking about any special tools just connecting a couple of pins in diagnostics port and?

I don't know what else to think of

Help

livesc400

How new are the plugs/wires? Have you also checked the water pump? It could possibly the timing belt as well. I doubt it's the fuel pressure regulator. Have you exposed your motor to water? Just curious because my lttle bro washed his engine and got water in the plug chambers. The symptoms sound similar. Gimme soem more info and I will try to help you out.

vredniykot

Well, the caps and rotors are fairly new (aftermarket thou) wires seem to be in good shape, no cracks etc. but not tested, maybe I should do that to make sure. Spark plugs are ok, very little carbon deposit.
I should have mentioned this in a first place: I'm doing an engine swap - 91 LS400 to 92 SC400 - something that I regret now (should have sticked with SC to SC ) but I can't just leave it sitting in the garage now.

I'm thinking now that the only original thing that was left from LS is intake manifold and fuel injectors, and I'm leaning now more towards ECU/fuel injectors conflict, but all the engine harness wires fit (no missing plugs/contacts)

No water in plug chambers.

livesc400

Try running some fuel injector cleaner (full system cleaning) or check your fuel filter as well.

vredniykot

Fuel filter was replaced before I did the engine swap.

So you think that LS injectors are compatible with SC ECU?

I've also replaced the fuel tank on this car. Apparently it has been sitting for a while and original tank had about half an inch of rust in it. I did tank and filter at same time. Old filter had white flaky kinda stuff in it.

I've also replaced every computer/controller inside the cabin. Original ones had water damage inside on the circuit boards

vredniykot

I think I'm gonna have to scrap this project

Parts anybody?

TxLexus

Sounds like you did alot of work already, dont put it off now.

The LS400 and the SC400 motor are the same. Only visual difference is the Throttle body and intake chamber. I think its position differently. I would of just swap this. And there you have a whole SC400 motor.

As far as the ecu and fuel injectors its the same too.

I would check for water in the block or white smoke. A blown head gasket point to the typical symptoms you described.

I would spend a little money to get new plugs, caps and rotors. I ve seen after market caps and rotors go bad very quickly. Check your Firing orders.

Good luck.

jeremyp111

Also put in new OEM wires while your at it. Try to narrow it down by going after the cheap and easy stuff first and post back how you make out.

vredniykot

I have swapped the trottle body but I left the LS intake manifold on because the injectors are a bit different
The very tip of the SC injectors is longer than LS' and it's too loose for LS' intake but plugs fit perfectly.
I looked at my original SC injectors and there is a couple of them have rust right in those holes where fuel comes out from and the rubber seals are all cracked. Can the rust be cleaned out and can I buy the seals? I don't really want to take it apart for nothing.
There is no white smoke and no air bubbles in coolant reservoir so I think head gasket is ok.
To bring the RPM to about 5000 I have to jerk the trottle really fast and when it comes to high RPM and I hold it at that position it dies sounding like somebody cut the fuel out.
Also in the very beginning when I just put the engine in and it didn't want to start, I took it to local mech. to read comp codes and they told me that the Mass AirFlow Sensor was bad (dealer quoted $1500 for new one), but I had a spare sensor laying around so I took it to them and they got the motor to fire up. The funny thing is that when I unplug the MAFS the car keeps on running and if I plug the 'bad' one in it still fires up and runs. Could it be that my mechanic is full of $h!t or do I have 2 bad sensors? Could the sensor be tested for operability? Probably could test it on another SC4 but I dont know anybody in the area who has one - pretty rare car in my neck of tha woods

vredniykot

I was trying to work on the car today, pulled all plugs out - fresh black powder coated ones so I took some fine sand paper to them (they gotta be replaced - the ground electrode of the spark plug has a very little spot where the spark hits that looks like lava rock surface) and i put the plugs back in, fire it up - still no changes, still same bad cough up and down the idle. After about 15 minutes of running the cats were glowing red - I felt the heat trough the floor while I was inside the car, so I look down and go -- HOLLY!!!

I think I might have found a tip on what I may have on my hands
I remembered about reading this post here and maybe I've got the same thing going on

But I've switched my coils with other set but I don't know, they might be bad too

That's probably why when I get the engine to rev up to 5000 and hold it there it feels just like somebody cut the fuel lines - cat sensor is probably telling ECU - hey, you're drowning me here, cut it out!!!
It is an ignition problem unless both of my cats are bad or exaust lines are clogged up ( damn, I still have to choose out of the 3 )

vredniykot

By the way, how much difference is there between stock and TRD coils (if there is a TRD one) in both performance and price?

vredniykot

I took off the front cats today . . . .
Trough right one I could see one penny sized spot of light
In the left one I can see a lot of light but its patchy, if you look close enough you can see something like leaves but more of a squarer shape

But it didn't solve the problem, car ran same for maybe 10 min and now it don't wanna start at all

I think I really need to scrap this one and buy one that runs ok

Where do I post for parts?

jeremyp111

Dude, before you go and part it out, you should take it to a dealer or reputable service shop and pay to have it diagnosed properly and get a quote to fix it or fix it yourself. I just went through a similar type of problem and it CAN get frustrating, but work it through and you CAN fix it. Mine turned out to be bad wires and a grounding problem. Now the car runs smooth as butter. Sure glad I didn't part it out!

livesc400

I am not sure but have you checked into replacing the O2 sensors or replacing them with some eliminators? You may have bad sensors. This definately sounds like an exhaust code resulting in a poor air/fuel mixture. Just my $.02. I'd get the codes checked out so you can isolate the issue. I'm sure the motor is fine. Just something with the ECU. Also check the wiring like Jeremy said. Good luck and keep us posted.

vredniykot

That's what I'm about to do next
Ms Emerald suggested the same thing

I f this is not IT - ?

Ahh, the possibilities!