1G So much I don’t know where to start with this 1G NT

[SplayTick]

New to the forum and new to these cars. I found myself in a tight spot due to illness and losing my job and then my jeep losing its engine. I picked up a 93 Laser RS for $700. This car has mostly sat for almost 5 years. It has a lot of issues and money is tight and this is my only vehicle. I will do my best to describe everything properly.

The engine idle surges
If the MAF is plugged in the car will start but dies immediately
The transmission is in limp mode
There is an exhaust leak (undetermined location at this point)

The previous owner replaced the TPS, MAF, and ECU as well as doing a full tune up on it. I have checked the resistances on the MAF and they check ok. I have checked the voltages on the harness side of the MAF plug and they check ok. I have cleaned the ISC as checked the voltages/resistances on it and they appear to be ok as well. I went to check the BISS and it appears it is completely missing and where it goes has a bunch of dirt/grime in it and though I don’t know where I should see threads I’m not seeing any.

That’s all I have at this point as between rainy weather and my new job I just started diagnostics have been limited. Any help I can get on where to start would be much appreciated. I attached photos of where the BISS should be. Also, the previous owner did tell me they adjusted the idle but I’m not sure how they adjusted it.

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[dwb]

That BISS looks like a rag crammed in there, probably because they lost the plastic BISS screw and it was idle surging. Definitely get that rag or whatever out and a new BISS screw/oring in there ASAP, it'll improve your idle significantly. Then I would perform a boost leak check - your vacuum lines look rotted and are probably leaking. Are you seeing a check engine light?

 

[SplayTick]

The MIL is on but that is because I’m order for it to run I have to leave the MAF unplugged. The BISS is definitely missing but it’s not a rag in there, it has a bunch of dirt and grime in it. I have scraped at it and it turns to dust but I’m worried about pushing it further into the TB as well as I’m having trouble removing the dust once I get it scraped loose. It is a N/T so a boost leak check is not applicable. I was wondering on the vacuum lines but haven’t had a chance to check them yet as I just picked this car up Sunday and have been busy with work.

 

[dwb]

Then I would perform a boost leak check

Sorry, didn't realize until now this is NA. Probably still a good idea to replace those vacuum lines though.

The MIL is on but that is because I’m order for it to run I have to leave the MAF unplugged. The BISS is definitely missing but it’s not a rag in there, it has a bunch of dirt and grime in it. I have scraped at it and it turns to dust but I’m worried about pushing it further into the TB as well as I’m having trouble removing the dust once I get it scraped loose. It is a N/T so a boost leak check is not applicable. I was wondering on the vacuum lines but haven’t had a chance to check them yet as I just picked this car up Sunday and have been busy with work.

Pull the throttle body, then you can have good access to both sides of the BISS and won't have to worry about that crud pushing through. Gives you a chance to clean/inspect it too while it's off.

The MIL is on but that is because I’m order for it to run I have to leave the MAF unplugged.

Might be other codes there besides the MAS.

 

[SplayTick]

I’m on my phone and can’t figure out how to reply directly to each one in a single message so I will do this as painlessly as I can. Lol

On the N/T part, you’re good. It happens to the best of us.

On the pulling the throttle body, I wasn’t sure if that would allow me access to both sides of the BISS port. Thank you for that info. We have rain coming the next 4 days and I don’t have a garage so that one might take a bit for me to get to.

On the vacuum lines. I had been seriously thinking about it due to the age of them. Is there anywhere I can find the info on how much I will need to buy as well as what fittings are needed to replace it all?

One more thing I forgot to put in the initial post, the vacuum switch that is mounted in the thermostat housing with the two vacuum lines going to it, it has had coolant leak on it and the outside of it has corroded a bit due to that. Should that be an immediate replacement or is that something I can let go until I have the other issues figured out?

 

[motomattx]

The vacuum switch is not that big of a deal, it is for emissions, BUT if the vacuum lines going to it are broke off or otherwise leaking, that would need dealt with swiftly.

 

[CrackedDSM]

There has got to be a major fueling issue if it runs with the MAF unplugged but dies with it. I would think vacuum leaks would contribute to the idle surge, but feel like they would be counter intuitive to the maf being unplugged. It’s not measuring any air so the fuel is just squirting in. Can you smell fuel especially with that exhaust leak? Wonder if you hear the injectors “clicking” with a stethoscope or if one or more is stuck open.

A boost leak test might not apply but it wouldn’t hurt to do a smoke test or pressurize the TB/IM and see if there’s a massive leak. How’s the oil? Smell like fuel? Seem thin? Throwing me for a loop that it runs better without a maf. Will it run and drive that way?

The trans in limp mode is a somewhat easy fix. You can hook up some toggle switches and make your own “shift box”, wire up the kiggly shifter mod and shift it via the gear shifter, or purchase an actual shift box like from forcedfour.com that will completely replace your TCU. Or you can pull the TCU codes with a multimeter, and/or have it repaired if it’s bad. Hooking up some toggle switches to the orange and yellow wires of the solenoids will quickly show you if something is wrong with the trans(it won’t shift right) or the TCU (it’ll shift perfect no issues) though so that’s honestly where I’d start after you get the weird unplugged maf issue sorted.

 

[dwb]

Do you know why the previous owner replaced the TPS, MAF, and ECU? Did he/she leave you with the originals? I have to question if the replacement ECU and/or MAF were known good. Might be worth a look at the ECU for leaking capacitors and correct part number for your application. Does your wiring look OK/not hacked with a clean connector at the MAF plug? Is the MAF clean and unmolested?

If this were a turbo 4g63, I'd also check out the CAS, coolant temp sensor and 02 sensor (and their wiring). Unfortunately I'm not familiar enough with the NA engine to know which of those components even exist. You could also cap the vacuum ports on the TB as a test to see if anything changes. Brake booster could be a culprit of a major vacuum leak also. That being said, I don't think your vacuum lines are the root cause of the only-runs-with-MAF-unplugged issue, unless you have a major vacuum leak. I think you're chasing a bad sensor or bad wiring somewhere. The CEL codes, if more than just the MAF, might help you identify the sensor.

Once you get the MAF issue figured out, then you can start troubleshooting the idle and trans issues. I wouldn't worry about the exhaust leak for now, unless it's associated with the 02 sensor.

On the vacuum lines. I had been seriously thinking about it due to the age of them. Is there anywhere I can find the info on how much I will need to buy as well as what fittings are needed to replace it all?

I long time ago I bought the "Larson Hose Kit" from RRE (http://www.roadraceengineering.com/nwdsm_larsonhosehasitsownpagenow.htm). I have no idea if they still sell the kit, but my hoses are still in great shape ~20 years later.

 

[SplayTick]

They replaced those parts because it was idling poorly. They didn’t do an actual diagnostic on it and was mostly just throwing parts at it. They did replace them with new parts. The ECM may have been reman but I’m not sure. I do have both computers. They did say when they replaced the ECM the problems seemed to go away for a day or two but came back which has me worried the ISC motor has possibly shorted the ECM.

As far as the codes go, if I plug the MAS in and start it, I can keep it running by giving it fuel and feathering the pedal. The MIL does not come on when I do that which leads me to believe there isn’t any codes other than the MAS. I don’t have an analog meter to pull the codes so I am going to pull a piezo buzzer out of something around the house to listen to the codes when I get off work today.

i forgot to add that I will cap the vacuum ports on the throttle body to see what happens as well.

The vacuum lines checked ok so I took a can of carb cleaner and started spraying a few areas that I knew to check. The areas around the throttle body as well as the breather tube caused no increase in idle nor did the areas around the intake. Two of the injectors do cause an increase in rpm’s when sprayed. Money is a little tight right now so until I can get full replacement injectors the parts store here has an injector o ring set in stock for just under $10 so tomorrow after I get off work I’m going to pick a set of those up and get them installed as long as it’s a somewhat simple process. If not it will have to wait until the weekend for them to be installed.

 

[CrackedDSM]

The vacuum lines checked ok so I took a can of carb cleaner and started spraying a few areas that I knew to check. The areas around the throttle body as well as the breather tube caused no increase in idle nor did the areas around the intake. Two of the injectors do cause an increase in rpm’s when sprayed. Money is a little tight right now so until I can get full replacement injectors the parts store here has an injector o ring set in stock for just under $10 so tomorrow after I get off work I’m going to pick a set of those up and get them installed as long as it’s a somewhat simple process. If not it will have to wait until the weekend for them to be installed.

Check and see if they still have the lower insulators too. Just because an injector is bad, doesn’t mean idle will change if you spray it. It means there’s a vacuum leak and if you’re missing an insulator that would be a giant leak. If there’s a cracked pintle cap or missing, that would affect the seal too. If you need a set of lower insulators, I have a set I can send you fo’ free if you need them.

Pull the fuel rail though. It’s three bolts, and you’ll need to pull the TB cable loose from the TB but it’ll be worth it. That way you can check the o-rings and the lower insulators and pintle caps.

 

[waltah]

With no BISS screw you're never going to have correct fuel/air at idle or low RPM. I'd fix that first because nothing else is going to make sense until you do. I wouldn't even bother to look for air leaks: You've got the Mother of All Air Leaks right there in your throttle body. Fix that, then see where you are.

The BISS controls a fixed (adjustible with the screw) flow of air around the throttle valve. Its normal position is maybe 1/2 turn, maybe a whole turn open. (Someone with an NA car can give you a better estimate). With the screw gone that's probably several times too much air.

Plugging the hole to the outside will just keep it cleaner -- not give you a way to get the right amount of air.

I'd pull the throttle body as suggested and wash that hole repeatedly until it's clean; you'll be able to see the fairly fine threads once you get all the dirt out. I''d guess you might have to get that screw from another TB unless someone knows a source for just the screw.

Get a rifle or pistol cleaning brush -- Wal-Mart has them and you can probably find a size that you can sort of screw down in there to clean those threads. Kerosene or maybe WD-40 would be a good way to flush the greasy dirt out.

When you get the screw, don't force it. It should go in freely until the o-ring enters the bore: If it doesn't the threads aren't clean enough.

The easy way, of course, is to replace the TB and you may get forced to do that but that's (ballpark) $100 for a used part so I'd definitely look for the screw first.

 

[CrackedDSM]

With no BISS screw you're never going to have correct fuel/air at idle or low RPM. I'd fix that first because nothing else is going to make sense until you do. I wouldn't even bother to look for air leaks: You've got the Mother of All Air Leaks right there in your throttle body. Fix that, then see where you are.

The BISS controls a fixed (adjustible with the screw) flow of air around the throttle valve. Its normal position is maybe 1/2 turn, maybe a whole turn open. (Someone with an NA car can give you a better estimate). With the screw gone that's probably several times too much air.

Plugging the hole to the outside will just keep it cleaner -- not give you a way to get the right amount of air.

I'd pull the throttle body as suggested and wash that hole repeatedly until it's clean; you'll be able to see the fairly fine threads once you get all the dirt out. I''d guess you might have to get that screw from another TB unless someone knows a source for just the screw.

Get a rifle or pistol cleaning brush -- Wal-Mart has them and you can probably find a size that you can sort of screw down in there to clean those threads. Kerosene or maybe WD-40 would be a good way to flush the greasy dirt out.

When you get the screw, don't force it. It should go in freely until the o-ring enters the bore: If it doesn't the threads aren't clean enough.

The easy way, of course, is to replace the TB and you may get forced to do that but that's (ballpark) $100 for a used part so I'd definitely look for the screw first.

Here’s the OEM screw and O ring from extreme psi. Just in case anyone needs it. Click me

 

[Dericsh]

I thought boosted fab made one too but I can’t find it on their website.

 

[waltah]

Good to know that the BISS screws are out there! I'd bet that the idle surge will go away when it's installed and maybe the MAF issue too.

Now about the transmission being in limp mode: I would not try to fudge it to go into gear. One of the reasons for the TCM to command limp mode (locked in 3rd gear, right?) is it thinks something is wrong with one or more other gears and is trying to limit the damage. Taking the TCM out of the picture with switches, etc. is okay with a transmission you know is good but you don't know that and maybe the TCM is saving you a bunch of repair work.

I would first look at the TCM codes and see what they say: If there's a story there, check it out. If you can borrow a good TCM that would be another way to go.

For what it's worth the only time I ever had a Mitsu in limp mode it was a bad TCM. '92 Expo LRV and eBay provided a working TCM.

I found myself in a tight spot due to illness and losing my job and then my jeep losing its engine. I picked up a 93 Laser RS for $700.

ST, you got balls o'brass. 'Sall I can say. Hope things are looking up now.

This car has mostly sat for almost 5 years. It has a lot of issues and money is tight and this is my only vehicle.

Cars sit, they pile up problems but most of it is hopefully little stuff. This is a good place to come for help with what must be dealt with.

 

[CrackedDSM]

Now about the transmission being in limp mode: I would not try to fudge it to go into gear. One of the reasons for the TCM to command limp mode (locked in 3rd gear, right?) is it thinks something is wrong with one or more other gears and is trying to limit the damage. Taking the TCM out of the picture with switches, etc. is okay with a transmission you know is good but you don't know that and maybe the TCM is saving you a bunch of repair work.

The TCU isn’t actually all that smart, or aware of what’s going on tbh. It will put things into limp mode (aside from being bad) for the dumbest reason. It’s not like it can measure pressures inside the transmission, or do anything of that sort. It doesn’t even really communicate with the ECU very much aside from getting an rpm signal. The caps also are susceptible to the same melting issue as the ECUs do when it comes to the ISC.

Basically, it just guesses. Pulling codes will somewhat help, but it’s more to figure out if the TCU is dead or not. The source code/.bin and .XDF for the 1g TCUs are out there if anyone wants to dig in it. Dave at EFISpecialities could tell you more as he’s a pioneer of this stuff.

But basically, only worry with switches is downshifting from 4th or 3rd to 1st on accident at moderate speeds.

 

[SplayTick]

Sorry for the long delay in a response guys. I’ve been busy with work and doing repairs on the car and didn’t see the notifications. So an update.

I replaced the seals on the injectors and checked everything out there. Those are good now. While I was doing those I found some SERIOUS intake manifold leaks. I got the new intake manifold gasket on earlier this morning and the idle surge is completely gone and the idle dropped down to 500 RPM and the car didn’t want to stay running. With no Biss I used the throttle cable to get it idling around 800 and the MAF is able to be plugged in without the car doing now as well. I need to get my hands on the replacement Biss and go from there on that.

The transmission is still in limp mode and I haven’t been able to look too much into that yet. I will be here later today.

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[SplayTick]

I do know that the previous owner said when he swapped the ECU out the transmission shifted fine for a little bit but then ended up going back into limp mode.

 

[CrackedDSM]

I do know that the previous owner said when he swapped the ECU out the transmission shifted fine for a little bit but then ended up going back into limp mode.

It’s kind of pain but go ahead and pull the TCU, and open it up. I bet $1 it smells like fish and has leaky caps. Very common issue on auto 1Gs especially with an ISC that has killed an ecu before or just in general with age. If it all looks perfect hunky dory then you can quickly click it back into place and pull TCU codes, but honestly it’d be easier to hook up toggle switches and immediately be able to tell.

Up to you though. Plenty of options. Check wiring to the TCU as well, because if it’s not getting a proper rpm signal or etc, it’ll think somethings wrong and throw it into limp mode.


Edit: man this makes me miss my auto 1Gs. Anyone want to go tradesies with me for one?

 

[SplayTick]

I didn’t get a chance to do anything else to the car yesterday as I had planned. Yesterday was my daughters 21st birthday and ended up being a lot busier than I thought it would. I’m hoping to be able to pull the TCU today after work. If it is leaking caps and nothing else I’m pretty handy with a soldering iron and will probably try to reman it myself.

 

[SplayTick]

Well, I think it’s safe to say the TCU is toast and this looks like it’s being a little soldering iron work. Looks like the traces are fried too.

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[CrackedDSM]

Well, I think it’s safe to say the TCU is toast and this looks like it’s being a little soldering iron work. Looks like the traces are fried too.

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Yep. Called it.

Get yourself a new shift box or see if Tom Dorris at ECMTuning will repair it.

 

[SplayTick]

Yep. Called it.

Get yourself a new shift box or see if Tom Dorris at ECMTuning will repair it.

I have a reman ECU that was only installed for about 5-10 minutes of run time. Would it be prudent to try to find someone to trade a known good TCU for that ECU or should I look at different routes and hang on to that ECU for a possible rainy day?

 

[CrackedDSM]

I have a reman ECU that was only installed for about 5-10 minutes of run time. Would it be prudent to try to find someone to trade a known good TCU for that ECU or should I look at different routes and hang on to that ECU for a possible rainy day?

I’d hold on to the ecu and either try to get the tcu repaired, find a shift box, install toggle switches to shift the transmission yourself, or wire up the kiggly shifter mod. On a 1g you can use the eco/sport button to enable OD.


Here’s how to make your own “shift box” with toggle switches. https://www.dsmtuners.com/threads/homemade-shifter-for-automatic.320324/ my old account was named “unwythe” so it’s me he’s giving credit to .


Here’s the kiggly manual shifter mod

https://www.kigglyracing.com/_files/ugd/0a98b0_41259167bd50427ab7b7a2a7ea37ce37.pdf (this makes your OEM shifter have full control of the trans, bypassing the tcu entirely. You have to shift every time yourself though.


And for a complete shift box solution that will make it be a full automatic and entirely replace the tcu go to forcedfour.com and check out their products.

As far as tcu Repair hit up ECMTuning.com and email Tom Dorris and ask if he’ll repair your TCU.

 

[SplayTick]

I spoke to the original owner (I know them outside of buying this car off of them) and I did have a little information wrong. The reman ECU that I have never did get installed. What they swapped was the TCU. They gave me the original one that came out of it. The one that is fried was a used one from a salvage yard. I can’t see any bad spots in this one.

Is it possible that any of the issues I already addressed would have had the TCU in limp mode?

I have checked the IAC and it checked ok on my multimeter. Is it possible that it could appear ok and not be? I want to try this other TCU but if there is a possibility that the IAC could still be burning the TCU I don’t want to risk it and will replace that before I try this TCU.

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[SplayTick]

Well crap. Never mind on the original TCU. There is a blown surface mount in the same area. The damage is nowhere near as severe as the other one is. I should be able to fix this one. I found an IAC online for around $37 + shipping. I think I’m going to throw one of those in and fix this TCU. I’m not 100% sure yet because I haven’t cleaned the board but it looks like it says it’s capacitor C3. Does anyone know the value on that or have links to a schematic I can look at? The top of the cap is completely burnt.

I cropped the previous picture and circled the offending surface mount component.

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