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Changed Timing Belt, Plugs And Wires


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On my 92LS400, I changed the timing belt and plugs and wires, etc. got everything back together and test drove it and it ran smooth. About an hour later I move the car and let it idle and the car started to almost stall out then idle up again. It did this every 10 seconds. When I drove it, when I pushed on the gas pedal, the car would not accellerate, even when I floored the pedal. Is this related to the timing? Or fuel related? I'm going to double check the wires etc.

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could be the timing is a little off

could be you didn't connect the plug wires back securely to cap or plugs.

it wouldn't seem to me its a fuel problem, as you have just changed out some ignition and timing components, and could have made an error........

my suggestion would be to take her apart again and go back over and double check your work.

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It could be this or that. but before we get into all the things it could be, I would double check that all plugs are good. That all wires are good (even out of the box they can be bad), and the caps and rotors are good. Also the timeing.

If after that and every thing is O.K. but you get the up and down idle I would look at the idle control valve. I just went though it with mine. A very costly part.

PM me if you want info on checking if it is you idle valve.

For a how to on tune up see:

By the way the idle control valve can be seen in the pic for step 4 at the uper right hand coner. It is dead center on the front of the top manafold.

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We checked the error code and got a 24-(IAT Sensor Signal).  Does anyone know what it is?

Yup, #24 is the intake air temp. sensor circuit...IAT. Basically, it's the air flow meter. Check to see that the MAF connector is connected. Your problem sounds like you've just not connected everything.....

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If you didn't already do so, unplug and then plug in again your MAF harness. Also, did you throw any other codes besides 24? You may have an open ground.

Based on what you're talking about, this doesn't sound like only an IAT sensor error. The Air Intake Temp Sensor (commonly called IAT for Intake Air Temp) measures the temperature of the air in the intake and allows the ECU to adjust the pulse width of the fuel injectors accordingly (on cars with computer controlled ignition, it also allows the ECU to control timing). The lower the air temperature, the greater the volumetric efficiency (colder air = denser air = more oxygen), and the more fuel that can be fed to the cylinder each intake stroke.

The ECU's response to error 24 is to hold air temp measurement constant at 68F. This shouldn't result in severe acceleration problems. You won't see the power you're used to, but it shouldn't stutter or anything else. However, drive around with a MAF harness unplugged and holy moly, the car will sound like you re-assembled everything backwards.

It doesn't sound like the IAC valve, either, as that primarily affects only the idle speed an shouldn't affect cruising.

Make sure to verify the MAF harness doesn't have any shorts in the wires. And double check that you don't have any other error codes popping up. It starts with the lowest code first, so 24 could just be one of a couple codes.

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Just spent 3 hours with tech suport to get my E-Mail working and they can't get it to work!!! so here is the text of the E-Mail I was going to send to you on the Idle Control Valve. I'm glade this day is ending :chairshot:

It's been a long day, but I just saw you post and your request for info so here goes.

Hopefully you know were the idle control is, if not I hope this is enough for you to find it.

This goes for a 91 LS400 I think other years are the same but I do not know.

Look at the engine, looking at the top of the Manifold. You will see that in the front in the center just under were the metal vacuum lines are is a large line going from a fitting on the manifold to the air intake, behind the mass air flow sensor. It has a small vacuum line (going to the PS pump) connected right by it on the air intake housing. This is the air line the Idle Control Valve sucks in air from.

The round silver and black thing with the plug on it in the center of the engine is the idle control valve.

With the car running at idle, pull the air line off the air intake at the side that connects to the air intake. Try not to brake the fitting for the small vacuum line (Like I did).

You should feel and hear air sucking down the line. If there is no suction the idle control valve is stuck closed.

As I have only done this with a bad valve I can not say what you will get if the valve is O.K., but I'm sure that if the valve is O.K., that what will happen is as you start to cover the hole, and decrees the air coming in, the valve should open up more to get more air in, as such, you should feel an increase in the suction. If you are getting an increase then the valve is in fact opening and closing.

If you have suction try moving you finger over the opening on the hose to decrees or stop the air flow.

If the valve is stuck in the full open position (Mine was), you can get the car running fine at idle by getting your finger over the hose just right for the air flow the engine needs.

I have been told you can clean the valve. You can't. I have completely taken mine apart. But you can clean the opening the valve plunger goes into. To clean it, with the car running, just spray some throttle body cleaner into the end of the hose and it will suck it in. This will clean out any carbon build up on the plunger and it's seat.

If you need more info let me know. I can get into telling you how to remove the valve. How to open it, and what is inside etc.

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I put a new MAF Sensor in, and the error code 24 went away, but the car still sputtered on acceleration and during idling. I'll check out the idle control valve, thank 914ls for the tutorial. I had an error code 71 (EGR Malfunction) before I did any work on my car and it ran fine. But now it's not. Could the EGR have anything to do with this. I'm starting to lean towards the plugs and wires that we replaced.

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Generally the EGR valve (Exhause Gas Recirculation) won't cause the kind of problems that you're having. It's only recirculating exhaust gasses into the throttle body, which wouldn't cause the kind of stuttering you're experiencing. Part No. 2562050010 if you need it - gasket is 2562750010.

I would take a look at the wires first and ensure that there's no shorted wires anywhere. I had a horrible experience with a Miata once - my fiancee had the wires/plugs replaced at a Grease Monkey and one of the plugs was shorting into the block because it wasn't insulated properly. You could see all the burn spots on the wire caused by the arc. It would run fine for a few minutes and then intermittently lose a cylinder. The engine would shake and shudder like crazy, and you couldn't get it up to speed at all.

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I think I found the problem. The #2 Ignition wire was pinched between the engine block and RH wire cover, this damaged the insulation and caused the wire to arc. Also the #4 wire had damage from !Removed! in the cover bolt. I verified this by cranking up my car and let it run with all the ignition wire covers off, and physically seeing the arcing. I bought new wires and I'll post the results.

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