High Idle above 3k - Error Code 51
 

Driving along today I had my car suddenly act as though the throttle was stuck partially open. I did not feel any extra play in the gas pedal but when I pshed in the clutch it rev'd above 3500 rpm.

Checked the error codes and all I am getting is 51. Anyone else run into this problem, before I start troubleshooting?

Don't know if it matters but recently on occasion when I start the car the check engine light, brake light and warning light for bulbs, come on. The three remain on until I shut off the car. Normally they are off when I restart, even if it is right away.


Thanks in advance.

Code 51 is indicative of either the A/C circuit being active or the IDL switch open while in diagnostic mode. The IDL switch is a switch inside the TPS which tells the ECU the throttle is open if the throttle is anything short of completely closed. Given everything you describe it sounds to me as though your throttle cable is sticking, throttle plate is sticking or the dashpot is sticking.

The power up diagnostic indicators should come on with the ignition in the "ON" position and remain on until the vehicle is started or the ignition turned off. They should all be off within about 5 seconds once the vehicle has been started.



NOTE: You CANNOT make any sensor or timing adjustments while you have a code 51.. Nor any other code for that matter, but people tend to think the code 51 is the exception. :dunno:

I know this is lengthy, I have run out of mechanical talent.
 

Thanks for the info.

I removed the TB and found that the nut from the adjustment screw for the throttle stop was gone and the screw had backed out and raised the idle. The warning light trio has been going on for months. Car was running smooth prior to this and now it's running on 4 or 5 cylinders.

Removed TB and did calibration on TPS. The TPS will respond to the settings and will test OK but the readings are all on the low side of the range given. I set the throttle stop screw so that is was just touching the lever. I am not sure that the dash pot screw is correct either. The car starts great and idles now at 1200 rpm's. When driving it is weak and rough running. Below is a list of repairs done in the last 6 months.

Head Gasket Plugs Water Pump
TB Cleaning Cap and Rotor Valve adjustment
Injectors cleaned New battery Thermostat

I have not reset the timing since adjusting the TB.

Search for tech and pulled ISC valve to clean. It did not look very bad but when I disassembled it I found 2 pieces of black rubber inside the ISC. They look to be a part of a rubber seal. They are about 4-5 mm wide and 2mm thick. By the picture it almost looks very similar to the seal used on the Turbo models next to the check valve. Only found 2 pieces, any thoughts on where these came from? The ISC seemed to have the correct gaskets. Put everything back together and the car runs the same.

Where did the rubber pieces come from? Does the ISC have a seal inside?

I am also concerned about the VSV, don't know if it's working right or if it would even matter.

Along with this I have an oil pressure gauge that normally shows 20 - 40 psi and occasionally drops to 0. Hat to say it but I have driven for MILES at 0. No extra temp or noise from motor. You think it's wild to drive on Empty try 0 oil pressure.

The rubber part you're referring to is the squared off O ring used where the ISCV's housing mounts to the upper intake plenum?

Part number:
90210-26001
http://www.cygnusx1.net/Supra/Librar...spx?F=2211&P=2

I could see how someone may have put it on an N/A engine if using gaskets from a universal kit... It would of course split from being crushed as the N/A's opening isn't as deep. It's quite possible and I can think of nowhere else for such a piece of rubber to have come from upstream.

You can't set the timing if ANY codes are present. If you set the timing after any of that previous work (or neglected to do so any time after removing the timing belt or distributor) then you should do so before mucking about with anything else.

The connector on your oil pressure sender is probably loose. It's located under the exhaust manifold and comes off sideways (not straight out). The sender is a metal can of sorts. Inspect the connector and the wire.

What VSV? There are three on the N/A. The TSRM covers how to test them.

That's good news on the oil pressure problem, will check that later today.

The timing was correct prior to adjusting the TPS.Do you think that it would be running like this if it were off? I will definitely will check it though.

Is it common to have ohm readings much lower than spec on the TPS?

Idle is at 1250 rpm's. Running on 4 cylinders. The only other thing I failed to mention is when I disconnected the TB the first time I dumped a bunch of anti-freeze on top of the motor when I disconnected a hose. Would that cause my misfiring?

Oh also the 3 lights went out and now just the yellow brake light warning light is on, but all lights are working.

Thank you for your input and help.

Don't know which part of "you cannot set the timing if you have ANY codes present" I was unclear on but you cannot set the timing if you have ANY codes present. So, if you had codes present you didn't actually set the timing... more likely put it off by 40 degrees.

The TPS is a wear component. If it's not reading within the range specified in the TSRM then you need to ... (care to guess what I'm about to say?) ... replace it. :D

Um, is this a rhetorical question? Electricity + wiring + spark plugs + water = bad stuff (in this case a short), so I'm going to have to say that there's a strong possibility they're related.

Pull the plug wires out and check how much coolant the plugs are swimming in. If it's a few table spoons then just pull the plugs and let it drop into the cylinders (there's no way you're getting it out... not even with a straw and it'll burn off in just a few seconds). If there's more than that the start pushing paper towels in there and soak up as much as possible. Dry the plugs and the plug wires very thoroughly.

That was it. I found a good bit of coolant in around 2 or 3 plugs. Did as you said and it runs like it did before I dumped coolant all over the top of the motor. Thank you.

My car still runs at 1200 rpm and has always had a high idle since I purchased it. The throttle stop screws are backed off and not doing anything idle related.
Is there a dash pot setting in the shop manual?

Has anyone had a problem with the water being pushed into the coolant overflow tank? This was happening before the HG repair and is still a problem.
Will a high idle do this?
No smoke from exhaust. No water in oil. No fluid on the ground.

Thanks again for the input on the poor running condition.

Dashpot adjustment. With the engine running have someone race the engine up to ~2500 rpm. Block the little vacuum hose coming from the can to the little filter and have the person behind the wheel let off. It should maintain an RPM of around 2200 while plugged and once released should come down with just a little resistance to keep it from snapping shut.

Other suspects are the air bypass / mixture screws on the AFM and on the throttle body... the are NOT user serviceable so naturally every dimwit f@cks with those first. Then the coolant temp sensor, A/C signal, vacuum leaks, stuck ISCV, bad AFM.

Coolant blowing out the reservoir? If not a bad radiator cap and not over heating, I've got some bad news for you. Test the coolant's pH for signs of exhaust gasses getting blown into the coolant system and check the oil for signs of condensation or thinning from fuel. Did you get the block and head resurfaced? MHG or OEM composite HG?

You where crystal clear. When I did the HG, I did not have any codes, that is the last time I set the timing. The code did not appear until the throttle plate adjustment screw backed out and raised the idle.
The readings are in the range but just very low on the range.


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How would you tell and what would you do "if" someone messed with the non-serviceable screws?


I picked up a new cap last night. I have not had any water in the oil nor does it blow smoke from exhaust. I did get the head resurfaced but not the block. I believe it was a OEM style gasket.