I keep getting an E26 and E27 which is "Shorted throttle switch signal" and "Open throttle switch signal". Every few days, I can't start the car. I can smell gasoline in the engine bay, but the thing won't start. It is a 1985 Deville with a 4.1. I have recently replaced the idle control module. Is there another module these codes are referring too?

Check the ISC motor, and its connector--IIRC, the codes refer to whether the throttle contacts, or does not contact, the ISC plunger. Scrape the top of the ISC plunger with a file, and check all the connectors/wiring to and from the control module...

I'm sorry, I wasn't clear. I replaced the motor. I will however, check all of the connections to make sure there is good contact. Is there a module that could be involved as well?

The codes refer simply to a loss of contact between the ISC motor and the throttle. These early EFI systems did not have Throttle Position Sensors yet, so the only way they could sense the pedal position was with a simple on/off (ground) signal, and vacuum signal from the MAP sensor. Somehow your system has lost this reference, so either it's a loose wire, or you might just need to scrape the surface of the plunger and/or the throttle linkage slightly to improve it. Check your fuel filter too...the gasoline smell and intermittent no-start both seem to point to that.

I beg to differ! This engine does in fact have a TPS (throttle position sensor). Located on the other side of the throttle body. So look at that connector that plugs onto it, either partially disconnected or in fact a bare wire touching. The locking tag breaks off easily and the connector can loosen. That TPS changes the amount of time the injectors (2) stay open referred to as pulse width. So, if the signal is wrong the injectors could be open too long causing the raw fuel odor. Open refers to a disconnected wire or harness, shorted means a wire touching metal. You might even find the TPS itself loose to the throttle body! If loose, you need the factory manual to adjust it to proper voltage at curb idle. Could the TPS harness be pinched under the air cleaner adaptor?

:owned2:Oh, my bad; it's been a while since I wrenched on a TPS. I should have known, the 3800 has one, why wouldn't these? I knew not looking for that Haynes manual would trip me up sooner or later!
I've seen that code before, but carnut is right...don't mind me...I think the pinched wire is a good one, since your codes are intermittent! :thepan:

The codes seem to be continuous but the starting issue is intermittent. I will take a look at the idle motor and the throttle position electric hook ups to see if I can find a short or corroded wire. What is the best manual to get for this old of a Caddy? I have gotten books before that were near worthless in descriptions and diagrams.

it left me stranded today. I can't see any touching wires anywhere. The only wires that are frayed, is a sensor that comes out the back of the intake manifold. I'm assuming this is the temp gauge right?

You need the factory service manual. Try www.hemmingsmotornews.com. a shorted TPS switch will, in fact, shut off fuel delivery at a certain throttle angle. If they short out its usually in a narrow voltage range, so they will run ok till that throttle angle is gotten to. If it were me and I had no manual yet, I'd get one from a wreck. Before removing it from the wreck, scratch around the two torx screws holding it on so you can swap without it being too far out of adjustment. Easiest to do by removing the three bolts holding the throttle body on, then lift it up while all the fuel lines are still hooked up. Then you can access the torx screws to mark the TPS prior to removing it. Swap it over and adjust it so the marked area is the same on your car. Also, PLEASE LIST YEAR AND TYPE OF CAR IN YOUR SIGNATURE PROFILE! was necc to scroll up 5 posts to remember what type of car you have.

Where is this Throttle Position Sensor? Is it something I can pick up from Napa?

Did you not read my posts on the 26th and 28th? passenger side of throttle body. Sure, NAPA probably has it, but you haven't confirmed it needs it yet. Thats why I recommend a used one to confirm diagnosis. They rarely fail.

ok. I replaced the TPS with another one and still the same thing: It will not start when warm. I was also told that the coil might be another place to start. I replaced that too without luck. I'm not sure what else within the ignition circuit would react this way. I thought that it might be low fuel pressure, except that when the car runs, it runs well. What else can I check? I hate to keep throwing new parts at this thing without finding the problem.

I feel for you!! But I too (87 Sedan DeVille w/4.1L) have the E26 code, almost non stop! I have priced a TPS at Napa, and it is $124.00. Wow, not much bang for buck there. I have tuned my throttle Position sensor, set too high (like 8.8 or so) on mine induced a problem with starting. I had to give her some gas to get it started. Also, when set at a higher reading, it then produced the E27 code. I have mine set back at a reading of 2.7 to 3.0 at an idle, and that seems to make her run better and start without having to give it some gas (peddle). I have not found out how to get the E26 code to go away either. I only hope to help, keep trying and don't give up!

the car keeps leaving me along side the road if I turn it off some times. I will probably sell the thing because of all its problems. Not worth a few thousand in parts....

I'm stumped too. Are you in a warm climate or cold climate? Has it had a tune up in the last couple years? If it were me, I would like to rule out a fuel delivery problem by putting a little gas in a sports water bottle and squirting a little in the throttle body to see if it fires up. If not then it is probably spark problem. I had an old Seville that drove me crazy for a month. When I finally borrowed a fuel pressure gauge, I saw that it had pressure when I turned on the key but when I started cranking it lost pressure. This was many years ago but somehow I tracked it to a safety switch wired in the fuel pump circuit. I bypassed it and cured the problem but I didn't like driving it without the safety switch. I just mention this because a fuel pressure gauge is a handy diagnostic tool to have in the tool bag. It's possible it could be something unrelated to the TPS. I feel for ya though because my first fuel injected car (Seville)would leave me stranded with no warning and made me wish for a dependable carburator. I know after a while no matter how nice the car is, you just don't want to spend any more time on it. I hope you can figure it out.

I keep getting an E26 and E27 which is "Shorted throttle switch signal" and "Open throttle switch signal". Every few days, I can't start the car. I can smell gasoline in the engine bay, but the thing won't start. It is a 1985 Deville with a 4.1. I have recently replaced the idle control module. Is there another module these codes are referring too?

Consider the possibility that the ignition control module is at fault. Often a failing module can manifest symptoms when hot but not when cold.
For purposes of clarity, is the "idle control module" you refer to, in fact, the idle speed control motor or did you mean you replaced the ICM (ignition control module)?
Some parts stores have the equipment to test the modules.
FWIW
YMMV

I replaced the idle speed controller. where is this ignition module? If I had a faulty ignition module, would I get a specific code for that?

I replaced the idle speed controller. where is this ignition module? If I had a faulty ignition module, would I get a specific code for that?

On my '93, the module is inside the distributor. If it fails, you do not necessarily get a code. There was no code when mine failed.

I re read my 84 Cad factory manual last night. Regarding codes 26 and 27, it says if the throttle lever does not come in contact with the idle speed motor at idle a code 26 will be set. It also says a binding TPS switch will set the 26 as well. So, when you replaced the idle motor did you manually retract it with car running then verify at least a .030 gap between the ISC and throttle arm? To adjust, with the car running, you move the throttle linkage away from the ISC, then while held, you depress the shaft on the ISC till it fully retacts, then quickly disconnect the wire harness to the ISC. The car should idle VERY slow, like 450 RPM. You should see the gap I refer to, approx .030. If not, then screw in the shaft on the ISC to get this gap. Then shut off car, wait 10 seconds reconnect the wiring to the ISC and restart the car. Now the ISC is set correctly. The TPS is a little more involved because it needs either a digital multimeter to set it or knowledge on the use of monitoring it thru the on board diagnostics. Nothing on the fault tracing mentioned a faulty coil or distributor module as being a cause of these codes. I think maybe you are over your head with the diagnostics? If you are determined to do this yourself, you must have the factory service manual and the proper tools.

Carnut,

You are both rude and helpful in all of your posts. Amazing...