Esprit won't idle more than ~5 seconds

[TXesprit]

My car is a 97 V8 USA-spec with straight pipes from the cats. Yesterday after driving for about 2 hours on the highway I stopped to fill up and noticed one of my pipes dangling - the pipe broke off at the weld behind the cat. Not sure how that happens. Now, I can start the car right up, but once it goes through the fast idle cycle, it lowers the RPMS and dies. If I give it gas during the fast idle, everything is fine, but once it trys to drop the idle, it dies, even when I give it gas.

Any ideas what may be the issue here? A couple of my non-mechanic thoughts:

- something to do with the pipe coming off has the readings going weird and causing the shutoff (but I don't know why, there are no sensors in the pipe that came off)

- bad cat (thereby causing the pipe to heat up and break the weld)

- bad 02 sensor

- ?

Any help would be appreciated. I'll try to take a picture of the pipe break if that helps.

[gmendoza]

Is there less exhaust flow out of one side? If yes, then it may be the cat but my guess is a bad Idle Air Control valve. Is there a Check Engine light?

Edited July 31, 2009 by gmendoza

[superdavelotus]

It's a tricky one but I had almost the same symptoms so here's what I'd look for:-

1. O2 Sensors or wiring coming off it.

2. Blocked Cat

3. Faulty IAC valve

4. Faulty ECU (dry joint driving the IAC valve)

The last two items don't throw up an engine check light. The first two should do but not always.

David Walters

[TXesprit]

Thanks for the suggestions. The check engine light is not coming up, so perhaps it's the IAC valve. Is there any way to check that, or is it something to just replace and keep your fingers crossed? I'm going to borrow an OBDII scanner this afternoon and see if that's picking up anything.

[lotus4s]

Did you check the wiring on the O2 sensors?

[TXesprit]

The O2 sensors are all connected and the wires appear fine. I used my rubber mallet and took a few taps on the cats to see if there was any rattling and they sound solid. I disconnected the battery for a few hours hoping a reset would help, but there was no difference. I'll call around tomorrow and see if I can find a new IAC valve and try that.

[TXesprit]

OK, plugged in an OBDII scanner and got the code P0135: O2 Sensor Heater Circuit Malfunction. I cleared the code and started it up multiple times but couldn't replicate the code, but at least it's a start. Looks like my next step will be O2 sensors...

[superdavelotus]

This is normally a break in the wire close to the plug. You'll need to check the wiring.

Apparently this is a common problem.

David Walters

[TXesprit]

It's been a long while since I updated this. Unfortunately, I'm in the same position, and I can't believe it's been this long.

I've downloaded Peter's scanning program (thanks!), and now I've got all sorts of great information about what's going on. The problem is - I don't really know how to figure out what it's telling me.

I'm getting relatively matching readings from the O2 sensors, which appear to be within the specified range. I'm considering these OK.

For the others, it's hard to tell what is normal and what is not. The only thing I really notice is the Fuel Relay #2 is always ON, and Fuel Relay #1 switches on after it starts and shuts off after the car cuts out. The MIL 2 Lamp is ON at the same time as Fuel Relay #1 says ON.

The other things I notice when the car is running:

- Intake pressure drops from 29.3 to 11.8

- IDLE DC drops from 89 to 68

- Pulse Width drops from 18387 to 4245

These go back near the original values when the car shuts off.

Any thoughts?

[Günter]

stock condition is that both pumps pressurise the system on start-up, and under WOT conditions. So you can see both pumps in the screen-shot/live data only on cranking and high speeds.

What does your idle-control say, is it repositioned after reset of the ECM ? (by disconnecting the battery, or with the throttle-pedal method )

With 11.8 you mean PSI -right !? The 918 engine is an 'normal aspirated' engine most of the time. Especially under idling there can't be high [positive] pressure. So as 15PSI is around atmosphere it sounds normal..

sidenote: as soon as you have problems with the O2-heater circuits, and maybe with an blown fuse too ...take a lok into the wiring shemes in the workshop-book. The heater circuit can affect other circuits on the fuse-line

Edited January 15, 2010 by G

[TXesprit]

I reset the idle-control via the throttle pedal method. I'm not sure if the sensor that monitors it is the "IDLE DC" or "Idle switch - input". If it is the "Idle switch - input", then it is showing "ON" the whole time.

The intake pressure is measured in Inches of Mercury (inHg). 1 inHg = 0.491098 psi, so 29.3 = 14.8 PSI when the car is not running, 11.8 inHg = 5.8 PSI when the car is running.

[Günter]

5.8PSI (around 40kPa) on idling sounds normal for me... . But can't say what your scanner should read on the OBD live-screen for the IdleControlValve.

[97-Esprit V8]

Will it run if you rev it? How many miles on the car? Has it sat for long periods of time?

Borrow or buy a fuel pressure gauge, check that the fuel pressure is good.

[TXesprit]

It will respond to the throttle only in the first few seconds, then nothing. Fuel pressure is there, and came out of the Schrader valve quite forcefully, though I didn't hook up a fuel pressure gauge.

I started testing sensors and relays, and the one suspect item is the Throttle Position Sensor. I noticed on the scan program that I was showing 0% throttle, and testing the TPS with a voltmeter shows zero no matter what combination of contacts I try. Could the ECU be controlling everything ok during the initial startup, then maybe it can't figure out what the throttle is doing so it assumes zero and sputters out? Has anyone replaced the TPS? Does this make sense? Can the tiny little sensor really be a $300 part?

[mike_sekinger]

You should be able to check the TPS without the engine running. Just hook up your scanner with the ignition on and you should be able to exercise the TPS from 0 through to 100%.

If you find the sensor at fault, I have a spare sensor that you can have, if you cover the shipping costs.

Cheers,

Mike S

[97-Esprit V8]

You should be able to check the TPS without the engine running. Just hook up your scanner with the ignition on and you should be able to exercise the TPS from 0 through to 100%.

If you find the sensor at fault, I have a spare sensor that you can have, if you cover the shipping costs.

Cheers,

Mike S

Sounds like a TPS, Mike you should change your signature to read:

More spare Lotus parts then sense...and generally a great guy!

[mike_sekinger]

Only generally a good guy?.......

Edited February 17, 2010 by mike_sekinger

[97-Esprit V8]

Only generally a good guy?.......

lol

[TXesprit]

Many thanks to Mike for the "new" TPS. I managed to replace it this weekend and she now starts and idles perfectly. It took a few minutes for the computer to re-learn idling under load, etc, but things are looking up.

Unfortunately, I have a new issue. It will idle fine, under load from the AC, lights, etc, but when I try to give it gas or drive it, the engine feels like it is getting choked. It's almost similar symptoms as before, where I can give it gas all I want and rev no problem for the first 10 seconds of startup, but once it drops to normal idle (~900rpm) it doesn't respond well to the accelerator. If I'm holding it steady, or letting off the pedal, no problem. Once I try to accelerate, it hesitates and stumbles.

I've tried different adjustments for the new TPS, with no difference. I'm hoping it's just old fuel (and unfortunately a full tank of it), but it doesn't seem to make sense why it would work fine for the initial startup. Any help on this one?

[TXesprit]

Just thought I would see if anyone has any ideas on my issues - I've tried resetting the computer again, let it idle for ~20 min, turned on the AC and idled more, then off again. It starts up no problem and idles smooth. Only when I give it gas does it stumble. If i drive it during the warm-up cycle it drives fine, only after a few seconds does it act up.

Could this be a bad ECU / computer? Ideas?

[Günter]

given the year of your car -first try out all other 'usual things' first... .

What means check that your engine 'breathes' freely -> air filter elements out, catalyst disconnected on both sides. This mreans it runs loud but should respond on your acellerating signal (TPS) like a wild dog. Most of the older cars suffer from blockage in the exhaust (use the search function on 'ceramic catalyst' -there are a lot of experiences within TLF like this..).

Second step is to check the real-time data stream wile idling and 'running in gear' on idling rpm via an OBD interface. Is there any not plausible reading (unfinished 'open loop' or non logic pressures/temperatures or seriously indifferent short/long time injection period reading between both banks, reset on idle-valve and so on)

Third step could be an check on the hardware -what means follow the workshop manual instructions (or Mikes documentation for timing-belt tension check in LotusEspritWorld) for timing position.

Think that's pretty much all you can do in DIY without any additional spare parts.

[TXesprit]

Wanted to give an update after finally taking it in to see the mechanic. Turns out we had two issues. First, one of the O2 sensors had loose connections, so was not always reading correctly. The key issue was the main fuel pump - it was working, but wouldn't pump more than enough to idle. On startup, the secondary pump is working, so that's why it would rev with no issues. After initial startup, I was showing enough pressure for idle, but when giving it gas, it just couldn't keep up.

So, new fuel pump, fixed O2 sensor wires, and we're back on the road. Thanks for all the help and suggestions.

Mike - Let me know if you'd like the TPS back, or if I should keep it in the rotation for the next person who might need one.

[mike_sekinger]

Hi Sean,

Nice to hear that you have solved your problem - shame that it is so late in the season.

Please send the TPS back, so that I can hold it in case anyone else is in need.

Cheers,

Mike S

[TXesprit]

I'll put it in the mail tomorrow.

At least in Texas, the "season" lasts all year for driving. In fact, the weather is just getting cool enough for the AC to keep up.