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Discussion Starter #1 (Edited)
Hopefully, someone can give me a little help/advice.

My Esprit has a stumble at idleand poor tip-in throttle response from idle.

When cold starting the car, it fires right up. But, then, it stumbles along ias it tries to get "into a rhythm." Not sure why, but the throttle jack solenoid doens't seem to be getting a signal to turn the solenoid on. (Update: just changed the solenoid for the EBPV and throttle jack.....so that may have fixed that issue, now)

Nonetheless, the engine shortly starts idling fine but it has a a continuous pop to the exhaust note..... bear with me.....it sort of sounds like this:

hmmmmmmmmm bup hmmmmmmmmmmm bup bup hmmmmmmmmmmmmm bup hmmmmmmmmmmmmm bup bup

to go along with this, if I stab the throttle from an idle, the rpms drop and the engine stumbles. If I slowly open the throttle, no problems at all. Also, there are no issues while driving at all. It seems to be a fuel/injector/rich or lean issue.

I have checked the vacuum lines, and fixed anything I saw that needed attention. I also checked fuel pressure, and that seems to be fine to. I have always used a listening device to listen for vacuum leaks at the intake manifold. I could hear anything, but you can't get to all areas of the manifold to listen to it.

Does this sound like a bad injector? I have read that the stock injectors don't spray very evenly and have a tendency to leak.

On a side note, i would say that my gas mileage is much worse than expected. It is hard to say though as I only drive the car about once a week and I usually "have fun" when I take it out.

Any advice would be appreciated, especially from those of you who have changed out your injectors.

thanks!
 

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When I had a bad injector on my 1994 S4, it took another out with it and was obvious i had to update/change my injectors.

Does your car start fine when warm?

I really think your "cold start stumble" is when our cars "forget" where to position the IAC valve for starting. You have to "re-teach" the ECU how to start the car. It is an easy procdure, takes about one hour. Start by disonnecting the battery, then reconnect after 10 seconds. Do you have the procedure? If not I can find it or someone can and re-post. I had this problem over 2 yrs. ago on my S4. I "re-taught" the computer, and the problem NEVER returned.

(I did later have bad injectors, but that was more catastrophic, like car missing very bad, not just a missfire, in my case.)

Let me know if you want me to find and post the procedure to "re-teach" your ECU how to cold start. mark j.
 

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First you need to make sure you don't have an air leak in the intake manifold. By the way, those aren't vacuum lines... You'll also need to check the condition of your intake manifold gaskets.

The symptom is most likely a problem with the IAC (Idle Air Control valve stepper motor) on the intake manifold. You'll need to use Freescan or EspritMon to look at the IAC counts, record data from cold to fully warm at idle (do not touch the throttle). The IAC should be between 20-40 when the engine is fully warm (~80C) at idle. If your IAC is too high it will cause the stalling and the stumble when you first touch the throttle before the engine is fully warm.

If your IAC is out of spec, make sure that it isn't due to an air leak in the intake manifold... Then there is a procedure for setting the minimum air rate bleed screw to get the IAC into the proper range, but it MUST be done with freescan.
 

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Discussion Starter #4
I used freescan, and the IAC seems to be fine. I suppose to should run a log though and post it up. I haven't tried logging anything yet with freescan.

Judgea, if you have that relearnign process that would be great.

In your opinions, is the "hmmmmmmmmmmm bup bup hmmmmmmmmmmmm bup" normal for these engines?
 

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QuadCam, no the burp is not normal. I had a prior 87 hci esprit, and it ran great, so when my 94 S4 started a stumble on cold start, I knew it was not normal. Of course, I started changing out parts for much $ and all to no avail.

Then a list member sent me this classified procedure. It may be common knowledge now, but apparently in history lotus would only divulge this procedure to dealers who could charge $ to owners who had this problem.

I am told that the problem could return, but after this procedure, my car NEVER had the problem again!

Here it is: 1) Make sure car engine is COLD.
2) Disconnect battery. MAKE SURE BATTERY IS FULLY CHARGED, hopefully you have a trickle charger. Wait 30 seconds and reconnect battery, leave trickle on.
3) Leave engine OFF. While off, press accelerator ALL the way down twice, slowly. Wait a few seconds, then, while engine off turn A.C. on all the way, and remember to turn fan switch on.
4) Don't touch accelerator, START CAR. Let idle for 15 min.
5) Then turn A.C. off, but LEAVE ENGINE RUNNING 5 min. at idle. Do NOT worry about erradic idle while you are standing by. It is learning idle all over again.
6) LEAVE ENGINE RUNNING, get in car and drive for at least 30 min., going through all kinds of driving, fast, slow, high rpms, etc.

Go home and forget about it until tomorrow. Problem should be solved. I have had my idle go very low occassionally, every few months, but NEVER stumble or die. Problem never returned for me. Worth a shot. Let us know. mark j.
 

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That's some crazy voodoo. Gotta love that kind of engineering.

Don't they have an idle re-learn button on the ODBII software for the V8 now?
 

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That procedure is described in the freescan manual.

Actually not voodoo just super simple computer management.

Disconnecting power clears the memory(as does a dead battery)

The computer with no memory then has to learn the sensor feedback and how to mange the different parameters.

Should start the procedure cold so that you get proper cold idle, recommended to do with high load at cold idle so car won't stall next time.

The step of pressing the accelerator to floor twice is to set the 100% throtle position for the sensor. This should be done with ignition on , but engine off.

The long idle and lenghty initial drive with variable engine speeeds is again to teach computer to manage turbo and injectors. It is actually rec to drive modestly for the first minutes and hard accelerate only once the computer has learned a bit. You can get overboost easily the first few times, but the computer learns to control that.

This procedure is recommended anytime engine management components are changed or you make other changes that affect fuel air or exhaust.

If a car is not running right it is sometimes the first thing to try after checking freescan for parameters or errror codes.

Randy
 

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good point I missed in the literature:

TURN IGNITION ON (BUT DON'T START MOTOR) BEFORE PRESSING ACCELERATOR SLOWLY ALL THE WAY DOWN, TWICE.

THEN TURN ON A.C., AND FAN

THEN START ENGINE ........
 

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Discussion Starter #9
Cool. I'll try the procedure.

Also, I did some more diagnosing of the throttle jack solenoid. The relay is fine. The solenoid is fine. I find that I am not getting a signal from the ecu to trigger the relay though. It seems that the ecu sends a a negative trigger. Is that correct? Now, I.need to check that wire to see if there is a break in the wire somewhere. I suppose I don't that to work as don't have a catalytic convertor anyway, but I'd still like to fix it.
 

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If you removed the Exhaust Back Pressure Valve or it is welded open then you don't need the throttle jack. Nothing to do with the cat.

Many owners have removed both, but you need to plug the vacuum lines and leave the solenoids connected for the car to run right.
 

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The ecu forgets where to set the IAC for cold starts. It "re-sets" after you go 20 or 30 mph, that is why it will start after warm. The method you will try teaches it how to re-set for cold starts. It works and is probably your problem based on everything you posted. Does it start fine when warm after a run?
 

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Discussion Starter #12
Judgea,

Starts fine when all warmed up. I still get the slight pops in the exhaust when idling though. They are quiet, but I notice them. To me, it send like a miss. I already changed the plugs, wires and coils.that didn't fix it.
 
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