Cold start problem

[Callaway]

Hey guys,

Ever since I bought my 1994 S4 about 7 months ago its always had a cold start problem. When the engine is completely cold (sitting for one or two days), the car will start and immediately putter out. It will usually do this again. Then on the third try it comes on but the idle is extremely erratic, shaking the whole car. It will usually shake around for a second and try to die, and then will eventually smooth to a 1600-1700 idle, and then lower down to 1000 rpms as it warms up (or if you give it some gas, the idle will drop like its going to die and then rev up, and then that smooths it out).

After you either give it some gas or let it smooth, it will start and idle just fine. I tried replacing the IAC, but still had the problem (albeit the new IAC completely seperated after a day and I had to put the old one back in, but I still think it worked properly for one start/run down the highway, in which I still had the cold start problem).

I now have freescan and my TPS appears to be ok (no voltage unless my foot is on the accelerator). From what I have seen the IAC appears alright (i've seen it settle to about 46 counts so far, will double check this more to see if it settles even further to 40). Anyone have any other clues as to what could be causing this to happen? I will definately get some freescan logs of the cold start here today or tomorrow. Thanks in advance guys!

-Callaway

1994 Esprit S4

EDIT (02/21/07): Link to a video of the problem:

Edited February 22, 2007 by Callaway

[Kato]

How's the O2 reading. Damage Oxygen sensors, or rather, knackered oxygen sensors, can give starting problems. Can't remember if it was cold or warm!

[Paul93Lotus]

Is your EBPV valve still hooked up? Check the vacuum line running to the valve to be sure it hooked up correctly. If there is a vacuum leak, it could lead to the EBPV valve closing and causing a stall condition. Also check to see if the valve moves freely. If it is sticking it could be causing warm up/stalling issues. It is probably better to wire it open or buy a spacer to replace it.

Another possibility is a fuel pressure issue...whether from the pump itself or from the fuel pressure regulator...though if you car runs fine after warm-up this is probably unlikely. There is a in tank fuel pump check valve that may be allowing pressure to bleed off after the car is shut off....maybe this happens over several days, but the pressure is ok when the car sits less than 24 hours.

Last but not least...coolant temp sensor.....if the ecu is getting a faulty reading it could affect cold starting and cause stalling.

Good Luck!!

[Callaway]

I'll have to look into the o2 sensor readings. Im not really sure what the normal values are as I haven't purchased the manual yet (need to do that here soon lol).

As far as the ebpv valve: I removed that and plugged the hose running to it quite a while back (been running straight out of the cat for some time, about to have a full exhaust job, sounds great though!).

For the coolant sensors i'd have to check those out as well. Dermot is looking over a freescan log for me and hopefully he will pick up anything out of the ordinary from the sensors.

It will only do it once the engine has completely cooled. I have parked it before in the morning and come back about 9-10 hours later and had it do the same thing, so it will definately do it again in under 24 hours.

Thanks for the replies so far guys, they are much appreciated! Hope to have this one sorted out soon!

P.S. Anyone think giving the relays a good cleaning would help things, guess it couldn't hurt?

-Callaway

1994 Esprit S4

Edited June 7, 2006 by Callaway

[Callaway]

Wanted to add that once the engine has warmed up, the idle is pretty smooth, although it does have a slight stutter every few seconds. I have been assuming this might be due to the valves needing to be put back to spec as I don't believe it has ever been done (car has 32,000 miles now).

-Callaway

1994 Esprit S4

[Paul C]

idle is extremely erratic, shaking the whole car. It will usually shake around for a second and try to die...

Ok, i know it's a long shot, but have you checked the Plugs & Leads?

(could be something loose/broken that makes better when hot?, but

don't waste hours down this route!)

[Callaway]

Ok, i know it's a long shot, but have you checked the Plugs & Leads?

(could be something loose/broken that makes better when hot?, but

don't waste hours down this route!)

<{POST_SNAPBACK}>

I did go ahead and replace the plugs w/ new ngk's awhile back in an effort to try and solve it. I was going to replace the wires but since there isn't any misfiring and it pulls smoothly throughout the gears I figured they were fine. Good suggestion though!

BTW anyone know what would be the best way to clean the relays? What should I use to clean them? Thanks!

-Callaway

1994 Esprit S4

Edited June 8, 2006 by Callaway

[Vulcan Grey]

Get your IAC to between 20-40 when fully warm at idle (82deg C water temp)

also check for intake manifold leaks like the hose from the fuel pressure regulator to the intake manifold, and the one to the charcoal cannister.

Your problem sounds exactly like when my IAC count was too high (or too low), so Marcus told me and I adjusted the minimum air rate bleed screw (while watching IAC in freescan!). Cured the problem.

[esprits4de]

I had starting problems that if the car reached the 85 deg. barrier after a short trip, a restart of the car ended in a cylinder drowning situation, at least similar to it.

I changed the ECU, GONE ! All other efforts did not help. If all else fails, fact is that if an ECU is defective, it shows as bad spirits. ECU OK it works, ECU defect it does not work. ( This rule does not stand ! )

[incautious]

The O2 should not cause this problem because the ECU ingores the O2 signal until the system goes into closed loop mode. On cold start the ecu only uses the tp sensor and the coolent temp sensors. One cause of this may be low fuel pump pressure. Static fuel pump pressure should be about 35psi(gm specs) after cool down it is not uncommon for the fuel pressure to leak down to 0. You may want to try and turn the key on and off a couple of times with out starting in order to prime the system . Every time you turn the key on without starting the fuel pump pressurizes for two seconds and then shuts off. It is supposed to continue pumping as long as the engine cranks and the throttle is depressed less that 3/4. but as you can see this can cause extended cranking or stalling until fuel pressure builds to specification.

[Callaway]

Update:

I have two freescan logs of a cold start. If anyone could analyze them and see if they see anything that might hint at what is wrong, I would appreciate it! (I'll have to email the files to you since the forum will not let me post them/PM them..)

Start 1 (description of the first file):

Car starts and stumbles for a second, then dies..

Start 2 (description of the second file)

I restart the engine and it still stumbles around alot, i.e. idle is very irratic. After a couple of seconds it smooths off, and then I give it some throttle and it smooths completely.

I also noticed today while taking a run down the highway and then pulling over that the IAC counts never would drop below 75 or so (this is after I pulled over and let it idle for about 8 minutes). I have a log of this as well if anyone would like to take a look at it.

-Callaway

1994 Esprit S4

Edited June 11, 2006 by Callaway

[Vulcan Grey]

Update:

I have two freescan logs of a cold start. If anyone could analyze them and see if they see anything that might hint at what is wrong, I would appreciate it! (I'll have to email the files to you since the forum will not let me post them/PM them..)

Start 1 (description of the first file):

Car starts and stumbles for a second, then dies..

Start 2 (description of the second file)

I restart the engine and it still stumbles around alot, i.e. idle is very irratic. After a couple of seconds it smooths off, and then I give it some throttle and it smooths completely.

I also noticed today while taking a run down the highway and then pulling over that the IAC counts never would drop below 75 or so (this is after I pulled over and let it idle for about 8 minutes). I have a log of this as well if anyone would like to take a look at it.

-Callaway

1994 Esprit S4

I still think its the minimum air rate bleed screw.

WHile running (fully warm idle), and with freescan running, adjust that protected screw on the throttle butterflies. adjust it slowly watching the IAC count on freescan, and stop when it is between 20-40.

Also make sure you dont have any intake manifold leaks.

[Callaway]

I still think its the minimum air rate bleed screw.

WHile running (fully warm idle), and with freescan running, adjust that protected screw on the throttle butterflies. adjust it slowly watching the IAC count on freescan, and stop when it is between 20-40.

Also make sure you dont have any intake manifold leaks.

Travis,

I checked the IAC counts last night w/ freescan. Once the car had warmed up to 82 degrees the counts variated between 39-44. Once it warmed up to 84-88 degrees, the counts seemed to fall to between 35-40. How does this sound? I tried to get to the minimum air rate bleed screw, however, it is quite hard to access. I gave up on pulling the cap off until I can devise a way to keep myself from dropping it into the abyss of the engine bay lol ! Considering the IAC counts, do you think that this is most likely down to an intake manifold leak caused by one of the vacuum hoses? Thanks!

-Erik E.

1994 Esprit S4

Edited February 6, 2007 by Callaway

[Vulcan Grey]

Travis,

I checked the IAC counts last night w/ freescan. Once the car had warmed up to 82 degrees the counts variated between 39-44. Once it warmed up to 84-88 degrees, the counts seemed to fall to between 35-40. How does this sound? I tried to get to the minimum air rate bleed screw, however, it is quite hard to access. I gave up on pulling the cap off until I can devise a way to keep myself from dropping it into the abyss of the engine bay lol ! Considering the IAC counts, do you think that this is most likely down to an intake manifold leak caused by one of the vacuum hoses? Thanks!

-Erik E.

1994 Esprit S4

Thos IAC counts are pretty good. I wouldn't mess with the minimum air rate bleed screw, it's likely it would just get worse.

It also doesn't sound like you have any manifold air leaks, since the IAC is in spec.

[Riddlemr2]

My car does the same thing. If I do the trick of turning the car to on for a few seconds without cranking, it has a much better chance of starting on the first try. Just like you, if the car is still slightly warm, the problem never happens. My car also likes to run greater than 2000rpm after a cold start for a few minutes, which I have been told is the computer's way of warming up the cat to pass US emmissions regulations. My only thought is that the later S4 cars did that to pass california emmissions standards (made stricter in '95) and the programming in the computer wasn't done quite right to make for a good cold start. Correct me if I am wrong, but the Esprit doesn't have a dedicated "cold start injector" which many modern cars use to help cold starts.

A leak in your intake system should make the idle erratic all the time. If it were bad enough to cause stalling at cold start, it would make for a very bouncy idle (plus or minus >500 rpm) or a very high idle...this has been my experience with vacuum/boost leaks in the past. It would also exhibit the stalling characteristic after any given start unless you have the highly unlikely problem of a leak that cures itself as the manifold warms up and expands.

Edited February 6, 2007 by Riddlemr2

[Paula&Marcus]

Hi Erik,

You say it starts immediately, but then it will die or it will idle very low, erratic and then after some time (20-40 seconds) it will catch and idle quite fine around 1600-1700 rpm, right ?

I assume you already have checked (or renewed) the obvious like spark plags, HT-leads, bad gas, ... If this is true, please do a test !

Let the engine fully cool down (it has to be dead cold !).

1. ignition on (you should hear the fuel pump running) Donot start the engine ! Ignition OFF again.

2. wait for approx. 10 minutes

3. ignition on (you should hear the fuel pump running again). Does it run longer or significantly shorter now ? Ignition OFF again.

4. wait for approx. 10 minutes

5. ignition on (how long does the fuel pump run now ????) longer ? shorter ? The same ?

6. ignition OFF

7. Press the accelerator pedal FULLY down (= 100% TPS) and hold it 100% this way !

8. ignition on and start the starter motor. Don't worry the engine will NOT start now (thanks god !), because starting with 100% TPS the ECU will trigger a special anti-flood-mode. Do this cranking for 5-8 seconds.

9. ignition OFF

10. ignition ON

11. Now try starting the engine WITHOUT pressing the throttle pedal.

Does it start fine now or does it do the very same like before ?

This test will tell us if you have an injector problem (not necessary a flooding problem, it could also be the opposite or just a air-trap-problem or a partially clogged injector)

Please tell us what happened !

Cheers

Marcus

www.PUKesprit.de

Hey guys,

Ever since I bought my 1994 S4 about 7 months ago its always had a cold start problem. When the engine is completely cold (sitting for one or two days), the car will start and immediately putter out. It will usually do this again. Then on the third try it comes on but the idle is extremely erratic, shaking the whole car. It will usually shake around for a second and try to die, and then will eventually smooth to a 1600-1700 idle, and then lower down to 1000 rpms as it warms up (or if you give it some gas, the idle will drop like its going to die and then rev up, and then that smooths it out).

After you either give it some gas or let it smooth, it will start and idle just fine. I tried replacing the IAC, but still had the problem (albeit the new IAC completely seperated after a day and I had to put the old one back in, but I still think it worked properly for one start/run down the highway, in which I still had the cold start problem).

I now have freescan and my TPS appears to be ok (no voltage unless my foot is on the accelerator). From what I have seen the IAC appears alright (i've seen it settle to about 46 counts so far, will double check this more to see if it settles even further to 40). Anyone have any other clues as to what could be causing this to happen? I will definately get some freescan logs of the cold start here today or tomorrow. Thanks in advance guys!

-Callaway

1994 Esprit S4

Edited February 7, 2007 by Paula&Marcus

[TurboSE-SLO]

I still think its the minimum air rate bleed screw.

WHile running (fully warm idle), and with freescan running, adjust that protected screw on the throttle butterflies. adjust it slowly watching the IAC count on freescan, and stop when it is between 20-40.

Also make sure you dont have any intake manifold leaks.

Hi Travis,

isn't IAC position below 40 low? My IAC is hanging around 40-70 when engine is warm. I have checked Freescan manual and IAC position between 40-70 should be OK.

RGDS, B

Edited February 8, 2007 by TurboSE-SLO

[Vulcan Grey]

Hi Travis,

isn't IAC position below 40 low? My IAC is hanging around 40-70 when engine is warm. I have checked Freescan manual and IAC position between 40-70 should be OK.

RGDS, B

Borut,

Here's what the manual has to say, this is also something that Marcus helped me with once and it fixed my problem with cold start stalling.

________________________________________________________________________________

________

EM-I.3 - THROTTLEBODIES

The throttle bodies are assembled to the plenum backplate and then balanced

at the factory as a set, using mass air flow measuring techniques. The throttle

plate air by-pass screws or throttle coupling balance screw should NOT! be

tampered with. The throttle bodies/plenum backplate assembly is supplied as a

single service item, and must not be disassembled.

The throttle stop screw (minimum air rate) is also calibrated at the factory,

with no subsequent adjustment being necessary under normal circumstances. This

adjustment should not be considered as controlling the minimum idle speed, since

the idle air control valve operates to increase or decrease airflow past the

throttle plates to control idle speed as commanded by the ECM.

If there is a complaint of high idle speed, vacuum leaks should be considered

the most likely cause. Because the electronic control module (ECM) 'learns' idle

air control (IAC), it is even less likely that a stalling complaint would be due

to incorrect minimum air rate. In either case, the 'Symptoms' section EMH.6 and

IAC valve check CHART EMH.3 - M should be referred to.

If it is determined that the minimum air rate is suspect, be sure the IAC

valve is not 'lost' (not actually at the location indicated by current IAC

'counts' ). The IAC valve could be 'lost' if ECM power has been interrupted with

the ignition 'ON', or the IAC valve has been disconnected with the engine running

since the last reset, as described in section EMH.2 - 0.

The minimum air rate may be checked using the following procedure:

1. Block drive wheels, apply parking brake.

2. Connect 'Tech 1' scanner tool.

3. Start engine and allow to reach operating temperature (about 82' C) and

'Closed Loop'.

4 . With A/C and all electrical accessories 'OFF', allow idle to stabilise.

5. Use 'Tech 1' tool to display IAC valve counts - if between 5 - 45 counts,

throttle plate stop screw adjustment is acceptable. It is important to allow

idle speed to stabilise to assure correct counts are determined.

If counts in step 5 are too low, check for intake air (vacuum) leaks at

hoses, throttle body and intake manifold, or damaged throttle lever, and correct

as necessary. Also refer to Code 35 and associated 'Diagnostic Aids' in section

EMH.4.

If no vacuum leaks or other causes of excessive air into the intake are

found, refer to the 'Throttle Plate Stop Screw (minimum air rate) Adjustment

Procedure' below.

If counts in step 5 are too high, check for damaged throttle lever or airflow

restriction by the throttle plate. If no problem is evident, remove intake

plenum cover and clean residue from inside of throttle body bores and from edges

of throttle plates. Use a lint free cloth with a suitable cleaner such as AC

Delco Carburetor Tune-Up Conditioner or equivalent. Do not use solvents

containing methyl ethyl ketone. Re-check IAC valve counts, per the preceding

procedure. If counts are still too high, refer to 'Throttle Plate Stop Screw

(Minimum Air Rate) Adjustment Procedure below.

Throttle Plate Stop Screw (Minimum Air Rate) Adjustment Procedure

Important: It is extremely unlikely that this adjustment will ever be

necessary on a throttle body that has not been tampered with after production!

Review the procedure detailed above before proceeding.

Remove the throttle plate stop screw anti-tamper plug and, in small (I actually don't have to remove mine, I found a screwdriver that works)

increments, (e.g. l/8 turn) adjust the screw as necessary to achieve a 'Tech 1'

scan count of between 25 - 40. Allow idle to stabilise between each incremental adjustment.

If it is necessary to change the adjustment more than one turn either way,

other causes of incorrect idle speed should be investigated as described above.

Ensure that the anti-tamper plug is refitted after any adjustment.

[TurboSE-SLO]

Hi Travis,

thanks for explanation. Probably Tech1 tool and FreeScan tool have a different scale. I never have any cold start problem. IAC position is always between 40 and 70.

bye, Borut

[Callaway]

Marcus,

I will try that test out and report back with my results! I wanted to add that my car has never gotten very good gas mileage. It generally gets about 14 mpg, and I don't hot dog it everywhere I go. I would think that I should be getting quite a bit better than this, as most owners report low 20's for city and high 20's for highway. Would this lend itself to an injector problem? I did try replacing the spark plugs around 30,000 miles but to no avail. The gas is also fresh, it's had this problem ever since I purchased it almost two years ago. Hopefully I can get this tracked down here pretty soon. Thanks for the advice, I appreciate it!

-Erik E.

1994 Esprit S4

[Riddlemr2]

Marcus,

I will try that test out and report back with my results! I wanted to add that my car has never gotten very good gas mileage. It generally gets about 14 mpg, and I don't hot dog it everywhere I go. I would think that I should be getting quite a bit better than this, as most owners report low 20's for city and high 20's for highway. Would this lend itself to an injector problem? I did try replacing the spark plugs around 30,000 miles but to no avail. The gas is also fresh, it's had this problem ever since I purchased it almost two years ago. Hopefully I can get this tracked down here pretty soon. Thanks for the advice, I appreciate it!

-Erik E.

1994 Esprit S4

Erik, it seems like our symptoms are similar. In other searches I have found a lot of people finding a fix with a new Lambda (O2?) sensor. That is what I will try first, but I'm having trouble finding where I can buy the sensor, what the part number is, and if there is a GM part number rather than a Lotus piece like other engine components. Can anybody help with information on buying one of these?

[Paula&Marcus]

Dave,

JFYI for the first 1-3 minutes after startup, the O2-sensor does not do anything ! Its not operating when cold. Thats the reason why the whole engine is running on a fixed table open loop mode till the O2-sensor has warmed up.

If there is a problem rigt after startup its very unlikely to be related to the O2-sensor.

Cheers

Marcus

Erik, it seems like our symptoms are similar. In other searches I have found a lot of people finding a fix with a new Lambda (O2?) sensor. That is what I will try first, but I'm having trouble finding where I can buy the sensor, what the part number is, and if there is a GM part number rather than a Lotus piece like other engine components. Can anybody help with information on buying one of these?

[Callaway]

Marcus,

I did the test and she still had the cold start symptom! The fuel pump seemed to run about the same length each time. I will get a video of the problem tomorrow and post it up for you to take a look at! Any other ideas? Thanks again!

-Erik E.

1994 Esprit S4

[martynv]

Marcus,

I did the test and she still had the cold start symptom! The fuel pump seemed to run about the same length each time. I will get a video of the problem tomorrow and post it up for you to take a look at! Any other ideas? Thanks again!

-Erik E.

1994 Esprit S4

Erik,

I've got a very similar problem with my SE and the starting and stalling situation seems to get worse the longer the car has been standing still unused. Freescan seems to indicate the sensors are Ok. The Freescan manual notes that if the ECU looses track of where the IAC position is, this can cause this kind of problem. There is a procedure in the back of the Freescan manual for reseting the IAC and obtaining the best possible idle and I'm going to try this next on my car before doing anything else just in case it might fix the problem. Basicaly you reset the IAC with Freescan and then disconnect the battery (or pull out the ECU fuse ) to reset the ECU then reconnect the battery. Next you start the engine with the Aircon and interior fan on and let it warm up for 15 minutes followed by a short drive to finally set the IAC postion correctly. Might be worth giving it a go :yes

Martyn

[Callaway]

I made a video of the cold start, perhaps it will help give everyone a better idea of what is happening. You will notice towards the end of the video when I restart the car that it kicks the idle up to almost 2000 rpms. If I restart the car again it settles back down to 1100 or so. Any ideas? Thanks guys!

Video Link:

-Erik E

1994 Esprit S4

Edited February 22, 2007 by Callaway