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Took my Turbo SE for its annual MOT and was failed for excessive HC and CO. When raising the idle to 2500 rpm values plummet to zero, but returning to regular idle sees them return whereupon they're all over the place.

 

At first I thought it might have been due to my high-flow cat, so I borrowed a factory cat from a friend and had the missus and my brother take it again today asI couldn't make it due to work - same issue, excessive HC and CO at 980 rpm. 

 

I'm currently flummoxed. From extensive forum-stalking I've noted that emissions can send people on wild goose chases that result in lots and lots of $$$ spent without a solution in sight...I'd prefer not to buy my way to success at this point. 

 

So....my situation:

 

O2 sensor is new and genuine (changed last year), see pic 

new HT leads from last year (Magnecor)

Slightly used spark plugs

New injectors (Five-O) from last year

 

I haven't had a chance to log Espritmon and won't until earliest next week, but I wanted to throw this out there in advance in case anyone has any good ideas.

 

The car itself runs fine with the exception of a weird issue which arose after switching the injectors last year - sometimes (when warm) it will start stuttering under acceleration (though no lack of power or boost with WOT), and take a while to return to normal behaviour. This is a sporadic issue though and I'm putting it down to possibly coil packs which I'll be switching out soonish. Furthermore I've had the rochester injectors refurbed and they're running perfectly according to the chart. 

 

The car idles just fine, and I adjusted the IAC counts with Freescan last year. It never bogs down or causes me trouble. No issues starting, warm or cold. 

 

So where to go from here?

 

Things to check:

Cylinder compression

Fuel pressure (not sure how to do this - don't have the tools outlined in the shop manual)

Functionality of charcoal canister (can force a purge in Espritmon?)

Vacuum leaks (smoke test?) 

ECU (switch for known good ECU? When should I suspect this?)

Fuel filter (looks pretty old)

Water temp sensor? (ECU isn't limiting my boost though)

 

Is there anyone out there who is an expert on emissions and who might know what the typical causes of high HC and CO are?

 

I've heard weird stories about ECU failures resulting in the dumping of vast amounts of fuel into the engine resulting in glowing catalysts etc....but as with the proverbial hearing of hooves, I want to think horses, not zebras at this stage. 

 

A beer to the first person who successfully guesses the root of this problem! By God I shall also mark the thread with "SOLVED" once its solved. 

post-14356-0-11094800-1429035595.jpg

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How's your air filter?  Clean or replace it

 

Which O2 sensor is that?

 

Which spark plugs?

 

Checking for vacuum leaks is always good, also the MAP sensor hose rubber elbows.

 

It could be possibly be due to the EVAP system, and the charcoal canister purging too much.  But less likely than dirty air filter or a poor spark.


Can you log some freescan data?


Which CAM timing pulleys do you have?

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Air filter - haven't checked, but I bought it roughly a year ago (K&N) - at that point I cleaned out the entire filter housing of old oil and gunk from the return pipe. 

 

Oxygen Sensor: It's part no. A918E0322F (the genuine replacement according to SJ Sports Cars) - a quick look in the GT3/V8 parts manual references section 17.06 re the O2 sensor and it's the same part, albeit beginning with B instead of A (might be a typo in SJ's catalogue)

 

Spark plugs - NGK BPR6EKN 1 "season" old (couple of hundred miles on 'em)

 

MAP sensor elbows - replaced the one going into the side of the engine. Believe I also checked remaining fittings replacing cracked elbows. I get a good idle so I'm not so sure of vacuum leaks but I can check if I can find a smoke tester somewhere.

 

CAM timing pulleys - I believe I'm running the stock setup. Don't think it's green dot pulleys on mine.

 

Freescan - I promise I'll get back to you. Most likely won't be able to log any data before next week (I'm off for a conference on thursday-sunday and generally only go to the car on sat/sun...long story....) , of course it's just a witch hunt until we get some data in. 

Edited by Vanya

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Ouch! Getting ready to take mine through Delaware state emissions for the first time so have the same fears for mine little baby as well so will be lurking on this thread.... Hope it is simple and cheap, Vanya.

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Vanya,

 

Have you looked at the Catalyst?

He said he swapped in a stock Cat for the high-flow one currently fitted, same issue.

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Yeah as CarBuff noted, I switched out the cat to a stock one and had the same issue - clean at revs, poor values at idle.

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Did you take the car for a good drive 1st

Get it well warmed up before the test. Mine has a sports cat and no issues.

Get geunine 02 sensor

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Hi Peter,

 

I thrashed the car REAL well before my first attempt, and I believe the same was done second time round. No effect. 

 

The car has a genuine O2 sensor fitted. 

 

My sports cat passed last year but at that time I got the impression the MOT guy wasn't too fussed about the values - he just took a read out 2 seconds after I let it drop to idle from 2500, and at that point it's clean. Only once it's sitting idling do the values go up. 

 

I've been told the Esprit should pass with almost no emissions as long as the engine is up to temperature. 

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What sort of range of excessive HC and CO are you getting? Min and (max values at idle)

 

I had a leaky vacuum one way valve that caused odd running at idle worth checking those

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I'll definitely go over all the hoses to be sure. When you say odd running you mean odd emissions, or lumpy idle? My idle is pretty solid otherwise - it doesn't drop revs when coasting to a stop or when starting from a standstill. 

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What sort of range of excessive HC and CO are you getting? Min and (max values at idle)

 

I had a leaky vacuum one way valve that caused odd running at idle worth checking those

 

CO is 1.7% (0,5 allowed) and HC is 175 (100 allowed) - values get progressively higher the longer the car is left idling. They are however perfect 0 across the board at 2500 rpm. 

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I've been tipped off regarding a garage that is kinder to sports cars, but if I'm pushing high HC at idle it'll just ruin my catalyst in the long run so I gotta find the cause anyhow. I did some reading in the EMH manual last night and now have a nice list of items to check!

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Update:

While in Istanbul my brother and the missus took the SE out for a run to collect some Freescan data. I've appended the file to this post. Upon first glance, most stuff seems to check out, except for the fact that the coolant never really warms up - doesn't even reach 82 degrees. 

 

They didn't drive as enthusiastically as I do (requirements for engaging secondary injectors are never met and they never used WOT) but there's probably still enough information at idle to shed some light on what could be causing my high emissions...

 

I've also noticed lately that it's never gotten warm enough to have to engage the fans, even after maneuvering into the garage where I park it (temperatures ALWAYS rise in there). Even my generally misleading dash gauges have looked suspiciously low. Oddly enough my boost hasn't been restricted. The good book states that engine coolant temp is one of the parameters used to calculate fuel delivery and its generally known that a faulty "shifted" coolant temperature sender wreaks havoc on performance.

 

What say ye?

 

2015 april.csv

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Def. replace the thermostat, in my experience they fail often (I am referred to as the Thermostat King over on LT, LOL).

 

If you are less than 78C the ECU thinks the engine is warming up and will restrict boost as well. 

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Hey,

 

Yeah just read a post by Travis in another thread and came to the same conclusion - ECU and dash sensors low = thermostat. But could 2 degrees be causing my emissions issue? Now I'm just confused. 

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Yeah I think the low coolant temp could definitely cause the ECU to en-rich the mixture... could definitely be the issue with high CO and HC...

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But that would then point to a ECU-temp sender issue, whereby the temperature of the engine is in contradiction to what the ECU thinks it is, hence affecting fuelling and perhaps resulting in a poor running condition. If it's the thermostat, doesn't that just limit the buildup of engine temperature? In that case the engine fuels as appropriate for 80 degrees all the time as opposed to 82 degrees? (I still haven't been hit by a boost limiting issue)

 

Did you see anything else "off" in the data Travis? I checked my O2 and ran a trendline through it - seems to be sitting at 0.45. Most other things check out too. My IAC might need a slight tweak as its at 40 right now (like having it at 30 or so) but I really didn't see anything too far out.

 

Anyhow I'll be changing over to the stock injectors this weekend and taking the car for a new checkup (only changing one variable at a time to determine the true cause) - I've read of some issues with FiveO injectors at low load - messed up fuel metering and similar stuttering issues such as those I've been having. 

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Your coolant temp is a bit lower than 78C...  I would change the thermostat anyways..

 

Your start water temp was 38C, but your MAT shows that it was probably quite a bit colder outside that day, the car was probably warmed up a  bit before data was started.

 

Your IAC at idle is a bit high at 40.  Between 20-40 is usually best.

 

Your BLM shows the car is very rich... 

 

Your secondary injector duty cycle is 0%, and your primaries are fairly low below 40%, though they didn't get a lot of boost during the test.

 

Your throttle response might be slow since your wastegate is almost never opening.

 

How is your fuel?  Is it old?

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Hi,

 

They had driven the car about 1 hour prior to making that run so it was still warm. 

 

They didn't push the car too hard so the secondaries aren't ever used in that run. I'll make a new run this weekend or during the week where I give it a good thrashing. I haven't noticed poorer throttle response than in previous years. From my experience boost builds up as usual, flicks towards 1 bar and then settles steady at 0.85 bar or so. Doesn't drop off. 

 

My fuel is old. I fill the tanks up to the top before putting the car in storage and then run that tank dry the spring thereafter. But I've done that the last 3 years and haven't had problems with it before. 

 

PS. Just want to thank everyone for taking the time to help me out with this.

Edited by Vanya

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could 2 degrees be causing my emissions issue?

The relatively un-sophisticated GM MPFI treats the 78C mark as an ON OFF switch.  So, YEAH.

 

Besides, even if it didn't cause the issue directly (by changing it's A/F values), a hot engine burns fuel cleaner and more completely...

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I think your oxygen sensor is faulty. 1.7CO and 175HC is not very rich, only just outside the pass. The old carb cars used to run 5.0% co at idle. You mention that your oxygen sensor flatlines at 0.45volts. This is not how they sre supposed to work. I have a carb/turbo so the next information is not specific to an SE. Here is a DIY test you can do which is a general procedure for O2 sensors which are designed to constantly monitor the oxygen content of the exhaust gasses before they get to the cat and alter them accordingly by instruction to the ECU.

Locate the plug which will probably have 4 wires. The colours may vary but 2 wires probably white will be the heater (12volts) and heater earth. The other 2 will be the signal wire (black?) and the signal wire earth. With your multimeter set to volts and the O2 sensor plug connected slide a probe down the side of the signal wire (you will find a safety pin works well). With the engine running at normal temp the sensor should switch regularly between 0.1 volts and 0.9 volts.

A constant reading of 0.9 volts indicates a rich mix (ie the ECU is trying to weaken it off), similarly a constant reading of 0.2 indicates a weak mix. To see if the O2 sensor is working for a rich mix of 0.9 volts introduce an air leak to seriously weaken the mix, this should get the O2 sensor to switch as it then tries to richen it up again.. Your reading of a steady 0.45 indicates it is not working. Introduce an airleak to see if it changes voltage.

By the same token a weak mix (0.2 volts) can be made to switch by richening the mix

This is just a general overview of testing an O2 sensor, if it doesn't apply to your car I am sure somebody out there will let you know. If you have a single wire sensor, this is the signal wire so the above still applies. Some ECU's are sensitive and don't work with an aftermarket universal sensor so original is best. Before you throw the old sensor because you cannot get it to switch, try running a direct earth to the signal wire earth (possibly grey) Hope this is some help, regards Roy.

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Says something about O2 sensors fluctuating between 0v and 0.9 v somewhere in the literature I'm sure

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Freescan manual has pics of how the trace should look.

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