Misfire, failure to start: DIAGNOSED!

[Fredjohn]

OK, in my aborted attempt to get to the local meet last Thursday the car was mis-firing at low revs, ie below 2000rpm, but it would tick over. As soon as I pushed the throttle it would hesitate, almost stall, but I could coax it above 2000rpm and could drive it.

Got home OK. Today I couldn't start it at all. Took out all the plugs and turned it over: good strong sparks on all 4 plugs. So plugs leads and coils all OK. Plugs well covered in petrol after all the attempts to start, I could hear fuel pump too, so I assume fuel is getting through. Oil and water levels all OK, and no milky sludge in oil cap.

Attached elanscan and got 4000 faults, but couldn't work out what they were! Did the CEL test and got 12,12,12, 31, 31, 31, 12, 12, 12, 31, 31, 31 etcetc.

31 is MAP sensor. Have checked WikiLEC and found suitable replacement, as well as at SJs, but yet to order.

My question is: would a faulty MAP sensor give the symptoms I am experiencing? If not, what is it?????

Thanks in advance.

[Rambo]

John, I don't know if the following will help or hinder...

I drove the Evora one day and things didn't quite sound right. Slight misfire, hesitation, MIL light on (presume same as CEL in the M100?), down 1 cylinder?????..........
So, I did some research and it suggested I investigate any fault codes using an OBD11 scan tool. I purchased one off the internet for about £25 and scanned for codes. It came up with P0175 (system too rich, bank 2)

It sounded a bit like your problem ie misfire, overfuelling etc... Further Google research directed me to the MAF sensor. It suggested removal of the MAF sensor (v easy on the Evora) and cleaning with a can of mass airflow sensor cleaner (£6 or £7 ex EBay) I did this twice and replaced the MAF sensor and cleared the stored code. Two months on, no further PO175 error codes, engine feels sharper/smoother..

So, maybe worth removing the MAF/MAP sensor and giving it a good clean. Worth a try anyway before you source a replacement and you will only have lost £7 if it doesn't work

Just a thought anyway.

[tb10]

Hi John,

Have you checked the CTS? If the ECU is getting a -40 temperature reading then it might be over-fuelling and you’ll have the symptoms you describe?

Cheers

John

[Fetnas]

In the early days of ownership of my Elan, I had a similar situation.

I was overtaking on the motorway when the car started bucking and being very difficult to drive and being very sensitive to throttle inputs.
I also got a MAP sensor fault, but the failure was the hose from the manifold to the MAP sensor. A previous owner had used some clear PVC hose to connect the manifold to the MAP line. This hose got hot and soft in the engine bay and when I went to over take, the turbo pressure popped it off and the MAP was no longer reading the manifold pressure.

Your issue could be a failure of the hose between the manifold and the MAP sensor. If the rubber is old and split, this could cause your issues. A quick and easy thing to check before putting your hard earned down on a replacement MAP sensor!

Good luck with getting it sorted.

[Fredjohn]

Thanks for suggestions everyone. I will proceed as follows

1) Remove MAP sensor and pipe and clean both with electrical contact cleaner.
2) Refit and test. If OK, job done.
3) If not, replace MAP, after 4).
4) Try to check CTS. I was unable to keep the engine running long enough to spot the CTS elanscan reading before and didn't save it. Maybe this time.

Then take it from there. As I was getting a 31 fault code (MAP) then that is more likely than the CTS, but symptoms are the same....overfuelling. So the CTS will be my second line of attack.

[Rambo]

Would it also be worthwhile disconnecting the battery for a few minutes and allowing the ECU to reset?

It might be worth a try to see whether engine runs better or longer to allow you to carry out Elanscan. You might find MAP sensor code 31 doesn't reappear

[Simon_P]

The MAP could be a secondary fault caused by it not running correctly.

To check the CTS just unplug it which will force the ecu into limp mode.

[Fredjohn]

Update
Disconnected battery to reset ECU. Reconnected.
Removed, cleaned, refitted MAP. No change still won't start/run.

Connected Elanscan and ran 3/4 times whilst trying to start. Got engine to run for about 3 secs at a time, and got some sort of readings, but may not mean much!
At various attempts, the CTS was reading degrees 16.5 then 18.5 then 20. Last temp figure as in the attached scan.

MAP reading is "low" when switched on but not running. Barometer = 1.0, MAP = 0.93. MAP failure or just small variation as both should be the same? Although it does appear to be measuring the pressure?

Engine didn't throw up any fault codes after the reset, but possibly wasn't running long enough to register.

Elanscan attached for those who can interpret it better than me.

MAPtest.zip

Elanscan file

(2.61 KiB) Downloaded 38 times

[Simon_P]

Did it run ok in limp mode?

[tb10]

It hasn’t slipped a tooth on the cam belt has it?

Have you checked the timing?

[Fredjohn]

Update
Put into service mode, still won't start.
Checked injectors and getting multiple clicks (normal mode, ignition on, manually open throttle). Can't tell how many clicks, but sure it's all 4
So moving on to something non sensor related that affects all cylinders equally such as FPR, fuel filter and timing/cambelt slippage
Despite all that I have ordered a new MAP sensor.

[Fredjohn]

Update
Fitted new MAP sensor and checked ignition again. One plug not sparking, replaced all 4. Turned key, it started! However, big flat spot between tickover and 2000rpm. Fine above that, but not perfect.
Confirmed fuel getting through, but decided to check fuel filter and the intank filter too. Took fuel sample not good. My wife's husband had put diesel in ilo Super E5.


Now in process of draining the tank, not an easy job. Will then refuel correctly, add some injector cleaner and give it a good run.
Big relief, but feel a bit of a Richard Cranium.

[dapinky]

At least you have a result - even if it shouldn't have happened!!!

[Rambo]

My wife's husband had put diesel in ilo Super E5.

FFS

Glad you're sorted now. No Xmas presents for him this year

[Simon_P]

That should provide some upper cylinder lubrication! 7% of it is the same stuff so you're halfway there.

Did your wife's husband put much in? The cost of the fuel would be the most annoying thing.

[Rambo]

7% of it is the same stuff so you're halfway there

I take it you weren't a scientist Simon

[Simon_P]

No, they were just meant as soothing words for Fredjohn 's wife's husband.
However, since you ask it did cross my mind that ethe two liquids are miscible and...

[Fredjohn]

Simon, they may be miscible, but they weren't missable.
See how I blended that into one homogeneous sentence?

At least I got to see the inside of the tank, fit new spark plugs and a new MAP sensor.

Thank you everyone for all your consoling words.

[Rambo]

Thankfully diesel into petrol is not as bad as petrol into diesel. I guess our little babies are now so old that either the petrol or diesel nozzle will fit the fuel filler neck?

As I drive a combination of diesel and petrol vehicles I always say to myself diesel, diesel, diesel or petrol, petrol, petrol as I emerge from the vehicle to fill up. And on my diesel van I have large yellow DIESEL ONLY stickers on the inside of the filler flap just in case anyone else fills up.

To say I'm paranoid about misfuelling is probably an understatement

[Kipperozzy]

My wife put petrol into our previous T4 campervan, 2.4 engine, thankfully it was nearly empty when she put the petrol in. I filled it to the brim with diesel and it ran better than ever
Unfortunately she also put diesel in our current vans water tank , think she is trying to make me fuel up the vehicles

Don’t let her near the Elan