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Mpi Rough Running


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#1 ski

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Posted 01 February 2019 - 04:44 PM

Hi all, 

 

I was wondering if anyone can recommend someone around Basingstoke to take a look at my MPI?

 

It failed the MOT on the Lambda been 1.19 on the 2nd fast run. I found the Y piece to be cracked. (HC and CO were very low)

I've taken the whole exhaust off checked it and re-assembled. I wasn't 100% sure about the Lambda so fitted a new one as well, one of the connector pins was actually broken so Ive had to solder a link in. 

 

Its now idling very rich and getting slight popping from the exhaust at idle. 

Seems fine when revved but its hesitant to sit at 850rpm, after revving its hovering at 1500 and is preferring 1100-1200 for an idle!

 

I removed the inlet manifold (Burlen alloy one), cleaned all the sensors and put the injectors in an ultrasonic bath, new rubber o rings on assembly. 

Cleaned all other sensor's on the inlet. 

 

Before it was boiling over, the header tank was suspect along with some of the radiator pipes, so I replaced this along with the water pump and heater matrix. 

 

Its quite tapey so I was going to check the tappet clearance next. 

Its got an OAP racing stage 3 head, 270 Cam, and 1.5 roller rockers. In the spec the fuel regulator is also modified. 

I have PC scan and ive plugged it in but no faults are showing, apart from the oil temp sensor as the connector is damaged. Idle correction/error is 300-400rpm. 

 

Thanks for any help! 

 



#2 cian

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Posted 01 February 2019 - 10:38 PM

What psi/bar have you set the pressure regulator

#3 ski

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Posted 02 February 2019 - 01:31 PM

It just seems to be a standard regulator on the rail to me?

Just been trying a few wires whilst it's running the isv seems have no effect on the engine interestingly. The coolant temp sensor seems correct on diag and also the inlet temp.
I know a breather is off on the photos (tb).

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Edited by ski, 02 February 2019 - 01:35 PM.


#4 Wiggy

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Posted 02 February 2019 - 02:12 PM

What sort of diagnostic equipment are you using? And what sort of data does it give you?

#5 ski

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Posted 03 February 2019 - 12:33 AM

This is what I'm using-
https://pscan.uk

It only seems to read error codes.
And I can view various live data, the only thing which seems off is the lambda sensor just displays as 0.49v and occasionally changes to 0.42v. But I'm not sure about the refresh rate, I'm still a bit suspicious about the lambda connector after finding one loose wire pulled out.

#6 Wiggy

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Posted 03 February 2019 - 01:42 AM

Ah yes. I was looking at getting a Pscan before I got my ACR4. Unfortunately the ACR4 doesn't seem to read the oxygen sensor voltage properly.

Anyway, you can send me your Pscan data if you like, and I'll compare it with my ACR4 data, on my similarly spec'ed MPi.

There's a thread at the top of this page detailing how to test an Oxygen sensor with a multimeter.

Can you set the IACV on the Pscan? If you've played with the throttle stop to adjust the idle, or changed the throttle body (I see you have), that could be a possibility too.

#7 ski

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Posted 03 February 2019 - 02:49 PM

Many thanks Wiggy, i suspect the Pscan is the same, im going to check it now with a meter. 

 

It was idling at 850rpm when warm a couple of weeks ago, so this fault has just started. Ive not touched the throttle stop, Ive done that with carbs before as a temp fix though! 

 

Im not sure how to log it, but this a cold start- 

 

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Edited by ski, 03 February 2019 - 02:51 PM.


#8 genpop

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Posted 03 February 2019 - 04:09 PM

Obviously camsensor and lambdasensor are not working, if repair doesn't help, i would change the coil too.

Post a new log when you have repaired this.



#9 Wiggy

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Posted 03 February 2019 - 04:42 PM

I had a cam sensor fault. Turned out the flywheel had slipped on the crank. (My own stupid fault) Thus the cam sensor signal didn't 'ping' at the correct time compared with the crank signal. She ran, but extremely poorly.

Or the sensor could be faulty. Or the cam could be timed in incorrectly. Did you do it?

#10 ski

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Posted 03 February 2019 - 05:34 PM

Thanks both, turns out the Cam sensor was unplugged. 

 

The lambda voltage I believe is wrong, I tested it was a meter and when squezing the fuel line to the rail the voltage does start dropping low. 

 

The idle seems to have gotten worse now. 

 

 

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#11 Wiggy

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Posted 03 February 2019 - 05:52 PM

So Pscan isn't reading the sensor voltage, and it's reading correctly via a multimeter?

Next time I pop into the garage, I'll record my readings for you.

When did it start not running right? Before or after the mods? All of a sudden? Gradually? Intermittently?

#12 ski

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Posted 03 February 2019 - 06:51 PM

Yep with a meter it seems to read 0.4-0.49v when I starve it of fuel it's dropping to 0.2v and under then allow more fuel and it's coming back up near 0.4v.

Mods went on 5-6 years ago, I've owned it a year. It always had a slight misfire at idle. It was running fine a week ago and just started this idle problem after going to a garage for a pre MOT check. I've searched for air leaks but not found any. It was a bit neglected so I've just been replacing a fair amount of parts.

Original emissions it failed on HC and after a full service it was fine. He did say the cat was a bit slow to respond.
The lastest one it failed on the lambda and I found 2 holes in the exhaust. I just want to get an MOT on it then I can drive it to a decent garage for a good check over. I'm going to take it for retest tomorrow and see what happens, it only needs to pass the emissions now.
It did also read 2000-3000 ppm on one HC test, next time it was totally fine!

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#13 genpop

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Posted 04 February 2019 - 07:39 AM

There seems to be a leak in the intake(High map and high rpm). Spray up everything between throttle and head with brake cleaner.This way you may find the leak.Have a look for the brake booster as well.Then check for the throttle cable.Even the throttle is shown as closed, there is a small throttle angle and the throttle position voltage is a bit high, it should be at around 0,5V.Change your lambda sensor. Check the crank sensor too..And at least have a look for somebody who has an oscyloskop to check the firing voltage of the spark plugs. The coils are not working simultaniously this may be the origin for a light hesitation in running.

The injector firing intervall is 720 now, i think it should be [email protected] wiggy: can you check that on your car?

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#14 ski

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Posted 04 February 2019 - 10:21 AM

Thanks Genpop.

I reseated the inlet manifold and took a look at the butterfly it seems someone has adjusted the throttle stop slightly to adjust the idle. Its now idling well.

Had it back on the machine and the lambda is still too high though. Its a new sensor and I've soldered a link over the connector for the 2 feed wires as the connector seemed damaged.

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#15 genpop

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Posted 04 February 2019 - 12:14 PM

Always post what your pscan shows. I fear your lambda sensor is not connected right.Take it out, connect it to the socket and switch on ignition .It should warm up  in a few minutes.Lambda voltage has to swing when engine is running.

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