[Sausager]

Hey guys. I've recently put a 16v mpi g16a into my SJ413. Did everything myself, incl all wiring. I drove the car the motor came out of before pulling the motor out and the motor was fine.

She started the first time I tried it after the conversion, no dramas there. On the first start, it idled high, around 2000rpm. I wasn't too fussed - it had no exhaust, intake wasn't set up properly, etc. I ran it like this a few times and always the same - 2000rpm constant idle

Then I fnished everything - exhaust, mounted the ecu properly, sorted out the intake, etc etc. Now it idles erratically. Starting from cold, it will immediately idle at 2000rpm for a few seconds then drop down to nearly stalling, then bounce back up to 1500rpm ish for a few seconds, then die down, bounce back to 1500, etc etc. It will keep bouncing like this and sometimes die when it drops down so low. While it does this I can smell a fair amount of fuel in the exhaust which I presume means it's running rich. It idles better when warm, but still erratically. The motor also doesn't run smoothly like it should. The car is driveable as it is but I don't know how sustainable it is!

I've also noticed that my CEL doesn't work. I wired in a separate dash-mounted red light so that I didn't have to bastardize my dash. I have tested the light, double checked my wiring for correct placement and continuity, and it all seems fine. But no light when I turn the key to 'on'. In fact, the only dash light I get when I turn the key to 'on' is the battery light. Should there be more?

The temperature gauge doesn't show warm. I was expecting maybe 1/3 or 1/2 way up the gauge, but the needle barely gets off the cold end of the line. I suspect the temp sender here, but I don't know for sure. Does the ecu take any reading off the temp sender? Judging by my wiring diagram it doesn't.

I have done the VSS swap. I have a 3 wire MAF.

Any ideas here people? I just can't seem to figure it out. Cheers!

[frak]

Sounds to me like a mistake in the wiring with the various issues you report.

Eg the ground is not.really a good ground due to some things attached to chassis ( which is measing up the signals being read by the computer and temp gauge etc) and/or chassis not well attatched to neg on battery.

Find a good sparky that could be a nightmare to find.

That is my guess. Hope somebody has a better one though.

[fordem]

Key on, engine off, you should get at a minimum - charge light, check engine light, oil pressure light and I believe the brake warning light, if the hand brake is up - the missing dash lights suggest there is no power going to them because they are all fed from a common source and are grounded to turn them on.

Regarding the temp gauge and the ECU - there are two temp sensors - a one wire sensor for the gauge, and a two wire sensor for the ECU.

[Gwagensteve]

The erratic idle can be caused by air pockets in the coolant at the throttle body. It's hard to bleed this area of the cooling system as it's higher than the radiator cap in a Sierra.

[Sausager]

So I have had a play.

I got my check engine light working. Fordem, your comment about earthing to switch on made me realise I had incorrectly assumed that they were positively switched, not negatively – ie so I thought that the common feed was a negative earth, not a positive haha. What a noob. So that’s fixed now and works well. The other dash lights are still MIA with the key in the ‘On’ position. I did notice a bit of corrosion on the back of the dash cluster though on that green film/circuit board so that may have something to do with it? I’ll have to investigate further.

Anyway, with my CEL going, I checked for codes and I got 12 which means all clear. In a way I was hoping for more than that!

Steve, is there a trick to bleeding that area of the throttle body? And Fordem, where can I locate and how can I check the two wire sensor for the ECU?

Thanks for the replies guys, very much appreciated!

[fordem]

Sausager wrote:

And Fordem, where can I locate and how can I check the two wire sensor for the ECU?

There should be two or possibly three temperature sensors grouped together in the thermostat housing - the only two wire one is for the ECU - it can be checked with an ohmmeter.

[Sausager]

Ok, so here's an update.

I drove the car yesterday for half an hour, and it was pretty tricky. It drove ok, but the throttle is really 'twitchy' - ie it revs quickly and revs drop quickly. So if you blip the throttle even lightly, you end up with quite a sharp jerk. It is liveable.

The main problem is the idling and general running. I took these following videos a week or so back.

This first video is of starting it stone cold. I am not touching anything else besides the key the whole time. You can see my battery light when the key is "on" and the bright red light you can see reflecting on the steering wheel is from my (super bright haha) CEL.
https://www.flickr.com/gp/125196140@N05/e2t561

This second video is of it idling a little later that same day, warm. You can see here that it doesn't run smooth - the motor shakes. It's not missing or anything like that, but it's just running rough. Revving hard (6-7k rpm) it runs smooth, but then back at low revs or idle, it's rough.
https://www.flickr.com/gp/125196140@N05/WoU69b

I drove it yesterday and it idled at 2k from cold, no bouncing. So I don't know why it's decided to run smoother yesterday?

Any ideas here guys?

[Sausager]

I'm still stumped here guys. I have done a bit more reading though.

Could the car be in limp mode because it's not receiving a signal it's expecting? If it was in limp mode, does the CEL stay on?

The motor, loom and ecu were out of an auto vehicle. Have I maybe missed a feed or an earth or something that the ECU is expecting to see from the gearbox?

[Sausager]

If my thermostat was poked and was stuck open or otherwise compromised, would or could it cause these issues?

[Sausager]

I'm still no further with this guys.

Today I took the MAF out and cleaned it again, no change. I also ran the car without the MAF and it drove pretty much the same except for it bogged really badly on acceleration. The CEL light was on too. If the MAF was bad, would the CEL be on? Does the ECU only throw a CEL if the MAF is missing or also if it's bad?

I'm super keen to have this going properly. Any ideas? A list of things to check? Anything?!

[fordem]

The on board diagnostics on the early EFI systems are quite primitive and will not sometimes not report a failed sensor - they will however always report a missing one. I've seen one situation where a failed MAF went unreported and the only symptom was high fuel consumption.

[samboy1123]

Park on an incline (bonnet up) then fill the coolant and tap all the coolant lines. Don't know a whole lot about these motors but it looks exactly the same as when I have airbubbles in my coolant but I have the gti motor.

May also explain why you're not seeing the temp come up.

[Grags]

are you sure there's no random vacuum leaks anywhere?

[Sausager]

Thanks for the replies guys. I have been away, hence the slow reply

I figured that the OBD was primitive. A shame that a misbehaving sensor doesn't throw a code That'd make life easy!

Samboy, I am going to have to give that a go. I have driven on a few good uphill angles a few times but never actively bled it on one. I'll try do that tomorrow.

And as for vacuum leaks, no I'm not sure. I am sure that there are no major ones. How significant would a leak have to be before it caused an issue?

I checked my plugs today. Do these say anything to anyone? Ordered from front to back:





My workmate has also recently bought a Vitara/Escudo with the G16a 16v in it, with the same motor as mine. I've noticed that his has a number of sensors deleted. From what I can see the IAC, EGR, charcoal canister and the associated solenoid, ISC and a few other misc things are all gone. All vacuum hoses and water lines, etc are all blanked off.


Would it be an idea to do this to mine to eliminate variables? I'm not too fussed on fuel economy, this only being an offroad vehicle.