Hesitation/misfire on 318is

[inlovewithRWD]

I'm wondering if you may be able to help...

Since having the timing chain replaced on my car replaced (probably unrelated) my car has developed a problem. When on a light and steady throttle the ar hesitates and feels like it's misfiring.

My first thought is to replace the plugs and HT leads, but I'd be interested in hearing if this is a common issue and easy to fix.

Cheers!

[moimo]

id bet its totally related, ill bet that you have a timing issue, and if you have just had the chain replaced id be inclined to start there. if the sprockets have been changed too which they should i would start with static cam timing, straight edge along the machined profiles of the cams at the rear, with the cam cover off, and check maks and alignment of camshaft sprockets, they can be out, but dont start thinking by a tooth or anything desperate like that, the 4 bolts that hold each sprocket allow for some rotation. once you are confident that your static timing is correct, then think about other options, assuming all was well before then i would reckon all will be well again, you could chase a fault thats not there unless you start with what you know has been done

Remove plugs, leads(Mark up) associated parts and cam cover
remove tensioner

ensure engine at TDC, marker/rod/dept guide in cylinder 1 through plug hole and rotate until at higest point. Loosen cam sprockets, recheck tdc (Mark inserted rod etc for subsequent checks), install engineers ruler as a flat across the machined faces of the rear or the cam shafts, adjust individual shafts if required, check TDC with marked rod. Now the arrows on the Cam sprockets have to be at 90 degrees to the cylinder head surface, not the floor, set these and lock up sprockets, refitt tensioner and associated parts.

if it is still missing then back to bascs, visually inspect the plugs, ceramic for integrity etc, check all leads, look at the coil packs for any damage, the CPS which is reposible in conjuction with the gap in the crank toothed wheel for initiation of the low tension circuit to create the spark is worth checking, visual, seating, and connection, followed by electrical resistance, stroboscopic timing could be done once the engine is running, this is where i can only be generic as my understanding is there is no adjustment on the M42 engine, but an inconsistency would show up with eratic movement of the timing mark rather than consistent advance on accelaration, indicating an error electrically Ignition components as the strobe light takes its pick up from the HT circuit.

it would then be worth chcking fuelling, some basic stuff you can do is use carb cleaner spray through the throttle body, check clean the ICV (idle control valve), and the MAF (pre intake airflow meter) check the TPS, throttle position swith on the trottle body, it is either on or off, it is not progressive. this would generall sort out idling, missin issues.

Finally check for air leaks, there is a maze of hoses, and if anyone doesnt go straight to the dealer and buy all these brand when they decide to keep an 1.8 M42 then you are asking for issues, even from BMW UK, i got the lot for a few quid, (each and there is several ) no amount of tape, silicon, and anything else is ever long term.

i guess im going on now, so id start with the job you have just had done and then as with all fault finding be logical, thorough and just because its new doesnt mean it will always work (look at our Goverment)

[redcar]

The M42 uses a progressive throttle position sensor. It has a carbon track so that is worth testing.

It's also worth testing the AFM as this can cause flat spots at a particular "speed"

Does the car perfectly?

[inlovewithRWD]

Thanks for the suggestions. I'm going to have a chat to the mechanic who fitted the chain (ex BMW technician) before trying anything to see what he says about the cam timing.

[moimo]

The TPS on an 36 1.9 M42 may well be a potentiometer i dont know, but the e30 varient comprises of two normally open contacts, one of which closes during idle and the other during wide open throttle (WOT), its nothing more than a pair of contacts and another pair inside a micro switch. The operations are at idle and at 70 percent throttle, if outside of those then adjustment required, they dont generally go out, and if they do its normally a lumpy idle and cutting out that follows. boring i know and worse still i could supply a pic of the inside of a tps.

[johnl320]

Surely needs to check timing, seeing as that has just been messed with and now the fault has appeared?

[redcar]

The TPS on an 36 1.9 M42 may well be a potentiometer i dont know, but the e30 varient comprises of two normally open contacts, one of which closes during idle and the other during wide open throttle (WOT), its nothing more than a pair of contacts and another pair inside a micro switch. The operations are at idle and at 70 percent throttle, if outside of those then adjustment required, they dont generally go out, and if they do its normally a lumpy idle and cutting out that follows. boring i know and worse still i could supply a pic of the inside of a tps.

Weird, I have a potentiometer TPS on my e30 318is.

[inlovewithRWD]

Surely needs to check timing, seeing as that has just been messed with and now the fault has appeared?

I'll be doing this next week, but just wanted to ask the Zone for ideas... Helpful as ever!

[johnl320]

The TPS on an 36 1.9 M42 may well be a potentiometer i dont know, but the e30 varient comprises of two normally open contacts, one of which closes during idle and the other during wide open throttle (WOT), its nothing more than a pair of contacts and another pair inside a micro switch. The operations are at idle and at 70 percent throttle, if outside of those then adjustment required, they dont generally go out, and if they do its normally a lumpy idle and cutting out that follows. boring i know and worse still i could supply a pic of the inside of a tps.

Weird, I have a potentiometer TPS on my e30 318is.

For once Redcar I am in agreement with you , thought my IS had one too

[redcar]

The TPS on an 36 1.9 M42 may well be a potentiometer i dont know, but the e30 varient comprises of two normally open contacts, one of which closes during idle and the other during wide open throttle (WOT), its nothing more than a pair of contacts and another pair inside a micro switch. The operations are at idle and at 70 percent throttle, if outside of those then adjustment required, they dont generally go out, and if they do its normally a lumpy idle and cutting out that follows. boring i know and worse still i could supply a pic of the inside of a tps.

Weird, I have a potentiometer TPS on my e30 318is.

For once Redcar I am in agreement with you , thought my IS had one too

m40 uses a TPSwitch, iS has a TP"Sensor"

More importantly, does anyone know how to completely and accurately test an iS TPS?

[Brianmoooore]

E30iS uses a potentiometer for a TPS. Test by connecting a 5 or 6 voly supply across the ends of the pot track, and monitoring the voltage on the slider as the throttle is opened.
Exactly the same method as for an AFM.
Before getting involved with all the technical stuff suggested already in this thread, I'd be checking the big air hose for splits, and also looking for any other air leaks in the area.