8v GTi dies when hot, but is fine when cold

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JimW
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8v GTi dies when hot, but is fine when cold

Post by JimW » Sat May 20, 2017 4:00 pm

Help - advice needed, please!

As the title says, really. And by "hot" I probably mean well warm (thermostat hasn't opened, but head - and distributor - are quite hot).

It'll start - and run - fine when cold, but after just a couple of minutes will start to miss a bit, then cut out altogether.
For a while, it'll re-start and continue running, but before long all it'll do is start, then pretty much immediately cut out - usually after misfiring for a second or two.

Immediately on startup, it always has picked up engine speed quickly, (I assume that this is due to a quick squirt of fuel initially), but, if warm, rather than settling down to an idle will now cut out - either with or without some misfiring first.

It is possible, with care, to apply the throttle at just the right time (e.g. just before it fires) and get the revs up - but it'll still cut out altogether after a second or two.
And, again with care, I can get the engine revving up & down - but it'll still cut out, just the same. Usually after spitting and (what sounds like) backfiring a bit.

This is an early type 8v GTi, with Jetronic LE3 and a (Bosch) distributor.

------------------------------

What I've changed/checked (all made no difference except as noted):

Ignition module (amplifier, I think) mounted on the distributor, replaced with brand new. In fact it was worse before I changed this - as it wouldn't start at all when warm.

Coil (didn't actually change it permanently, but tested with a new one).

Swapped round the main HT lead with one of the plug leads.

Distributor cap (which is only a few year old, anyway, like the HT leads & rotor arm) was a bit oily - although not at the business end. Cleaned out.

Fuel pump seems OK - after all it does actually start. I held the pump whilst the engine started & then cut out, I could feel & hear it working for the duration. I also loosened the clamp at the (pump end of the) fuel rail slightly - fuel sprayed out, so it seems to be under pressure alright.

12v supply to the coil (and I think hence to the Ignition module) is just 0.2v or 0.3v down on battery voltage.

SAC - I squashed one of the (air) pipes pretty much flat, thus blocking air flow virtually completely.

CTS - I assume this is the sensor with a two-pin connector, on the side of the SAC body (diagram in Haynes is a bit confusing here).
Checked resistance when hot/warm - around 1200 ohms. Will remeasure resistance and also check cold reading.
Also disconnected it altogether.

Fuel pressure regulator - I just sucked hard on the vacuum hose.

Advance/retard - again, just sucked hard on the vacuum hose. Seemed to hold the vacuum.

Sparks - removed no 1 plug and checked for sparks. Obviously working fine when the engine starts, but unsure about the part where it cuts out.
A bit subjective, but my impression was that the sparks were somewhat irregular - certainly not the steady 5 or so per second I was expecting (engine speed after the initial starting burst is certainly lower than tickover, so I'm guessing about 600 rpm).
However, this could well be due to the fact that the engine - at this point - is firing every now and then, so engine speed could well be up and down a fair bit.

------------------------------

It seems to me that this can't be an issue with a single plug, HT lead, injector, etc. as - essentially - it'll either run or it won't. There's no running on three, for instance.
In fact I can't see it being the rotor arm, distributor cap, fuel pump, etc. either - as I reckon that once "failing" (for instance hot), it'll stay failing until the condition has cleared.


So - does anyone have any experience of a problem like this and remember what the issue was?
Or, failing that, what's my next step in the diagnosis?

Many thanks,
Jim.

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Re: 8v GTi dies when hot, but is fine when cold

Post by peterwight » Thu Jul 13, 2017 9:26 am

I read your post because I still have the problem that I collected advice from members about some time ago (hot engine wont start till cooled down) BUT your the symptoms of your dilemma are similar to those of my Audi having a blocked air filter. It made an effort to keep going but shut down automatically due to lack of air. New filter/ no prob. Regards,PW
A BX fan since buying a 1983 1.6 in 1987 and subsequently a 1.9GTi, three 16valvers and a diesel Meteor. Their deaths have us done parted, save for one 16V sold for restoration, hopefully underway.

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Re: 8v GTi dies when hot, but is fine when cold

Post by Jaba » Thu Jul 13, 2017 12:13 pm

One important but easy check: does the rev counter become unstable with the misfiring indicating loss of ignition pulses. If not then fuel becomes a suspect. The symptoms would fit a too rich mixture when hot so check the sensors, are there two on your system or just one, for reading the correct range of temps from cold to hot.
These sort of problems seem to crop up on the early GTi with a flow meter so it is worth checking this. Also look for a bad connection or internal wire break.
Check the fuel quality in a glass bottle and perhaps consider the fuel filter if it is not newish.

Going back to ignition, the distributor supplies ignition pulses so this ispossible suspect if the rev counter flipflops.
The Joy of BX with just one Citroën to my name now. Will I sing Bye Bye to my GTI or will it be Till death us do part.

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Re: 8v GTi dies when hot, but is fine when cold

Post by RobC » Sat Jul 15, 2017 9:10 am

Couple of thing so to note: in my expericennew "pattern" ignition modules are rubbish, so unless you've fitted a new Bosch one I'd still be suspicious of that.
Also I had this same issue a while ago and thought it was ignition-related: turned out to be a blocked fuel filter! On the gti since it's hidden away under the rear wheel arch the fuel filter does tend to get overlooked.
1991 Citroen BX 16v

JimW
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Re: 8v GTi dies when hot, but is fine when cold

Post by JimW » Thu Jul 27, 2017 12:02 am

Thanks to those who posted responses - much appreciated!

I did - after some effort - get this sorted out. A while back - apologies for not updating sooner.

Quick answer (as RobC suggested) - Ignition Amplifier (ignition module) was the problem.

At the time, I had 3 of these:
  1. "Original" - a Bosch "MTR02". I'm pretty sure this was the original (e.g. from when the car was built).
  2. "Old" - an Intermotor AIM4555. Replaced the original with this many years (probably about 10) ago, in an (unsuccessful) attempt to fix a minor issue.
  3. "New" - a Febi/Bilstein something or other, don't have the part number. Got this from ECP in an attempt to prove/disprove that the Ignition Amp was actually the problem.
So you'd think that a new part would be a) working and b) useful in ruling out a possibility.

Wrong on both counts!

I managed to find the Original Ign Amp, fitted it and, from then on, no problems. Actually, that's not quite true, as I had another quite unrelated issue (which, thankfully, didn't take too long to diagnose).

Before I'd really got to the bottom of this Ign Amp problem, I was wondering whether I had a distributor issue.
Looking on the Peugeot 205 GTi forums - at distributor problems - I noticed someone recommending H&H Ignition Solutions.
They are pretty close to me, so I popped up to see them with a 205 1.9 GTi distributor I'd bought, which they were able to quickly test for me.
I'm afraid I didn't get the name of the chap who I saw (although I'm pretty sure it'll begin with an "H"), but we chatted about various things re. these Bosch distributors.
He said, referring to the Ign Amps, that they "see some horrid parts".
Further, the only ones they recommend (and in fact sell @ £25) are made by Mobiletron (part no = IG-D1910H).

So my bad part went back to ECP - thankfully for a refund - and I'm currently running with a Mobiletron Ign Amp (and have been for a few weeks, now), with my "Original" in the car as a spare.

Looking back, I reckon my "Old" part had been playing up for at least a couple of years - every now & then it would cut out, but restart after a minute or two (usually after I'd shaken the car about thinking it was a fuel issue).
Also, right at the end, you could make the engine cut out just by pushing on the Ign Amp (e.g. pushing towards the distributor body). This is partly why I went and bought the "New" one.

These Amps do get quite hot - even on tickover, after a bit - and I'm sure they'll get even hotter whilst driving.

The "New" part would fail after just a few minutes on tickover, sat on the drive.
I'm pretty sure I never even drove the car with it fitted - thankfully!

So, my conclusions:
  1. Always have a known good Ign Amp - and the minimal tools needed to fit it - in the car.
  2. Mobiletron appears - at least so far - to be the way to go.

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Re: 8v GTi dies when hot, but is fine when cold

Post by RobC » Thu Aug 10, 2017 10:44 am

Glad to hear you've got it sorted - and thanks for the tip on a suitable replacement!
1991 Citroen BX 16v

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Re: 8v GTi dies when hot, but is fine when cold

Post by Dragon Man » Fri Aug 18, 2017 10:16 am

something with those ignition modules always go. i also have 2 Fiat Panda 4x4's and they also eat ignition modules.
theres a reason why they fail though, its because the ignition coils resistance has gone too low.. it puts way more strain on the ignition module.

if you can and have 2x ignition coils, check the resistance on both and see which one is the highest.
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