89 replies to this topic

[Ozymandias]

Thanks FlyingScot and spiguy!

 

I've fixed the broken purge valve pipe now, just using another bit of pipe.

 

spiguy, your advice on checking the other breather hoses was inspired and absolutely spot on! There was a small hole in the breather pipe that goes from the rail to the advance/retard on the left hand side of the cylinder block. It's now taped up (waiting for a new hose to arrive) and everything is (touch wood) working fine again.

 

I also replaced the air inlet sensor and spark plugs, double-checked the valve clearances and gave the vacuum hoses a once-over - apart from a couple of misfires immediately after starting when blipping the throttle yesterday, it's been fine - sailed to work this morning without so much as a stutter.

[spiguy]

excellent. That's great news!   If you find that the slight misfire when blipping becomes a feature, check those vac lines again. I had this, when the short pipe from the inlet to the fuel trap had 'kinked' I had made my own one up from normal vacuum pipe (intended for use with vac advance on a normal distributor) but the plastic was not heat resistant enough, and had softened with the heat back there. The car drove fine, just sudden throttle application gave a sort of hesitation / misfire. basically what was happening was that the vacuum in the pipe couldn't vary fast enough because the pipe diameter had reduced due to the kink, acting like a sort of restriction. This effect could also be created by pushing the pipe on a bit too far and reducing the diameter of the hole to be smaller than the pipe diameter. Lesson learned - use the proper pipe and if in doubt, change it, they aren't that dear from minispares.

[Ozymandias]

Gah - spoke too soon, the stuttering's started again... :-(

 

It's fine when she's fully warmed up, but for the first 15 minutes of a drive she's struggling - feels like getting too much/not enough fuel. Back to the drawing board...

[spiguy]

What is the temperature gauge indicating during this time? The engine should be up to temperature in about 5 minutes. If it is taking a long time to get to normal running temperature, maybe your thermostat is stuck open or has been removed?

[Ozymandias]

The temp gauge seems OK and gets up to temperature in about that time (it never EVER goes above the line, even when the auxiliary fan kicks in when sat still for a while on a hot day - I've always wondered if this can be right!)

 

That said, she was behaving fine on the way into work this morning, barely a stutter - I do hate these intermittent problems!!

 

I've got her booked into the garage this Friday because she needs new oil and fuel filters anyway, so I've asked them to have a look (and check the oxygen sensor if they've got the right kit).

[spiguy]

So are you saying that it can take up to 15 minutes for the engine to reach operating temperature? That is not right and suggests either a stuck open or missing thermostat. The car should be fully warmed up within a few minutes of driving in normal ambient temperature conditions. My car is up to temp in about 5 minutes. If yours is taking 15 minutes, then that could explain why it drives like a cold engine for the warm up period, because it is a cold engine...

 

Alternatively you could have poor coolant flow through the water fed inlet manifold, and as the coolant temperature sensor is mounted in the inlet manifold, it relies on this flow both to indicate temperature on the gauge, and also for the ECU to base it's control on. In that case the ECU could be holding the car at cold running settings even though the engine is actually up to temperature.  Another option is a faulty coolant temperature sensor, which would have the same effect as either way the ECU will believe it to be indicating the actual engine temperature.

 

One quick way to get an idea of what is going on would be to run the engine until the top radiator hose gets hot - this indicates that the thermostat has opened and coolant is now flowing to the radiator. The car should be up to temperature in 5 minutes or so (maybe a little longer if just idling). At this point check the gauge - it should indicate the engine is up to temperature. Note that the top hose should not just gradually heat up, it should remain fairly cold until the thermostat opens then go quite quickly hot.

 

If the hose just gradually warms up instead of being coldish then hot, that suggests missing or open thermostat. If the hose temperature behaves normally, but the gauge still shows cold, then that suggests poor coolant flow or faulty coolant sensor.

 

If you do this test and post back results maybe we can diagnose a little further.

 

Does your heater work?

Edited by spiguy, 16 June 2015 - 11:44 AM.

[Ozymandias]

So are you saying that it can take up to 15 minutes for the engine to reach operating temperature? That is not right and suggests either a stuck open or missing thermostat. The car should be fully warmed up within a few minutes of driving in normal ambient temperature conditions. My car is up to temp in about 5 minutes. If yours is taking 15 minutes, then that could explain why it drives like a cold engine for the warm up period, because it is a cold engine...

 

No, it gets to temp in about five minutes - sorry, I didn't make it very clear!

[Ozymandias]

 

So are you saying that it can take up to 15 minutes for the engine to reach operating temperature? That is not right and suggests either a stuck open or missing thermostat. The car should be fully warmed up within a few minutes of driving in normal ambient temperature conditions. My car is up to temp in about 5 minutes. If yours is taking 15 minutes, then that could explain why it drives like a cold engine for the warm up period, because it is a cold engine...

 

No, it gets to temp in about five minutes - sorry, I didn't make it very clear!

 

To clarify - the temp gauge reads normal driving temp (just below the line) after about five minutes driving - but when the stutter happens it is normally much better after about 15 minutes of driving.

[FlyingScot]

Check the PTC and see if you can borrow a code reader might be quicker to check some the the items.

FS

[Ozymandias]

It's got worse - she was stuttering so badly this morning, even when warmed up, that I had to drop her off at the garage on my way to work (and walk the rest of the way, humph!).

 

Starts non problem, idles no problem, but hesitates and stutters on pressing the throttle and misfires throughout the range (except idle or very light pressure on the accelerator), very jerky and much-reduced power. :-(

[FlyingScot]

Did you check the throttle position sensor ? (TPS) post #6

FS

[Ozymandias]

Did you check the throttle position sensor ? (TPS) post #6

FS

I didn't get the chance to do that - now it's at the garage I'll ask them to check it!

[Blatherskite]

Check the PTC and see if you can borrow a code reader might be quicker to check some the the items.

FS

PTC on our SPi has never been connected (burnt wiring...) in several years here in Norway, and even in the depths of winter (-20c or so) never had a problem. I would suggest the fault is elsewhere...

[Blatherskite]

It's got worse - she was stuttering so badly this morning, even when warmed up, that I had to drop her off at the garage on my way to work (and walk the rest of the way, humph!).
 
Starts non problem, idles no problem, but hesitates and stutters on pressing the throttle and misfires throughout the range (except idle or very light pressure on the accelerator), very jerky and much-reduced power. :-(

What Spiguy wrote: "the coolant temperature sensor is mounted in the inlet manifold, it relies on this flow both to indicate temperature on the gauge, and also for the ECU to base it's control on. In that case the ECU could be holding the car at cold running settings even though the engine is actually up to temperature." might be a clue. Had similar to what you describe (especially when pulling out of a junction in front of a speeding truck...), and eventually found the coolsnt temp sensor connector was loose. It was disconnecting at crisis moments, making the ECU give "choke" to a hot engine, and it didn't like it! Reached up from underneath & pushed the connector back on, and vips! No more "choking". I would suspect the coolant temp sensor with poor connection might be your problem.

[peter-b]

In the process of trying to get my spi to run right I noticed the heater pipes going into the manifold had almost blocked right off to the point that after a blat around the block on a really cold night there was actual frost on the manifold near the throttle body and the temp guage would actually read too low. I removed the pipes, beadblasted it inside and fitted brass hose stubs. Seemed to fix that problem atleast