Loss of power/backfire after engine gets hot

Has the valve lash been checked? Lost

 

WUR failure, aneroid leaking. Check the fuel pressure

 

I won't argue with Constance. She's the expert. But I would wonder why your engine is overheating. You should definitely look at that. The 328 has a decent radiator and cooling system. You should not be overheating.

I would suggest you start with the basics. Make sure that the fans are working and coming on when the engine heats up. And make sure they are turning in the correct direction (drawing air through the radiator). If the fans aren't working, especially in slow traffic, you will overheat. If you are sitting still for a long period, it helps to rev the engine up to around 2500 rpm to help the coolant circulate.

If fans are working properly, then start considering problems with the cooling system. You might want to replace the thermostat. Also, check the radiator and make sure it is not clogged. A 25 year old radiator could probably stand to be recored. I had this problem with my '86 when I got it a couple of years ago. I recored the radiator, changed the thermostat, put in fresh fluid, 50/50 mix, with a bottle of Red Line Water Wetter, and the car runs a nice, steady temperature now, no matter how hot it is. Also, if you still have the original hoses, consider changing them while you are at it, and be sure to bleed the system properly.

Just a thought.

 

p.s. Could be a problem with the water pump impeller. If you do everything else and still have a problem, check the water pump.

 

It is a subtle problem and nobody can be really accurate from far away. I suggest the best course of action is for you, or your mechanic, to check the fuel pressure of the CIS system. System pressure, control pressure, cold, and hot are all important.

 

What version 328? Euro, CH87, US?

 

Sounds like an electrical/ignition problem to me. You are getting fuel but intermittent spark.

 

well, since your car is injected and mine is carbed, I can't really say anything more without sounding stupid to the experts here, but whatever is controlling the fuel/air mixture is slightly off at high temp, which would cause backfiring or popping. this may also explain the petrol smell, because the system is putting fuel into the cylinder that isn't being fully ignited by spark.
That means Constance is probably right that the warm up regulator could be the culprit--because it is perhaps feeding too much fuel in when the engine is already hot.

 

Mr. Bowl (or others), how would valve lash contribute or cause the symptoms explained above, I am curiuos.

 

Maybe you should check the distributors for oil contamination. It could be a leaking cam seal and the oil might cause no firing at times. If there is no oil leakage, it could still be a problem with the HT leads or HT extenders. I did not really have problems with the ignition on my 328, but when I took the leads apart to change the red cover (it was broken here and there), I measured the leads and got very different results, including no connection. The sparks may still get through to the spark plugs - but it is better if the impedance in the wires are the same across all leads.

 

Glorio I wish I read this thread earlier as I would have told you that it was the HT leads.
The exact same thing happened to me on my Euro 328.

I had two leads that were faulty and they were the leads on the front bank.The leads were original as the car only has 21000 miles on it.

I replaced the leads and it has run perfect ever since.

 

The symptoms are shouting out ignition leads or plug extenders.

 

When the lash is too tight it only gets worse as heat builds up and then unburned fuel is ignited in the exhaust system. When I purchased mine one EX valve actually had a negative value and it started fine but when it reached temp the front header would glow and the exhaust would pop. The fix was easy and the EX valves were replaced with SS.Needless to say there are several scenarios that would produce these symptoms. lost

 

Not sure how different the 328 is than my QV, but I had the exact same symptoms (and I mean EXACTLY). It was a bad crank position sensor. Car would heat up and the one (of 3) at the 11:00 position would fail.

Those things go bad after awhile.

 

Interesting ... I did some work near the crank sensor (there are two sensors, one for the speedo and one for the ignition, I think, correct me if I am wrong) and noticed that the wire was almost broken for the front-mounted one (closest to gas tank). The jacket had been worn down at a certain location revealing one of the inner wires and down to bare metal. I am not sure what could cause this other than vibration from the engine. Anyway, I fixed it before anything would happen to the wire (water ingress, cut-off, short-cut to ground etc).

 

A QV has 3. I wasn't sure about the 328.

 

The 328 has one TDC sensor and one degree sensor. If either of these were to completely fail the engine would stop. It is possible that they could be flaky though and giving low output, or a wiring problem such as a poor contact. The connectors on the 328 above the LH top shock mount are prone to water ingress and corrosion and the sensors go through here.

Its definitely an ignition problem so if the ignition leads and plug extenders have been ruled out (have they?) there is not a huge amount else it could be. Also check the LT connectors on the bottom of the coils for corrosion.