Starts ok - stumbles as soon as engine warms up

[johnny_buchanan]

Red Dust; my lately not so trusty '88 350 tbi; is now having the symptoms described in the heading.
So, when cold starts on a button and runs smoothly untill warm. This is when the prob. starts. Rough running, rich I thinkm and hesitancy. Will stall or if shut down will not start again.

I've changed the maf, distributor and ecu (at least, been trying to figure this out in bursts for a long time) Actually thought we'd nailed it when new ecu was plugged in, It started, alas only briefly so no avail

Before the ecu change it would only start with serious cranking and then run badly. With the new ecu it now works few minutes, makes me think that somehow this is ecu related?

Ideas, pointers?

TIA,
-J

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[PlayingWithTBI]

Are you getting any Malfunction codes? It could be your EGR valve but I wouldn't throw any parts at it until I checked for codes and put a scanner on it to see what's going on. At the very least you can do the "paper clip" trick.

https://www.freeautomechanic.com/diagnostictroblecodes5.html

 

[johnny_buchanan]

Ok,
I'm getting codes 15 and 43.
Knock sensor/spark conrol circuit fault and Coolant sensor low or open.
Ideas? Coil??

-J

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[Greasemagnet]

Maybe an intake leak, it seals when cold but as the metal heats up and expands creates a leak ?

 

[Greasemagnet]

Clogged fuel filter / fuel line, perhaps it is not clogged when you first start it be ause the crap may be heavy but slowly clogs the filter/ line as it runs causing a partial blockage making it run bad, after fuel pressure drops the crap sinks to the bottom ?

 

[thinger2]

So you have a knock sensor code and a coolant sensor code and it stalls when it warms up and it wont restart?
Im assuming you set the timing to 0 with the reference wire unplugged when you replaced the distributor.
Take a look at the knock sensor and its wire first.
And then the coolant sensor.
In fact, though I dont recommend just frosting it with new parts.
Your parts are so old it needs them anyway.
Use the ac delco.
A code 43 pops up for all kinds of reasons
It probably was not an ecm problem to begin with but was caused by faulty open loop/closed loop reference from bad sensors or bad wiring.
The ecms in these are pretty durable so unless you have actual livestream data that shows a failure, its a bad input from a sensor or multiple sensors

 

[johnny_buchanan]

Ok. Seems that this issue has been sorted. ECT sensor change has remedied this particular issue. New back brake shoes and cylinders installed and water pump started leaking... New pump. Now it is starting to look like I can finally book an mot-inspection

-J

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