Rough Running

Rek

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I need a bit of help diagnosing what could be wrong with the running of my E9

The engine is a 535i 3430cc 1989. Originally the car was not EFI so I fitted a swirl tank and all was well with the car. I then moved to Tanks Inc in tank Walbro with built in baffle. All was well. Among the work I completed was to replace all the injectors and rubbers eliminating a number of vacuum leaks along the way.

Then things started to play up. The car would start but when hot in traffic, it would mis fire, display the symptoms of a faulty fuel pressure regulator valve - hesitation when accelerating etc., I replaced the FPR twice to no avail.

Faulty pump? I took the Tanks Inc module out and noticed some of the sealant they recommend was washing around the bottom of the tank which I cleaned out. I had a spare Bosch 044 so removed the old Walbro - fixed a plain pickup and put the Bosch in line underneath the car beside the rear right wheel. I also changed the fuel filter. The Bosch is very noisy and sounds like a gaggle of geese hissing, but I thought that any concerns about fuel pressure will go away.

So what now? Now it is lumpy and misfires when cold although it starts OK. It has the same fuel starvation issues. Once its warm the engine runs fine and is responsive and smooth. After a while sat in traffic, it starts to misfire again, and the fuel starvation seems the same. The temperature gauge never moves above mid way point.

Things I think I need to do.

Test the temperature sender - next on the list.
I have a stainless steel exhaust that cooks the rubber drivetrain components so part of the solution was to have the exhaust wrapped. There is a section of rubber fuel hose from the tank, through the pump and then to just in front of the rear wheels, picking up a metal feed after that. Could this section expand if it is heated causing the fuel starvation? In stead of cooking the drivetrain, it might be cooking the fuel pipe. It seems warm but not too hot to touch. I have some steel braided hose which might work.

I am wondering whether I have two issues rather than one. One when the engine is cold, and another when the body and attached bits under the car heat up. Does anyone have any other ideas or tests I can do. Any help gratefully accepted.
 

Rek

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Not stuck any more.

After a replacement fuel pressure regulator, replacement fuel pump, replacement throttle position sensor, still no resolution.

Remove distributor cap and cleaned the contacts. Refitted cap and the car is running perfectly again.

Bogging down seems to be a problem with these engines and there are numerous fuel and electrical issues which cause them.

Next time someone has this problem I can offer advice and guidance having researched and diagnosed the problem and reached the solution. I will be pleased to help anyone with a step by step process to eliminate known issues in a constructive manner. All you have to do is ask.
 

Rek

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Trust you know this site http://www.hiperformancestore.com/Motronic.htm which is fabulous.

The distributor cap on these cars is finicky. They can also get micro-cracks that you cannot see but markedly affect driving.

I hope you dont have a cold start valve issue, they are a PIA to change.
I tried the link but didn't get a result. Cold start is fine. I do have a fuel pressure drain on standing overnight but this might be from the check valve in the pump. This means a few cranks, but nothing untoward.

One thing I do not have is the 1-2 second priming of the fuel lines on ignition before starting which would mean instant starting. I can live with it, but on the donor car it worked and now the engine is in mine it doesn't. I've changed out the pump relay and there is not earthing of the terminals of the relay holder. It seems that the CPU is not getting some signal from somewhere to make this happen.

Right now, there are other fish to fry.
 
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