Hi there

Just put our 1970 914 back to fuel injection from carbs and it purred for the first 30 minutes in slow moving traffic but then it began to cough and then was quickly nearly kangarooing down the street. It was fine idling but trying to pull away and driving it, it sounded as though it was misfiring or coughing or not running on all cylinders.

What's the checklist for trying to solve the problem?

Thanks!

I would start with fuel pressure.

Check the throttle position sensor. Adjust, clean or rebuild.

Ignition. Always start with ignition. Also make sure the basic engine is in good shape, valves adjusted and decent compression, etc.

--DD

If it starts and runs fine when it is cold then starts sputtering check the CHT sensor.

Where there any mods to the engine, cam, displacement?

Took the car out again today,fine for the first 20mins then the problem returned.The engine has had no mods done to it and prior to fitting the Fuel Injection the car was running great
Thanks for any help that you can give

Did you change the fuelpump from the low pressure carb pump back to a higher pressure FI fuel pump again ?

Sounds like CHT sensor.

If it had a carb pump, would it run great for 20 minutes?

Have you checked the CHT as suggested yet?

Mine used to do that -intermitted bucking. I almost parted the car. I tried a bunch of things but I think it was just bad electrical connections.

Are the CHT sensor still available to buy new

Just found out The CHT censor was brand new out of a packet , that's one thing eliminated

I can't be sure but I think it was the wires around the tach and making sure the timing was correct that eliminated the bucking. I pulled off all the ground wires and cleaned them as well as the wires for the coil, ect.

I had done the chts but it didn't fix it.

Are all the FI parts original and proper according to the rennlist site?

All the parts are original with NOS Bosch fuel injectors , we had 3 sets to choose from

There are several FI troubleshooting guides here:

http://bowlsby.net/914/Classic/TechNotebook.htm

And if you determine that you need a new harness...let me know.

Your FI points in the distributor have grease on them.

Did you take the fuel tank out? Pinched fuel lines underneath are a common problem.

Yes ,removed the tank and cleaned, the sock was all clear.On top of the ECU there's a grey knob that turns and clicks is there a best position for the knob to be to help with the running of the FI

In the middle is the best position generally. Or, if there is a mark on the ring around the knob, any pointer on the knob should point to that mark. (That is evidently where it was set at the factory.)

Actually, the best position is the one that makes the idle nice for you at this exact moment, but that's not really what you were looking for...

--DD

The previous owner of my 74 had told me they replaced the CHT sensor so I tried everything else and nothing worked. I decided to check the CHT and it turned out that the PO had stripped the threads when he put it in so it was loose. When I fixed the threads everything started working great! Also check the wire leading to it!

I don't think you have the right ECU. Our early 1970 does not have a knob on the ECU. The adjusting knob was added to the ECU's on lster models so they could trim the idle & emissions. As suggeted above, please check the F.I. part numbers on the site Bowlsby suggested to make sure they are correct for your model year. For best performance, the distributor, the ECU and the MPS all need to be compatible with each other. Also check the Auxiliary Air Regulator ("AAR") to make certain it is functioning properly. If the AAR is not closing entirely when the motor warms up (i.e., after 15 or 20 minutes) it will put the engine in an excessively lean condition and act like a vacuum leak. You will spend many hours trying to find a mysterious vacuum leak, when it is the AAR that has gone bad. (Don't ask me how I know.) Our car ran fine when it was cold, but terrible once it warmed up becasue the AAR was bad.

You won't know until you check the ohm values of the sender when hot & cold.

My web site (see sig) has detailed troubleshooting info for all D-Jetronic components.

Do check the cht, i have them if you need it, but id suspect its ok..
Does sound like fuel control

just something else to consider, the coil. when the coil starts to breakdown, they run fine cold, as they heat up, they expand and the windings separate, causing the condition you describe. try a coil swap and see if things change.

Changed the Relay board today ,Our very own MR 914 had a similar problem with one of his 914s and it turned out to be a connection in the back of the Relay board a connection that controlled the petrol pump.Going to take it on a long run tomorrow and see what happens ,I'll keep you posted with the results (fingers crossed )