'71 914 with 36K miles. Engine wasn't well cared for by PO's.

I used to have problems with poor running when the car was warm but a new chts solved the issue and the car has run well for 800 miles.

The engine problem started last week. Drove 30 miles on a cool day and car ran great. Parked for 2 hours and then started back up. Car idled poorly (lumpy) and drove even worse. Car bucked, hesitated and would not accelerate smoothly. Ran poorly for 30 miles, I got home and parked it for a couple days. Took car out over weekend and it ran great. 100 miles and no sign of previous poor running. Drove car today and the poor running returned. Made driving miserable. Hesitates at every rpm and is barely drivable.

Any ideas?

Thanks, Mark

Are you running carbs, or djet?

djet - all stock.

Most intermittent problems are caused by something loose: Wire, Clamp, Points, gasket... Start poking around

Crap in the gas tank pulling to the pickup screen then floating away when the car is off??

fuel filter

Yeah, what Mike said. Back to the basics. But be careful as you poke around as you can knock stuff loose as you do. You can cause more problems than you started with. Ask me how I know. Oh, don't forget the ground strap on top of the tranny.

I agree with the above , start with the fuel filter , then check for loose and frail wires.

Check your FI harness to make sure it's OK. From the Jedi Master regarding the CHT sensor/wire:

Shorted: The ECU interprets a shorted sensor as a signal to lean out the mixture (about 30% leaner). The car may run and start in this condition, but will have poor idle and drivability. Check by disconnecting the sensor from the wiring harness and checking the resistance to ground. Note that shorts are often intermittent, caused by nicks in the sensor wire and by exposed contacts to the wiring harness touching ground.

If the FI harness wiring is bad, or if you have a non-insulated connection that is hitting the frame / engine tin you'll get your symptoms. I suppose your replacement CHT could have gone bad as well.

If you doubt your fuel pressure, stop over and borrow a fuel pressure gauge to tap into the system as another troubleshooting step.

Overhauled the TPS. Car ran great for a day then back to poor running. I have the day off today and will try some more.

When the car is running is running poorly can you tell if it is running rich based on the exhaust? Does it stall? If so is it hard to start and floods? Your symptoms plus these were my symptoms of a bad CHT wiring harness lead, not the CHT itself.

If not I too would suspect fuel delivery or possibly ignition? Points or Pertronix? Once I had the lead on points get pinched in the dizzy cap which stripped a section of insulation and made intermittent contact with the dizzy body thus grounding power to the points resulting in intermittent poor running.

I've had the cht sensor itself get a little bit loose & result in intermittent bad go ground there......

New CHTS 2 months ago. Screwed in tight. But I will check over things today. I miss driving her.

Everything is still stock. 36K engine that wasn't pampered. Car will run great going 9 miles to work and then run like crap on the way home. Either good or bad between turns of the key. Never both in the same drive. I think its electrical, not fuel. Car always starts easy and never stalls. New dizzy cap made no difference.

I might have figured it out - stay tuned.

Success - A couple days ago I took off each plug wire and listened for a change in the engine. One of the wires made no difference when removed. Ordered new plugs and wires and just installed tonight. Took the car for a short run and everything was great. Ran better, smoother and quieter than ever before. I'm hoping this thread is done. Thanks everyone!, Mark

If it comes back. Check the FI grounds under the intake on the engine case.
I think there's five all together.
That's the last poor performance issue I had to chase down. Acted the same, nothing in one cylinder. But the nothing was caused by one cylinder getting no fuel.

Rough running is back
I will follow previously posted suggestions as well as replacing points and cleaning injectors.

See if you can get it to run poorly once it is running well. This is interesting that it sounds as though it is either running well the whole trip or crappy. I am still thinking fuel is the problem. An in-line pressure gauge would help rule out fuel supply pressure and power to the pump. Then go to the injectors (grounds are the most likely culprit).

I'f I knew what it took to run crappy, I would have already fixed it. But I get what your saying and I'll work on what you suggest.

Go back to the cylinder that was bad.
Pull the injector out.
Put it into a quart jar. Crank the engine and see if your getting fuel.

What I've found.
Issue with trigger points. Two cylinders or all will be having issues.
Issue with a ground. One cylinder is having issues.

When Ryan brought his car up from Silverton. It was driving like it had 40hp.
That was one cylinder not getting fuel.

Fuel-Spark-Air

I put in a new fuel filter, Car ran great. Parked it for an hour and then tried to drive to work. Car bucked worse than ever before and I turned around 1/2 mile down the road. Back to the drawling board

Fuel injection relay?

There is a small braided ground wire in the distributor housing. If this is broken from the distributor internal base and only getting an occasional ground it may be causing similar symptoms.
I cannot recall if this is present in the d-jet dizzys or if its just the L-jet ones, but
It's probably worth a look to see if it is intact and at least exclude it as a possibility.

If you are sure that you had it isolated to one cyl. ,concentrate on the wiring to that injector. I do not remember djet well, but on L I recall that injector wires losing insulation and touching can cause some severe running issues. I feel for you, the hardest thing to find is the one that comes and goes.

As someone mentioned above, fuel-spark-air. Question - since I've never owned a 914 with FI, do you guys have the same style rubber sleeves that join the runners to the intake plenum that can be seen on the single progressive Weber setups? Those can begin to crack and leak air, which can be intermittent based on how the rubber warms and cools.

There are 3 white grounding wires near the back wall of the engine compartment area (the other side is the rear trunk) near where the engine lid closes that are prone to come loose. Those wires are spade connected to a grounding block with 3 spade terminals. Mine had come loose which resulted in only 2 cylinders running out of 4. I made this discovery while cleaning out some leaves and debris in that corner of the engine while it was idling rough and when the engine smooth out when my hand grounded the loose wires, I found out the cause.

picture?

It is on the top bolt on the passenger's side that holds the engine and transmission together at the engine bay.

Other ground locations- Grounds

While that will work just fine, that's not where the factory put them. They are normally found on the rear most top bolt, where the two halves of the case meet.

No wonder why my harness stretches some.

Did you verify fuel pressure during your issue? I bought an inexpensive fuel pressure test kit from HF and left it in line until I dialed in my DJET. At least with the gauge you will be able to cross it off the list as possible problem.

I agree with you that it sounds like an electrical issue. you might want to R&R (remove and replace) all connectors and check the integrity of the wires and connections to each connector.

I had a similar problem once. It was a dropped valve seat. Most of the time it would be fine but sometimes it must have gotten crooked and ran on 3 cylinders. When I finally tore down the motor, I was shocked how loose the seat was. It was amazing the car ran at all. Most of the time it did pretty good. I hope this is not your problem.

Given Mark's reply, I think it's time for a leak down or at least comp check to rule out mechanical problems.

Listen to the starter crank. I first noticed my third (sigh!) dropped valve seat because the starter went "RR-RR-RR-..-RR-RR-RR-.." instead of making a consistent noise. It was fighting compression on three cylinders, and not on one.

It's not a definitive test, but if it sounds like that you can be pretty sure you have zero compression on one.

--DD

I hope not as well! I'm still replacing gaskets, gas and vacuum lines. I will send out the fuel injectors this week and then work on getting the engine back into the car.

Thanks everyone for the suggestions.

Reinstalled engine. Engine started to run worse than before. Brad Mayeur took a quick look at Hershey. Said it was only running on 2 cylinders. I installed new (used) wire harness and ecu. Didn't fix the problem .