D24 misfiring on cyl 4# at idle

[Echo1975]

So I have noticed that for a long time the engine has had a bad shake at idle so now I finally decided to find out what's wrong so I started cracking the injector lines and opening cyl 4# line makes no difference to the way the engine runs even though fuel started spraying from the line.

The engine smooths out at about 1200 rpm and runs like an inline 6 should but at idle it shakes like a 3 cylinder.

Also the exhaust manifold is 90f cooler coming from that cylinder than the other cylinders.

I did a compression test through the glow plug hole and it went to over 320 psi instantly and that's where my gauge maxes out.

I think that leaves the injector or the injection pump as the culprit. I checked the injector spray patterns around 6 months ago and all were good but I couldn't check the opening pressures due to the gauge not functioning on my test tool.

If the opening pressure is wrong, will it cause a misfire resulting in cooler exhaust temps?

[ngoma]

Yes, also check valve clearances.

Check compression again with a diesel (higher gauge range) compression tester.

If the problem is at the IP, it probably would be the delivery valve as the IP is a rotary style (one piston pressurizes all the lines).

When testing injectors it is important to test spray pattern (which you did), and also POP, and drippage. Must not drip or even moist at the pintle needle when sitting at just below POP for 10 seconds.

Probably the quickest next step would be to swap the injector to another hole, see if the problem follows the injector. Make sure you have new heat shield washers, or are able to reform them.

[Echo1975]

Originally Posted by ngoma

Yes, also check valve clearances.

Check compression again with a diesel (higher gauge range) compression tester.

If the problem is at the IP, it probably would be the delivery valve as the IP is a rotary style (one piston pressurizes all the lines).

When testing injectors it is important to test spray pattern (which you did), and also POP, and drippage. Must not drip or even moist at the pintle needle when sitting at just below POP for 10 seconds.

Probably the quickest next step would be to swap the injector to another hole, see if the problem follows the injector. Make sure you have new heat shield washers, or are able to reform them.

Today I changed the injector to one from a working engine and I tested the pattern on both and saw no problems but the engine still only starts running right at 1500ishm rpm. The cylinder starts sputtering at around 1200 rpm resulting in the engine
shaking violently.

I only notice this in 2 ways when driving which are reduced low end torque and revs rise quicker after rpm reachers around 1200.

I have adjusted the Valves under 6000 miles ago so I highly doubt that.

I read another post about the exact same issue where they sent the pump to be rebuilt and after no response so I guess it was the pump.

I have never opened the injection pump so should I try removing the delivery valve for cleaning etc and should I try swapping two of them to see if problem goes over to the next cylinder?

[ngoma]

Your troubleshooting step was a good one (replacing suspect injector with a known good one) but better would be to swap the suspect injector with one from another cylinder. See if the problem follows the injector. Then, depending on the results, start looking at the delivery valves or other.

[Echo1975]

Originally Posted by ngoma

Your troubleshooting step was a good one (replacing suspect injector with a known good one) but better would be to swap the suspect injector with one from another cylinder. See if the problem follows the injector. Then, depending on the results, start looking at the delivery valves or other.

It's fixed now. Delivery valve for 4 cyl was missing the spring

Friend gave me one from a 1.6d and it fit.

I have never had them off so it must have been the doing of the previous owner but for some reason it just got worse lately and I only noticed it then.

[ngoma]

Wow! Missing spring would cause erratic injection behavior for sure! How long was it like that? Was it intermittent?

Job well done.

[Echo1975]

Originally Posted by ngoma

Wow! Missing spring would cause erratic injection behavior for sure! How long was it like that? Was it intermittent?

Job well done.

It must have been like that for over 6 months but lately it got so bad that I had to investigate. Before the job the engine shook so much that you could see the entire car shaking from behind and the gear shifter jumped around a stupid amount.
Now the gear shifter stays almost completely still and I can't feel the engine running when inside the car

I'm amazed by the torque I have now because I can easily take off in 2 gear without any throttle. I instantly noticed a massive improvement in city driving because now I don't have to down shift nearly as much.

I was just driving home and I didn't even notice my rpms were at 1000 in 4th gear when turning and the car didn't start shaking at all. Before I would have instantly noticed the crazy vibrations when rpms fell below 1500 and be forced to down shift into 3.

The advice definitely helped a good bit in finding the issue. It was definitely delivery valve related but not in the way I was expecting at all haha