Engine Surging After Installing Cleaned Injector

[lazabby]

My engine was running well except for a slight rythmic drop in RPMs. I had noticed that there was a strong gas smell when starting and I had a hot start issue. I sent my injectors off to be cleaned and two of them were stuck due to being dirty. I've reinstalled the cleaned injectors and now the engine surges when I start it. I can't find any vacuum leaks. I adjusted the idle screw about 1/8 of a turn either way (replugging the hole after the turns to make sure there are no leaks) and there was no difference in the surging. There is an engine knock too. What should I check? Spark plug wires to make sure something didn't get knocked loose? What else?

[jawn101]

By idle screw do you mean mixture screw? In the fuel distributor? That should always be the very last, last resort of adjustment and only done with a carefully monitored dwell meter. As you already discovered it didn't help the situation... but will probably make more problems down the line.

Is the idle microswitch fully closed? How did you check for vacuum leaks? With a smoke machine?

[lazabby]

By idle screw do you mean mixture screw? In the fuel distributor? That should always be the very last, last resort of adjustment and only done with a carefully monitored dwell meter. As you already discovered it didn't help the situation... but will probably make more problems down the line.

Is the idle microswitch fully closed? How did you check for vacuum leaks? With a smoke machine?

The mixture screw. I visually checked for disconnected vacuum hoses and tries spraying starter fluid to see if there was any sudden surge. I don't have a smoke machine. Don't know about the microswitch yet. Spark plug lines appear to be secure.

Is there a way to upload videos on this forum?

[Rich]

Is there a way to upload videos on this forum?
Yes.
Use the Insert Video button/icon in the second row of the menus you see when you start writing a Reply to a post. Just to the right of Insert Image icon.
You will see a list of the video hosting sites it can pull from so check that first, then upload a video to one of those sites, insert the URL for it into your reply.

[David T]

How are the injector seals? If they are hard and not sealing well they will leak a lot of vacuum.

[lazabby]

How are the injector seals? If they are hard and not sealing well they will leak a lot of vacuum.

Injector seals are brand new.

[lazabby]

Here's a link to the video.
https://youtu.be/pYjmI9viFkU

[Rich]

Thanks for the video. Not the worst I've seen but it does need attention.

Back to one of Jawn's questions: Is the idle microswitch activated at idle? Slowly release the throttle linkage by hand with engine off. Listen for the switch to click just as the throttle closes.

And make sure the throttle linkage does close all the way. The throttle arm (near the microswitch) should bottom out on the bracket. Every time.

Trying to rule out the linkage-related stuff first.

[lazabby]

Thanks for the video. Not the worst I've seen but it does need attention.

Back to one of Jawn's questions: Is the idle microswitch activated at idle? Slowly release the throttle linkage by hand with engine off. Listen for the switch to click just as the throttle closes.

And make sure the throttle linkage does close all the way. The throttle arm (near the microswitch) should bottom out on the bracket. Every time.

Trying to rule out the linkage-related stuff first.

Throttle appears to be working properly. Microswitch appears to be functioning. At idle, the plate on the microswitch is off the white button and it is popped up. After turning the throttle to simulate giving it gas, the plate pushes the white button down. Not far but it does get pushed down.

[Jonathan]

Throttle appears to be working properly. Microswitch appears to be functioning. At idle, the plate on the microswitch is off the white button and it is popped up. After turning the throttle to simulate giving it gas, the plate pushes the white button down. Not far but it does get pushed down.

Hi Shannon, just to clarify, I think Rich was asking you about this microswitch:

http://store.delorean.com/p-6743-microswitch.aspx

And not this one:

http://store.delorean.com/p-6650-microswitch-with-flap.aspx

They're both important, and can both affect the idle, but they do two different things.

The 1st link is the switch connected to the throttle linkage from the throttle spool and when you take your foot off the gas pedal, it is supposed to spring back to rest and that little stub pushes the switch to activate the idle speed motor. The lever arm pivots together with the butterfly valves which are located inside that double barreled looking pipe and this is where the air is metered into the engine.

The 2nd link is the full throttle microswitch (with the flap) and the idea is that if you floor the gas pedal, the throttle spool rotates enough to push the little flap and the backside of that flap pushes into that little plunger. That is meant to send a little more fuel into the engine (while you're passing someone, etc.) and have the gas pedal max'ed out. If you have an automatic trans, you'll have a second microswitch mounted on top of the one with the flap, but the 2nd one comes without the flap. It is also a full throttle switch, but this one plugs into the connector not used on manual trans cars and tells the automatic trans to shift down one gear.

I was also going to originally say I would recommend checking the injector seals as that was what you said got worked on most recently and would explain an air leak.

One thing extra I did notice is that (to me) it looks like your cold start valve assembly is rotated a little farther forward (towards the rear of the engine/car) than it normally should be. It might just be the angle of the video, but if that was loose enough, you could be having an air leak under where that connects. It shouldn't be able to pivot back and forth easily (even though it is easy to make it do this) as there is a bolt and copper washer on that connection trying to keep it tight.

[lazabby]

Jonathan - the first link you listed is the one I checked - part 102778. It seems to be functioning properly. Injectors have new rubber boots/seals. I'll take a look at the cold start valve. My schedule is busy for the next two days so I won't be able to get back on this until Tuesday.

[Bitsyncmaster]

A common problem with any engine work is your vacuum solenoid connector gets disconnected. That will cause idle problem if disconnected.

[David T]

A common problem with any engine work is your vacuum solenoid connector gets disconnected. That will cause idle problem if disconnected.

Vacuum leaks are the #1 cause for hunting (surging) at idle. But ANY imbalance among the cylinders can cause it. That means each injector, intake and exhaust valve, spark plug, etc, MUST be tuned as closely to each other as possible. On one car the reluctor gap inside the distributor was not equal on every point causing an imbalance. Often when you fix one thing it may make the hunting seem worse because now the motor has become more sensitive to other imbalances. The place to start is to check and adjust all of the valves and do a cylinder compression test. If you can't get all of the cylinders within 5% you will never get it to stop hunting.

[lazabby]

Vacuum leaks are the #1 cause for hunting (surging) at idle. But ANY imbalance among the cylinders can cause it. That means each injector, intake and exhaust valve, spark plug, etc, MUST be tuned as closely to each other as possible. On one car the reluctor gap inside the distributor was not equal on every point causing an imbalance. Often when you fix one thing it may make the hunting seem worse because now the motor has become more sensitive to other imbalances. The place to start is to check and adjust all of the valves and do a cylinder compression test. If you can't get all of the cylinders within 5% you will never get it to stop hunting.

One thing to remember, the car was running fairly well before I had the injectors cleaned. I think I must have knocked a vacuum hose loose somewhere.

[David T]

The possibility exists that after cleaning the injectors, some are working much better than before. Before they may all have been working equally badly and now some are better than others. You could remove them and see that they all have good patterns and flow equal amounts of fuel.

[lazabby]

Ok I got the problem solved. Before the injectors were cleaned the engine was tuned to those injectors. St least two of the injectors were stuck open and the others were not spraying well. Now that the injectors are spraying properly the engine was surging. I had to adjust the idle screw counterclockwise until the idle levelled out. Now it's idling well.

[Bitsyncmaster]

Ok I got the problem solved. Before the injectors were cleaned the engine was tuned to those injectors. St least two of the injectors were stuck open and the others were not spraying well. Now that the injectors are spraying properly the engine was surging. I had to adjust the idle screw counterclockwise until the idle levelled out. Now it's idling well.

Adjusting the mixture screw for best idle is not a good idea. You will most likely adjust to a mixture so rich the lambda unit is now beyond its control. Sure your idle will be smooth but your MPG and emissions will be bad.

[PJ Grady Inc.]

Adjusting the mixture screw for best idle is not a good idea. You will most likely adjust to a mixture so rich the lambda unit is now beyond its control. Sure your idle will be smooth but your MPG and emissions will be bad.
He turned the CO adjustment left which is leaner so that is not the case here.

[lazabby]

Anyone have any tips on how to "easily" remove the fuel injector located on the driver's side closest to the front? The one that's blocked by the cost start valve?

The car idles fairly well when warm but hunting when cold. *sigh*