High idle and sluggish acceleration

[eldusto84]

My Delorean is having a two-fold issue right now: when I start the car up, it idles in the 2000RPM range. If I tap the gas pedal slightly, the engine revs and then dips back down to the normal 800-900RPM range. However, if I push the pedal again, the RPMs jump back up to around 2000RPM or even a bit more. The same happens if I'm on the road and shift into neutral while coming to a stop- RPMs jump.

At the same time, I'm also noticing that the car is extremely sluggish with acceleration. From a dead stop in 1st gear, the car chugs like it's not getting enough fuel, then all of the sudden lurches forward and accelerates normally. Shifting into 2nd and 3rd initially has the same issue- the car struggles and then surges forward after a few seconds.

Any ideas here? These issues continue even after the car has been running for several minutes. I took the WUR apart just to see if it was faulty but it honestly looks fairly clean (although I didn't take the filter screen out). I've recently replaced the two fuel lines coming out of the fuel pump, along with installing a new pump wire harness. I also put in a new relay kit (including RPM relay).

[Jonathan]

Sounds to me like the throttle spool and cable and butterfly valves are not moving freely. Could be one or more of those that aren't springing back to their default position as they should. Could be the spring in the throttle spool, could be the spring on the idle switch lever arm. When you have to "snap the gas" to get it to settle back down to a proper idle, it can often mean things aren't going back to their proper rest position on their own. Lube things, clean things, take apart if necessary to do this. Your lever arm linkage may need an adjustment if there is too much slack in it.

The sluggish part upon acceleration may be a different issue. I would suggest focusing on what I mentioned above, get those parts moving freely and seeing your idle go back to where it should be, and then tackle this other issue. Do one first, not both together.

[David T]

I agree you probably have 2 separate problems. The throttle linkage, throttle spool, micro switches all need to be checked, adjusted, lubricated. As for the acceleration problem, make sure the frequency valve is buzzing. Also make sure you have no vacuum leaks.
David Teitelbaum

[eldusto84]

I checked the frequency valve and it is indeed buzzing. I unplugged the electrical connection, cleaned it out and plugged it back in. Doesn't seem like that did anything. So onto the vacuum lines I guess. What is the best way to check for a vacuum leak?

As for the high idle/throttle issue, I had this problem several months ago and I thought I had fixed it by adjusting the throttle cable on the spool. So either the cable has loosened up again or I need to look at something else...

[DeLorean03]

Ok, reference this (thank you SpecialTAuto):

18028

Go to the back of your car and rev the throttle slowly, or do it by use of your accel pedal with the car in neutral and parking brake on until it idles high. Once it does this, go to the area of the car pictured. Take a small screwdriver (microdriver, like the screwdriver jewelers/watch repairmen use) and trip the microswitch (black rectangular switch in photo) with the microdriver. If that makes the idle come back down, the microswitch screw is not tripping the microswitch.

If you engage the microswitch with the microdriver and the idle stays high, it could be that the idle speed screw is too far in, not allowing the throttle butterfly plates to close entirely, and when you rev the accel pedal, you're giving it enough "oomf" to just barely shut the plates. So if the idle remains high with the idle microswitch tripped by a screw driver, loosen the idle speed screw with the idle microswitch tripped the whole time. You should hear the idle come down after a few turns on the idle speed screw.

If both those screws are set right and the linkage that connects the throttle spool assembly to the idle microswitch has not been adjusted at all, I'd be willing to bet it's a sticking throttle cable. Casey and I replaced mine with a new one from SpecialTAuto back in 2009. I used to have to ALWAYS "rev my throttle" one time to bring it back down - drove me nuts.

[Timebender]

Interesting. I was going to say it sounds like the choke is stuck. My older VW bus' electric choke would not unwind, thus opening the valves, and I'd be stuck at a high idle. I'd tap the throttle, and it would close, then as I'd give it gas it would get stuck again basically flooding the engine.

[eldusto84]

Ok, so I'm pretty sure I've narrowed the high idle issue down to the little throttle assembly rod. The joint that connects to the microswitch lever has a bit of play in it, and I can wiggle it slightly without it moving the lever at all. I'm assuming I will have to tighten the rod so there's more tension when the throttle spool pulls it. Now my question is- how the hell do you even remove this part? The nut that connects the lever to the butterfly assembly is right up against the intake manifold.

[elfking]

Don't forget to check the little springs in the throttle body ( deacceleration springs ) I just replaced mine ( whole butterfly assembly) and it fixed my high idle issue... You can pull off the W pipe and open the throttle and look... These are bad.18199

This is what they should look like:
18200

Just a thought of something to check !

[David T]

I think you are referring to the Quadrant Link. It is threaded right hand on one end and left hand on the other like a turnbuckle. Undo the end nearest the throttle spool by removing the spring clip and popping the joint apart (like the ends on the door struts). Unlock the nut and screw it so it is just a little bit longer. Lubricate both ends.
David Teitelbaum

[DeLorean03]

Ok, so I'm pretty sure I've narrowed the high idle issue down to the little throttle assembly rod. The joint that connects to the microswitch lever has a bit of play in it, and I can wiggle it slightly without it moving the lever at all. I'm assuming I will have to tighten the rod so there's more tension when the throttle spool pulls it. Now my question is- how the hell do you even remove this part? The nut that connects the lever to the butterfly assembly is right up against the intake manifold.

Just disconnect the side the attaches to the throttle spool and adjust that side. Don't bother getting to the other side - a one-sided adjustment is capable of fixing this problem. Yes, shorten it - I shortened mine jjjjuuuuuuuuuuuuuusttttt to where the end of the throttle rod connected to the ball of the throttle spool assembly.

[eldusto84]

If I pop the rod out of its little balljoint, will it be a problem popping it back in? I'm just paranoid and don't want to pay $50 for a tiny piece of metal if it breaks :)

[David T]

It pops in and out, just REMOVE THE SPRING CLIP FIRST!
David Teitelbaum

[DeLoreanDMC81]

So I had a similar problem years ago myself. I remember it took like 4-5 tries to get the car actually started, once I did it would idle high for a while then finally come down to where it was suppose to. Also whenever I would drive the car it was extremely sluggish. I took it to my good buddy Cliff's shop down in Lebanon, Ohio, he knows everything about these cars. So we took off the mixture control unit and swapped it with another one. Nothing happened. So we put my original one back on, then took off the catalyst and knocked out all of the honey comb on the inside because it was extremely plugged up. So now that there was nothing in the catalyst anymore we thought that would help it. Still didn't do anything, the car still had no power and was absolutely horrible to drive.

So I finally took the car to Dave Bauerle's shop and within an hour he found out what the problem was and had the car running like a champ. Turns out it was Warm Up Regulator that had gone bad and was causing problems the whole time.

So maybe that might be your problem as well? Sadly after 30 years these things do wear out and you have to be replaced.

Good luck to you!

James
6408

[Jonathan]

If I remember correctly, if you only pop off one end of the rod, you will have to make your length adjustments by one complete revolution at a time. Meaning, if you turn it in or out less than 360 degrees, the socket to go on the ball won't line up. Much like the door struts. I am guessing if you have both ends off, you could make smaller adjustments and still have the opportunity to line up the faces of the two ends, but I'm not sure about that as I've never had more than just one end off.

[DeLorean03]

If I pop the rod out of its little balljoint, will it be a problem popping it back in? I'm just paranoid and don't want to pay $50 for a tiny piece of metal if it breaks :)

No, as long as you are gentle. Remember when working on any car, gentleness will speed up the process a lot faster than brute force and breaking something else.

As David said, take the lil safety clip out (similar to the door struts), and then just gently wiggle it back and forth, and it should pop out. Adjust, pop back in, put safety clip back in, and see if car idles better!

If I recall correctly, you said you rev the accelerator pedal to make it comes down. If that's true, test your idle by very slowly and gently raising your idle by the accelerator pedal - NOT by the throttle spool assembly. If you can make the idle behave by use of the accel pedal = so far so good.

If it is good in your garage, take the car out for a light spin/drive around the neighborhood - see if the idle behaves. If it does, hit the interstate a good 10 minutes. If it is good after the interstate, you are golden!

[David T]

If you take one end off you do have to make your adjustments in 1 turn increments. As I said earlier, there is a left hand thread on one end and a right hand thread on the other end (like a turnbuckle). If you loosen both locknuts and turn the rod, you can make a much finer adjustment without removing the ends.
David Teitelbaum

[eldusto84]

Alright, so I tightened up the rod and everything is running much better now. Idle drops down to normal! The only thing is that I noticed the balljoint that connects to the microswitch lever was missing its saftey clip. Is this a dire replacement? I wouldn't want the joint to pop out unexpectedly.

NOW...onto Part Deux of this thread- the sluggish acceleration! From reading previous threads on here, it sounds like the most common culprits are bad WURs, vacuum leaks, and fuel pump-related issues. What would be the first logical step here? I've already taken the WUR apart and examined it, although I didn't clean out the screen because it looked fairly clean. My fuel pump looks newer although I suppose that doesn't mean it's working like it should be. Not sure how to go about dealing with vacuum leaks other than the smoke trick others have mentioned here.

Any other tips or hints on where I can continue looking?

[DeLorean03]

Ok, you need this:

http://www.thetoolwarehouse.net/p-6972-tool-aid-33865.aspx

That is the BEST way to know if your CPR/WUR is working correctly.

I have one - haven't had to use it yet - but if and when I do, I'll KNOW my WUR is good or not right out of the gate. Not trying to be a jerk - just suggesting it as it is an INVALUABLE tool for our cars.

[Ron]

Ok, you need this:

http://www.thetoolwarehouse.net/p-6972-tool-aid-33865.aspx

That is the BEST way to know if your CPR/WUR is working correctly.

I have one - haven't had to use it yet - but if and when I do, I'll KNOW my WUR is good or not right out of the gate. Not trying to be a jerk - just suggesting it as it is an INVALUABLE tool for our cars.+1!

[David T]

Sluggish acceleration can be caused by many reasons. I would start by doing a compression test and then maybe a tune-up. Once the motor warms up the CPR doesn't do much unless it is not hooked up correctly. The vacuum hoses tell it when the motor is under a large load and causes the CPR to richen the mixture like an acceleration pump. Check the vacuum hoses to the CPR and make sure the check valve is correctly installed. The clip is not essential but you should have one.
David Teitelbaum

[eldusto84]

I will check the WUR/CPR again. Could a bad fuel filter be the culprit here?

[Bitsyncmaster]

I will check the WUR/CPR again. Could a bad fuel filter be the culprit here?

Fuel filter is rarely the cause but we did find one that was completely plugged. That's why a fuel pressure gauge is such a valuable tool.