Idle hunting problem maybe the last question?

[delorean928]

I searched a lot about the famous Idle hunt problem and If I make a resume of what I found or did'nt find it's that there is no solution?
I read everything I could know about this problem including very descriptive and precise theories but no solution to fix it.
In all posts I did'nt read that someone found a working solution beside leaning the mixture but playing with mixture screw is a risky solution (that I believe).
I also read that it is not so annoying after all and many keep their D's like that. My car has the same symptom when cold and I hate it.
I already spent many hours and $$ on its restoration and I would like to bring it as close as possible to the mint condition and get rid of that darn problem.
I can't believe that these cars were like that when brand new. Were they?
Do all the DeLoreans left have Idle hunt?

[DeLorean03]

Not to rub it in, but this is one of the many reasons I hired Eddie to change my engine and install EFI on my car. I just got tired of that "idle hunting" crap.

Apparently, if the stars and planets line up perfectly, you can get it to where the idle system idles 100% perfectly, and I have yet to see a DeLorean do it. Even the Stage 2 DeLorean Jay Leno had on his show did that back in 2010-2011, and that's a "big money" fully-refurbished DeLorean if memory serves me correctly.

Not trying to spend your money; I'm just saying if you want to get rid of that behavior, you nearly have to go EFI. At least, that is what I did.

[David T]

Not to rub it in, but this is one of the many reasons I hired Eddie to change my engine and install EFI on my car. I just got tired of that "idle hunting" crap.

Apparently, if the stars and planets line up perfectly, you can get it to where the idle system idles 100% perfectly, and I have yet to see a DeLorean do it. Even the Stage 2 DeLorean Jay Leno had on his show did that back in 2010-2011, and that's a "big money" fully-refurbished DeLorean if memory serves me correctly.

Not trying to spend your money; I'm just saying if you want to get rid of that behavior, you nearly have to go EFI. At least, that is what I did.

Comparing with a Stage II is not valid because the cams make the idle "lopey". It is possible to get the idle smooth once the motor is fully warmed up but it does take everything to be working correctly (and I mean EVERYTHING!).

[krs09]

Things I've played with to figure out my idle hunting issue - Had to jump the idle speed thermister (after installing the new one in the VOD, may have been bad out of the box), replaced the WUR, took out and cleaned the valve in the Idle speed motor (carb cleaner to make the "door" swing open and closed cleanly (helped alot!), mix the air/fuel (as close as I can get it without a dwell meter), Checked and replace all injectors, and now my D runs better than it has this whole time ive had it (yr 1/2) after some big time rebuilding. Dont think all of this was needed but the cleaning of the Idle speed motor was the quickest and cheapest fix

[DMCMW Dave]

Most likely the pin backed out of the connector shell on the thermistor. You can live without it.


Sent from phone

[krs09]

Most likely the pin backed out of the connector shell on the thermistor. You can live without it.


Sent from phone

Yeah, I just jumped it behind the driver seat and so far so good. I was wondering if it was ok to just leave it like that, I guess so. Thanks Dave, you are the man! Don't forget that. :wink:

[Bitsyncmaster]

Yeah, I just jumped it behind the driver seat and so far so good. I was wondering if it was ok to just leave it like that, I guess so. Thanks Dave, you are the man! Don't forget that. :wink:

It may affect your cold starting since it will close the ISM quite a bit thinking it's very hot with a jumper to replace it. Would probably affect my ECU more than the stock ECU.

[opethmike]

Comparing with a Stage II is not valid because the cams make the idle "lopey". It is possible to get the idle smooth once the motor is fully warmed up but it does take everything to be working correctly (and I mean EVERYTHING!).

Did you even watch that video? There was nothing lopey going on; that car had a BRUTAL hunt with huge revs going on.

[DMCMW Dave]

It may affect your cold starting since it will close the ISM quite a bit thinking it's very hot with a jumper to replace it. Would probably affect my ECU more than the stock ECU.

There are two cold sensors (one is actually a switch) so we need to be sure we are talking about the same one.

The thermistor raises the idle speed slightly when very cold. I'm not aware of it's direct impact on the where the idle motor is set during cranking, but you are probably right since you've reverse-engineered that system!

IMO few owners are running the cars much below 50 degrees (i.e. in winter) so it may never be noticed, but if it's an issue the car will seem to idle slow when cold and could take an extra crank or two to start.
---
The Thermal Enrichment switch only closes at about 50F or below. It does exactly the same thing as the full throttle microswitch, in fact they are in parallel. It can't impact the idle ECU at all. I don't believe this is the one he's talking about but it bears mentioning.

[DeLorean03]

Did you even watch that video? There was nothing lopey going on; that car had a BRUTAL hunt with huge revs going on.

Right ? It was BAD......

[Rich_NYS]

I bought my car last month and have no other experience w/this system, just sharing my cold-weather observations (living in upstate NY.)

When I first got the car, it didn't hunt at all....temperature was ~ 45F.

I've since changed the fuel pump hoses & fuel filter, and developed a slight fuel hose leak at the accumulator.

The last few times I started the car it was 20F to 30F and it hunted during cold-idle for 2-3 minutes (I think.)

[Bitsyncmaster]

There are two cold sensors (one is actually a switch) so we need to be sure we are talking about the same one.

The thermistor raises the idle speed slightly when very cold. I'm not aware of it's direct impact on the where the idle motor is set during cranking, but you are probably right since you've reverse-engineered that system!

IMO few owners are running the cars much below 50 degrees (i.e. in winter) so it may never be noticed, but if it's an issue the car will seem to idle slow when cold and could take an extra crank or two to start.
---
The Thermal Enrichment switch only closes at about 50F or below. It does exactly the same thing as the full throttle microswitch, in fact they are in parallel. It can't impact the idle ECU at all. I don't believe this is the one he's talking about but it bears mentioning.

The thermistor is what I am talking about (it's about 400 Kohms very cold and 1 Kohm hot). Both my ECU and the stock ECU set the opening of the ISM using that thermistor when starting. I also use the thermistor for deceleration idle speed to quickly set the ISM.

[Elvis]

There are simple ways to improve idle hunting by installing 1-2 potentiometers in the idle ECU.

But after I was told around 10 years ago - people want it that way, it makes them feel like
the car lives - I said - OK, I'll keep that info on my computer.

And since my 33 year old car is idling pretty good with the original system,
I'm not even using it myself.

The magic word - well known for people who know something about control loops - is :
dead time !

[delorean928]

Next things i'll do will be cleaning the idle speed motor and checking vacuum leaks with a smoke machine. I saw the problem starting at a temperature around 60 f.

[Rich_NYS]

I bought my car last month and have no other experience w/this system, just sharing my cold-weather observations (living in upstate NY.)

When I first got the car, it didn't hunt at all....temperature was ~ 45F.

I've since changed the fuel pump hoses & fuel filter, and developed a slight fuel hose leak at the accumulator.

The last few times I started the car it was 20F to 30F and it hunted during cold-idle for 2-3 minutes (I think.)

I started it tonite at 42F. After about a minute it seemed like it was starting to hunt, but seemed more like a rough idle than a hunt. It rough-bounced between 9K-10K then leveled off within 1-2 minutes.

[D Knight]

Mine idles perfectly. No issues anymore. When I first brought it back, it did hunt. A small vacuum leak will cause it. Have it tested with an evap smoke machine.


-D Knight-

[delorean928]

Mine idles perfectly. No issues anymore. When I first brought it back, it did hunt. A small vacuum leak will cause it. Have it tested with an evap smoke machine.


-D Knight-

Wow I think you're the first one I read who has no problem with the idle!!! It means it's possible :aniclap:

[opethmike]

Wow I think you're the first one I read who has no problem with the idle!!! It means it's possible :aniclap:

Mine was stock K-Jet for the first four years I owned it, and I had zero hunting problems the entire time. Completely possible. :)

[delorean928]

Not to rub it in, but this is one of the many reasons I hired Eddie to change my engine and install EFI on my car. I just got tired of that "idle hunting" crap.

Apparently, if the stars and planets line up perfectly, you can get it to where the idle system idles 100% perfectly, and I have yet to see a DeLorean do it. Even the Stage 2 DeLorean Jay Leno had on his show did that back in 2010-2011, and that's a "big money" fully-refurbished DeLorean if memory serves me correctly.

Not trying to spend your money; I'm just saying if you want to get rid of that behavior, you nearly have to go EFI. At least, that is what I did.


What approximately could be the cost for an EFI conversion? :umm:

[opethmike]

Mine cost me $1,200 in parts and I did the work myself. I imagine a professional install would be twice that.

[delorean928]

Mine cost me $1,200 in parts and I did the work myself. I imagine a professional install would be twice that.

Not too bad!! :)
Do you like it or regret it? How does it behave compare to the CSI?

[opethmike]

Not too bad!! :)
Do you like it or regret it? How does it behave compare to the CSI?

Absolutely love it. Really let me dial in a solid tune with my big cams and exhaust headers. Honestly, I never had any issues with my K-Jet, so I can't really say better in that sense. But it IS less issue prone (far less moving parts and vacuum nonsense, etc), and I think if something goes wrong, easier to diagnose.

I mostly just did it as a "science project", in that I wanted to learn EFI, and I wanted to tinker.

[jamesvnz]

my D hunts from 500 to 1000 I turned the idle/throttle adjustment screw a few mm to the right and she perked up a few rpm

it may idle at 1000 rpm now but it dosent idle hunt who knows being a delorean it may start hunting again in the future

james

[delorean928]

my D hunts from 500 to 1000 I turned the idle/throttle adjustment screw a few mm to the right and she perked up a few rpm

it may idle at 1000 rpm now but it dosent idle hunt who knows being a delorean it may start hunting again in the future

james
You did'nt touch the mixture adjustment just the Idle speed screw?