Rich cold, warm lean.

[DeLorean03]

So I haven't had enough fun with my car, so I figured I'd start working on this new problem:

FYI: I am running open loop.

This only started happening after replacing my cap and rotor last week - AKA - this is a 1 week old problem I've been diagnosing.

First, my engine is tough to start cold - like it takes almost 5 seconds to start, and even when it does, the engine is rough and you can tell not everything is "firing right" the first 3-5 seconds.

Once the engine is running good, it does the typical idle hunt for a minute or so, then the engine is solid and steady running.

As the engine warms up and I start to drive it, a random miss rears its ugly head - and only when I am idling at a stop light or a stop sign. You'll feel the miss just for a second, and you might feel the miss as you gently push the gas, but it's a single hiccup/miss and then the car is cruising beautifully. If the car is in motion, the engine is strong and everything is firing just as it should.

So the engine is warm, go park the car and get something to eat. Be gone anywhere from 5 minutes or more, the car is just as tough to start warm/hot as it is cold.

Lastly, as the car is good and hot, the transmission shifts up and down as it should with one noticeable exception. First, before I describe the issue, the transmission is shifting FINE - this is NOT a transmission issue. So anyways, when the transmission downshifts, the RPMs go way down - like sometimes below 500 RPMs, the battery light will flicker every now and again, and the engine catches and goes back to 900-1000 RPMs. To me, the transmission is downshifting and pushing the RPMs up as it should as it downshifts, but something is nearly killing the engine (close enough to make the battery light flicker a tiny bit).

It's almost as if the engine is rich when cold or lukewarm, and then the engine is lean when warm or hot.

As I pointed out, this ia a relatively new issue. I did notice my car was getting harder to start when cold or warm as March and April went by (read: car sits for more than 5 minutes, it is going to take 3 seconds to start)

2 weeks ago when I was struggling with the "Uh Oh...." thread, I measured by fuel pressures, and I noted the control pressure was at 58 PSI (max should be 53 psi). I wouldn't think that the CPR could cause this much trouble: cold and warm starting issues, nearly causing the car to die when the auto trans downshifts, AND a very small miss when idling...? That's an AWFUL lot of trouble for just the CPR.

Rest pressure was 43 PSI (still need to test it for 30+ minutes sitting) and main pressure was 78 PSI.

DMCMWDave and I have talked about this a bit, and I wanted some more ideas/input - a bigger discussion so to speak. I am still working on the things he suggested too, which I'll mention later. I don't want to say what he thinks it is and get the "oh yeah...that's definitely it!" mentality going - I want everyone's suggestions to be what they think it is first.

I'll be at work today and tomorrow, so I won't have any new input until then.

Last issue was cap and rotor. Let's see what this issue will be (: !

[DMC5180]

How many items did you disturb while doing the Cap and Rotor change? Wire harness connections? vacuum line connections? did you break any Fuel lines loose moving things out of the way for access?

[Bitsyncmaster]

Since your running open loop, it is hard to say what your problem would be. The K-jet system interacts with all the components. It would be my guess your WUR is causing your problems but that's not to say a new WUR will fix it. Do you know what your AFR is when starting a cold engine and what the AFR is with the warm engine.

Your hot start problem sounds like the rest pressure time is to short.

[DeLorean03]

How many items did you disturb while doing the Cap and Rotor change? Wire harness connections? vacuum line connections? did you break any Fuel lines loose moving things out of the way for access?

To do the cap and rotor change, I moved the mixture unit as one piece out of the engine entirely, meaning i took all the fuel lines off the FD with the exception of the line that goes to the CSV. Any wire harness and vacuum lines that are in the way to get to the cap and rotor, off they went. I will admit, I have been in the VOD area nearly 4 times in 4 months for various reasons, and there were times I went fast. I plan on going all the way back under the intake and going slow (2-3 hours) rebuilding the top of the engine to make 100% sure without a shadow of a doubt that everything is good. I may have boo boo'd something one of the last times I've been in there lately.


Since your running open loop, it is hard to say what your problem would be. The K-jet system interacts with all the components. It would be my guess your WUR is causing your problems but that's not to say a new WUR will fix it. Do you know what your AFR is when starting a cold engine and what the AFR is with the warm engine.

Your hot start problem sounds like the rest pressure time is to short.

I don't understand, the WUR could be the problem but a new WUR may not fix it? Could you clarify please?

AFR = I don't know what that stands for. Once I know, I can better answer your question =/.

[Bitsyncmaster]

Since you are set the mixture (AFR = air-fuel-ratio), how do you set your mixture? The warmup regulator (WUR) is preset to richen your mixture from 14.7 AFR to about 10 to 12 ARF when the engine is cold. So if your mixture is set to rich via your setting then the WUR increased the fuel that much more. So you may need to adjust your WUR to a non-stock setting or get your mixture setting close to 14.7 AFR (which is stock with closed loop).

[DeLorean03]

I don't utilize any tools for setting the AFR with open loop. The only thing I adjust for AFR with open loop is the mixture screw. I do that because once the O2 sensor is unhooked, the car is highly enrichened, and of course vice versa when the O2 sensor is hooked back up. I get the car to where it idles solidly with a hot (cooling fans have cycled once) engine, and if it idles good with no missing in drive = all good.

I have never liked the closed loop system. That constant flucuation of the air and fuel ratio constantly correcting itself drove me bonkers.

[Bitsyncmaster]

I don't utilize any tools for setting the AFR with open loop. The only thing I adjust for AFR with open loop is the mixture screw. I do that because once the O2 sensor is unhooked, the car is highly enrichened, and of course vice versa when the O2 sensor is hooked back up. I get the car to where it idles solidly with a hot (cooling fans have cycled once) engine, and if it idles good with no missing in drive = all good.

I have never liked the closed loop system. That constant flucuation of the air and fuel ratio constantly correcting itself drove me bonkers.

If we ever meet up at a tech session. I can bring my AFR meter that clamps on the tail pipe. If you still have a CAT that affects the accuracy a little but it will give you an idea. If you adjust it for best running engine your probably in the 12 AFR range. So expect about a 15 to 20 % MPG reduction.

[DeLorean03]

If we ever meet up at a tech session. I can bring my AFR meter that clamps on the tail pipe. If you still have a CAT that affects the accuracy a little but it will give you an idea. If you adjust it for best running engine your probably in the 12 AFR range. So expect about a 15 to 20 % MPG reduction.

Sounds good! My exhaust is a one piece tig welded unit that Eddie Ghesquire made, so there is no CAT anymore (I assume CAT = catalytic converter).

I guess the best thing I can do is tear down to the VOD and slowly rebuild everything. I will probably order new gaskets as well as all new copper crush washers. I cannot imagine re-using the same copper crush washers on the fuel lines would cause the problems I am currently having.

Is the WUR being at 58 PSI with a typical max PSI of 53 something to consider replacing? I would like to open it up and clean the mesh screens out first, but I can't help but take note of that reading and wonder ....

[Bitsyncmaster]

Sounds good! My exhaust is a one piece tig welded unit that Eddie Ghesquire made, so there is no CAT anymore (I assume CAT = catalytic converter).

I guess the best thing I can do is tear down to the VOD and slowly rebuild everything. I will probably order new gaskets as well as all new copper crush washers. I cannot imagine re-using the same copper crush washers on the fuel lines would cause the problems I am currently having.

Is the WUR being at 58 PSI with a typical max PSI of 53 something to consider replacing? I would like to open it up and clean the mesh screens out first, but I can't help but take note of that reading and wonder ....

It's not easy to rebuild the WUR, but definitely make sure the screen is clean. When the engine first starts cold the control pressure should be down around 20 to 25 PSI and it quickly rises from there. I think mine stops rising at about 50 PSI.

[DeLorean03]

It's not easy to rebuild the WUR, but definitely make sure the screen is clean. When the engine first starts cold the control pressure should be down around 20 to 25 PSI and it quickly rises from there. I think mine stops rising at about 50 PSI.


Good to know! When I measured last time, the control pressure was at 58PSI. I'll have more time to troubleshoot starting maybe tomorrow. My fiancee' moved in, so we're getting her all situated and good to go. I'll keep in touch with everyone and let everyone know how things go as the week goes on!

[DeLorean03]

All right, so for those of you that are interested, it looks as though I mostly fixed the problem. This post is for posterity's sake - just in case someone else comes along and has the same issues I did.

So I had a nasty situation where the RPMs were falling as the auto transmission downshifted. It was like the engine was getting so lean that the RPMs fell way down (at and sometimes below 500 RPMs), and the engine would just barely hang on. When a transmission downshifts, the RPMs are supposed to go up, so this was opposite the behavior it was supposed to display.

Also, I had a random miss occurring. Basically, if I was at a traffic light or stop sign, the engine would idle fine, and then you would feel a very small miss occur. It would do it idling, or you would feel it a tiny bit as you pulled away from a stop sign or traffic light. It would pretty much only happen once, and then the car would be fine and drive smoothly.

Also, I had really tough warm and cold start issues. The cold starts were so bad, I pretty much to resort to swapping the control pressure regulator's grey plug onto the cold start valve, and even when the car would start, it was darn rough. Warm starts weren't as bad, but still the car idled pretty roughly the first 3 seconds or so before smoothing out.

Up to today, I had the car to where it idled great with no hunting - remember that for later.

So today, Jessica and I went underneath the intake manifold. It was a great learning experience for her, and she did a great job. Part of it was to show her that going underneath the intake is not THAT bad when you have someone there who's done it before. The other things was I suspected the ported vacuum switch could be bad. I will admit it; I shotgunned that one, but I had the part, and I was teaching Jessica how to get to the VOD, so it was one of those "why wouldn't you???" moments.

Also, there's a pretty big vacuum hose that goes from a barb on the back of the intake manifold on the driver's side to a metal line that leads to the vacuum modulator on the automatic transmission (AT). Well, mine has a clamp on it, and it had been clamped on so long that the tip of the barb was starting to cut the rubber hose as well as some hairline cracks (probably about 1/8" long) were present on the edge of the hose where it meets the barb.

Now, just FYI, that rubber hose is not available from DMCH (to the best of my knowledge), so I had a chance to do some garage tinkering. Basically, the tip of the hose has an inner diameter of about 3/8", but then the inner diameter shrinks dramatically to a side I did not take the time to measure, but it is considerable smaller than the tip. So what I did was cut off the tip that had the hairline cracks and where the barb was cutting into the body of the hose, then I took a drill with a 13/64" drill bit (Difference between 3/8" and 13/64" is 11/64"...I wanted the hole to be right below the size of 3/8"), and I hollowed out the vacuum hose so it would be a tight fit on the intake manifold barb. After doing that, I placed a plumbing clamp on the hose where it meets the intake barb, and I snugged it down good and tight.

Lastly, when I installed new fuel injectors a couple weeks ago, I neglected to install new fuel injector boots. So we installed new ones today, and when squeezed, the old ones had some hairline cracks where they met the fuel injectors.

So those were the three things we did, and then we put the engine back together with fresh copper crush washers, with an exception on the 14mm end of the CPR line that goes to the top of the fuel distributor (just forgot).

Now remember when I mentioned that I had the car to where it idled with no hunting? Well, after taking the car for a drive, I noticed when placing it in park, the engine started hunting. That suggested that we had fixed some possible vacuum leaks with the work we did - less air and the same amount of fuel = enriched car. So I leaned it out a bit (I run open loop), and so far the car is running and driving pretty well!

So anyhoo, there you go, nice detailed post in hopes that it will help someone else down the road!

And this is my girl having fun (:

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[Dangermouse]

A Flogging Molly fan, I see :)

[dvonk]

And this is my girl having fun (:

so, if the point of this was to make us single nerds jealous, youve succeeded. :tongue_stick: ;)