'DE bogging has returned, Arghh! / Reasons for running lean?

[slipnfall]

Hi Folks, Please bare with me here, I'm going to spill it... I originally had this problem when I first got the car running: problem is I don't know WTF I did to remedy it.(and obviously the fix didn't hold!) I know I messed around with the EGR system. First here are the symptoms:

On cold starts(after car has cooled completely), the car will buck violently when giving consistent gas[pedal]. This will occur in 1st-3rd, ONLY for about 4-5blocks. After that it's fine. If warm starting, no problems. Occasionally(once or twice), it will buck slightly when cruising in 4th, around 45-50MPH.

Now, I also just baselined, and found out I'm running a bit lean. Could the bucking and lean conditions be side-effects of the EGR/BPT system malfunctioning? I have a feeling these two problems are related. What other factors will induce lean A/F? Just some other guesses: mis-firing would dump unburnt fuel into exhaust, so that couldn't be it. New OEM O2, MAF re-grounded, tested FYI.

I have verified EGR valve is not stuck/sticking, and the BPT valve is not leaking(via hand-pump off the car). Of course no ECCS error codes. The EGR-to-BPT vaccuum hose has been replaced, however it is *ever* so slightly kinked. Apparently the DE's have a restrictor in the BPT-to-EGR hard-line to increase vaccuum pressure? True?

My understanding of the EGR valve is this: under cruise/light loads, EGR solonoid activates via ECCS: this allows manifold vaccuum source to be routed to BPT valve. The BPT bleeds this vaccuum to the EGR proportional to the ammount of backpressure. Would a 13yr old catalytic conv. influince the BPT operation? Overally intention is to reduce combustion temps/lower COx. Is a side-affect of EGR operating leaning the mixture out slightly(to increase efficiency?)?.

Thanks for reading, any insite is appreciated! Baseline dyno is at: zerothread?id=143466

Regards,Jamie

[slipnfall]

I forgot to mention, tomorrow after work I am going to try using a hand-pump on the back-pressure input of the BPT. If idle is influinced, it would seem the entire system(minus exhaust) is OK.

Also I just want to confirm: if the ECCS does not activate the EGR solonoid, this means there is NO vaccuum source to the BPT: as a result, the EGR can NOT open, no matter what backpressure the BPT see's, correct?

I'll get a CONSULT datalog tomorrow morning starting out, to see if any of the sensors are skewed when cold.

'slip

[slipnfall]

Ok, I did some testing after work today:

1-manual operation of EGR causes engine to sputter: good, exhaust gasses are getting to intake.

-raising/blipping throttle does NOT move EGR valve(maybe it shouldn't, no load on engine)

-applying a pressure to the bottom of the BPT does NOTHING to idle. No movement of EGR

-no vacuum source TO BPT valve, at any RPM(ECU may not be activating solonoid)

-manually actuated solonoid control valve(12V) with engine running: it clicks, but no changes to BPT source vacuum. I should mention I did not try to reverse polarity, so this may not mean anything

-vacuum at idle is 17.5-18hg. Blipping causes it to spike to 20, drop to 15, raise back up.

I have a consult log, so I will post that next.

Thanks for reading, any insite is appreciated!Jamie

[s13sr20chris]

bro, you are barking up the wrong tree. lack of egr will never cause a bucking condition. excess egr will though. do you get any backfires when bucking? i would love to watch the maf voltage while its bucking.

[slipnfall]

Heh, it's hard to express a laugh and sigh at the same time.

I'm working on getting some images of the log file graph. Do you have Excel, b/c that would make things way easier.

[slipnfall]

Ok, here goes. FYI if you want to view the entire log file(w/original values), it's at:http://home.pct.edu/~klijam64/stuff/buck_log.zip

Dark purple is EGR signal on/off(on is 30, off is 5)Pink is TimingMaroon is MAF%: (voltage/5.00V)*100Dark Blue is RPM/100LightBlue is Throttle%(same as above, /5.0V*100)Yellow is speed.

[slipnfall]

starting out

[slipnfall]

(snipped some uneventfull data out) Notice timing fluxuating.

In gear, turning around in cul-duh-sak

[slipnfall]

bucking begins in 1st: notice speed toggling between 11.2mph and 12.5. MAF signal seems a little bumpy.

[slipnfall]

lastly, small buck aroud 25mph:

[slipnfall]

I should have gotten a better graph of the timing: durring the start of bucking, the timing is at 51-52* ???? Doesn't fluxuate with the speed, but damn that's a lot of timing. Falls back to 34*, rises to 52* quickly(at about 15MPH), then drops quickly again to 38*. From 7:39:26 to 7:39:40 time frame. WTF.

[NISTECH]

looking at your graphs the tps and maf ar in unison with the exception of that garbage with the maf when first taking off. taking the rest of the graphs into consideration I an disregarding that. How ever your rpm and timing seem to be in unison [for the most part with a couple exceptions 1 is when it advances for no real appearant reason. But at that time you are begining to buck pretty violently as your rpms drop out pretty good and then snap back. Looking at all that extensive data I am still guessing here but take a look at your distributor cap and see if it was made in italy or if it has heavy tracking inside of it. The RPM dump strongly suggests your misfireing to the point of no fire for a substantial period relative to the graph.

[slipnfall]

Thanks for digesting all that. I guess I just wanted to help you guys help me, not just some vague 'it bucks' post.

Anyways, the distributor is the Mitsubishi type IIRC, and the cap/rotor are local-chain auto part brand. I had a really tough time getting the rotor on(actually broke one) to the point I had to lightly tap it on w/a hammer.

I intended to get an OEM cap/rotor, since I need some other oddball parts anyways. I spec'd out the ignition coil, and power transistor, both fine. When you say tracking, I assume you mean marking around the inside of the cap where the rotor contact travels?

So 50-52* of timing is considered normal? Esp on a cold start, low speed like that? I would think that degree would only be reserved for very low load, highway cruising.

Regards,Jamie

[NISTECH]

Timing will very quite substantially typically it is 30 degrees of advance above base timing. You base timing is 20Degrees before TDC IIRC. So in the neighbor hood of 50 degrees is not unexpected. At freeway cruise speeds your should only see around 13 to 15 degrees of advance over base.

When I say tracking I am refferring to carbon tracking [looks like cracks in the plastic] Look over the cap for a "made in italy" stamp. could be on the inside or out. typically inside. could even have a sticker on it.

[slipnfall]

Inspected the cap: there are white 'streaks' after(or before, not sure which direction the rotor rotates) each contact, on the plastic, inside, about 1/4" long. The plastic portion of the rotor is quite white also on the end.

There was a dark gray, ash-like powdery substance that fell out when I removed the cap. Is this from normal contact wear?

No Italy stamp. I do see what look like hairline cracks in the plastic. They at the same place on the outside of the cap. There are two about 1.5" long, extending from the base to near the contacts, another about 0.5" long. Looks like from the plastic mold/casting, but they wouldn't be on both sides.

I can get a pic tonight if you think it will help.-Jamie

[slipnfall]

My friend said that the cracking didn't look like tracking, that it was from the mold. Typically tracking is from wire terminal(on outside) to ground, or between 'points' inside. The white arcing is on the leading edge of the terminals, and starts about 0.3" away.

[s13sr20chris]

do theese graphs show any gearchanges? timing changes can be really drastic during gearchange. i saw a few maf hiccups that make me wonder. by all means, make sure your basic tune-up stuff is good first. im having trouble with converting your numbers. what is maf voltage at idle? will she mess up with maf unplugged? do any of those tps spikes not correspond with what your foot was doing on the pedal?

[slipnfall]

No gear changes, but the drops in TPS are where they are made(with a corresponding rise in MPH). In the first graph, I didn't touch the throttle. MAF voltage looks to be just rising and settling.

The TPS and MAF numbers on the graph are converted to % of full scale(5Vdc), to make scaling the graph easier. To convert the TPS and MAF graph numbers: Vdc = (#/100)*5.0Vdc

Average MAF voltage from after it stabalizes, to before I touch the throttle, is 1.37Vdc.

I never tried driving w/MAF unplugged. I want to see tomorrow morning if disturbing the cap/rotor made a difference(there was a *lot* of dust, which I presume is carbon) inside. I should note also: the center 'button' contact on the rotor: there was a *lot* of white under the spring button, which tells me it was arcing. This should remain in contact 100% and not arc at all, right?

Oh I forgot to answer your last question chris: no backfiring.

Some of the TPS spikes near a shift are simply me babying it while cold(goosing throttle slightly to hit the right RPM). The first spike(graph 2) before I get moving is to get her in 1st gear(can be a pain). The next low dip(axis marker 1161) is me slowing for a speedbump. The third graph illustrates the bucking: it's really hard to maintain a consistent pedal pressure when it's lurching! Last graph I hit 2nd, and slow for a stop sign.

::edit:: FYI, the first graph is me actually starting the car ::edit::

[NISTECH]

THere should be minimal arching in the cap. some whitish around the plug wire electrode is ok as it has to jump the gap, but anywhere else it should not exist. if you have tracks in there as you mentioned I would just replace it. Go factory if you can.

[s13sr20chris]

no backfires? prob not a lean condition then. still, if its slower than a dead miss i tend to look for fuel problems. could be injector circuit. may want to monitor inj circuits(power and ground) while bucking.

[slipnfall]

Yes very well could be, fuel pump and injectors are close to 14yrs old. I'm going to take a look at the alpha and base oxygen readings in the log, but IIRC, they didn't dip or spike at all.

New rotor and cap is on the way, but some other parts are holding the order up. It might be 1-1.5weeks untill I get them(MidWayParts).

Thanks again for the help guys. I'll follow up ASAP.

Jamie

[slipnfall]

A/F looks good, but the AAC was going nuts trying to compensate. A/F base was at 100 throughout. I presure durring cold-start, the ECU is open-loop, because there wasn't much change in either durring the bucking. Once it warmed up, you can see the oxygen signal oscillating.

[slipnfall]

Hey guys, I had a thought, and wanted to run it past you. I'm still waiting on cap/rotor BTW.

What's the chance that this could be purely mechanical? Reason I ask is today when I started out, it was bucking pretty bad, so I popped the clutch in: it immediately stopped. The RPM's were rock solid, though high due to cold-start(arou 1300rpm or so).

I made a bad move with the open differential when I first got the car running. I basically ran the diff low on fluid for about 3-4miles, untill I noticed the gawd awfull noise was from my car! I refilled, and ever since I have a 'whirring' from the rear. I can hear it 'oscillating' in the rear, like the input bearing to the diff has like a warped spot in it.

Your thoughts? Possibly after it's rotated 30-40 times it warmes up, gets lube, and settles down. I think the 'on cold starts' remark in my first may have been misleading: I can remote start the car, have it running for 10mins, and the bucking still occurs(although the temp gauge still reads dead cold untill I get moving some).

[NISTECH]

No the diff wont cause a bucking like that but The worn gears could definitly effect fuel economy.

[slipnfall]

Ok well I thought it was worth bringing up. I get ~28MPG now, so no complaints there.

Anyways, I'm going to disconnect my TPS tomorrow morning, just to completely rule that out: they should show up on the logging, but I want to be sure before I move on to something else.

[slipnfall]

Man this is really getting frustrating. Whatever is causing this, can't be doing the rest of my car very good... plus I look like a 15yr old learning to drive clutch.

The other TPS made no difference. What boggles me is when I pop the clutch in, the RPM's stabilize and the bucking stops. So to me if it was fuel or spark related it would continue to act up... unless it's an issue while under load. And once I drive for 5-10mins it goes away.

...still waiting on cap/rotor...when they get here I might as well do plugs and re-ohm my wires.

Other thoughts are the ign. coil: once warmed up maybe it starts conducting better?

Out of ideas,Jamie

[NISTECH]

coils USUALLY act up when they get hot not cold. Any way you can get a good O2 sweep when this occurs? I dont know how your meter is set up but if you could graph it at .2v per division and 200ms per division you could definitly see if it is fuel/ignition related that way Your o2 fluctuation would have sharp drops in it when the failure is occuring if it is a misfire.

[slipnfall]

The above logging is basically the datastream from the consult port: I *do* have the Oxygen/Base readings from the above session. However, I don't know if it's because the O2 sensor isn't warmed up yet, or if the ECU just doesn't read the signal while in cold enrichment: but, the O2 signal isn't oscillating durring the major bucking. A/F base is fixed at 100 durring this period. See below graph, again this is from the same dataset as the above images. From top-down:Blue=A/FPink=TimingMaroon=Maf %Turqois=AACPurple=EGR(30=ON, 0=OFF)Dk.Blue=RPM/100Lt.Blue=TPS %Yel=MPH

I do have a digital multi-meter with datalogging, but I wouldn't have any other base time references(ie RPM or speed).
Modified by slipnfall at 11:26 PM 11/15/2005

[slipnfall]

Below is after the car has been driven for about 1-2minutes, and is warming up. You can see some oscillation in the MPH, but the RPMs do not reflect any bucking.

::edit:: Very top line in graph below is A/F base(not shown in previous image). AAC valve(in %open IIRC), is steady below, but erratic above. **The entire dataset/logging up to this post was on a cold start(ie hop in the car in the morning and take off)**. Tomorrow morning I will allow it to warm up for a good 10mins, then log. Hopefully by then the O2 readout will be ready to reveal something [crossing fingers].::edit::
Modified by slipnfall at 11:22 PM 11/15/2005

[Magnes]

The apparent oscillation in the MPH is misleading. The precision of the speed value is quite low, showing only differences of 1.25 MPH or more. If you happen to be driving at say, 10.6-10.7 MPH then the graph will appear to jump violently between 10.00 and 11.25, when in fact the computer is just rounding off to the nearest value.

Most bucking will be invisible to a speed or RPM plot, you have to figure out when the symptoms occured and relate them to the graph rather than the other way around.