Intermittant idle and power problem. Lots of code data (long)

[shojuan]

sdpatt:
The EEC does not use the CID signal except to synchronize the firing order during starting. Once set, it can't change. If the car starts okay each time (without bucking or backfiring), the TPS is likely to be okay.

The car starts each time, but when it's hot and really acting bad it will backfire quite a bit. So I guess you're telling me my CID can't be bad?

You should not be surprised to see the 73 code for the knock sensor, but instead the 25 code. You may not be able to produce a knock during the test so as long as your engine is not having knocking problems while driving, the sensor is working.

The car hasn't knocked while driving since the summer of 2001. It definately hasn't done it since I did my 60k and decarbon. I even ran a tank of 87 in there once and no knocking (did feel a teensy bit weaker with that tank though).

The 73 code says that the throttle position sensor is not providing a signal showing the true throttle position if you are in fact opening the throttle more than 25% during the KOER test. You may need to replace the TPS with a Wells TPS215 for $18.99 from AutoZone.

I replaced the TPS with a new motorcraft part when I did my 60K. I swapped my bad one back on last night to see if it made a difference. No difference in the bad behavior.

The code 91 with new O2 sensors says that you still have a vacuum leak. But that shouldn't cause the backfiring. It almost sounds like you ar experiencing cross-firing from leaking spark plug wires when the engine gets hot. How old are the wires?

The wires are brand new motorcraft from FPN, replaced during 60K 4000 miles ago.

Maybe I've got a flakey coil pack that craps out when it gets hot? Could it be a bad ICRM relay module? Bad computer? Or most likely a bad wire somewhere, maybe a common power circuit in the wiring harness that feeds TPS, knock sensor, ingnition?

Rick

<small>[ November 30, 2002, 03:40 PM: Message edited by: shojuan ]</small>

 

[shojuan]

OK, today I bought a cylinder of MAPP gas and some 3/32" brass rod. I've got a some boric acid powder in the medicine cabinet that I can use for flux. I went to walmart to get some cheap welder's goggles but the cheapest they had was a face shield for $17. I didn't buy it. Do any of you have experience with brazing using MAPP gas and air? Any advice? Can I just wear sunglasses? I'll be reading this tomorrow before I attempt, so any advice would be appreciated. I've never brazed or welded anything before, just soldering copper pipe with propane.

I pulled the EGR pipe off tonight and yup, sure enough it has two big holes in it. Maybe I'll snap some pictures later, I'm sure some of you would be curious to see what it looks like. There's a section of thinner flex pipe between the rigid pipe and it's there I have my holes. Actually they are cracks about halfway around. I'll try to braze those closed tomorrow.

The holes in the EGR pipe would explain the rear bank lean because air would get sucked in like a venturi effect. Now it could be responsible for my bad idling problem. The computer doesn't start EGR flow until the car is hot. But once when it was acting badly I disconnected the EVR solenoid harness and it didn't change anything. A few other times I've pulled the EVR vacuum boot off of the EGR valve and that didn't change anything. Maybe the computer was already so confused at that point that it was running with a really bad set of values. Or maybe there's a wiring problem.

If it weren't for my doubts because I've disconnected the EGR electrically and the vacuum control with continued problems, then it would be easy for me to say that when the car gets hot a bunch of unmetered air is getting sucked in the EGR pipe when the valve is opened. Well, one thing's for sure. If I'm sucessful with my brazing repair of the pipe tomorrow then some of these codes should disappear. Wish me luck!

Rick

 

[shojuan]

Here are pictures of the EGR pipe. There are two cracks on the flex portion that go almost all the way around. I opened it up a bit on one of the cracks. The last picture shows the pipe with the flex portion all squashed together. The silver trapezoidal shaped thing is the PFE (pressure feedback exhaust) sensor for an '89. Later SHOs use a DPFE sensor. I made a crude trace of the pipe on a piece of scrap paper in case the pipe breaks in half so I know the shape and general orientation of the thing.

Rick

 

[luigisho]

Bah! Dump that whole system. Fill the holes and get a non CA computer!

<small>[ December 01, 2002, 10:03 AM: Message edited by: luigisho ]</small>

 

[shojuan]

luigisho:
Bah! Dump that whole system. Fill the holes and get a non CA computer!

That wouldn't be a bad idea. In fact I almost bought a B9B computer the other week, but it was a bit more than the wife was comfortable letting me spend.

Well a couple updates, I might be onto something here. Turns out MAPP gas and air (no seperate oxygen tank just my late grampa's old propane torch head and a $10 cylinder of MAPP gas (didn't feel like shopping around for a $5 cylinder)) is plenty hot to melt brass. I used some solvent on the egr pipe, then wire brushed it with a stainless brush on my dremel, then some more solvent. That didn't clean it up as much as I would have liked, but I had to make do and I just used lots of boric acid for flux. My brazing technique leaves a lot to be desired. Eventually I was able to wet the metal pipe enough to get a big ugly bead of brass to fill in all the gaps. Hehe, I almost think that half the gaps are filled in with flux instead of brass which would not be a good thing.

Anyways, the pipe is sealed, I'll probably try to smooth out the bead with a file and the dremel and look for spots that need filling in. I blew through the PFE sample tube, plugging the exhaust and intake manifold sides with my thumbs. It holds pressure that way. If I take my thumb off the intake manifold side some air flows through! I imagine the valve in the closed position should hold pressure and not allow flow into the intake manifold. I'll try cleaning the carbon out of the valve to see if it will seal better. I think this could explain why I still had problems even when I disconnected the EGR system electrically. If that valve was allowing flow when it's supposed to be closed then I would have had an air leak through the cracked pipe at all times! A bigger leak when the computer tries to open the valve, but a small leak when the valve should be shut! Any opinions on this?

Keep your fingers crossed for me.

Rick

 

[luigisho]

Good luck Rick. And I wasn't kidding. Fill the damn holes and get another computer. thumbs_u

I may have an extra B9B1 laying around.

<small>[ December 01, 2002, 05:48 PM: Message edited by: luigisho ]</small>

 

[shojuan]

luigisho:
Good luck Rick. And I wasn't kidding. Fill the damn holes and get another computer. thumbs_u

I may have an extra B9B1 laying around.

That would be great! Let me know if you have it.

Well I filled in the EGR tube cracks with brass. No more code 33! No more code 41 and 91! KOEO gives me an 11! thumbs_u

KOER still gives me a code 25 and SEFI still gives me random bad cylinders (it changes every time)

The idle is much better now! I'm pretty sure fixing the EGR tube solved the bad idle problem for the most part, the car shouldn't be dangerous anymore (I was worried about it stalling in an intersection. In fact it gave me a lot of close calls in traffic running errands).

Now I need to figure out why I'm getting bad cylinders during the SEFI test.

Rick