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

[shojuan]

This problem started up a few weeks ago when I drove my wife up to San Francisco on a hot day 11/14/02. Had a lot of 90-105 mph driving. The symptoms are car stumbles during idle, doesn't want to hold an idle and sometimes backfires when trying to rev off idle, sometimes holes in the power curve, sometimes it just feels like the whole fuel curve is ******** to a limp home mode. Often the car is fine when cold until it gets heat soaked but lately, sometimes it has idle problems when cold. I've been collecting codes every of couple of days. Here's what I've got:

Original (152,000 mile O2 sensors) and y-pipe installed:

11/14/02:
KOEO 33, 41, 91
KOER 91, 25

11/18/02:
KOEO 84, 33 (I had disconnected the EVR solenoid connector to see if my EGR system was affecting the idle. It wasn't)

11/19/02:
KOEO 33, 41, 91
KOER 26, 41, 91, 25

ran a 2nd time
KOER 26, 41, 91, 25

11/20/02:
KOEO 33
KOER 11
SEFI 1, 3, 4, 5

ran a 2nd time
KOER 35, 25, 91

Replaced O2 sensors with new Bosch 13942 and new catless y-pipe:

11/21/02:
KOEO 33
KOER 91

ran a 2nd time
KOER 25, 26, 91
SEFI 1, 2, 5, 6

ran a 3rd time
KOER 12, 26, 91, 25

11/22/02:
Car was cold. Drove 6 minutes.
KOER 11
SEFI 1, 2, 3

drove car an additional 6 minutes, mostly WOT
ran a 2nd time
KOEO 11
KOER 11
SEFI 9

drove car an additional 15 minutes
ran a 3rd time
KOEO 33
KOER 11
SEFI 1, 2, 4

11/23/02
Took car to run errands 20 miles away. After the sitting in parking lot at first stop for 1/2 hour car had crap idle, had a hard time revving up off idle, and backfired a bit. Ditto for all remaining stops. Put in a full bottle of redline SI-1 cleaner into almost full tank. Droving home did an Italian tuneup up the big hill (3rd gear, foot to the floor until almost to redline, then kept throttle at about 6000-6500 rpms). Ran codes upon arrival at home, about 2 hours after we left home to run errands.

KOEO 33
KOER 12, 26, 91, 25
SEFI 1, 2, 3, 5, 6

11/25/02
1:30 AM, weather was cool and foggy.
Drove 30 minutes, a lot of WOT, italian tuneup up big hill mentioned above but fourth gear this time, about 100mph, wasn't at WOT up the hill so the HEGOs were being used. Car was strong.

KOEO 33
KOER 25
SEFI 3

drove car another 10 minutes, up same hill and back
ran a 2nd time
KOEO 33
KOER 11
SEFI 2, 3, 4, 5

edit: ran some more codes at 4PM today:
11/25/02 4PM cleaned IAB (it was clean, ports were clean (4000 miles since 60K intake cleaning)), cleaned throttle body (it was pretty clean), checked MAF connection, reset idle: it idled like a champ. Went for 15 minute drive, it drove great, came back still idling well. Put car on ramps, tightened y-pipe exhaust clamps, then ran codes.

KOEO 33
KOER 91, 25
SEFI 1, 2, 5, 6

ran a 2nd time
KOER 91, 25
SEFI 5, 6

car idling like crap now after shutting down pulling jumper and restarting, backfires when revving off idle.

Please help me decode the mystery of what's going on! I know what the code descriptions are but the cause and intermittant nature is what I need help with because the car will run great when cold and for a while when warm.

Rick

<small>[ November 25, 2002, 07:17 PM: Message edited by: shojuan ]</small>

 

[luigisho]

Weird stuff. I'm not sure about the sefi codes. The 33 is EGR not opening
The 25 is Knock sensor not sensed during dynamic response test
The 26 is MAF
The 12 Is unable to control rpm
The 91 is No HEGO (left) detected

How do all these connect? Not sure. It looks like there is trouble processing the sensor data. Whether that's a loose ground, faulty wire, relay or pcm problem????

 

[SLOSHO89]

Did all this start to happen all of a sudden? It seams weird that you have so many different codes flying around. They don't really seam to be related either.

Efren

 

[sdpatt]

Sorry for the code overflow. It looks like you have a bad MAF or intermittant connection to it that could be causing the lean condition. There were codes for lean on both front and rear banks. Unlikely due to O2 sensors. There is also a non-funcitonal EGR valve or blocked EGR passage. Check the nostils first. California car?

 

[shojuan]

SLOSHO89:
Did all this start to happen all of a sudden? It seams weird that you have so many different codes flying around. They don't really seam to be related either.

Efren

The EGR problem has been there since early July. The code 25 has been popping up now and then since July. I doubt those are related to the problem I have. Disconnecting the EGR has no effect on the problems. I suspect I get the code 25 because the computer goes to a wimpy "limp home" mode and refuses to advance the ignition to the point of knocking during the KOER test. I have no proof that this is the computer's strategy, it just seems to make sense. The nostrils are squeaky clean (18 cans on B12 to clean the intake including the nostrils). Before and after I did my 60K I always got 9's on the SEFI test.

The codes 12 and 26 are completely new to me. My car never gave those codes before 11/14/02. However I didn't start reading codes on my car until early July 02, so who knows if they've popped up in years past when I've had similar problems.

Scott,

The code 41 never came back after I replaced the O2 sensors. Re: The EGR, I either need a new PFE sensor and/or need to get my EGR pipe brazed. My EGR valve is fine, nostrils clean, and I'm pretty sure my EVR solenoid valve and plastic plumbing are OK. Yes, it's a California car.

Would a fuel pump be able to cause these problems? Nick Chrimes told me fuel pressure problems are rare on SHOs, either the pumps work or they don't usually. If my MAF's bad then Proflow for me. My wife will **** me, but if I let her drive the car the way it is, if she stops to do errands after work it might **** her in an intersection. I know I had problems with near stall in the intersections on a trip to walmart and costco tonight. She has use of one of my Dad's new toyota work trucks for a week then she'll need the SHO back. Probably would get the 75mm bullit Proflow. My wife would strangle me bad enough for that one. Besides maybe the Pro-M 80mm is only good for an extra horse or two?

Sorry for giving you guys so much to read. I really appreciate any help I can get to get us out of this mess.

Rick

 

[93MTXSHO]

Rick,

That sounds like my wierd problem this summer. The car had been acting kind of retarted for about 4 days, after a bit of good spirited driving, winding it out in 3rd and about 85MPH, etc. All of the sudden the CE light came on. I was so happy because I finally figured that I could pull some codes, but no dice. The stupid computer wouldn't even run the self test. The car would idle from anywhere in the 800-2700RPM range. Had good power, although would not turn on cooling fan, backfired at idle and during acceleration. Not to mention that just driving down the road was a chore. If I tried to give it too much gas it would choke out and come back, and it would never allow WOT. After I took it to the shop because I was completely dumbfounded. They got different codes every time the checked for everything from the CPS to CID to ECT to O2s to MAF. It even stumped them as to what was wrong. Turns out all it was was the PCM. I thought it was the fuel pump, so I replaced it, but that didn't help anything. That's just my experience.

 

[sdpatt]

The nostrils may be clear, but did you check the system for actual flow? You can remove the 8mm Allen plug from the backside of the intake's driver side to get a clean shot at the long horizontal tunnel from the EGR ****** to the vertical riser below the nostrils. If you havven't already done so, place a hose in this post and blow to confirm that you are getting flow through the EGR plumbing.

Have you tried driving without the MAF connected? Did it make any difference? That would point to the MAF. Since it is so easy to exchange, you could borrow the MAF electronics package (two screws, one connector) from another SHO to test the results.

 

[DougLee25]

You could also try another computer to see if that helps. Sometimes when they go, wacky codes seem to appear from nowhere.

Doug

 

[SLOSHO89]

Hey Rick,

I'll be up this weekend for thanksgiving. If you have any extra time I could stop by for a few minutes. I'm thinking that you have a hole in the EGR tube. I was getting 41, 91, and 33 when mine was messed up. We could also switch MAF's to see if that is causing it. Did you clean the EGR passage all the way through untill you could blow air through it?
Ohh, and what is the PFE sensor? Is that the little black box that is stuck to the back of the rear head?

Efren

 

[shojuan]

SLOSHO89:
Hey Rick,

I'll be up this weekend for thanksgiving. If you have any extra time I could stop by for a few minutes. I'm thinking that you have a hole in the EGR tube. I was getting 41, 91, and 33 when mine was messed up. We could also switch MAF's to see if that is causing it. Did you clean the EGR passage all the way through untill you could blow air through it?
Ohh, and what is the PFE sensor? Is that the little black box that is stuck to the back of the rear head?

Efren

Yes!!! I'll have free time, any time this weekend or the days before. Yeah, I cleaned the nostrils until they could flow really nice. I ruled out the possibility of them being plugged because when I apply a vacuum with my handheld vacuum pump/gauge to the EGR valve the exhaust flow will take the idle down to near stall (this assuming I do the test when the idle is behaving otherwise).
A hole in the EGR tube wouldn't surprise me. I had a bit of an exhaust leak into the engine compartment before I switched my y-pipe. I was hoping it was just the y-pipe leaking at the donut and wafting back to the bay but I think the leak is still there. It's hard to tell now without cats because the exhaust migrates forward from the muffler tips and stinks everything up.

The PFE sensor is the pressure feedback exhaust sensor. It's the silver colored box that the EGR sample tube goes into. Later SHOs have a DPFE (differential pressure feedback exhaust) sensor. I think theirs is located up near the top on the rear of the exhaust manifold.

Switching out MAFs would be great.

Rick

 

[shojuan]

DougLee25:
You could also try another computer to see if that helps. Sometimes when they go, wacky codes seem to appear from nowhere.

Doug

I almost bought a B9B from Tim Dahm off of ebay last week, but when it went past $40 I backed off. ****, I really only wanted to spend $22 for it. Damn cheapskate mentality! Where are all my credit cards? Where is all the money I used to make?

Rick

 

[shojuan]

sdpatt:
The nostrils may be clear, but did you check the system for actual flow? You can remove the 8mm Allen plug from the backside of the intake's driver side to get a clean shot at the long horizontal tunnel from the EGR ****** to the vertical riser below the nostrils. If you havven't already done so, place a hose in this post and blow to confirm that you are getting flow through the EGR plumbing.

Yup, I put vacuum on the EGR valve a while back when Steve suggested it. The nostrils breathe as well as I do after a couple of Sudafed.

Have you tried driving without the MAF connected? Did it make any difference? That would point to the MAF. Since it is so easy to exchange, you could borrow the MAF electronics package (two screws, one connector) from another SHO to test the results.

No, I haven't tried driving it like this. I did once pull the MAF connector in between code reading tests when the engine was acting up and the rough idle would correct itself when I did this. Weak power when I revved the engine, but it was smooth.

Rick

<small>[ November 26, 2002, 04:58 PM: Message edited by: shojuan ]</small>

 

[shojuan]

OK, the car had been sitting all night. So at 4:30pm 11/26/02 I took it out for 10 minutes then took tests.

KOEO 33
KOER 11
SEFI 5

ran codes a 2nd time

KOEO 33
KOER 73, 25 (surprised at 73, I gave it plenty of throttle)
SEFI 2, 3, 6

ran codes a third time

KOER 91, 73, 25 (again surprised at 73. I took the thing to about 6700 rpm during dynamic response test!)

By now the car was warm and heat soaked enough to cause the rough idle. So I disconnected the MAF and the idle went instantly smooth. Of course CE light popped on. I took the car for a brief drive. It was a bit down on power. Really not more so than when it has been running like crap before. It drove smooth and idled smooth. Came back and tried to see if it would run the KOER test with MAF disabled. It wouldn't, just ran long enough to spit out a code 98 and 66 then stalled.

Can I be fairly sure that the bulk of my problem (apart from needing to get my EGR system functioning again) is either a bad MAF or a bad MAF circuit in the wiring? Could it be a bad PCM or a faulty ground somewhere?

Efren, I look forward to seeing you in a couple days. Let me know as soon as you're ready to get together so we can see if a MAF swap fixes the problem. If it does then I guess I'll be in the market for a new (higher performance ) MAF! Oh, BTW I'm pretty sure I must have a leak in my EGR tube because when I started the car up, I immediately gave the EGR a sniff test (nose 1" above the EGR valve) before the tailpipe fumes had a chance to waft forward. Yup, I smelled exhaust. Also, when I did the decarbon a couple months back I got white smoke in the engine bay when sucking in the cleaner and then later the water.

Rick

<small>[ November 26, 2002, 08:28 PM: Message edited by: shojuan ]</small>

 

[SLOSHO89]

Rick, having a hole in the EGR tube will not emit exhaust gasses, it sucks air into the exhaust syyem and will throw a lean code, which you had.

 

[shojuan]

The EGR valve isn't open all the time, it follows a certain strategy based on temperature and rpms IIRC. So I think a leak in the egr pipe would put out some exhaust gas under certain circumstances? Wouldn't it? shrug

Rick

 

[sdpatt]

You may want to verify that the bottom end of the EGR tube is correctly bolted to the cast iron exhaust manifold. That would be a source of exhaust leak to the engine compartment. I have seen a broken weld that holds the tube to the ******. Had to remove it and have it re-welded.

 

[shojuan]

Well Efren came over yesterday and we swapped MAFs. Didn't fix it. There was even more backfiring than usual during idle and while trying to build revs off idle.

Could the problem be a bad CID sensor? I've never gotten a CID code. I know if there was no signal there would likely be a code and the car would just take several tries to start but would then run fine. How about if a CID sensor starts putting out whacked output while the car is running? Does the computer monitor its signal after initial startup and could a flakey CID on its way out be causing my problems?

I'll check to see if autozone has the wells F134 in stock when I return a dvd within the hour. I would really hate to shell out $30 and find out it's not the problem though.

If it's not the CID, then I guess I'll have to start tracing the wiring.

Also, we both figure that I have a small leak in my EGR pipe, not nearly as big a leak as Efren had when he got his car. Maybe I'll just buy a cylinder of mapp gas for my propane torch and have at it myself. Guess it's as good a time as any to learn some brazing technique (maybe I'll have to tell the wife, "but we really need an oxy-acetylene torch so I can fix the exhaust!"

The last paragraph aside, I'd appreciate any comments about the possibility of the CID being the problem. Thanks.

Rick

 

[luigisho]

It sure possible. Too bad you didn't yank Efrens CID from his car and swap that too.

 

[shojuan]

luigisho:
It sure possible. Too bad you didn't yank Efrens CID from his car and swap that too.

It was dark by that time. He says he has two in his garage/trunk. One is definately bad, the other one he's not sure about.

Rick

 

[sdpatt]

The EEC monitors the signal from the CID sensor while the engine is starting and while running. That is how it can set a CID code even if the engine started okay. 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.

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 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.

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?