Ok, I need some brainstorming on engine issue...

So, I am starting to get a little frustrated with this issue.

This is on the '96 BTW. Still has a high idle but runs awesome when you first start it.

Then, once warmed up (I guess the computer kicks it out of open loop and starts to read sensors?) it will start to lightly cut out under load. Still idles smooth (but high if not in gear) and runs PERFECT above 60 MPH. No stumbling or cutting out. Only at low speeds..and the longer you drive at low speeds the worse the cutting out/light popping gets. So its parked for now until I can figure this out.

CEL will come on after 20 mins or so of driving . Pulls code 174 (Right bank lean) Nothing else.

Things I have checked

-all vacuum lines, hoses

-EGR was programmed out and I have a delete plate on (sealed well)

-TPS was swapped out with a spare I had, no change

-Seafoam'd upper part of the engine...no change

-No exhaust leaks at headers or reducers/flanges.

-Not an O2 problem (at least the 2 fronts) I swapped both newer ones out with stock ones and no change

The rears are O2 Sims...they have LED lights on them that do blink...so I assume they work




I can make a video of the issue tomorrow for you guys. Forgot my camera this morning and gotta play a wedding now.

Any ideas would be welcome...I also have a spare MAP sensor and TB I can throw on to test if need be...

Injectors? Intake manifold leaks? PCV valve? Check the plugs for fouling?

Thank you Robert!

I do have a spare set of injectors...but if one was bad, would it not idle smooth or run well at all?

-PCV is new


I will check for an intake manifold leak...will check all the bolts tomorrow!
I will also pull the plugs too, they are all new. Hopefully none turned bad that quick. Ugg. I did check the connections at the coil and all plug wire connections are good to go as well.

Any other things you guys can think of please? I will be working on it a little bit tomorrow...

too much air could cuz the idle to bump up


have you gotten a datamaster log of it?

Agree with sprocket - too much air would explain both symptoms. When cold the extra air is leaning out the normally slightly rich start up mode and causing a high idle. Once it goes to the sensors it's running lean because unmetered air is getting into it *somewhere* and the computer can't compensate enough to get the right mixture. The fact that it only reads one bank lean points to most of it ending up on that side of the intake for some reason- possibly at the fuel injector seals?

A vacuum gauge may be able to tell you if you have a leak. It works best if you know what the reading was when it was running right, but if it shows up as low (<16) and it's mostly stock, you probably have an issue. Other folks use a propane torch and run it around suspected areas to try to detect a change in idle - this is considered dangerous by some but has been used by people for years - you just have to be careful.

A good article on vacuum leaks:
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bigoldv8 wrote:

The fact that it only reads one bank lean points to most of it ending up on that side of the intake for some reason- possibly at the fuel injector seals?

Another good suggestion,. i had 2 bad injector o rings on the flamed black thing,. had the same issues as you,.i bank lean,. surging, stalling, but ran fine at speed,.

Nick

If nothing else, switch the injectors side to side and see if the code switches sides too. Once you do that, then go back and switch only the front 4 injectors and see if the problem switches again. If it doesn't, you've narrowed down to which injectors (or their o-rings) are questionable.

sherlock9c1 wrote:

If nothing else, switch the injectors side to side and see if the code switches sides too. Once you do that, then go back and switch only the front 4 injectors and see if the problem switches again. If it doesn't, you've narrowed down to which injectors (or their o-rings) are questionable.

or you could just buy a bag of the o-rings and switch them all. (wouldn't hurt) as I recall the bag of 'em was not very much $$$

ok! I have my list now...feels good to have some direction!!

I do have another set of injectors/fuel rail/reg from a 100k Fleetwood. If I can't get the o rings today...I might just swap those in as I know they work (heard the car run before Mike and I pulled the engine)

if an injector O ring is leaking its pretty obvious,..it'll be compromised somewhere, inspect them carefully,.
Nick

Nick, could you just spray starting fluid on the injector O-rings and see if the RPMs go up? That would show the leak pretty quickly.

New O rings, new intake manifold gaskets....still acts the same. Also swapped out the MAP sensor.

High idle (1600-1700 RPM), but drops down to 800/900 RPM in gear. Also...if I rev it a bit the idle will jump and hold around 1800-1900.

Runs smooth and down right awesome until 15-20 mins into the drive. CEL comes on and the studdering starts. Gets worse the more you drive at low speeds.

Here is a video. I started it about 17mins into the drive once I could feel the studdering start...CEL light comes on and you can hear it progress as time goes on (really bad around min 3:06 on..hardly gets out of 1st gear from the take off)

Frustrating! I don't see what could be leaking. Did not have time to pull the plugs yet, but if one was fouled...would it act up right from the get go? Could this be a MAF issue? I really don't think its a leak, this has to be a sensor or electrical issue...?!?!

.

Grab a spare PCM and see what happens...

I am sure to catch a boatload of crap over this but I just remembered this trick and it works very well.
As a youngster way back in the early 70s I discovered a sure fire method for finding a vaccuum leak.
Nowadays you have these fancy ass smoke machines but then all we had was a vac gauge which onlys
verifys a leak but doesnt show where.
Go find someplace that sells incense and buy the biggest stick available that produces lots of smoke.
Unplug all fans and park where there is minimum air movement and fire that bad boy up.You will have to
make sure you isolate your air filter intake opening too.
Real simple just hold the incense close to the injectors/intake gasket area and watch.Any vaccum leak
no matter how small will suck that stinky smoke in and there is the leak.Use the smaller sticks in the
really confined areas.
SOUNDS STUPID BUT THIS WORKS!
I remember putting a header and intake with a holly 2 barrel on my little brothers Pinto and it was idling
rough and the incense worked great.The damn smoke would actually stall that little 2 litre when we got
close to the leak.
One other thing is never assume anything,go back and verify that those O2 sims are not malfunctioning
in some way.
Good Luck and yes I used that incense for other purposes too!
Jim aka Flasheroo

Have you scanned the IAC counts to see what the IAC is doing?

I agree with Jason - you may try a PCM if one is available.

Chris, there are only 3 things that can cause a lean condition.

Too much air
not enough fuel
a sensor that "thinks" that one of the previous conditions exist.

this is how I would troubleshoot (keep in mind that I am NOT in any way ASE, or any other acronym- certified)

For no particular reason, I ASSume that a lean condition = less fuel so check pressure. If good, while car is running bad, unplug each injector and see what happens (no spark = rich condition?) If nothing happens, the injector is bad.First check for power ( I know, no power will throw another code), then replace the clogged/bad injector.If the injectors are good, I would start with the air. Check if the MAF is in correctly (I know, I know..... I've done it TWICE!!) evidently there is an arrow....... [You must be registered and logged in to see this image.]

Check all connections, then hook up a vacuum gauge. Vacuum good? Damn. OK, now it's sensor time. Because most sensors will through their own code, I would ASSume again that the O2 is having a bad day and swap sides and see if the code changes. If not, they are good. After that, you are on your own.

Wait, did you do anything to the heads? Would a bad valve seat cause this? Or a bad/weak spring?

Have you verified that the throttle body is actually closing all the way? Maybe your TPS or IAC need to be adjusted? Try forcing the blades closed with the car running by putting pressure in the opposite direction on the "throttle arm/spring assembly" thing.

First - Why the high idle?

Have you verified the IAC is working?

Have you disconnected and plugged all the auxiliary vacuum connections (HVAC, canister purge, opti vent harness) to ensure they aren't causing it?

Second - Did you change the injectors?

A leaking injector can cause the remaining cylinders on that bank to lean misfire as the PCM attempts even out the O2 readings.

Based on the number of failed injectors I've seen recently, I'd go ahead and swap them out anyway if you have a good set on hand.

It's not a bad idea to check the new ones with 12 volts to verify they will cycle before installing them.

- J

LS2 will fix the problem,..

ok! Thank you guys a lot for the info I owe you all a beer or root beer float...or something at the 'Fest next year
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JaySS wrote:

First - Why the high idle?

Have you verified the IAC is working?

Have you disconnected and plugged all the auxiliary vacuum connections (HVAC, canister purge, opti vent harness) to ensure they aren't causing it?

Second - Did you change the injectors?

A leaking injector can cause the remaining cylinders on that bank to lean misfire as the PCM attempts even out the O2 readings.

Based on the number of failed injectors I've seen recently, I'd go ahead and swap them out anyway if you have a good set on hand.

It's not a bad idea to check the new ones with 12 volts to verify they will cycle before installing them.

- J

That high idle is confusing me. I really can't find a vac leak so it leads me to think sensor issue (or PCM tune) I do have an extra IAC ! I will swap that over to my TBody and see if that changes anything. Wondering if I will still have the other issue if I solve the high idle (or if they are both related)

Don't have a way to scan it myself (I only have the OBD1 AKM cable..but might talk a buddy into letting me borrow his OBD2 one if I give him mine to use)

I have looked at all the vac hoses (including canister since I can still easily see it too) Also double checked the Opti Vent harness since I did install a new one (old one was rotted)

Did not change the injectors, just new O rings. But I will test the ones I have (and extra set too)
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toomanytoyz wrote:

Have you verified that the throttle body is actually closing all the way? Maybe your TPS or IAC need to be adjusted? Try forcing the blades closed with the car running by putting pressure in the opposite direction on the "throttle arm/spring assembly" thing.

I have done that (forcing blades closed) No change. I changed out the TPS (no change) but another vote for IAC!
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Krzdimond wrote:

Chris, there are only 3 things that can cause a lean condition.

Too much air
not enough fuel
a sensor that "thinks" that one of the previous conditions exist.

this is how I would troubleshoot (keep in mind that I am NOT in any way ASE, or any other acronym- certified)

For no particular reason, I ASSume that a lean condition = less fuel so check pressure. If good, while car is running bad, unplug each injector and see what happens (no spark = rich condition?) If nothing happens, the injector is bad.First check for power ( I know, no power will throw another code), then replace the clogged/bad injector.If the injectors are good, I would start with the air. Check if the MAF is in correctly (I know, I know..... I've done it TWICE!!) evidently there is an arrow....... [You must be registered and logged in to see this image.]

Check all connections, then hook up a vacuum gauge. Vacuum good? Damn. OK, now it's sensor time. Because most sensors will through their own code, I would ASSume again that the O2 is having a bad day and swap sides and see if the code changes. If not, they are good. After that, you are on your own.

Wait, did you do anything to the heads? Would a bad valve seat cause this? Or a bad/weak spring?

Ok, I did try some of this after you wrote in. If I unplugged an injector when it started running bad...it got worse.
MAF arrow is right (lol...I did that once too) and I will also have it tested this weekend too (putting it on a buddies wagon)
I did swap out O2s (both sides) and no change. Gonna get a working vacuum gauge too. Nothing on the heads though...
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jayoldschool wrote:

Grab a spare PCM and see what happens...

sherlock9c1 wrote:

Have you scanned the IAC counts to see what the IAC is doing?

I agree with Jason - you may try a PCM if one is available.

IAC! Gonna try that tonight or tomorrow night!!
Do not have an extra PCM, but working on that...
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Flasheroo wrote:

I am sure to catch a boatload of crap over this but I just remembered this trick and it works very well.
As a youngster way back in the early 70s I discovered a sure fire method for finding a vaccuum leak.
Nowadays you have these fancy ass smoke machines but then all we had was a vac gauge which onlys
verifys a leak but doesnt show where.
Go find someplace that sells incense and buy the biggest stick available that produces lots of smoke.
Unplug all fans and park where there is minimum air movement and fire that bad boy up.You will have to
make sure you isolate your air filter intake opening too.
Real simple just hold the incense close to the injectors/intake gasket area and watch.Any vaccum leak
no matter how small will suck that stinky smoke in and there is the leak.Use the smaller sticks in the
really confined areas.
SOUNDS STUPID BUT THIS WORKS!
I remember putting a header and intake with a holly 2 barrel on my little brothers Pinto and it was idling
rough and the incense worked great.The damn smoke would actually stall that little 2 litre when we got
close to the leak.
One other thing is never assume anything,go back and verify that those O2 sims are not malfunctioning
in some way.
Good Luck and yes I used that incense for other purposes too!
Jim aka Flasheroo

Heh, I can try that too! My in-laws will think I've lost my mind, but I know they already think that. Thanks for the tip! The wife can grab some from a friend of hers today.
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phantom 309 wrote:

LS2 will fix the problem,..

Yes it would. Trust me, I wish I could put any LSX in the wagon. Someday...when I undo those 8 bolts...

FWIW, I had my wagon's injectors serviced by WitchHunter performance. For $170 or so, I found out that I had no less than two bad injectors. Money well spent.

OK. So the high idle is now fixed

It was indeed the IAC!! WHOO!!

I still have some stumbling after 15+ mins of driving still. So still gonna check some more stuff. But the idle is very nice now.

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