'94 explorer erratic idle, changing RPM at random

[Birdman1]

Hi guys,
I have a '94 Explorer 2dr, 5-spd, pretty much stock drivetrain. for a few weeks now it will most days start and run fine, but some days it won't start without giving it gas, then it will idle very low, barely 500rpm. the RPM will randomly (truly random, just once in a while) jump several hundred, then come back down, this is almost dangerous as closely as my wife follows people sometimes. the check engine light has NOT been on at all.
I have cleaned the MAF thoroughly (twice) and cleaned the IAC well. I read up on this site on how to pull codes, so today I had my wife sit and write down numbers as I counted them (KOEO). they looked as follows:
565/565 // 112/215/721/112/215/721/1.
We then went for a 45 minute drive to run some errands, and halfway thru this the CEL came on. stopped at one last store and came out, the CEL was back off.
When we got home, we pulled the codes again. now they look like this:
565/565 // 112/215/721/133/112/215/721/133/2. (looks like it added a 133)

the 565 appears to be the canister purge solenoid (which looks to be a ***** to get to), which makes sense since the truck has randomly had a dead gas smell off and on for a long time. The 215 is something to do with the coil, but the truck does not miss or really act like an ignition problem to me. the 112 says intake air temp sensor, and yes the truck was fully up to temp (although I do have a 160 T-stat in it, but it has been there for 2 years now with no problems).
My questions:
can any of these make it run this weirdly?
what the hell are 721 and 133, they are not on the lists I have found here.
what does the single number at the end mean?

So, I am going to unhook the battery for a bit, hook it back up, have the wife drive it for a couple of days, then pull the codes again, and report back.

I am stubborn about running out and buying various things until I have even a half-assed clue what is going on.

I appreciate any and all help you Explorer guru's can give me.

 

[Roadrunner777]

I don't have those two mystery codes in my books either.

 

[Hoof Hearted]

Don't have the 721, but 133 is the upstream o2 sensor (Bank1) try replcing that then read codes again

 

[MrShorty]

565/565 // 112/215/721/133/112/215/721/133/2.

It is interesting that there's a stray 2 at the end of the CM codes. Any possibility that you've included the separator pulse in the first 112? If I work backwards and assume that first 1 is the separator pulse, I get 565/565/1/122/157/211/33(2)/122/157/211/332 all of which make sense. A possible explanation??

 

[Birdman1]

well damn, I guess in all my reading I never caught the fact that there is a separator pulse, that does drasically change things. thank you.

last night I unhooked the battery for about 20 minutes, hooked it back up and ran a couple more errands, about 15 or 20 minutes driving time, then pulled the codes again. I got to wondering how many years those codes had been in there and therefore mean nothing to me.
it still has the 565/565, but after that it said 111/111 which is all systems ok? is there no separator pulse if it is 111-systems ok?

My wife drove it to work today, I plan to pull the codes again this evening and see what it says about commuting for a day.

So my question now, could the 565 -(canister purge solenoid) make it run as erratically as I am describing?

 

[MrShorty]

is there no separator pulse if it is 111-systems ok?

There should still be a separator pulse between the KOEO and CM codes, even when KOEO or CM report pass 111.

During your test drive, did the symptoms manifest?

Have you tried the KOER test?

I wouldn't expect a CANP fault to cause it to run rough, unless the fault causing the CANP code is effecting another system.

While your checking the codes, I'd probably test fuel pressure (especially when it is stumbling) and check for any vacuum leaks to see if those look right.

 

[Birdman1]

Well, I am back.
the truck is no better, still popping thru the intake, jumping 500 or more RPM at random, at idle, while driving, totally whenever it feels like. It's half assed dangerous sometimes. but no missing, all cylinders are hitting fine.
After the last set of codes that I listed here, I unhooked the battery for half an hour, hooked it back up, then my wife continued driving it to and from work for 2 weeks, then I borrowed a friend's fancy digital code reader. It said the 565 code first (canister purge solenoid), then 111, which means all happy, correct? I just finished putting plugs and wires on it since I never have since we have owned it, the plugs looked pretty toasted and loaded with crusty stuff, and the gap was .010 to .015 over, however this did nothing for the surging BS. So, I am now going to go out and change the purge solenoid, but I really do not see how this is causing the surging crap.
any other ideas or thoughts?
thanks for any help.

ps, I have looked all over for vacumn leaks, I see nothing. It has never really had a stumble, just erratic, self changing RPM.

 

[Birdman1]

purge canister solenoid, throttle body gasket(had to make my own, nobody had one until Tuesday), replaced nearby vacumn lines, none of this stuff stopped the surging Bullshit.
this truck is about a pain in my ass.

 

[nitro71]

Just keep whittling the codes down. Have to get those fixed first.

 

[Birdman1]

ran the codes again last night, getting all "1"'s now. I am out of ideas on this truck.

 

[MrShorty]

Did you ever check the fuel pressure/fuel delivery?

 

[Birdman1]

Mr. Shorty: No, I have not checked the fuel pressure yet, 1. I do not have a gage, 2. I really do not feel like this is a fuel issue.
it makes lean popping sounds in the intake, then the engine takes off, then comes back to idle after a few seconds. never any missing, stumbling or any of that stuff. running down the highway or even around town, it runs strong, never the slightest symptom of running low on fuel.
regardless, I suppose I will need to buy a pressure gage soon, seems like something I will use occasionally.


this evening I am going to attempt the KOER codes since the KOEO ones are all cleared now. I'm going to borrow my friends code reader with the digital output, so it should be fairly simple. should this tell me about fuel pressure issues?

I also put a new IAC valve on it last night (I had tried cleaning it a few weeks ago). did nothing at all for it, maybe even worse. if I unplug it, it actually runs ok (with the old and the new), just slightly low idle.

thanks for your help.

 

[Birdman1]

ok, so the new IAC valve made the situation WAY worse, now it takes off way more often, and it revs higher yet when it does it. Is this a clue in itself I am wondering? Like maybe the new valve is a POS, worse than the old one, and that is still the real problem?

I ran the codes again last night, KOEO= 111.

KOER = 412 and a 538. neither of these tell me a damn thing. from my searching, the 412 is "can't control idle speed" I already know that. the 538 means I neglected the goose test, which i did not. I ran the KOER 5 or 6 times, a couple of them I floored it hard enough to make the tach snap to 4000 to 4500 RPM or so. same 2 codes every single time.

anybody got any good Ideas?
thanks

 

[Roadrunner777]

If you do anything that affects idle, it is a good idea to disconnect the battery for 30 minutes. This will cause the computer to enter a 'learn idle' mode. After reconnecting, drive 20 minutes or so of a normal driving mix.

 

[Birdman1]

thats a thought, I did not unhook the battery after changing the IAC. I will try that this evening.
thanks

 

[Marv]

Check the vacuum with a vacuum gage, should be around 20 inches vacuum at idle. That's the first basic check for the past 100 years.
You can put all new sensors on and clear all the codes and it still won't idle right with a vacuum leak
Marv

 

[MrShorty]

the 538 means I neglected the goose test, which i did not. I ran the KOER 5 or 6 times, a couple of them I floored it hard enough to make the tach snap to 4000 to 4500 RPM or so.

If you know you did the goose test at the right time during the test, and the PCM didn't register, that suggests a fault. Goose test basically looks at two things: change in the TPS, MAF, and engine RPM (CKP) outputs. 1st thing I'd probably check is the TPS, because it is probably the easiest. TPS is a basic potentiometer. Make sure the TPS output is changing smoothly throughout the throttle's motion.

 

[Birdman1]

yes, I don't see how I could have gotten it wrong that many times. I was using my friend's Innova scanner, the screen tells you exactly when to do each test, steering wheel, brake pedal, floor it.

Mr. Shorty: what do you think of the fact that a new IAC valve made the problem MUCH worse, same exact problem, but way more often, and more RPM? of course it got a little worse with new plugs and wires too, it's way stronger now.
My wife is driving it with the IAC unplugged today (runs just fine, just idles a little on the low side.), the stupid truck is getting dangerous for her.

I will play with the multimeter tonight, thanks much

 

[Birdman1]

and shouldn't the TPS throw a code of some sort? on the KOEO or the KOER?

 

[MrShorty]

and shouldn't the TPS throw a code of some sort? on the KOEO or the KOER?/quote] Yes, there are other KOEO, KOER, and CM codes that a TPS can throw. If the computer were smart enough, maybe it would do all the diagnosis for us. I tend not to completely trust the computer to see and report all faults. Perhaps it is the kind of fault that the computer can only see during the goose test or who knows. All you have to go on is that the computer isn't seeing the result of the goose test, and it's up to you to determine exactly why the computer isn't seeing it.

I was using my friend's Innova scanner, the screen tells you exactly when to do each test, steering wheel, brake pedal, floor it.

I only mention this because I can't be there to see exactly what is going on, and I've never used a scanner. I have noticed that the window for doing the "goose" test is pretty narrow. If the scanner were "late" in telling you when to do the goose test, the PCM might miss it.

what do you think of the fact that a new IAC valve made the problem MUCH worse, same exact problem, but way more often, and more RPM? of course it got a little worse with new plugs and wires too, it's way stronger now.

I'm not sure what to make of it.