Can muffler being off cause rpms to jump?, The EGR and CAT idiot lights are on Options

[914zim]

Fellas:
I have a '76 914.
I've removed my muffler(s) to get my car to run.
Turns out it is rusted plugged or full of rodent nests.
Anyway, now it'll run (LOUDLY), but the rpms jump
from 500-3000 at a consistent frequency.
Could having no muffler attached cause the jumping?
IOW, if I put a new muffler on, will the rpms hold (idle)?
Thanks,
Andy...

[Joe Bob]

Hunting idle usually means an intake leak somewhere.

[ArtechnikA]

Anyway, now it'll run (LOUDLY), but the rpms jump
from 500-3000 at a consistent frequency.
Could having no muffler attached cause the jumping?
IOW, if I put a new muffler on, will the rpms hold (idle)?

what is that consistent frequency ? once a second ? every ten seconds ? every minute ? all D-Jet cars will hunt at idle a little, but that seems quite excessive. i'm not quite sure what you're describing. are you saying it idles at 500 rpm, and then periodically jumps to 3000 rpm, and then instantly drops back down? ('cause that's the impression i get when you say it "jumps from 500-3000 rpm") if that's not actually what it's doing, perhaps a better description is in order... i can't imagine what would describe the condition i think yoiu're describing, but probably i have the wrong impression of what it's actually doing.

however - check everywhere for vacuum leaks. check all the grounds. i do not believe the muffler is a major factor in this behaviour.

IIRC - the CAT and EGR lights are controlled by an odometer box that lives up front - perhaps in the passenger footwell area. it should have a reset button. but i've never worked on a '76, so please take that only as a general guideline and not gospel - IOW - don't go off into a blind alley just on that description, but i believe it is generally correct...

[boxstr]

Sounds like you should be looking elsewhere for the hunting idle. Mike is correct, vacumm leak. Get a proper muffler on the car and get some brake cleaner and when the car is running spray in suspect areas for a vacumm leak. Probably a bad hose or one that has come unplugged in the intake area.
EGR/Cat counter is located under the carpet on pass side under a small wood cover. There are two reset buttons, one EGR the other CAT. Press and they will cancel the EGR lite on at the gauge, it will not cure yuor hunting idle problem.
CCLINHAYNESVILLE

[914zim]

Thanks fellas!
I'll try to describe it again. How's this?

The tach needle is constantly moving (jumping) between 500 and 3000 rpms as if I was pumping the gas pedal every second.

I will double check all my vacuum lines again. I did get a complete vac line kit from AA and have replaced them all. Maybe I missed one or one's fallen off.
I did get a hand drawn copied diagram with the kit, but I think it leaves a little to be desired.
Anyone know of another good reference?

Andy...

[ArtechnikA]

The tach needle is constantly moving (jumping) between 500 and 3000 rpms as if I was pumping the gas pedal every second.

okay - if that's what it's actually doing, you described it pretty well in the original post. i was just having a hard time believing it was doing that...

a 2500-rpm rise and fall every second is far from the normal D-Jet 'hunt' which might be a couple-hundred rpm rise and fall over several seconds.

i'm mystified, but i don't claim to know much about T-IV's so maybe it's something simple and obvious that i've just never encountered or heard about before.

there are several explanations for high idle (not 3000 rpm tho...) and several explanations for 'hunting' but an engine that goes "vroooOOM! vroooOOM!" all by itself repeatedly is beyond anything i've experienced ...

i'm watching this thread for whatever it turns out to be ... good luck !

[ChrisReale]

Your car was tuned with the stuffy muffler (more back pressure). Now that there is no back pressure, you will have to re-tune. Get a good muffler, and then look to tune it.

[redshift]

Get some started fluid, and start looking for holes, carefully.

I have had a 1.7 go uber-nuts on a vac leak, that sounds insane though.. you can't mean every second.. that's nuts.

ThIS (IMG:style_emoticons/default/boldblue.gif) ThReAd (IMG:style_emoticons/default/clap56.gif) iS (IMG:style_emoticons/default/boldblue.gif) uSeLesS (IMG:style_emoticons/default/clap56.gif) WiThOuT (IMG:style_emoticons/default/boldblue.gif) a WaVe (IMG:style_emoticons/default/boldblue.gif) FiLe!

heh


M

[914zim]

Redshift: You're right.
I need to look into getting a wav file of it...
Chris: You make be right, but my car sat in an unheated garage for 4 years without ever being started.
I assumed the plugging was from rust and condensation from it just sitting. I'm guessing it ran fine before it was put away. Who knows for sure.
Thanks guys!
Andy...

[ArtechnikA]

tell you what it's sounding like to me - you've got two dead cylinders. D-Jet injectors fire in pairs, and i bet one pair isn't. the 1-4-3-2 firing order means the two cylinders on each side fire consecutively. so maybe you're hearing --- -- that'd make the engine rev up on the two firing cycles, then slow down on the two misfire cycles.

check your trigger points, and injector grounds.

it's gotta be -something- ...

[914zim]

First of all I just noticed I'm listed as a "Senior member"
How the hell did that happen!? I'm about as clueless as they come when it comes to troubleshooting car problems!! Can I change this?

Anyway, I'll read up on the trigger points (in the dizzy, right?).
Injector grounds... what is that, the mounting brackets?
I think I'll need a little help on looking into these issues.

Thanks alot!!
Andy...

[ArtechnikA]

First of all I just noticed I'm listed as a "Senior member"
How the hell did that happen!?

I'm about as clueless as they come when it comes to troubleshooting car problems!! Can I change this?

Anyway, I'll read up on the trigger points (in the dizzy, right?).
Injector grounds... what is that, the mounting brackets?

the system ascribes "senior member' based on the number of posts, unless you override that field with one of your own (on mine, for instance, i have my 'real' name since my user name is my Porsche- company-affiliated business name, but i'm not trying to hide who i am ...)

yes, trigger points are in the base of the dizzy, and there is one switch per pair of injectors. all the injectors "should" ground to a common grounding point located (somewhere) near the exact center of the engine block. a few other things ground there too, i think ... also check the individual connectors at the injectors themselves.

you'll learn all there is to know about diagnosing car problems if you're interested in doing it. BTW - there's an excellent description of D-Jet principles of operation of Brad Anders' website (someone else will have to point you with a URL tho...) and Dave Darling has a troubleshooting checklist on te Pelican site. i don't know the URL for that, specifically, either - i don't own any D-Jet cars ...

[914zim]

OK, just a test to see if I changed my profile correctly...
Andy...

[914zim]

OK, that's better.

[Brad Roberts]

Where are you on this Andy ??

[SirAndy]

i have had similar symptoms when i had a big vaccum leak.
idle between 500 and 2500 ...

in my case the AAR was going "kaputt".
if the AAR is shot, it'll leak air into the system even if all hoses are connected correctly!

take the 2 hoses off the AAR and plug them (just use your fingers for testing) and see if the idle is more stable.

Andy

[914zim]

I didn't have any 914 time today, but yesterday I got it to stay running because I took off the muffler. I'm guessing it was rusted up inside or maybe clogged with rodent nests after sitting for 4 years.
Brad, since the last time you posted to me, I've installed a new coil and added the Pertronix (as you suggested a few weeks back).
So, now I have 2 separate issues (I think):
1. Sometimes I get nothing when I turn the key or even if I use the remote starter switch. I don't hear the fuel pump buzz, no dash lights, no starter engagement, nothing, completely dead. Then after scratching my head and tapping around for a few minutes, it'll turn over and start up right away. Battery is fully charged. Some of the guys seem to think I need a new ignition switch and I've heard about this relay under the seat, but I haven't looked into either of these yet.
2. When it does start, the rpms jump from about 500 to about 3000. It's like I'm pressing on and off the gas pedal every second or so. It'll run like this as long as I want it to (doesn't die). With the muffler off it's super loud, but at least it runs now. Rich suggested the trigger points in the dizzy and the grounding of the injectors. I need to find out more about these 2 items.
Andy is suggesting the AAR. I'm not sure what or where this is, but I'll check around to see it I can find out more.
Any specific info on all of this is appreciated. I'm planning on some 914 time tomorrow night.
Thanks for hanging in there with me on this guys! (IMG:style_emoticons/default/pray.gif) (IMG:style_emoticons/default/pray.gif)
Andy...

[Carrera916]

Andy...

Without meaning to insult or anything like that....if your car has not been started for four years, would there be any chance that the car may have gummed up injectors and old gas?

Vacuum leak is one thing, if hoses are checked out okay, check all the componments that the vaccum hoses are connected to. MAP can leak like crazy when it's diagram (inside the MAP) fails. If you have a hand held vaccum induce tool with gauge, use that and start sucking the air out of MAP and other componments for leaks. Usually, once you set to certain vaccum reading, leave it there for at least 15 min and see if it holds up the vaccum.....if not, then time to find replacements....I know there's a good reference info somewhere in this web regarding to testing the vaccum system....i can't remember where....can anyone tell him where?

I'm in middle of a similar problem right now but with other BS interfering the performance of running engine, I found that when I pulled out the wire to the air temp sensor at the intake chamber, the engine behaves for while till something else interfers the running condition...soo I dunno what's up that yet but this would give you an idea that you would need to check everything related to the D-jet system before you can fine tune it.

j

[Carrera916]

Andy....

Brain fade here....MAP.... I meant the MPS!!! Sorry about that!

j (IMG:style_emoticons/default/confused24.gif)

[SirAndy]

AAR = Auxiluary Air Regulator (did i spell that right?)

besically, a controlled vacuum leak to help with cold start.
(car idles higher when cold).

if the AAR is shot (not closing after a minute or so) your car will have a massive
vaccum leak and the FI tries to compensate, hence the "hunting" at idle.

the AAR gets fresh air through a hose from the air-cleaner which is then routed
into the intake part of the throttle body.
easy way to check the AAR is to take the hose on the intake side off and plug it.
the idle should come to a rest (might still not be at the right RPM thought, if the engine needs adjustement).

find a D-Jet diagram to help locate the AAR.
Andy