13Beast REW

I had my alternator tested at autozone a few weeks ago and it came back ok. I know that a bad alternator could cause the bogging issue that occurs under 1K RPM and its possible that there is an electrical issue as the stock volt meter drops below 12 volts under 1K and the dash lights dim if they are on. I doubt that this would have anything to do with the hunting idle issue though. I'm thinking the clogged diffuser may have played a major role in the hunting idle and maybe even some of the vacuum hoses so none of this work has been in vain.

There are just too many variables as to why this motor isnt idling. I'm really trying to avoid ruling poor compression. This is a relatively low milage motor being an 86 with only 136K miles on the clock. So aside from poor compression, I know that the 1K+ engine speed requirement for this motor to stay on would be due to poor fuel delivery, poor sparking conditions, or poor air metering from either a bad sensor or air leak.

Of all of those my guess is the sparking condition is the easiest issue to eliminate, followed by fuel delivery and last air metering although I've done almost all that I know can be done in regard to verifying air flow.

I guess I just need to tackle them in that order.

Amur_

Don't. The secondaries aren't involved with either start-up or rpms below about 3600...

13Beast REW

OK fine, scratch that idea. Thanks for the reponses too btw. So the plan for tomorrow is replace the injector o-ring, verify correct voltage output from the alternator, and rewiring the S4 TPS. I also came across some info on pulling the codes from an FC since it has not check engine light... I'll gp through that as well tomorrow. I'll post any relevant pictures.

vintagespeed

If you suspect the alternator as a possible cause, take off the belt. This'll tell you right away if that should be pursued.

Amur_

http://teamfc3s.org/info/articles/errorcodes/main.html

13Beast REW

OK I got the injector o-rings on there and got the S4 TPS spliced together and in place. After raising the idle adjust screw all the way (too the point the thread is showing above the UIM) and adjusting the TPS all the way down, I got the car to stay on even with the hunting idle. So now it will stay on and the engine speed will vary from 1500 to 1650 when the motor is warm.

So I know there is a vac leak somewhere and a heavy one at that since when I took the car for a test drive and tried to ride it down the street at 2.5K it wouldn't hold steady. In the same pattern as the idle the car would buck and the RPMs would drop and go back up.

I got the car back to the garage and popped the hood. It stayed on which is a good thing. I started to check for a vac leak using someone's suggestion to spray butane all over the UIM while the car was running and see if the engine speed changes while spraying. Well that idea didnt work but it mad sense. Next I tried using throttle body cleaner and put the little straw on the bottle to concetrate the spay jet. Srayed it on the UIM right next to the solenoids and the irratic idle quickened. Stopped spraying and it slowed back down a few seconds later. So now I'm thinking that the UIM gasket really is damaged and I'm about to go order a new one.

13Beast REW

I ordered both UIM gaskets and they should be here on thursday. Hopefully tha will be the end of this problem.

bigfellowrx7

Hey, I am having this EXACT same prob with my 91 non-turbo. See... this place in muncie indiana told me that they thought i had blown apex seals and i neede to replace the engine... so i did. I just got the motor in yesterday and it is doing te exact same thing it was before. I have no idea what to do. Please keep posting what you are doing so i can try what you do and we will figure this out!! im not much of a mechanic but i will try. I am desperate to fix this car. Thnx

13Beast REW

Hey no problem. Thats really why I keep posting anyway. If you notice, not many people are actually responding to this thread. I figure someone else is probably having the same issue I'm having so I post all the way through fixing the problem; everything I do and the effect (or lack of effect) that everything had.

People always want to scream "search"... I've searched and applied alot of what I've found through searching, but I'm not incompetant when it comes to repairing cars, I like to work through my own problems and brainstorm at the same time. I never ask people whats going on with my car and how do I fix it, I throw my thoughts out there and ask for other peoples thoughts and ideas and build off of that.

I'm pretty sure at this point that the final problem is the manifold gaskets so I'm just waiting for those to come in and I'll see what's what after putting them on.

Amur_

So we're talking near/under the BAC? You've got two vac lines under there. The big fat one and the small 4mm one. Did you try spraying directly on either of those?

And I'm not a fan of using carb/tb cleaner b/c it has solvents in it and it could/will shorten the useful life of any rubber it contacts (like hoses that you soak with it...)

13Beast REW

No didnt spray the hoses. I just replaced them all so I wouldn't suspect them to be bad. After taking another look at the spray can it was actually intake cleaner not sure if there is a difference in intake cleaner vs carb/tb cleaner but I have that also. Oh, and yes i'm talking about the gasket next to the BAC.

Raymr

Check your LIM-to-engine gasket. Those leaks are tough to detect but you might hear it using the rubber hose method. Mine had a cheap paper gasket that squished out of a narrow section and made a huge vacuum leak. Use the more expensive metal gasket if at all possible.

13Beast REW

Unfortunately I didn't get completely finished as I had hoped. It took me almost a day and a half to get off 90% of the LIM-UIM gasket. After getting to that point I was exhausted an needed to get the car back together so I could get it out of the garage so I siliconed the new gasket onto the manifolds and put the motor back together. it most definately did not fix the problem but at first it seemed to be the same as before. I ran and tweaked the car for 30 minutes straight without it dying so now its able to reach 1000 rpm without bogging out. Well that was until about 20 minutes ago. Now the leak seems so bad its amazing the car even starts at all.

When you first start it all seems normal for about 5-10 seconds. Then if you dont do anything the car just shuts off. If you try to hold the rpms at say 4K, the motor will rev to 4K then drop to 2K even if your foot stays solid at 4K. After dropping, the engine speed will stay low for 3-5 seconds and then will start to step back up usually in jumps from 500 rpm to 1000 rpm. It takes about 2-3 seconds to climb back up to 4K but once there, the engine will only hold that speed for maybe a second.

IMO, this doesnt describe the situation well enough but I can't think of a better way to put it but anyway... thats the stauts right now. If I have the energy I'll try for the LIM-engine gasket tomorrow.

Amur_

You're kidding?! Lemme guess - you didn't have a wire wheel to take it off with?



To be absolutely clear, we're talking about the joint between the dynamic chamber (it has '13B' stamped on it) and the top of the ducts down to the motor?



I'd call this a *big* clue.

Assuming the core is fine, I'd guess that something is muddling either air intake or fuel delivery...

Fuel delivery - have you added ground wires to the engine bay? Sounds like an odd question, but trust me. Taken alongside this:

I wonder if the whole damn mess isn't purely electrical. You may be barking up the wrong tree.

Have you looked at your battery terminals? The connectors? Are they clean and snug? How about the wires to the starter? The wire to the alt? (circled below)




Ground wires:

Instead of going after that gasket tomorrow, try that.

13Beast REW

No wire wheel. I've always just used gasket remover and razor blade scraper. I'm under the impression that the particular gasket I was working on had either never been changed or only changed once. I say that because the gasket (paper) was solid and an hour of soaking in gasket remover only softened a layer of the gasket about as thick as a strand of hair.

That one (dynamic chamber<->UIM) and the next lower one (UIM<->LIM). I have one more unused gasket which goes between the LIM and the engine.

Granted its not the most accurate depiction, the car does not smell as though it were running excessively rich. I havent really noticed a fuel smell comming from the exhaust at all.

I'm beginning to think that I must have missed an important vac hose. After reassembling the motor, I tried the spray test again, this time rather than only spraying around the dynamic chamber, I spray everywhere before and after the TB listening for variations in the engine speed. Anywhere that I sprayed after the TB cause a noticable variation.

[qutoe]
... have you added ground wires to the engine bay?
[/qutoe]

Not yet. I began reading up on grounding issues in anticipation of making a stab at it but didnt feel that I'd read enough yet. I'll take your suggestion and try at that next. Today is supposed to be a pretty busy day for me but hopefully I can get around to the car before 10pm. Thanks for the additional info. The entire rotary community needs more willing thinkers like yourself.

Amur_

I've never had to separate those two pieces, but I did briefly try once. I was amazed at how they refused to budge. I think that they're assembled at the factory with the expectation that no one will ever try separate them..



Okay. One important comment: do NOT put silicone/RTV on these two later gaskets. UIM/LIM sits right below the secondary injectors, which will wash the silicone away (down into the engine.) Ask me how I know.
And I replaced the LIM/engine gasket about two years ago. No silicone/RTV and no sign of a leak...



And it shouldn't be. I'm wondering if a poor grounding sitch is making life difficult for your injectors.



Stay after that. And switch methods - it may help find more clues. Start using water (garden hose.) Flowing slowly, go from spot to spot. Spray it onto a surface if need be.



Yer welcome. I just know that if I were in your place I'd be pretty let down if no one tried to help.

13Beast REW

Never got back to working on the car but thats the plan for tomorrow.

13Beast REW

Ok, well the car stays on now even with the hunting idle and the idle adjust screw is now lowered to a reasonable level. I do have one other thought though regarding the hunting idle.

In a situation where the hunting idle was cause by a vac leak, the variation in engine speed should not be noticed while the car is being driven right? What I mean is that when trying to coast at a given speed (like 30 mph) the car will buck along to the same rythem as the motor when its trying to idle. I've had hunting idle issues in other cars before including my FD but the problem never extended into while I was coasting down the street. Quite honestly the problem never persisted through even holding the RPMs at a give rate while sitting still. Does that just mean that this is a large leak that I'm dealing with or that it'd be more related to a fuel issue (or even spark).

I made the check engine light according to the write up for S4's and I have no codes. Both lights just come on for 3 seconds when I turn the car on then go back off.

Haven't attacked the grounding just yet but I'll get around to that soon.

13Beast REW

One more thing, I just noticed one of the air pump hoses is damn near split in half. What symptoms would a damaged air pump hose produce. I'm not hanging on this too heavy because the area I'm doing the spray in is no where near the air pump but it'd be nice to know regardless.

rice eart 17

man i hope ur engine gets straightend out. i have an 89 n/a GTU and i seem to have almost the same problem. the car will start fine, and rune fine until it gets warm, then when i allow the engine to idle, it will cutt off. i am no mechanic, and that is a problem. any quick suggestions?

13Beast REW

Nobody knows about the air pump?

13Beast REW

OK, well anyway. I went out and did some of the grounding. From the negative battery terminal to the chassis, tranny to chassis, and also paralleled the alternator wire to the positive battery terminal. This actually had a noticable effect on the way the motor was running. The engine now revs ALOT smoother. Before, it would breakup while going through the full RPM range.

So now that its pretty much the only thing I haven't done, I'm going to go start on the LIM->engine gasket. Hopefully I'll get it done today but if not then it will atleast get completed before the weekend.

13Beast REW

I've the UIM off right now and just had a thought about the engine's reaction to the spray test. At the time that I'm spraying the intake cleaner around the UIM, if spray gets on or in the EGR wouldn't that also cause a change in the way the motor is running? If that's the case, wouldn't that discredit the whole spray test?

mack123

iTrader: (4)

I would check your compression. what you describe is the same stuff I was going thru on one of my rx's last year, I spent hours and hours, and $$.

When I finally decided to hook up the gauge,and it took only a few minutes to test, then I knew, the rear rotor was bad.

Doing a test is easy, and I know some guys dont want to do it, they think its like the ultimate doom if it fails, and dont want to face the whole new problem. Rebuild. I was that way. Now one of the first things I would check on any rx is the compression.

Hope all works out.

13Beast REW

For completion I'm posting that I've resolved the issue with my car's idle. Its not too often that I see resolutions posted on here anymore. Seems like as soon as people fix their problems they just forget about their thread. But anyway....

I never actually pin pointed the problem, it was a vac leak though. I ended up replacing all vacuum hoses, all of the manifold gaskets, the intake manifold itself, I'm still using my original throttle body though, replaced the TPS, BAC, Air bypass solenoid valve, and all solenoid. As I did with my original intake manifold, I COMPLETELY cleared off any remaining gasket before placing the current one on and cleaned the diffusers. I also did a bit a grounding work.

I dont think that resolving the problem really required all of what I did but seeing how the car was new to me and as far as I can tell, the motor had not been very well cared for, I figured replacing all of the things that I did was in my best interest.

End result... the car is back on the road