Jump to content
SiriusBlack

87 XT idle issues. Dies when in gear.

Recommended Posts

Posted (edited)

 

welcome to page 3 folks...

Is this baby happy to rev up and down in N or P?

No hesitation?

Feel like doing a manual conversion?

Edited by Step-a-toe

Share this post


Link to post
Share on other sites
Posted (edited)
8 hours ago, DaveT said:

The way I'm reading the above - Ohm readings are meaningless if there is a power source in the circuit - battery, or running alternator.
If the battery was disconnected, well, the key changing the ground resistance as described make no sense.

 

9 minutes ago, DaveT said:

Key on, causes current to flow.   The current interferes with the current from the ohm meter,  throwing the reading off.

Resistance on a meter is just measuring voltage drop. The meter is applying voltage, and seeing how much the drop is. While you aren't getting an accurate measurement of the resistance, the meter is telling you there is a voltage drop. The better option is to run the meter in voltage and read the actual voltage drop from ground to ground. It should be sub 0.1V.

Edited by Ionstorm66

Share this post


Link to post
Share on other sites
1 hour ago, SiriusBlack said:

@Step-a-toe It has no problem whatsoever revving in P or N, no hesitation or anything. It wanders at idle and dies once put into gear.

Have you checked your transmission fluid ?

May also be the vacuum advance is not working.

Share this post


Link to post
Share on other sites
5 hours ago, SiriusBlack said:

@Step-a-toe It has no problem whatsoever revving in P or N, no hesitation or anything. It wanders at idle and dies once put into gear.

you are at the point where I used to say convert to a manual box , mainly for not understanding automatics.

Have you AC ? Thinking if you have it on to add small load to engine, twerk PS at same time to add bit more load to see if these alone mimick same when D or R is selected.

Share this post


Link to post
Share on other sites
On 9/24/2020 at 6:52 PM, SiriusBlack said:

I am trying to fix an insanely irritating idle problem on my 87 XT. EA82T engine MPFI. Its the one that sat for 17 after my dad fixed the heads and I recently got running. When it idles it wanders by about 200 RPM either way. The main big issue is that when it is in gear (Auto Tranny) it dies if you don't feather the throttle, as you can imagine that would make in town driving a pain. I have checked all the vacuum lines to the best of my knowledge. Scoured the shop manuals i have for the 86 year. Cleaned the idle air screw and the EGR air bypass solenoid as I originally thought it was the IAC valve. I have tested and replaced the vac line to the tranny from the intake manifold. And replaced the vac hoses from the pressure ports on the front of the throttle body. I cleaned the main throttle butterfly as it was suggested that that being dirty could cause this issue. I have triple checked the timing both valve and ignition. The only other thing i can think of it might be is the Aux Air Valve on top of the thermostat housing. I had pulled the electrical plug from it when it was idleing cold and it made no difference. It was my under standing that if you do that when its idling cold there is supposed to be a major idle change? I sort of suspect that it has to be a vac leak somewhere, because the engine gets kinda hot despite an upgraded cooling system and new thermostat. I have been beating my head against the wall about this problem for almost a month. If any of you can help me I would be forever grateful.

Sounds like a vacuum or unmetered air leak to me.

Regardless,the first thing to do is verify proper fuel pressure before wasting time on other items.

In addition,I would probably try pinching the return line on the fuel pressure regulator progressively closed to increase fuel pressure and richen the mixture hopefully smoothing the idle.

Or,feed it a little propane for the same purpose.

What is the O2 led on the ECU doing during the wandering idle?O2 sensor voltage?

Unplugging the auxillary air valve won`t suddenly alter idle speed because the valve itself is thermal.Leaks in the hardened hoses connected to it could be a problem.

Check the large rubber intake boot carefully.They crack and have many possible leak points.

My car has a wandering ilde at a certain rpm during warmup due to a bad spot  in the airflow meter.

The egr valve might not be seating all the way.

Any codes?

 

Share this post


Link to post
Share on other sites
Posted (edited)

Well, we have eliminated pretty much everything else and are now thinking it is a fuel pressure issue despite the new pump. When we raise the fuel pressure it just barely keeps it from dying when idling alone not in gear. There is probably still gunk and varnish in the lines and the injectors despite my cleaning them. So I plan to pull the injectors again and install new, plus give the lines another cleaning. Now my question is this, I know that injectors from a nissan 280ZX are direct bolt in and have almost double the flow capacity. I planned to run them when I finally switch to a megasquirt ecu for tuning purposes. What I need to know now is if the stock ecu can properly manage the nissan injectors, can I get the nissan ones now and run them without the megasquirt?

Edited by SiriusBlack

Share this post


Link to post
Share on other sites
Posted (edited)

Is the regulator bad? You can get a cheap-o inline gauge to check it.

 

With new injectors you will double the fuel going into the engine. Most stock ECUs will only trim 20% fuel before throwing a code. 

 

To clean injectors is easy. Take them off. Get some carb cleaner with a spray straw, a 9v battery, and some test leads.

First make sure the input side is clean, and open. Lots of injectors have a tiny screen inside the input side. They will pull out.

Hook the leads to the injector from the battery, and then spray the carb cleaner down the injector. You should see some come out the other end slowly. Some times you gotta seal up the input side to the straw with your fingers to get it though. Make sure you're wearing safety glasses.

 

Also if you do one type of injector a lot, you can rig up an injector cleaner. Find an old intake and fuel rail, and rig a pump to flow cleaner though the injectors. I've done this with ford injectors for ages.

Edited by Ionstorm66

Share this post


Link to post
Share on other sites

If it could be fuel pressure, T in a mechanical gauge. 
On one of my SPFI cars, the regulator died, dropping the pressure, and it would starve for fuel.  All kinds of bad though, idle ok, sometimes, sometimes not.  Barely could get any power.  

Of course, I made the mistake of assuming it was the fuel pump and replaced it, only to find I still had the problem.  Swapped another regulator from one of my spare engines, and it was a lot better.  Initially it would only handle about 3/4 throttle, so I bought a separate add on regulator, planning on setting it up and I'd be able to adjust the pressure.  Then one day before I actually installed it, I was driving, and discovered I had full range of throttle working.  So far, it still is.

Share this post


Link to post
Share on other sites

Ok , I suggested to T in a fuel gauge, or I used an old mechanical oil pressure gauge. Dave suggests to do the same. Think I suggested just after the fuel filter. Dave hasn't said where, but when you think about it, once you know pressure at fuel filter, somehow you want to check on the injector side of fpr

Share this post


Link to post
Share on other sites

@DaveT I had thought about replacing the pressure regulator, but it doesn't lack power once you rev the engine a little. It revs happily, just has a really crummy idle that also kills it once in gear.

Share this post


Link to post
Share on other sites

Ah, yes, that doesn't make me think low pressure. 

Share this post


Link to post
Share on other sites

Need you to differentiate revs happily past idle in gear, stationary, foot on brake or driving out on the road?

If you get it driving on road at normal road speeds and loads, how does it all go?

Is this query currently just the same as you started this post three pages ago?

Sitting in car all ready to go off , operating temp, you select D and idle goes bad, stalls??

If you left footed the brake, right foot the juice to keep a higher idle, prepared for a WHACK THUMP into D, keep higher idle, could you drive off merrily or even as if you stole it, or it giving you the pips and hate it. Would it give you no trouble until you come to a stop?

Or will it give you grief backing off down a hill?

Share this post


Link to post
Share on other sites
Posted (edited)

It wanders when in idle and in P or N. Wanders up or down about 200 rpm. If I put it in gear without feathering the throttle it struggles then dies. If I double pedal it I can keep it running while in gear. If I hold the brake and throttle it up, then throw it into gear the engine is fine. It spins the wheels then goes just fine. I've never gotten it up to highway speeds as it isn't licenced, I've gotten it up to 30 MPH on my own land. No studder or backfire when I throw it into gear with the engine throttled up and I release the brake.

 

As far as we can tell there is absolutely nothing wrong other than the idle. We believe that the fact that it dies when put into gear, is simply the engine being unable to handle the load of the transmission due to the crummy idle.

Edited by SiriusBlack

Share this post


Link to post
Share on other sites

You have checked everything people have suggested.

If you have plated the EGR and left it plated, plugged off the PCV by capping it and leaving it capped, plugged off FICD between thermostat housing and intake....

What else have we got...?

Cap off the booster and vacuum ports you have nowhere but the throttle body to leak air to change speed at idle...

So then it has to be the load of the transmission causing speed to drop...yeah?

Your idle speed don't go higher than your set speed does it?

Rather drops with load of P and D and goes back to your idle set speed?

Share this post


Link to post
Share on other sites

It does go higher than my set speed.

When it's cold it idles around 2200 rpm and goes down as it warms up. Once warm it idles around 1200 because if I try to set it lower it dies immediately. When idling at that 1200 point it wanders up and down. Rarely steadying at any point.

Share this post


Link to post
Share on other sites

Crumbs !

The idle speed numbers you give help us understand better.

I think you can get an idea of how the O2 sensor is running by reading the ecu led in the side. Wonder if I am correct and you find that info in manual.

Sounds like it is possessed !

Share this post


Link to post
Share on other sites

Since the idle tried to smooth when we increased the fuel pressure, I plan to pull the injectors and clean them again. Then I'm going to completely flush the steel lines on top of the manifold that feed them fuel. After that I'll go from there.

Share this post


Link to post
Share on other sites

Tore it apart now to install new injectors. When tearing it apart I found a rock hard and busted vac line with an orifice behind the power steering pump. I replaced that, but will go ahead with cleaning the fuel rails and installing the new injectors since I have it apart anyway. I suspect that line could have been the issue, it would have created a vac leak.

  • Like 1

Share this post


Link to post
Share on other sites

Sadly I've failed again.

I got it all put back together with the new injectors and that vac line fixed. It still has the same issues. I'm going to try and get a video of it running, which I will then post on the Facebook USMB counterpart. Hopefully that can give you guys some more info. In the meantime I'm pretty much back to square one and would appreciate any other suggestions.

 

Here is the link to the videos.

https://www.facebook.com/groups/UltimateSubaruMessageBoard/permalink/3525592547503216/

Edited by SiriusBlack

Share this post


Link to post
Share on other sites

Upon further testing, we believe the problem is caused by something in the electrical system. More specifically the ignition pulse. My tachometer goes up and down all over the place without the engine speed actually changing. The ECU receives info from the tach and adjusts the engine from that info among other things. We hope that if we can fix the tach, it might help the idle.

Any info you all might have on the digital tach, ignition system and ignition pulse specifically would be a big help.

Thanks in advance.

Share this post


Link to post
Share on other sites

Seen bad leads make some other makes tacho bounce and carry on. NewHT lead fixed

Share this post


Link to post
Share on other sites

We are now looking at replacing the disty. There is a new one on rock auto, but it lacks both the vac advance, and the 5 connectors under the cap that mine has. Is anyone able to tell me if it'll work anyway?

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×