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Strange running 930 after engine rebuild. Thoughts?

I would like to ask the 930 turbo experts for help in diagnosing my poorly running engine issues.
It is a 1987 930 turbo all stock except for a 1 bar boost spring and an adjustable BL-WUR.
This past winter I had a local wrench rebuild the top end of the engine as I had a broken head stud. The car ran surprisingly well even with the broken stud. I installed an Innovate wide band A/F gauge about a year ago and before the rebuild the engine would idle at 13.8, cruise at 14.0 and while under boost run 12.3 plus or minus .2 so it never ran what I would consider lean. I had the A/F gauge on there for a while before rebuild so I know how it ran before all this.
Now after the rebuild it runs lean. I have the idle set to 13.8 and it idles at 950 steady as a rock. When I press on the throttle jus a little bit it immediately goes lean to 16.5 Ė 17.0 and wonít have good throttle response at all. Not drivable at all. All this is taking place while parked and is no different while driving. I donít run it as its way to lean for a turbo. It also will pop when you try to give it more gas pedal.
I checked the WUR and itís right on spec. I even removed the adjustable BL-WUR and installed my stock non adjustable one and it ran the same. So itís not the WUR
Fuel specs are 6.75 bar system pressure.
Non adjustable WUR:
2 bar at 50 deg F cold pressure
3.9 bar warm up pressure
2.9 bar @.5 bar pressure on the boost port.
These specs are the same before rebuild and it ran great.
Timing is set to 2 deg BTDC vacuumed hose installed.

So my question is what would make it go lean just off of idle and stay lean through out to WOT?
Keep in mind this engine has maybe 2 hours on it.
One thing I noticed is there was no vacuum on the hose that hooks to the outside of the pot on the dist. shouldnít there be some vacuum at idle on this hose?

Iím wondering if there is a vacuum leak somewhere.

OK fellow Pelicans what do you think it is?

Old 04-05-2013, 06:34 PM
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If you had a serious vacuum leak I would think your idle AFR would show it as well, but maybe not. Try squirting starter fluid or brake cleaner around all the intake injector blocks. Perhaps your wrench over-torqued them and cracked a couple to where they're sucking air.

Couple other thoughts: I wonder if the metering arm is moving freely. Almost sounds like it's not, since you go instantly lean when pressing on the gas. If the arm doesn't pull down in response to air flow then you wouldn't be getting the fuel needed. Don't know why this would be affected by a top end rebuild, though, but you never know. Pull off the air cleaner and push down on the metering plate to see if it moves freely. And/or, start the car up and push down on the mixture adjusting screw to where it contacts the metering arm and push further to see if your car will stumble from being overly rich.

One other thought: There is a frequency valve back behind the fuel distributor that's part of the Lambda system. If perchance your wrench had unplugged the wiring to it, you will see a very lean condition that cannot be corrected with any amount of adjustment. Do a listening check: Turn the key but don't start the engine. Force the pumps to run by pulling the green connector behind and on the left side of the fuel head (it connects to the metering arm via a micro switch). Pulling the plug will make the pumps come on as well as the frequency valve. You should be able to hear the valve's obnoxious buzzing. And while doing this test, go up front and pull each fuel pump relay one at a time and listen for the affected pump to stop running....just to confirm that both pumps are operating.

That's a start, anyway. More help to come I'm sure.
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Old 04-06-2013, 05:53 AM
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Have you verified ignition timing?

Edit: see that you are 2 degrees BTDC at idle vacuum hose connected. Depending on year, the test should be done with the hose connected, or disconnected...there should be a sticker in the engine compartment that denotes the spec for your car.

What about firing order? It's pretty easy to mix up a spark plug wire or two.

Start with the easy stuff.
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Last edited by jwasbury; 04-06-2013 at 06:31 AM..
Old 04-06-2013, 06:26 AM
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Quote:
If you had a serious vacuum leak I would think your idle AFR would show it as well, but maybe not. Try squirting starter fluid or brake cleaner around all the intake injector blocks. Perhaps your wrench over-torqued them and cracked a couple to where they're sucking air.

Couple other thoughts: I wonder if the metering arm is moving freely. Almost sounds like it's not, since you go instantly lean when pressing on the gas. If the arm doesn't pull down in response to air flow then you wouldn't be getting the fuel needed. Don't know why this would be affected by a top end rebuild, though, but you never know. Pull off the air cleaner and push down on the metering plate to see if it moves freely. And/or, start the car up and push down on the mixture adjusting screw to where it contacts the metering arm and push further to see if your car will stumble from being overly rich.

One other thought: There is a frequency valve back behind the fuel distributor that's part of the Lambda system. If perchance your wrench had unplugged the wiring to it, you will see a very lean condition that cannot be corrected with any amount of adjustment. Do a listening check: Turn the key but don't start the engine. Force the pumps to run by pulling the green connector behind and on the left side of the fuel head (it connects to the metering arm via a micro switch). Pulling the plug will make the pumps come on as well as the frequency valve. You should be able to hear the valve's obnoxious buzzing. And while doing this test, go up front and pull each fuel pump relay one at a time and listen for the affected pump to stop running....just to confirm that both pumps are operating.

That's a start, anyway. More help to come I'm sure.
Mark: The metering plate moves freely like a ballance beam scale and once there is pressure on the system when the pumps are running there is a slight pressure or stiffness to the metering plate. I think thats normal? Anyway it feels the same as when it ran well before rebuild. I will check the intake blocks for cracks / vacuume leaks. I know they are new and hope there not cracked from overtightening. I will check the frequency valve. I don't remember any noise comming from that area. The only noise I could hear was the pumps.
I did check the pumps and both are running. If there was only one pump running wouldn't the system pressure be low? I want'ed to spray something on the intake blocks but worry about a fire. Is there a way to hook up a vacuume guage to the engine and see if the vacuume is correct? If there is what should the reading be?
The mixture screw on the fuel dist.will change the engine speed and seems to work as it should. One note though with reguards to your first line about the idle being affected by a vacuume leak, the idle screw seems like its close to being bottomed out like 1/4 of a turn from being bottomed out to get the idle to 950 warm. Isn't that an air bleed screw? That may point to a vacume leak as It wasn't like that before. I wonder just how much of a vacuume leak it take to get an engine to run lean like this? Seems like it needs to be quite a large leak to have an effect like this but not sure. The reason I say this is avery one of the old intake block were cracked and the engine ran good. By the way I did check the AAR and it works as it should. Compleatly closed after about 3 or 4 min and no leaks there.

Jwasbury: I will check the firing order but I think it runs to good at idle ( like before rebuild) to be out of wack but will check anyway just to scratch it from the list. Ing. timing is supposed to be 26deg at 4000 rpm. The starting point is 2deg at idle. I know this from the before rebuild settings. It's close like plus or minus 2 deg as it sits now.
Keep the ideas comming and I will check them one at a time. I'll keep you posted.
Old 04-06-2013, 07:34 AM
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Update:
Ok Sprayed starting fluid in the vicinity of the intake blocks and instantly the idle went down as the A/F ratio went to 10.1 from 13.1 (cold engine) pig rich. This is with the air cleaner and IC on so couldn't pinpoint the exact location of the vacuum leak. I'll remove the IC and air box to pinpoint the leak. Question. I never ran the engine with IC and air box off. If I block off the AAR I should be OK to just idle the engine to check it right? Or is there anything else I need to do?
Old 04-06-2013, 08:35 AM
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Quote:
Originally Posted by DeFreest View Post
Question. I never ran the engine with IC and air box off. If I block off the AAR I should be OK to just idle the engine to check it right? Or is there anything else I need to do?
Without the IC hooked up, there will be no air drawn down through the fuel distributor metering arm and since it won't deflect, the fuel pumps won't run and the fuel distributor won't open up the necessary ports to send fuel to the injectors.

With some creativity a person can hit the local hardware store and scab together the necessary parts to link the throttle body intake with the fuel distributor housing. I've seen a few posts here for that but would have to do some searching.
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Old 04-07-2013, 09:29 AM
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I may not have to run it with IC removed. Just finished removing IC, Air box and BOV housing and found all of the intake manifold nuts were loose. When I say loose I mean 1/2 of them were backed off 1/3 of a turn and the rest were just barley tighter than finger tight. So my next question is if these were torqued to specs would they have loosed up in 2 or 3 hours of run time? I think not. Has anyone tightened up the manifold only to have them loosen up that much? The intake block and gaskets are new and I was told they were Porsche parts. Your thoughts please?
Old 04-07-2013, 10:47 AM
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tighten them up see how it runs. might be super easy solution
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Old 04-07-2013, 11:19 AM
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I could do that but I a little peeved right now as I just spent a lot of money to have some one do this. I have to wonder what else is loose. Not something you want to find right after a rebuild. OK I looked but can't find the torque specs for the manifold. Anyone know what the proper torque is for the nuts on the manifold?
Old 04-07-2013, 01:28 PM
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Quote:
Originally Posted by DeFreest View Post
I could do that but I a little peeved right now as I just spent a lot of money to have some one do this. I have to wonder what else is loose. Not something you want to find right after a rebuild. OK I looked but can't find the torque specs for the manifold. Anyone know what the proper torque is for the nuts on the manifold?
torque specs
Old 04-07-2013, 01:53 PM
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Ronnie's.930
Thank you.
Old 04-07-2013, 01:59 PM
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And FYI- as I recall, several of them won't be reachable with your torque wrench socket setup, so get a feel for what 18 ft lbs feels like with a box end wrench on some of the easy ones so you aren't way off on the ones you need it for.
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Old 04-07-2013, 02:10 PM
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Personally, I would be super pissed at the wrench that you paid good $$$ for a "quality" job. No excuse, those should not just back themselves out if they had been properly torqued in the first place.
Beyond all that, it does appear you've found your problem. Every cloud has a silver lining after all.
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Old 04-07-2013, 03:20 PM
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Update, Tightened up the manifold, rechecked the timing and noticed that the vacuum hose, the one that has a vacuum on it at idle, was connected to the retard side of the Dist. vacuum pot. Moved it over to the outer vacuum port and swapped the boost hose to the retard side of the pot. Runs better but not as good as before the broken head stud. I'm not impressed at all with the rebuild and all of the rookie mistakes that were made so contacted the owner of the garage and will drop the car off. This has got me really pissed off. The owner is a good guy and I know he will make it right but it hard to keep calm.
Thanks in advance for letting me vent.
I don't know how SCHNELE did it!
Old 04-13-2013, 02:02 PM
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Yes let him go over everything, maybe he rushed it. Timing, fuel pressure, air leaks etc. I would be pissed also but just be a little patient ,maybe you will learn some things as you stand over his shoulder this time.
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Old 04-13-2013, 02:41 PM
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What's your timing at at 4000 RPM? If AFRs are good, there isn't too many other easy things it might be (i.e., cams are not timed correctly?)
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Old 04-14-2013, 04:15 AM
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I have been diving into it more and have found this.

Ing. timing is confusing. Starting point for a 930-68 USA is supposed to be 1 +/- 2 deg ADC and final is 26 +/- 1 deg BTDC. at 4000 RPM. I don't have someone to help this week so I cant check 4000 RPM. Doesn't matter because I runs so bad I'm afraid to rev it to 4000. Seems to run better when I turn the distributor all the way to the end of the slot. Dist turned CW to the end of the slot. Throttle response is good. but timing marks off when I check it with a timing light. Around the mid point between TDC and the 26deg mark. Also the vacuum line that has actually has a vacuum on it with the engine warmed up was connected to the retard side of the pot. The side closest to the dist. housing. I switched that around to the outside of the pot away from the dist body. Not sure but if they placed the distributor of by one tooth would that have the same effect? Don't know about the cam timing. He says he has it right but he did say if was off when he checked the engine before rebuild. Not sure about that either as if he cant set the timing right what's to say he has the valve timing right. What a mess.
Old 04-14-2013, 08:00 AM
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I also don't have anyone to look at the tach and tell me when the motor is spinning at 4000 rpm while I'm back there working the throttle by hand in the engine compartment.
It needs to be up to 4000rpm because checking the ignition timing at 4000 rpm with the vacumm hoses disconnected from the distributor is only checking the total centrifical advance.
There is no more centrifical advance above 4000rpm because it is maxed out by then.
This is what I do and maybe it will work for you.

I sit in the car and rev it to 4000rpm and I listen and try to remember the sound of the motor like a musical note or pitch at 4000 rpm. Then I go back and rev the engine up by hand on the throttle butterfly linkage and listen for the same engine sound or pitch to the rpms while watching the timing light to read the igntion timing.
To make it easier you can rev it to 5000 rpms and the timing wil be the same as 4000 rpms because the centrifical advance is already maxed out and won't go any higher. So, if you're reving up it by ear like I do, go a little higher than 4000rpms to check maximum centrifical advance just to be sure. It won't hurt anything and the timing will be exactly the same.

As far as your distributor vacuum pot hose locations, on an '87 distributor the vacuum hose that has vacuum at idle should be on the vacuum retard pot like it was. Thats the one on the right closest to the distributor body.
You said you changed that hose to the other one which is the vacum advance and boost retard pot so you now have it wrong.

The vacuum retard line only has vacuum up until around 1500 rpms and then it goes away because the edge of the throttle butterfly changes in relation to the tiny hole in the throttle body bore above that point so it no longer has vacuum similar to intake manifold vacuum there.
It's purpose is to retard timing at idle and during closed throttle deceleration to lower exhaust emissions and heat up the catalytic converter. It does that because retarded ignition timing has higher exhaust temperature.

You should put the hoses back where they were because the way you have it now you no longer have vacuum advance to give you more power during acceleration and you may not have boost retard any more and that could easily damage the motor under boost.
Old 04-14-2013, 08:54 AM
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Quote:
I also don't have anyone to look at the tach and tell me when the motor is spinning at 4000 rpm while I'm back there working the throttle by hand in the engine compartment.
JFairman, Thanks for the idea. I'm not sure I could reach the throttle linkage as I have the stock air filter housing and inter cooler and there no room anywhere to reach by hand. You have a custom air filter?
What's your thoughts on the timing marks? I can set it close but the closer I get to the recomended timing the worse it runs. Timing is set to 1 deg ATDC at 900 RPM per the factory manual on section 10-02 for a 930-68 engine. With this setting, as before the rebuild, it was very close to the 26 deg BTDC with hose disconnected. When it's set to this timing is runs like crap. Before rebuild it ran good. Mind you this is all with the car parked and not on the road. It runs so bad ,lean and no throttle response until you get it to 4000 range of RPM where it comes to life but still lean. Fuel pressure and volume are good.
I think gsxrken was right when saying ignition timing or valve timing. I originally thought it was the loose intake manifold but that was only part of the problem.

Thanks for clearing up the vacuum hose for me I will switch them back but I know it's not the whole problem.
Old 04-14-2013, 10:07 AM
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Yeah I remember how weak they are with stock 1987 ignition timing. Is idle timing 1 degree ATDC with both vacuum hoses connected? It's been so long since mine was stock I don't remember what the origonal stock timing was at idle.

I have a K&N air filter on the CIS air flow meter instead of the origonal air cleaner so access to everything is easy.

If the origonal red fabric colored vacuum advance hose is still on there replace it with a new hose because they dry rot and crack under the fabric covering and you can't see that it has cracked. Then it leaks vacuum and doesn't do it's job. The origonal vacuum retard line is covered with blue fabric. They don't last and if they are still there they should probably be replaced.

I've modified the centrifical advance curve in my distributor and installed an MSD 8760 boost timing retard box with MSD 6al ignition. It makes a huge improvement in low rpm torque and drivability in these cars below 3000rpm.
My timing at idle is around 12 to 15 degress btdc. Steady cruise it's around 34degress btdc and during boost it's about the same as stock, right around 26 to 28degrees btdc. I also have WMI to reduce any detonation. E10 93 octane gas quality varies alot too.

Optimum ignition timing and aftermarket air cleaners have all been covered a bunch of times in previous posts. Some searching on ignition timing, MSD ignition, and K&N or fabspeed air cleaners on this forum will probably find all the information eventually.

Something you could easily try is just leave the vacuum advance line connected to the vacuum advance pot and remove the vacuum retard line from the retard pot and plug it with a small bolt or screw or just leave it hanging for a test.
Then check the timing at idle and see if it advances and idle speed comes up. That should help drivability a bunch right there and you'll still have the same boost retard if the vacuum advance line and pot are working correctly.
Like that you'll still have centrifical advance, vacuum advance, and boost retard and some more power and better gas milage below 3000 rpms.

Check the timing though to make sure everything is still in a safe range.

The vacuum retard line and vacuum retard pot only work to retard timing somewhere around 10 degrees from idle up to around 1500 rpms and during closed throttle deceleration at any rpm. It is for lower emissions and other than that they do nothing at all.
With your current 1 degree atdc at idle you could probably get out and run faster than the car will leave from a stop. I remember what it was like...

Old 04-14-2013, 11:18 AM
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