86' Won't Tolerate a MAF after ~15 mins??

[Foreverzero]

The Problem:

 

* The car will start up, idle, and run fine but after 10-15 mins or less, it will become completely undriveable. Idles very low, bucks a little bit, and wont' accept any input from the accelerator.

* Since the car is an 86' I've been running with the MAF unplugged which cures that problem completely but invites another....

---> With the MAF unplugged, the throttle response is kinda poor, and it's running pig rich

 

 

The Rundown:

 

* The car is an 86' wide body with...

• HRC Super 16G
  
• 2.5" Aluminum Hardpiping, HKS SSQV, & moddd stock intercooler
  
• 3" Turbo Back, Ported Manifold
  
• MBC set at ~13psi
  
• few other misc things that don't affect airflow

* Plugs, wires, injector clips, MAF, have all been recently replaced so I know none of them are the culprit. (Even the MAF and IAT pigtails are a-ok)

* Compression is fine, head gasket is fine, NO boost leaks ( A loooot of maintenance has been done on this car)

 

 

With that being said, I'd really love to get my response and MPG (crappy as it is) back. I can't think of anything that would cause something like this BESIDES possibly my O2 sensor. I'm no genius when it comes to our stoneage EFI so I wanted to get some input from you guys as to whether or not a faulty O2 could possibly be the cause or whether or not I'm overlooking a crucial element.

 

Thanks for reading and I'm looking forward to hearing all of your input

[Komeuppance]

First, you NEED to have the MAS plugged in for your car to operate properly. Just because it runs without it plugged in is not a solution.

 

I was going to say boost leak, but it seems you've already tested for that. With it running that rich, I'd be weary of your oil's condition being over saturated with fuel.

 

Do you have your MAP sensor (aka Pressure Sensor, black box on the firewall above the brake booster) connected properly?? The vac line should run to the altitude sensor (aka Boost Solenoid, small black cylinder with three vac ports next to the brake booster). The altitude sensor will have a vac line that runs to the intake manifold just below the throttle body. It should be connected to a vac port closest to the firewall.

 

If you still have your stock boost gauge installed you can see if the MAP sensor is working correctly.

 

Got a pic, thanks to Couth:

http://img25.imageshack.us/img25/6207/dscf00801272096.jpg

On the left (with blue spade connectors is the solenoid[substituted] and the right is the MAP sensor)

 

That is what I would rectify first. After that, you need to check to see your CTS (coolant temp sensor) is working correctly, and then do a proper TPS/ISC reset.

 

-Robert

[Foreverzero]

Thanks for the quick response, the pic was helpful too. I checked and verified that the MAP and Altitude sensor's vacuum hoses are running to their designated ends and that there are no holes in the hoses. I know the car is designed and built to run with the MAF plugged in, but the car has had this problem for so long, and it's been my daily the whole time, so I haven't had much of a choice but to go with the lesser of two evils and run the car as is. Till now of course.

 

I have no idea how to check the integrity of the Coolant Temp Sensor or how to correctly do a TPS/ISC reset...

[Komeuppance]

The reason you have terrible throttle response and it's running rich is because there is no MAS. The only way to fix that is plug in the MAF.

 

Re-reading your post it seems that your CTS is faulty. To check it you will need to have the engine fully warmed up, and use a multimeter to test the resistance. It should read 296ohms at 176F, 1.1Kohms at 104F, and 2.5Kohms at 68F. The ecu must be off or connector removed from sensor to test this. You can also remove the sensor and put it in hot/boiling water to test it's resistance.

 

http://starquest.i-x.net/viewtopic.php?t=1097&sid=37ddfca34169f3d18f76ba1dc03d90b4

Study this post describing the sensor, testing procedure is on the 7th post from the top.

 

-Robert

[Komeuppance]

TPS/ISC Reset procedure (copied straight from the FSM):

http://www.starquestclub.com/forum/index.php?showtopic=27979

 

This must be done with the MAF plugged in, and the timing set correctly (vac advance unplugged) at 10BTDC.

 

Here are some good resources for you to study and reference:

SQ Frequently Asked Questions

 

S.O.S. Manuals (How to with pictures, just ignore the delusional old man ramblings)

 

1986 Factory Service Manual

 

Keyword Search

 

-Robert

[jayro]

what about ur fuel pump? could be on its way out because mine was super rich and would die out after 15 mins. after a while it moved to 10 to 5. swapped it out and it was fixed. just a thought after you do the tps isc reset

[Indiana]

When it starts to run like crap, unplug the CTS and see if it changes. CTS adds in fuel for cold motors like the choke on a carburetor. Its not to add in more when its hot and when they go bad they can.

 

It might also be the wrong plug is on the CTS, the plug has a black wire in it.

 

CTS has the end molded in the plastic in an oval shape.

http://www.b2600turbo.com/images/ECICTS.jpg

 

 

[Foreverzero]

Komeuppance, thanks again for the fast and detailed response. I had no idea there was this wealth of documented information in the S.O.S. manuals. I'm pulling the CTS sensor tonight and having a friend with a multimeter come over tomorrow afternoon to test the resistance in a pot of hot water.

 

 

Egg ---> Face ..lol

 

Indiana, thanks for that pic. Don't know if I would've been able to find the CTS without it

[Indiana]

they can check out with that test good but when installed in the intake if they are bad or cracked and failing the resistance isn't changing the voltage back to the ECU so it can still cause problems. You can start up the motor and run it and check resistance there no need to use a pan of water. What happens as its warming up is what matters. Sometimes once its completely warmed up its ok its just getting there.

[Foreverzero]

they can check out with that test good but when installed in the intake if they are bad or cracked and failing the resistance isn't changing the voltage back to the ECU so it can still cause problems. You can start up the motor and run it and check resistance there no need to use a pan of water. What happens as its warming up is what matters. Sometimes once its completely warmed up its ok its just getting there.

 

Hmmm I see. Would it be wise for me to still test it then? The problem doesn't cease when the car is completely warm. Much to the contrary, it only starts once the car has been running for a few minutes and has reached normal operating temperature.

 

Does my original suspicion of the 02 Sensor seem like it's worth checking out or ?

 

Also, if I'm reading the S.O.S. manual correctly then I should be removing the CTS's 2nd Terminal with the Yellow/Green wire to test the resistance, correct?

[Metric-man]

A couple Simple things to check to help you decide where to start

 

From what you describe on the MAP sensor connections your cars production date is after June of 85 and before June of 86 .

 

Checking engine electrical self Diagnostic port

(ECU error codes)

 

 

http://img208.imageshack.us/img208/2935/tbifuelturbocharging038.jpg

 

http://img832.imageshack.us/img832/8533/tbifuelturbocharging039.jpg

 

http://img209.imageshack.us/img209/3134/tbifuelturbocharging040.jpg

(Fault code #4 is not applicable to Starion/Conquests)

 

 

 

For 87 and newer Starquests... (still a good tip)

http://www.starquestclub.com/forum/index.php?showtopic=28043&view

 

 

 

Voltage and pin outs on the 86 ECU, (only for those confident/competent with an electrical Multi-meter)

Caution must be used while accessing the pin outs on the ECU,

because of the possibility of shorting out the circuity and rendering the ECU to be unusable (junk)

 

http://img413.imageshack.us/img413/4067/tbifuelturbocharging037.jpg

This also lists the alternate diagnostic port pin out location for 85.5 and 86 Intercooled ECU's

 

 

ECU pin out locations

 

http://img190.imageshack.us/img190/8166/tbifuelturbocharging048.jpg

 

 

http://img211.imageshack.us/img211/7405/tbifuelturbocharging049.jpg

 

 

http://img141.imageshack.us/img141/4530/tbifuelturbocharging050.jpg

 

 

http://img708.imageshack.us/img708/1949/tbifuelturbocharging051.jpg

85.5 and 86 intercooled ECU pin outs are the same*.

 

It is best to only check the O2 sensor after the car has warmed up,

and has gone into closed loop mode.

One way to determine if the vehicle's engine is at a sufficient operating temperature,

is to check the upper radiator hose, and if it is hot and coolant is flowing through it,

your car should have gone into closed loop, meaning the O2

(oxygen sensor is being used by the ECU to determine which programed fuel map should be used,

in determining how much the fuel injectors should work).

 

The flashing that is mentioned in the above link*, is because the stock O2 samples on a narrow electrical scale between

0.4 and 1 volt, to be more accurate it is best to use an oscilloscope to view the actual width and strength of the current,

because an O2 can test good on voltage but still be faulty because it can be out of frequency range to be effective.

The most direct way to test the O2 sensor is back probing the sensor's connector with a long T pin being careful not to short the sensor out,

and using a small alligator clamp attached to your voltage meter (Multi-meter)

 

If unsure if your O2 is giving false positive readings and an oscilloscope

is not available you can try replacing the one in question with a known good one.

If you do not know the history of the one currently being used it is a good idea to just go ahead and replace it,

because they do wear out and can become lazy and or inaccurate with mileage and use.

 

Coolant leaks are notorious for shortening their life spans in which they should be good for about 60,000 miles in normal use.

Carbon deposits accumulate on their outer casing and they can be cleaned by wiping with a cloth or compressed air but,

manufactures discourage using harsh chemicals to clean them, (after all they are suppose to be sensitive electrical instruments).

 

There are 2 and 3 wire o2 sensors available that use voltage to preheat the sensor's element,

but they are not read any faster than the single wire oxygen sensors,

because the Ecu still waits for the CTS to reach its operating temperature before switching over

to the O2 sensor for fuel management although the preheated sensors can be more accurate during cooler ambient temperatures for initial cold start ups, but these should not be confused with wide band oxygen sensors that are available,

for after market fuel ratio meters used for fuel management devices; stand alone ECU's and piggybacks.

 

I would recommend testing your CTS as Robert has suggested,

I would also recommend you testing your upper radiator coolant thermostat, and be sure it is with in the correct temperate range for your current weather conditions because the CTS has difficulty reaching temp if the thermostat opens prematurely and does not allow enough time for the coolant to circulate and warm the CTS to specifications.

 

Info about running with out the MAS in a 86

http://www.starquestclub.com/forum/index.php?showtopic=28102

[Komeuppance]

Error code #4 is applicable to pre 86's.

 

-Robert

[Foreverzero]

Well I just got done testing the CTS. We checked the resistance at multiple temperatures before and during startup (with it unplugged of course) and couldn't get a reading off it at all. Just had the OL displayed. I take it this means the CTS is completely broken.

 

 

On a side note, do the CTS's readings still matter when the car is completely warm and running or is it just a mechanism for use on startup before the O2 has warmed up?

[Komeuppance]

CTS is integral for the fuel mixture at almost all operating temperatures besides COLD.

 

Autozone or similar will have one in stock most likely, for $20. You could also get an OEM one which is about $40+.

 

-Robert

[Foreverzero]

CTS is integral for the fuel mixture at almost all operating temperatures besides COLD.

 

Autozone or similar will have one in stock most likely, for $20. You could also get an OEM one which is about $40+.

 

-Robert

 

 

Aah I see. Well I'm gonna go pick up a new CTS and probably a new 02 as well. I'll update this thread in about a week whenever I get the parts in and see how everything turns out. Fingers crossed :X

 

 

Komeuppance and Metric-Man, I'm always astounded to see how our community goes out of it's way to post not just a one sentence response to ailing members but full, informative, posts with scans, links, and educational material to really help him or her. Thanks much you guys

[OPTIMUSPRIME]

http://www.bitcore.org/stuff/Knightrider_turbo.gif

 

Foreverzero LOOOOOOOOOOOOL

This is what happend when you fix the CTS

Edited February 15, 2011 by OPTIMUSPRIME

[Indiana]

I'm always astounded to see how our community goes out of it's way to post not just a one sentence response to ailing members but full, informative, posts with scans, links, and educational material to really help him or her. Thanks much you

 

 

How about this one...

 

 

83-86 fuel systems

http://www.b2600turbo.com/images/151.jpg

 

87+ fuel systems

http://www.b2600turbo.com/images/14-14.jpg

 

Its the 02 for this ECU you need to be concerned about. The CTS you could do without. Want to test that? Its easy just heat up the car and unplug it then wait till its cold the try and start it with it unplugged. It can't be a bad sensor but none is better than a bad one. You've got an 86, get the injectors out and have them cleaned you have two that may be leaking and spraying poorly and they are larger than a primary from an 87+ so you have a problem twice as bad if they are dirty.

[Cloud81918]

Sorry to steer a bit off but I have an 86 as well and my boost soleniod is broken. Where can I find a replacement or the substitution?

[Komeuppance]

You can use on of the solenoids off the throttle body for the EGR system. It has a yellow paint dot marking it, with three ports, just like the original one.

 

Thanks to couth, we have some pictures of it:

Did you make sure the solenoid valve next to the pressure sensor is good? I had similar problems and here is my solution.

 

The old valve was dead ( I put 12v on it and it did not click).You can put your finger on the valve while the car is at idle to feel it click on/off every so often.My '86 ran like crap, kinda like what you discribe....so I decided to use the valve that was use for the emission control stuff.

http://img27.imageshack.us/img27/8836/11258637.jpg

http://img25.imageshack.us/img25/6207/dscf00801272096.jpg

 

Now my car run like a champ.

 

 

-Robert

[Foreverzero]

 

Its the 02 for this ECU you need to be concerned about. The CTS you could do without. Want to test that? Its easy just heat up the car and unplug it then wait till its cold the try and start it with it unplugged. It can't be a bad sensor but none is better than a bad one. You've got an 86, get the injectors out and have them cleaned you have two that may be leaking and spraying poorly and they are larger than a primary from an 87+ so you have a problem twice as bad if they are dirty.

 

Whoa it's like a cheat sheet! Those are now saved to my hard drive I'm definitely going to be replacing the 02 to see how that goes. The injectors were out last summer when I replaced the injector pigtails and they were both in good shape. Perhaps there's something else I haven't thought to consider

[JohnnyWadd]

How come the service manual does not have the part where you ground the throttle body as part of the ics reset?

[Indiana]

How come the service manual does not have the part where you ground the throttle body as part of the ics reset?

???

 

There's a slightly difference procedure for the 84-86 idle set you'll need the service manual for that. You have an 86?

[JohnnyWadd]

???

 

There's a slightly difference procedure for the 84-86 idle set you'll need the service manual for that. You have an 86?

 

No i don't, its part of checking the nose switch on the the ics.

[Komeuppance]

It's called the idle switch in the FSM, and there is a separate test and set procedure for it.

 

-Robert

[87Jassic]

i guess this never got fixed.