95 GP intermitant miss OBD1.5 question

[Galaxie500XL]

Someone else correct me if I’m mistaken, but I think you have the roles of the 3x and 24x swapped. I do know from an unfortunate personal experience on a very rainy July day that a bad 3x crank sensor will stop an LQ1 cold. 

[matt1970]

Daughter blew the solenoids in her honda transmission so sons gp was pushed back.Last Thursday figured it was a simple 15 minute fix so with his car at the end of the driveway started pulling the sensor.The metal tab pops off intermediately then the plastic just crumbled as I tried to pull the stuck sensor out.The few breaks when  it wasn't thunder storming,sleeting or hailing I would go out and fight with it.Soaking it with PB Blaster and a bit of blood from the exhaust shield repeatedly over 2 days and a pair of vice grips finally pulled it out.The new one is installed but the pigtail feels loose.My son test drove it 5 miles down the highway then shut it off for 10 minuets.when he restarted it had the same miss.If you don't feather the gas pedal it dies when you drop into gear.He was only half way to running temp but like before if you wait another 15 minute it started up fine drove home and died as he pulled into the driveway.I have a new pigtail but after that I am out of ideas again.

[matt1970]

Gallaxy500xl I tried starting the car with the sensor unplugged (just curious) and there was no spark so you may be right.

 

So far knock on wood it has not acted up again. The pigtail was loose because the silicone gasket fell off the plug during the repair I found it in the driveway.I snaked the sensor wires out of the engine bay to replace the pigtail.What was left of the plastic wire loom crumbled and fell off into a pile of debris.One of the wires where it runs along the oil pan gasket had been rubbing and wore the insulation off.Looks like it was randomly grounding the sensor wire.

 

Thanks to everyone for your impute! Hopefully this thread is done.

[matt1970]

Unfortunately it did it again......

The pattern is:

drove it 15 miles to work.Let it sit 8 hours drove home with no issue.

Next day drove to work, went to lunch 5 hours later no issue.

drove home 3 hours latter and it was cutting out and died at red lights on the drive home.

 

I was looking online reading forums.I saw several people had similar symptoms and the issue was a small hole in the fuel tank. They claimed the tank was not holding vacuum so the pump was not efficient  somehow when the engine was warm at all.I couldn't wrap my brain around how low tank vacuum could lower rail pressure and cause flooding...??? When I got the car the fuel pump was dead so I replaced the pump and filter but never managed to get the pump to seal to the tank correctly.The trunk gets a bit of fuel smell on hot days. Anyone have a clue what they could be talking abought?

 

Is it possible for a fuel injector to stick open when it gets warm?

[Imp558]

What city do you reside in?

[55trucker]

 

 

 When I got the car the fuel pump was dead so I replaced the pump and filter but never managed to get the pump to seal to the tank correctly.The trunk gets a bit of fuel smell on hot days.

 

Is it possible for a fuel injector to stick open when it gets warm?

If the pump assembly is not sealed properly you'd definitely smell the fuel from that area of the tank, you'd also see the stain on the tank from overflowing fuel, most definitely when full. I would not think that temp should make any difference.

When you fill up the tank next time get under the vehicle and inhale......the tank never goes into a *vacuum* situation unless the fuel filler cap is restricted to the point where it cannot breathe. It has a one-way internal valve that will allow air to flow into the tank but not in the other direction. The EVAP system is constantly drawing vapors into the engine via the EVAP solenoid & the vacuum port in the intake.

 

When was the last time an emission test was done?, at such times the fuel filler cap is checked for proper operation (at least it is here).

 

can an injector become open when hot? ...I suppose so but I've never come across one, more likely to become dirty inside and the pintle cannot close at all. If you did have an injector with this issue that cylinder would constantly flood, never fire properly (the plug would be fouled), the fuel rail would not hold pressure, the o2 wouldn't last too long & the cat would eventually be ruined.

[matt1970]

IMP; I live in Illinois unincorporated county 15 miles from St. Louis.

 

Trucker: If you live near Chcago,Springfield, or Belleville il and your car is 96 or newer they do an obd scan for emitions codes.I live close enough to Belleville that I have to get tested but this car being 95 is exempt. When I did the fuel pump I cheated and cut a hole in the trunk then made a access panel with a foam seal.The gasket that came with the pump would not sit in the top plate groove so I reused the old seal.If they were referring to the 2 inch rubber pipe on top of the pump had a pin hole that would make a little more sense.Something must have been lost in translation between the mechanic to the forum.My mother in law told me the mechanic fixed her bad gas mileage with new shocks.???? and a tune up.

 

I have never herd of an injector sticking open only when hot but seams plausible.I was curious if anyone else had ever herd of it happening.  Last time the car acted up in the driveway The o2 sensor was reading 5.7 volts.Fuel mix was good even though it was not firing on all 6 cylinders.I will pull the plugs again and see if any are showing signs of fouling yet.

 

Back to my original question on this thread.If the service engine light never turns on.Dose that show that the computer never sees the problem? I have an elm327 scanner.Is there any way to change the cars pin out so it can be monitored or is the "obd1.5"operating system completely incompatible?

[55trucker]

You've mentioned in your earlier postings that you've never seen a check engine light at all,

 

are you certain the bulb will actually light up?

 

Not familiar with the Elm scanner, I was under the impression that they are simple coder readers. OBD 1.5 for 1995 requires a dedicated scanner to access the particular system that the electronics used for that year.

[FordMan77]

Don't know if I've ever tried to read live data with mine, but I've got an Actron scanner that I bought specifically to read my 95 Bonneville when it was having issues, and it is OBD 1.5 as well.  Might have to throw it on and see if it can read live info.  If so, maybe I can help you out. 

 

And I'm not sure if the 95 GP ECM is the same way, but I know on the H-body there were issues where the ECM/PCM would start to fail and do weird shi*t and not throw any codes.  I had a stumbling/miss problem on my Bonneville that I just couldn't track down.  Was even worse when trying to drive it.  Finally gave in and bought a used PCM with matching codes off og Ebay, threw the EPROMs in it from my old one and it fired right up and hasn't had an issue since.

[Imp558]

Not throwing a code doesn't mean there isn't a problem. For instance a friend of mine had an IAT reporting values that would only exist inside an oven or in Hell and the PCM was just fine using those numbers.

He got killer gas mileage for a while there with an engine that had little power and ran crazy hot.

[matt1970]

Trucker,

When you turn the key to the run position the service light comes on so the light works.I was saying it never comes on with the engine running,no matter how poorly.

 

fordman imp,

I have built plenty of motors and wiring harnesses from scratch for 1950s to 2000s cars.But I am the first to admit once you get inside the computer I am a complete NOOB! I am interested in how to reprogram but it is a steep learning curve and kind of expensive curiosity.I know how to pull and lookup codes for obd 1 and 2.That is pretty much my limit.Just trying to figure out how to do that on an obd1.5 is limited info and allot of contradiction from different people.I have found two sets of trouble codes for the car.One is an obd 1 other is pbd2 list..I was looking looking for codes showing "sensor out of rang". Logic being if it runs no mater how poorly a sensor is signaling, but not the correct signal.If it can only spot "no signal", out of rang will throw no code (imps example) If it has a code "out of rang" and I have no light then it is not a signal out of range.....That makes so much more sense in my head..hope you fallowed that logic.

The elm 327 is a code reader and live scanner.I got it 2 weeks ago as a late birthday present.I installed the program onto my laptop but I still need to locate a usb Bluetooth fob so I can link them. This thing is for obd2 but If I move the signal ground and power wires on the car the sensor should link.Now it is a matter of can they speak the same language.

 

Fordman, what part of St Louis are you in? Sorry...What high school did you go to.lol local joke.

[FordMan77]

I live out in Old Monroe currently (Winfield area off Hwy 79) but work in Chesterfield.  Still have family up in North County so I'm always floating around somewhere.  Belleville/Collinsville isn't a far drive for me.  Heck, I need to get out to Speedway soon to scrounge for some parts as that's my normal haunt so you're likely about another 15 min from there.

 

Maybe check gmforum.com and see if they have a list.  I use that site a lot for my 95 Bonneville since it runs the same bastard obd setup.

 

And just for the record- Hazelwood East, lol...

[matt1970]

Had a chance to pull the plugs.123 and 5 look like new still.4 and 6 look like lead fouling or too hot.Since I am pretty sure my son is not using leaded gas at all I am leaning towards lean condition.I will check the fuel pressure one more time since 4 and 6 are at the end of the rail.(Side note) today I found the schrader valve this car supposedly did not have from the factory.Then check the injectors when I replace the intake gaskets that are most likely the problem.Think the gaskets are 10 +/- year old felpos.

[matt1970]

Finally had a free day to work on the GP again.The upper plenum gasket bolts were torqued to 5inch pounds.I removed them with socket and extension. No socket wrench required. Exited I found the problem.I cleaned the surfaces,installed a new gasket and torqued to 18ftlbs. Now It idles at 2000-3000RPM occasionally surging,and has no power when driving.Checked for vacuum leaks,iac tested and cleaned,map tested.The pcm has to relearn trims but I have started it to running temp adding loades and driven it 20 miles.Anyone know if there is a required procedure for "retraining "the pcm?

[55trucker]

Oh, for heaven's sake, I'm thinking that your engine is the DOHC, I see it's an L82,

 

2000 rpm makes me think of a vacuum leak. How long does the rpm stay AT that rpm? ..a code will set for *out-of-range-idle-rpm*

[matt1970]

Trucker,The rpms don't drop with engine temp if that's what you are thinking.At least 10 min or so before I shut it down.It may have a code but obd1.5 and no ses light coming on.I ordered an adapter for my scanner It should be in this weakened. No worries.I forget what engine I am working on all the time.Hard to keep track and gets worse with age Couldn't figure out why auto correct kept misspelling vacume. Apparently according to google I have been wrong for over 40 years!.You might appreciate the full story.

After getting the motor together I reached in and hit the key.As I am watching the motor run the RPM slowly climes to 4000RPM bouncing off the limiter.Of course at this moment the door swings shut with power locks engaged. I was distracted mid job and forgot to tighten the EGR bolts creating a major vacuum leak.I flooded the engine with throttle body cleaner to shut it down. Got the spare keys to get back in then tightened the EGR and restarted.the motor.It sputtered and coughed out the cleaner then ran good.Let it sit and idle up to temp,turned on the lights and AC.Idle dipped then stabilized immediately like it is supposed to.Shut it down and waited 15 min. Restarted fine.Drove around the the neighborhood for 15 min. of stop and go.all good.Let the engine completely cool overnight. Next day the RPM were at 2000 and it has no torque. It was working to clime a 5 deg incline hill at 60 mph.At one light had to keep my foot on brake and gas to keep it running.Now it is consistently idling too high when I start it.

 first thing I checked was vacuum leak. Carb cleaner and propane all over the plenum and clamped off vacuum ports one by one to eliminate a downstream vacuum leak.No change in rpm.Blocked off the EGR port to verify it wasn't stuck open.Cleaned carbon off the IAC pintel and seat. Verified it was actuating with the key. Now that I am thinking abought it there was no oring seal on the iac. Checked the MAP sensor again since I had to pull it off to check the vacuum lines under it.

 My plan is install an O ring on the IAC,see if the plugs tell me anything,reset the computer again.

[55trucker]

Well, if the O ring is indeed missing from the IAC housing that would be a source for a vacuum leak.

[matt1970]

knock on wood, fingers crossed, and trying not to jinx it, the beast lives! This car has always run a bit rough but back in February I gave it a tune up.After a few weeks it started missing after parked.Tested compression found a crack in #1 spark plug must have smacked it when installing #3.Replaced it and all was good for a few days.then it came back.Found a crack in #2.Must tweaked it when I pulled it out.40 years working on cars never broke a plug.I must be due.so replaced it. All good for a few days.Found a crack in #4 and #6 was a little burnt so I replaced both..Ran too lean got hot and cracked..?? Ran good other than RPM issues. Then started missing again.#2 and #3 carbon trail and big old crack.Nope its the plugs!! Pulled all the autolites out, installed ac delcos and an O ring on the IAC. Still not perfect but better than it has ever sounded.While it was idling I unplugged the IAC  for a few seconds and RPMS are now holding at 1200. Unplugged the TPS for a few seconds now there is no hesitation in the throttle and idles smooth.This car never had a smooth idle! So major tune up,decarb,new seals,some preventative part replacement and get rid of defective junk plugs and it runs like a new (old) car.

 

Thanks to everyone for your help.If it acts up again I'm taking out to pasture and shooting it! lol

matt