95 engine issues - Page 2

metallica21156 · #16 11-01-2009, 09:06 PM

it never gave a running spec. just bled down, and prime pressure. when we drove it we had a gauge hooked to it and pressure was always up. i have the service book for the truck and it says egr is affected by map sensor, tps, engine coolant temp and ita. but all of them are reading good. do you happen to know what ae clamp is? i saw it on the scanner. sometimes its on and others its off. never stays on though. the new thing i experienced with it today was having the egr plugged into another egr not connected to the engine and i commanded it open 50% or more with a scanner the engine would start to stumble and then rev up and recover. its never done that before. usually it would open it up and run like nothing changed. also tried driving the truck with the dummy egr in place and it was still commanding it to open just like the one attached to the engine.

manicmechanix · #17 11-01-2009, 09:16 PM

Quote:

Originally Posted by metallica21156

the new thing i experienced with it today was having the egr plugged into another egr not connected to the engine and i commanded it open 50% or more with a scanner the engine would start to stumble and then rev up and recover. its never done that before. usually it would open it up and run like nothing changed. also tried driving the truck with the dummy egr in place and it was still commanding it to open just like the one attached to the engine.

What kind of scanner do you have? Anyway, do you mean you commanded the EGR valve 50% with the old EGR valve that's installed and the engine didn't stumble before, or this is the first time the dummy EGR caused a stumble? I'm not sure why unhooked EGR would cause a stumble..I don't know if the computer was trying to take counter measure like enrichening in anticipation of the larger EGR flow that didn't actually exist or why it didn't do it before?

What I was saying is it's possible there's nothing wrong with PCM or its sensor inputs in regard to the EGR command but maybe the EGR is not really opening the way it's being commanded and the PCM doesn't realize it?

I'm not saying the EGR valve is bad and replace it, I'm just saying it'd be nice to have that a different one installed and see how it ran

.

metallica21156 · #18 11-01-2009, 09:59 PM

i have a snap on scanner. and yes i didnt remove the old valve. i left it on the engine and using a functional test i commanded it open. i've done this before and never had a issue. it was idling and when i commanded it open is when it stated having issues and revved up to recover. if i have have the egr hooked up the way its designed then that's when if i give it gas it stumbles but that's also cause it opens the egr up to 60% open. i did also pull off the egr and cleaned it. with the engine not running i commanded it to different % and it moved like it should. so i dont believe the valve is bad. just for some reason the computer thinks it needs to open it. even with it unplugged i get 0-6 spark knock so i know spark knock isnt causing it. although while driving the computer is running 34-36' of timing. i'm also running premium fuel. i dont know if that timing is right. i know before when i ran regular i could only get 20 if i was lucky but it had alot of spark knock.

manicmechanix · #19 11-02-2009, 02:29 AM

OK I was just saying the computer might be commanding the proper EGR valve percent opening but the EGR valve might be opening further than it's supposed to. It would be hard to tell just how far the EGR is actually opening and the computer might not know it's opening more than commanded. I don't think the earlier model EGR has the on board diagnostic to detect this and set an EGR code like later linear EGRs. I could be wrong. but assuming the wiring harness is sound and the computer is getting the right TPS and Map reading, what else besides a faulty EGR is left besides the ECM itself?

Maybe Old Master can figure out something for EGR %. Maybe your EGR is fine and it hesitates with the EGR hooked up because your CPI is dirty/partially clogged? Sometimes dirty injectors hesistate when engine hot and in closed loop and with EGR because the injector duty cycle is so low.

metallica21156 · #20 11-02-2009, 05:18 AM

it has the linear egr valve. as for the duty cycle it runs around 50%. i've seen the computer command the egr to 150% but the duty cycle is at 50 so it opens to 75 or 80.

old_master · #21 11-02-2009, 07:43 PM

Quote:

Originally Posted by metallica21156

... i have the service book for the truck and it says egr is affected by map sensor, tps, engine coolant temp and ita. but all of them are reading good. do you happen to know what ae clamp is? i saw it on the scanner. sometimes its on and others its off. never stays on though....

Those are the sensors the ECM gathers data from to determine when and how much EGR to apply.

The "ae clamp" is a mystery, the only thing I can think of is possibly "ac comp" which is the air conditioning compressor. Some OBD systems monitor when the compressor clutch field is energized. That would also explain the on again off again status.

Have you checked crankshaft / camshaft correlation? It must be set as close to zero as possible, plus or minus 2 degrees. Usually, but not always, it will set a P1345 DTC if its too far off.

metallica21156 · #22 11-02-2009, 08:34 PM

how do i check it? what do i look for on the scanner? as for the ae clamp it has nothing to do with the a/c. a/c was off and it only came on when the truck started to stumble.

old_master · #23 11-02-2009, 09:07 PM

A code reader will not access it. Only the "enhanced" scan tools will access it. Depending on what scan tool you have, it may call it camshaft timing or cam retard, or something along those lines. Flip through the options and it might tell you. It will show a reading in degrees, and will remain constant. If the distributor is removed and not installed correctly, (off a tooth) it will affect cam / crank correlation. The distributor will only lock in one position and is not adjustable. Sometimes it's necessary to grind the distributor mount to "fine tune" it.

metallica21156 · #24 11-02-2009, 09:11 PM

as far as i know its never been removed and i've had the truck for 6 years. the scanner i have is the snap on mt 2500 so i can read all the sensors and what they are doing. so do i check this at idle? the other thing i forgot to mention is that i noticed with egr unplugged the idle is inconstant. it idles fine but then drops off like the a/c kicked in but then recovers. the egr never opens during this time. but the ses light is on because the egr is unplugged. is that norm? i know the a/c compressor is off though.

metallica21156 · #25 11-02-2009, 09:16 PM

i just checked the scanner and all i have is spark mod and the timing. the timing moves around but the spark mod stays at 0.

metallica21156 · #26 11-04-2009, 09:55 PM

how would dirty contacts on the cap and rotor affect this? pulled mine today and theres white powder everywhere. any ideas or why? cap and rotor is maybe a year old.

old_master · #27 11-05-2009, 03:38 PM

When the cap and rotor are replaced, silicone dielectric grease is applied to all contacts both inside and out of the cap. When the engine is running, the current passing across the contacts causes the dielectric to crystalize. It looks like corrosion or a white powdery substance. It's suppose to be there, if it's not, somebody didn't do their job when they replaced the cap!

Dirty contacts would not necessarily cause your problem. A more common reason is the aftermarket caps have poor insulation from the tower connection that the wire connects to, to the contact that you see on the inside of the cap. Stray spark jumps around as a result, and causes poor engine performance. AC Delco caps don't have that problem.

metallica21156 · #28 11-05-2009, 06:33 PM

well i replaced the cap and rotor with accel one's. no one sold any that had brass in it but accel. the engine runs better but still having issues. next i'm gonna replace the egr valve and see what it does. i'm out of ideas.

manicmechanix · #29 11-05-2009, 07:29 PM

Did you ever try fuel cleaner to see if it made an improvement?

manicmechanix · #30 11-05-2009, 07:35 PM

Quote:

Originally Posted by old_master

When the cap and rotor are replaced, silicone dielectric grease is applied to all contacts both inside and out of the cap. When the engine is running, the current passing across the contacts causes the dielectric to crystalize. It looks like corrosion or a white powdery substance. It's suppose to be there, if it's not, somebody didn't do their job when they replaced the cap!

Electrical is not my strong suit so maybe you could clear something up for me

. One thing I was never sure of with dielectric grease is how does it not block electrical flow at the connecter where it is needed? Is it because the connector pushes it all away? Seems like some of it would remain there as a film, especially where there is a gap between conducters like cap terminals to rotor.

My understanding of dielectric grease is it keeps moisture and corrosion of of the connecter which is good and also is not very conductive to electricity so it prevent electrical "leaks", which is also good. But that leads me back to my question. Doesn't it add resistance and block electrical flow through the connecter on the contacts or not?

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