GM Repair Questions? Ask a Mechanic for Answers ASAP
When you unplug the cam sensor you send the pcm into a base line setting for fuel delivery. If unplugging the cam sensor makes it run correctly, then The first thing I would check would be the fuel pressure. If the fuel pressure is below 60 psi, then you will have one of three problems, the fuel filter is stopping up, the fuel pump is not pumping hard enough and needs to be replaed, or the fuel pressure regulator is not holding pressure and needs to be replaced.
i will have to see if the local parts store has a fuel pressure guage
ok. let me know what the pressures are.
ok...first tiem I have used this...I can let you know tomorrow?
yers that will be fine. do you know how to get back to tehis string?
Look in you r email and there is an email from just answer. In that email is a link " get your answer here", just click on the link and it will bring you right back here. Then post a mesasage to this string and i will be right back with you asap.
perfect...thx. tty later
chat with you alter.
well...everyone should own a fuel pressre guage, right? it tests 56 lbs at idle
at key on/key off when the pump runs it jumps to 64 lbs
when you shut off after running it holds pressure at 56lbs
Thoise are good pressures.
Now i have to find another direction to go in.
Can you unplug the ect " engine coolant temp sensor?
The ect will be up next to the thermostat housing, and will have a yellow and a black wire.
See if the engine will start and run better with the ect unplugged please.
may have to wait for daylight....plus its raining!
I will give it a try in teh morning
That sounds good. i will be back online around 10:30 am eastern time.
ok...glad you are leaning toward not being fuel pumo or fuel pressure reg...bot llok nasty to change!
Yes they are a pain to change, and the fuel ppump is not so cheap.
Chat with you then.
Disconnected the ect. Started engine which idled rough and accellerated poorly. Engine was "shuddering". Drove for 10 miles and got temp gauge to normal operating temp. Performance and engine miss did not ever get any better.
Unplugged Cam Pos Sensor and ran great.
Not sure how the ect works other than its resistance changes as the temp changes. So should it run bad with it unplugged?
BTW...having the ect unplugged made no diff. the vehicle behaved the same as when it was plugged in.
Let me look up a few things.. The ect works as you are thinking, but it too regulates fuel mixture based on temp. Did the check engine light come on with the ect unplugged?
it's been on due to the unplugging of the CPS
Where any new codes set?
sorry...I dont have a code analyzer...shade tree mechanic
I miss the 70's
Be right back.
Here is what I ahev found out about your cam sensor. The cmp should not cause a miss or any driveability problems. It is only used to detect a missfire in the engine. YA right, we both know that that is not true as you can unplug it and the engine will run right.
Have you looked into the back side of the mass air flow meter to see if there is any dirt on the sensors inside of it?
they looked clean to the naked eye
you could see the tiny little wires crossing the other wires
and there was no dust or dirt on the tine wires?
did not look like it
HOw many miles do you have on the engine?
last fall when the MAF failed, if you unplugged it , it ran better...if you unplug it today it makes no diff
If you have thr cam sensor unplugged will unplugging the mass air change the way the engine runns?
not tried that...brb
ok...ect plugged back in...MAF unplugged...Cam sens uplugged...runs good
plug cam sens back in with MAF unplugged and runs bad. like flipping an ON/OFF switch
I hat eto say it but I believe the pcm is where your problem is. there are two ways to go about correcting the pcm, you can try to have it reprogramed, or get a new or used pcm. If you replace the pcm the new or used pcm has to be reprogramed before it will work in your van.
There is an outside chance that the crank sensor is bad,
But I would not place money on the crank sensor. " not much of a gambler".
the crank sensor went out last fall and was replaced at a dealer in Liberal KS. I now am missing a left arm and leg by the way...but I suppose it could be faulty
we were on a vacation and it shut down on the side of the road
he "put two guys on it" to get us on our way. funny it took the same amount of time as one.
Is it posible that the distributorwas loose and the distributor has turned?
I hate the " look out of towners, lets get all we can" shops
I dont think so...I did read about how the gear on the dist shaft can wear...
it's been a gradual thing over the last few weeks ...started out running rough just when u first started it to running rough all the time
I have heard people say that the gear cn wear, but i have never had to replace a gear for the distributor, unless the distributor was sizing up.
I first had thought bad gas but ran that tank out and fill up at a place we get gas all the time at wioth no issues on our other cars
if the gear was the problem, then the miss woudl not change with unpluggingthe cam sensor.
replaced fuel filter...old one had a little resistence but was a yr old
I hate to say it but it sounds like the pcm is breaking up the signals it is getting.
MAP sensor? have not changed that yet
A map sensor can cause the engine to miss, but I have never unplugged the cam sensor to see if the miss will clear up, so I can not condem the map sensor, but that does not mean it is not possible
A map sensor for this engine is not to bad, around $30.00. And is a hole lot less then a usd pcm and programing.
so botXXXXX XXXXXne...we use this vehicle for short trips...not a daily driver...will it hurt anything running with the cam sensore unplugged?
From what I can tell the only thing that woudl be efected would be the pcms ability to determine what cylinder is missing if you leave it unplugged.
whats wierd is when it is unplugged no cylinder misses!
I agree with you it is wierd that the miss goes away.
I hate to so lets try swaping a part out, but in this case I believe that you may be onto something with the map sensor. DO you mind replacing it to see if it does clear up the miss?
sure...at this point I will try dang near anything. looks like an ECM runs $156 at OReilly...not as bad as I thought
But then you have to have the pcm programed ontop of the replacement.
speaking of dealers...I initially took this to our local GMC dealer...he quoted me $757 to do new plugs wires cap and rotor. I told him no way.
true...what should that normally run?
At the dealer it runs around $135.00, but oreilly's may be able to program it for you. There is one store here in chat that can do it for me, put of the 7 stores near me.
ok...I will get a MAP sensor at lunch and give it a shot...it's sort of like playing the slots in Vegas...you reach a point where you think if you just keep going you will eventually win!
I hate to say it but you are right. With out a good scanner to see what is realy going on, it is a roll of the dice.
I'll get back to you
drum roll please....
MAP sensor fixed it
was a bit worried though...installed it and plugged all components back in....still ran crappy. unplugged cam sensor and drove home.
decided to plug cam sensor back in while it was still running...no difference! still idled great. went for test drive and ran perfect. I am guessing it just took abit for the ECM to relearn.
now at idle you cannot feel in the steering when that it is running.
accelerates fine at all speeds.
SES is still on but hopefully will reset after some key cycles. Is there a way to reset it? Disc battery?
so with all tuneup parts, cam pos sensor, MAP sensor and my shiny new fuel pressure gauge I am still way less than half of what my dealer/robber wanted for a tune up!
oh, and your $$ ;)
meant to say above: now at idle you cannot feel in the steering WHEEL that it is running.
btw....$75 for oreilly to have an ecm flashed
I am so happy that the map sensor corrected your problem. To reset the codes in the pcm and turn off the ses, disconeect the negutive batter cable ofr 2 minutes.
was i correct in my assumption that it would take a bit to "relearn"
WIt not clearing the codes after you installed the map, yes that is very posible.
The pcm would have had to " try" to get a good reading not knowing that the map had been changed as the pcm know that things where not right,
great! well thanks for all your help. I just got off the phone with the local dealer and vented ! I am clicking "Accept" now!
You are very welcome.
Well...I know I closed this out but I guess it wasnt really the MAP sensor that fixed it. It appears like it was because the van had warmed up to normal operating temp and the miss went away. I am going to replace the engine coolant temp sensor and try it again. It still only runs well if the dist module is unplugged (matters not if the van is cold or warmed up...runs perfectly).
I do have a new litttle thing to add...there is an occasional "clunk" in the tranny or torque converter when going downt the highway like is is locking or releasing. Not sure which. Shifts through all the gears fine. Happens if I am running in OD or 3rd.
good to know...I will let you know what I find...
I was reading that the ect tells the PCM to lock up the torque converter at certain temp as well...hopefully this will fix all my issues!
thank you for the update.
We are going to have to get down and dirty to solve this problem. YOu will need to get a digital volt meter so we can do some testing to see if we can solve this problem. You can get a cheap on from your local auto parts store for about $20.00,
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You will also need a test light,
With these two tools we can solve this problem together. do not get the expensive tools as they are hard to deal with and quite frankly you just do not need the more expensive tools.