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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Tazman on April 26, 2017, 07:52:03 pm
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A few days ago I found a leak in the manifold gasket so I had them replaced. Still had issues then found the PCV valve was faulty and it ran great. Then on the way home today while sitting at a light it up and died, started back up by from there on I had to put it into neutral while at a light. With that I thought the MAP sensor was faulty but no code 33 or 34 were present. I have checked all the lines repairing what was needed. This only happens when warm, works fine till then.
Thanks,
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Check the ignition timing and make sure the distributor clamp is tight. Spray for vacuum leaks. Temporarily disconnect and plug the vacuum hose attached to the EGR valve to see whether that makes any difference.
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dont really think the map sensor will cause it to stall
IAC, O2 and TPS will
http://forum.73-87chevytrucks.com/smforum/index.php?topic=29996.0
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What gets me the most is it rarely happens the same way twice. I can be sitting at a light all is well and boom it happens, if I put it in neutral and it runs as smooth as can be. I start it in the morning letting it warm up and all is fine, I go down the road and it acts up. Frustrating is putting it mildly.
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Disconnect and plug the vacuum hose to the EGR for a few days to see if the symptoms abate. Don't be concerned if an EGR code sets during that time - it can always be cleared.
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Do the test bd said to do. It will take you seconds to do and will easily eliminate this common problem as the culprit or pinpoint it as the source.
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Did it and plugged the hose, went for a short ride. Will know more in a couple days. If the EGR valve is the issue it is inly two weeks old but you never know.
Thanks
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The problem is not the EGR valve that you are trying to pinpoint. When you unhook the vacuum source you are not testing the EGR valve, you are testing it's actuation circuit. If it is staying on the EGR will open when it is not supposed to. So if you unhook and your problem vanishes, you know the problem is in that circuit.
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Well it has been a couple days and I knew todays test would tell if plugging the EGR hose would help. In short five mile drives all was well but today I have to go 45 miles and not all was freeway. Right before getting to my destination I noticed it starting to struggle when sitting at lights . I would put in neutral and that would take care of it. Yet one time when I did not it died and it took several seconds to get it restarted. Now back in the garage I plan to look into the connections after it cools down. Will let all know what I learn.
Thanks
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For the peace of mind I thought I would check the timing. So I was getting ready to that when I realized the markings were covered in dirt and gunk. While cleaning my mind woke and thought how can this be this dirty when just three weeks ago the timing had to be reset when the intake manifold had been removed. So I proceeded to check the timing and found it to be way off, I'm talking 8 degrees off. Got it set to where it should and it made a big difference, while out for a drive I stopped by the shop that did the work and asked how did you check and adjust the timing? I was told the guy who worked on my truck was no longer working there, gee I wonder why.
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i wonder if "that guy no longer works here" is what most places tell their customers to make it seam like theyve already taken care of the issue. when in reality the guy is still working there
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Timing is not the main issue. I have another issue which if affecting the timing to the point it moves all over the place when the idle is erratic like it is now. I have taken a video but it is to big for this post. It shows the tach needle bouncing up and down .I have looked for leaks with no luck ,all I have is an injector making a rattle .
I can email the video if anyone wishes to see it.
Thanks,
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If your idle is erratic, your timing will be erratic. Start over, describe what's going on now. What symptoms are you having, is everything hooked up working correctly now, just erratic idle?
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When in idle it gets very erratic unless I put it in neutral and is okay. Is good while driving till I come to a stop. I have checked and checked for vacuum leaks but I still think there is one. It is hard to check around the distributor and that end of the manifold. I am thinking of taking it back to the shop that did the gasket install, but I need to find the leak first.
Thanks,
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Tell me, can a torque converter be the cause of this?
Thanks
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Unplug the 4 terminal connector at the trans. see if the problem goes away.
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No that was no the issue, I did take the time to spray carb cleaner again and again did not find anything. While at it I gave the TBI a bath which did not hurt. It did seem to idle better but when put into gear back to the erratic idle it went. When my wife gets home I will have her hold the brake while I look under the hood.
I appreciate all your help!!
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Double check the firing order, check fuel pressure. You need to provide scan data
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The firing order is fine, went to a shop today with a smoke machine, and they found the leak. So now the shop that did the manifold gaskets will be doing it over again. Needless to say I will be going to the shop with the smoke machine in the future. They also checked the fuel pressure and found that the injectors were pushing to much fuel. I had noticed one of them making a rattle so it is good they are both now replaced, the others had 229k miles on them, not bad. Truck is starting and running better but the vacuum leak still shows. Look to get that fixed soon.
Thanks
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So where is the leak they found with their smoke machine?
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In the front, easy to see with the smoke. Very hard to spray anything there because of the fan.
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Took it back to the original shop to have the intake gaskets replaced again. Took 1 guy about three hours to do it but I saw him working on another at the same time. On the way home the same issue arose, while sitting at a light the tach would jump as did the idle. I have no way of knowing the gaskets were really changed. I did see gasket sealer smudged over the area the smoke had come out. So I took it to the shop that found the leak and after telling them the symptom's were the same they said it most likely was still leaking, but they will not look into it unless they can fix it, so I would be paying to have this done twice. Not being made of money I left. I do have one question. When they hooked up the smoke machine they used the line going into the brake booster, is it possible to hook a gauge to that line to tell if the gaskets were leaking?
Thanks
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i do my own work when i can. cause i know to most shops youre just money. they may or may not care if they get it fixed 100%. can you take a picture and circle where it was leaking from? i know you said the front but is the the front of the intake or near cylinders 1 and 2 or what?
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:-\
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i wonder if "that guy no longer works here" is what most places tell their customers to make it seam like theyve already taken care of the issue. when in reality the guy is still working there
Where the smoke was coming out is to the right of the temp sensor.Actually about dead center.
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Think about it. You put smoke in the brake booster port to the carburetor.....Every open intake and exhaust valve, the throttle body, the PCV, the breather, the crankcase, the tail pipe, every vacuum hose, where else do you want to see smoke come from?
Take the throttle body off and replace the base gasket.
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Think about it. You put smoke in the brake booster port to the carburetor.....Every open intake and exhaust valve, the throttle body, the PCV, the breather, the crankcase, the tail pipe, every vacuum hose, where else do you want to see smoke come from?
Take the throttle body off and replace the base gasket. They were already replaced.
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im still confused as to where you said the smoke came from. take a picture or find one online and circle. we cant really properly diagnose anything online. we can tell you what to check and how to check but you have to listen to us. we need as much visual aid as we can get you have to be our eyes, ears and hands
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My point was the test is invalid. You need to get some serial data at this point. Sounds like you're barking up the wrong tree on this.
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My point was the test is invalid. You need to get some serial data at this point. Sounds like you're barking up the wrong tree on this.
How can I have data when there have not been codes show up?....Yes the check engine light is on when starting the truck.
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My point was the test is invalid. You need to get some serial data at this point. Sounds like you're barking up the wrong tree on this.
How can I have data when there have not been codes show up?....Yes the check engine light is on when starting the truck.
There's a way to plug a laptop or smartphone into the port and record what's happening
Sent from my iPhone using Tapatalk
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you cant really trust the OBD1 system and tell you the truth you cant really call that an OBD at all. its ALDL (Assembly Line Diagnostic Link). it can tell you where to start but even then sensors need to be tested. generally speaking i may be distracting you from your real issue. but like one of the quotes in my sig say "When you have eliminated the impossible, whatever remains, however improbable, must be the truth" ~Sherlock Holmes
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My point was the test is invalid. You need to get some serial data at this point. Sounds like you're barking up the wrong tree on this.
How can I have data when there have not been codes show up?....Yes the check engine light is on when starting the truck.
A fault code is not data stream. Anyone who has an OBDI setup should have a method of access to view data if they are trying to fix/maintain their truck themselves otherwise you will spend more money throwing parts at it over time. Why keep guessing? No it won't tell you what's wrong but it will give you the ability to drill down and find the problem without firing the parts cannon. There are several methods you can use to gain access, a scan tool, you can find used OBD1 scan tools cheap, winaldl with a laptop, bluetooth adapters and smartphone apps albeit Droid or Apple.
you cant really trust the OBD1 system and tell you the truth you cant really call that an OBD at all. its ALDL (Assembly Line Diagnostic Link).
I am not sure what you are saying? Didn't you know part of the programming logic is the Maury Povich lie detector test?
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I used WinALDL on all my TBI trucks. Still have the laptop and connector here somewhere... You need an older XP Operating system.
http://winaldl.joby.se/ is where to get setup instructions and the software.
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I have yet to get what is needed to get the data stream but I continue to try things. Once again I checked the timing and reset it. In doing so I unplugged the (I forget)tan wire with the black stripe.When done the ECM searched and found the idle again and off I went. After driving a distance yesterday and taking it to work today I noticed the idle was low again. So I adjusted it to where it should be. Tell me if this happens is my ECM on its way out?
Thanks,