95 engine issues - Page 4

manicmechanix · #46 11-13-2009, 03:36 AM

OK then you're saying now it runs fine with the new PCM? I was just curious so did you just swap a PCM out of another 95 or was it a new reprogammed PCM?

metallica21156 · #47 11-13-2009, 10:12 PM

im gonna have to check the ground on sunday. i did however do the ground update for the ecm a while back. the one where you add the wire into the harness. just to eliminate that possibility. the ecm was from another 95 with the cpi and obd2. i never knew there was a such thing as the theft deterrent. can you explain in more detail? it runs fine as in it drives like the other ecm is in it. still opening egr when it shouldn't. i cant see 2 ecms having the exact same issue. where does the ecm get its gound? the engine block or the body? i measured from the intake,a/c compressor and altenator shell and connect the other wire to the batt terminal. then thats when i was getting the reading. i checked it on another car and i only got 5 ohms resistance. could that small extra amount cause all of this?

old_master · #48 11-13-2009, 10:26 PM

From 5 ohms to 107 ohms makes a huge difference when it comes to digital electronics. Check both ends of the body ground: On the negative terminal of the battery, there should be a 0 gauge wire and a 10 gage wire. The 0 gage wire goes to the engine block and the 10 gage wire will connect to the body, usually on the radiator support close to the battery. There are other ground straps on the vehicle, usually there's one attached to the bulkhead, (firewall) near the heater hoses and goes to the back of the right cylinder head. That particular ground is usually a braided type cable with eyelets on each end.

manicmechanix · #49 11-14-2009, 04:47 PM

I got it now, you're saying no change with the PCM swap. For theft deterrent I was asking if the truck had Passkey or Passlock, but I guess it doesn't. I'm sure you heard of them

. Well so far it sounds like you have narrowed it down to a poor engine ground. I think if you check all the engine grounds, body grounds, and the ground integrity from the PCM, it'll probably be running better.

metallica21156 · #50 11-14-2009, 11:07 PM

i plan to do that tomorrow. i dont think they had pass-lock back then. all i have is keyless entry which is done by a dealer installed alarm.

manicmechanix · #51 11-15-2009, 12:14 AM

I wanted to throw a wild guess out there. Do you think the reason you are seeing wider EGR duty if you really are, might be because the PCM is compensating for the lower back pressure exhaust you have on it when does its I/M readiness testing? I'm not sure if the system has that kind of capability or not to tell you the truth. Anyway, if it were compensating it wouldn't affect the engine running bad problem you are having, just possible create wider duty cycles, unless they are fixed.

old_master · #52 11-15-2009, 04:18 PM

Quote:

Originally Posted by manicmechanix

I wanted to throw a wild guess out there. Do you think the reason you are seeing wider EGR duty if you really are, might be because the PCM is compensating for the lower back pressure exhaust you have on it when does its I/M readiness testing? I'm not sure if the system has that kind of capability or not to tell you the truth. Anyway, if it were compensating it wouldn't affect the engine running bad problem you are having, just possible create wider duty cycles, unless they are fixed.

Some vehicles were designed with a means of measuring backpressure and adjusting EGR accordingly. For example, Ford uses a DPFE sensor, and many manufacturers used a transducer, but this particular system does not have any sensors for measuring exhaust backpressure. Excellent thought though.

manicmechanix · #53 11-15-2009, 09:48 PM

Quote:

Originally Posted by old_master

Some vehicles were designed with a means of measuring backpressure and adjusting EGR accordingly. For example, Ford uses a DPFE sensor, and many manufacturers used a transducer, but this particular system does not have any sensors for measuring exhaust backpressure. Excellent thought though.

Well I was wondering if this GM system might be able to calcultate EGR flow during the emissions monitor test or whenever by comparing RPM drop to expected for the EGR duty cycle. I doubt this one can but I seem to remember that later model GM EGR can calculate flow without a separate sensor, but I might be mistaken.

metallica21156 · #54 11-16-2009, 02:49 PM

cleaned all the ground from the batt. now i get 0 ohms to the engine as well as the ecm. still now change. but i think whatever is going bad is getting worse. my idle is really rough now. as for the egr. this system opens it during decel to see the map change. thats how it checks flow. its not some much im worried about it opening. its that when it opens i loose like half of my power.

manicmechanix · #55 11-16-2009, 05:10 PM

I forgot what all you did so far but if the idle's still rough, I think you should go back to checking engine condition-compression test, vaccuum, and consider that it might have dirty injector poppets. I think you should try some Techron fuel injector cleaner and see if it helps.

metallica21156 · #56 11-16-2009, 06:11 PM

i know it idles smoother if i make it have a vac leak. i need to check compression yet.

metallica21156 · #57 11-23-2009, 11:46 AM

well the latest is that i started it the other day and it started idling high again. hooked up the scanner and it said that the throttle % was at 6% and the idle switch was open but the tps volts was at .66-.68. i revved the engine and the most i could get the injector pulse width to was .8ms. turned off truck. waited 5 seconds. restarted and it was back to norm. rev engine and i saw the injector go over 3.0ms. then i watched egr and noticed it wasn't moving. volts on egr was 1.06 but egr position was 0 and it was being commanded 0. truck the truck for a drive and the entire time it stayed at 0. turned off engine. waited again. restarted and engine was back to opening the egr under load. only 2 things i saw that were different. the egr volts was 1.06 and it said ignition dtc-yes. still no ses.

metallica21156 · #58 11-23-2009, 07:42 PM

forgot to add that it was commanding the iac to 150 when it was running high idle. when it calmed down after driving it, it was commanding between 0-2.

metallica21156 · #59 11-29-2009, 03:52 PM

checked timing today and timing is in line. no slack in timing chain. changed out distributor with no change. any ideas?

metallica21156 · #60 12-08-2009, 08:51 PM

????

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