95 engine issues

hooked truck up to scanner today and checked codes. it came up with a p1406 but no ses. cleared the code took it for a drive and it came back but still no ses. it said p1406 egr pintle position ckt problem. now is there a problem with the egr or something else cause a false p1406?

replaced with new egr. no change. replaced iac. no change. any ideas? i also got another injector unit. will try replacing that soon.

With everything that you've checked and done, something struck me as odd... in one of your first posts....

i've checked fuel pressure and leak down. i've even driven the truck while watching the pressure and it never feel below 65psi. it has the cpi spider.

The highest fuel pressure reading you will ever see is when the fuel pump is running and the engine is off. Spec for 95 CMFI is 58psi to 64psi. Granted, a reading of 65psi may be high, an error in the guage may account for that and I wouldn't worry too much about it. However, when the engine is running, manifold absolute pressure is applied to the back side of the diaphragm of the fuel pressure regulator which lowers the regulated pressure. GM does not publish "engine running" fuel pressure specs because there are far too many variables involved. But, you should see a drop in pressure when the engine is idling or decellerating, (high manifold vacuum). At cruising speeds vacuum is lower causing fuel pressure to rise slightly. At wide open throttle, (low or zero manifold vacuum), fuel pressure should rise up close to the reading you got with the engine off. I'm wondering if there's a slight restriction in the fuel return line. Also, what is the leakdown rate? After the system is pressurized and the pump shuts off, fuel pressure must remain above 53psi for 3 to 5 minutes. Just a couple of thoughts....

hooked truck up to scanner today and checked codes. it came up with a p1406 but no ses. cleared the code took it for a drive and it came back but still no ses. it said p1406 egr pintle position ckt problem. now is there a problem with the egr or something else cause a false p1406?


If you are getting an EGR ckt code, have you checked out the EGR ckt and connectors really good? This might have been your problem all along, but it seems like early on you said the ckt checked good.

Also what old master said about the fuel pressure would be good to check out. I don't know if you checked out the base mechanicals like compression and how the vaccuum looks at various throttle postions. Your problem could be fuel delivery, maybe the injector spider, but I remember you saying truck runs good with EGR unhooked.

well replacing the egr took care of the p1406. the fuel pressure at idle if i remember correctly was 56-58 psi. when driving it was all over the place but held good pressure. i dont think its a fuel issue. i'm thinking more of maybe ignition but what throws it off is egr unplugged = a very powerful engine. pluged in it drives like a 4 banger. as i said before when we check the fuel pressure we used the alldata specs and everything measure correct. we didnt do a bleed down test though. the truck starts fun. i still get like every 6th or 5th start it see throttle position without any throttle input. hook up the scanner and the voltage feeding the ecm is .68 but it will show anywhere from as high as 6% throttle to 2%. im thinking that whatever is causing that is what my issue is but its hard to figure out when everything is reading correct. i even tried pulling the fan belt off and driving the truck in case of alternator feedback or something but that still left me with no change. by the way i have a good 5 volt reference at the tps and map. the only thing that i also saw in the scanner was in the tranny section it said the tps was out of range but i was told it could just be a program issue with the scanner. in the engine section it says its within range.

replaced the tps again. still no change. voltage is up to .78 now.

What does your engine temp look like with the scanner?

engine temp is fine. i've replaced the sensor already. its about 2-3 degrees different from the intake temp. so i know both of them are fine.

You know, I re-read through this whole thing again, one thing that I noticed, is that you can shut off and restart and get it to run better, or differently, so my question is....have you checked your ignition switch? How old is it, could it be that the contacts are worn and causing a little resistance? By the sounds of it, you have changed almost every sensor of there, have you looked and made sure your engine harness isn't damaged/frayed/cracked at any point?

the engine runs perfect if the egr is unhooked so i dont think it has anything to do with voltage anywhere. its a sensor that looks good or something like that. since i changed he egr valve it hasnt done its thing of showing throttle when there is none. currently i just still have the issue of it opening the egr while under load and no knocks.

??????

I think Blazes9395 is onto something with the ignition switch, doesn't hurt to check. Voltage in should equal voltage out.

If that's not it, then what I would do next is start it until you get it where it's running bad, then measure the voltage across the MAP and TPS wires (between sensor and PCM) no wire should have more than .1v across it. Probably check all the sensors to be sure. Some scan tools will "guess" at a value if it has enough data for it. For example, if it has MAP, RPM and IAT, it may show a very accurate TPS when the PCM may not be getting an accurate reading. I think the MT-2500 will do a "generic" datastream, which only shows the PCMs inputs with no calculated values.

well the last 2 things i did was replace the egr valve and the tps again and for the past month its been starting fine. no more high idle but it still has the egr issue.