Grenade Posted August 9, 2015 Share Posted August 9, 2015 Quick background on my rig. 1992 With a lower mileage vg30 just swapped in. New plugs New wires New ignition coil Aac valve is good 10ohm Air valve is good 70ohm EGR passes stick test TPS is good 1k-9k Timing is 15 deg btdc Battery voltage when running is 13.5 vdc New Cap and Rotor No ECU codes. When I start the truck and its warming up it runs good. I'm able to drive normally and there is no sputtering or missing. After its gets warmed up it begins to hesitate and stumble. I can limo it back to my garage but it will continue to do this until I let it sit for a while. Then I can start it back up and all is good for a little till its warmed up again. My fuel pressure is at 43 psi when testing the pump, but I'm not sure what it is when driving as I just can attach a gauge and dead head the pump. Could this possiblly be the O2 sensor? Any help would be greatly appreciated. Thanks! Link to comment Share on other sites More sharing options...
krmiller07 Posted August 9, 2015 Share Posted August 9, 2015 Have you checked the injectors? Link to comment Share on other sites More sharing options...
MrEviLDeD Posted August 10, 2015 Share Posted August 10, 2015 (edited) This similar problem has happened to me. For me I found it was a bad MAF connector. I have since fixed it and cleaned the MAF (procedure found online here I believe) but when it would happen I would need only open the hood and very lightly tap on the connector and everything picked right up. Not saying this is the same problem you are having however it might be based on the symptoms. Easy to rule out by checking the MAF connector. Good luck. Edited August 10, 2015 by MrEviLDeD Link to comment Share on other sites More sharing options...
Grenade Posted August 10, 2015 Author Share Posted August 10, 2015 Have you checked the injectors? All the injectors were resistance tested before the swap. They all were right at 12.5 ohms. Other than a "balance" test by unplugging each one to see if they cause the engine to slow down is there anything I can do? Link to comment Share on other sites More sharing options...
Grenade Posted August 10, 2015 Author Share Posted August 10, 2015 This similar problem has happened to me. For me I found it was a bad MAF connector. I have since fixed it and cleaned the MAF (procedure found online here I believe) but when it would happen I would need only open the hood and very lightly tap on the connector and everything picked right up. Not saying this is the same problem you are having however it might be based on the symptoms. Easy to rule out by checking the MAF connector. Good luck. I forgot to put in my original post that I have checked the maf and it is within factory service manual specs. I also have added a ground wire to the harness to help with the recap issue. I had not cleaned it because it looked clean when I did the swap. I will double check tomorrow. Link to comment Share on other sites More sharing options...
adamzan Posted August 10, 2015 Share Posted August 10, 2015 I would inspect the coolant temperature sensor and the o2 sensor. You can just unplug the o2 to test. Sent from my SGH-I747M using Tapatalk 1 Link to comment Share on other sites More sharing options...
Grenade Posted August 10, 2015 Author Share Posted August 10, 2015 When you say I can just unplug it to test it, what would the symptoms be? I've been working on looking this over again today and on a hunch I decided lay night to order a new Bosch oxygen sensor and an oem temp sensor last night. Well today during some more trouble shooting I found that maybe the temp sensor is goofy. Also I unplugged the O2 sensor and the truck kind of cleared up but was still a little stumbly. Also, I now have a 33 code on the computer so I am thinking all my issues may relate to the oxygen sensor. I'll replace both of them and report back. Thanks again fellas. Link to comment Share on other sites More sharing options...
adamzan Posted August 11, 2015 Share Posted August 11, 2015 If you unplug it and it runs better, then the sensor is bad. Link to comment Share on other sites More sharing options...
Grenade Posted August 11, 2015 Author Share Posted August 11, 2015 If you unplug it and it runs better, then the sensor is bad. Got it. I'll check this out Link to comment Share on other sites More sharing options...
Grenade Posted August 17, 2015 Author Share Posted August 17, 2015 Well over the weekend I got both of these sensors (Oxygen and Coolant Temp) changed out. Huge difference. At the same time I cleaned out the MAF and that helped out quite a bit too. I am going to do some more cleaning of the sensor tonight (I didnt pull it off the housing, just sprayed the cleaner into the ports) by removing it completly from the housing (like the how to) I will report back and let everyone know how it goes. The truck ran for about 30 minutes with out a total loss of power/missing but something is still not right. I feel like its down on power somewhat still but I have not taken it out for a major drive since I cleaned the MAF. Link to comment Share on other sites More sharing options...
Grenade Posted August 25, 2015 Author Share Posted August 25, 2015 Just wanted to report back on how everythings been. Truck runs great. No more misfire or stumble. Cleaning the MAF, Changing the oxygen sensor, and the coolant sensor seem to have gotten rid of any issue's I had. The truck seems to run so smooth I cant tell if its on while at a stop light. I will run some more fuel injector cleaner through the tank and maybe some Berrymans Fuel Injector kit too. If anyone has any stumbling missing hesitation or just plain lack of power check these things out asap. They will haunt you if you dont. Thanks again. Link to comment Share on other sites More sharing options...
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