73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: bryanedp9 on August 29, 2016, 12:30:45 pm
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Okay so my 400 seems to slip when I try to get on it too much, but the real issues are I'm throwing a 24, 32, and 44 codes for VSS low voltage, EGR, and O2 lean exhaust, respectively. The EGR hose was plugged. I plugged it back in but have noticed no real difference. Not sure what it should feel like when working.
As well, the speedo reads about 8mph at cruise when it works. Often it will work upon startup then ease down to 0 after awhile. The speedometer cable itself was a little loose at the tranny. That combined with the gauge replacement (mentioned below) makes me uncertain about the wiring behind the cluster. I'm guessing the gauge is controlled by the VSS which is learning from the cable and some kind of pickup wheel with the VSSB. No idea though.
The oil pressure gauge never reads lower than 30 when running, but during idle, coast or light throttle it maxes out, only trying to come back down if I throttle it a bit. Not sure if it's a high-volume pump or some short/grounding issue. I'll try to get a mechanical gauge to check.
The temp gauge was replaced with a sunpro under the dash. Doesn't get much over 195.
I get a ticking that I thought might be flexplate but a buddy thinks exhaust. Its speed is rpm dependent but volume is consistent.
This may or may not be related to the backfiring I get coasting, downhill, and on decel. Even on the straights it can pop a bit if I don't throttle. On the flipside, when climbing after a downshift the exhaust tone can become a bit quieter with some hissing until I get the check engine light, which usually but not always goes off after I've planed out and dropped the engine speed a little.
Anyhow, I know I've got some shadetree tricks to help diagnose, but I've only had one other TBI truck before and didn't work on it much. Anything you wanna throw out there is appreciated. Thanks
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I see now I put this in the wrong place.
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If the vehicle is a 1973 - 1987 squarebody truck, the thread is in the right place. But, don't leave it for people to guess. What year/model truck are you working on?
http://forum.73-87chevytrucks.com/smforum/index.php?topic=5220.msg24910#msg24910
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Sorry about that. I just figured it more of an electrical issue at this point. It's an '89 R3500 dually
But it's gotten worse, or a new problem has arrived. At a certain rpm it starts cutting out and bucking pretty bad. At first I thought maybe the torque converter but it may be fuel or VSS related for all I know, but it didn't throw any codes. It started this as soon as I got on the highway the other day. I couldn't get over the mountain into town safely so I turned around. It can't get above 25mph or so now though. Cuts out like that revving in park as well. I'm trying a new filter, then a fuel pressure tester. I sprayed to check for leaks at idle but couldn't find any.
It may be the distributor or wires as well. I'm hoping it's not a valve sticking.