Been chasing this down for weeks now, mostly by reading this forum and trying everything. Learned a lot and really appreciate everyone who posts useful stuff.
I got a 1987 2500/V20 (5.7 TBI) off of a guy who was an "engineer," which is code for "cut every wire in the truck four or five times and drilled so many holes the dash is Swiss cheese." It's only got 70k miles on the body, and the engine is on its third block - he put a crate motor in it and it had a wild nut or something, so it got a new block about 30k miles ago. The thing absolutely purrs at idle now, but -
I have the usual symptoms - running hot - it sits at 210 at idle but runs steady 235-240 at 55mph - (new thermostat, radiator, and CTS), it was idling really high (replaced the IAC, fixed that), and stutters at 65mph in 3rd gear. One other thing that's weird is that the in-dash volt meter reads 8 or 9 volts. When it's running it reads 14.5 at the battery, and I've checked all over looking for a bad ground or cut wire or something. I've gotten a couple of low voltage to computer SES codes. I've also replaced the TPS, MAP, and.. whatever the other sensor on top of that little tree is. No change. Smellin' fuel real bad and all that, too.
He told me right when I bought it that his mechanic had "done something" to make it pass smog. Who knows what. Timing is about 2deg advanced with the ETS or whatever cable unplugged.
I finally took the throttle housing thing off to watch the jets and man is is pouring out fuel. I took a short video of it. Be careful, it's loud. This is at 800rpm at idle:
Is the O2 sensor next, or do I just take this damn truck on a one-way trip to the pickypull?
Yep that showed me what I was looking for and while it looks a little funny with the splices it looks o.k.
how new is that cts?
What I would suggest you do is run winaldl on a laptop and look at the sensor read outs to see which sensor is faulting. The cable can be made for almost nothing or bought for maybe $20 on ebay. the software is free just google winaldl.
Thanks, I may take a shot at that. I was reading some more last night and now I'm wondering if I have a bad ground somewhere, too since my voltmeter is so low and my oil pressure gauge bounces around.
yeah I would say but really hard to tell. I agree that it is likely a grounding issue. What you could do is get an ohm meter and touch the engine ground to battery ground. should be zero resistance to ground. There should be a strap behind the engine from passenger head to fire wall. There should be a strap front passenger side down low to frame. Yank on them good to make sure they dont look ok but are actually rotted.
Well, the O2 sensor looks brand new and the battery - to ground is .2 ohms. I can't trade the line from the O2 into the cabin right now. I'll take a look at that windows code scanner deal.
replaced my o2 sensor and my cabin temp sender with units from picknpull. truck is running much better, less hesitation at full speed.
oil pressure is still off the charts - 50-60 no matter what the engine temp or speed. oddly, my battery gauge has gone back to normal. i wonder if the old o2 sensor had a short or something.
i also took the entire throttle body off the same truck at pickypull and i'm gonna try just cleaning and straight swapping the injectors tonight. i didn't realize how cheap it is to get them rebuilt and matched, so may do that.
winadl USB cable should be here tomorrow or tuesday.
as for the oil pressure: i have run multiple rounds of cleanout stuff through the engine as the original oil i got it with looked like it just came out of the ground and stank bad. now it's running clean and clear but i'm wondering if some gunk got stuck up in the lines or cooler.
You can also check grounds or almost any other wire by measuring between both ends with a voltmeter while the truck is running. For example, put a meter lead on the battery -ve terminal and the other lead on the firewall. Or, put one lead on the battery +ve terminal and the other lead to the fuse block in the interior. You should measure close to zero volts if the wire is OK. Sometimes an ohmmeter check can lie to you.
Also, grab both ends of any suspect wires and give them a solid pull. Any wire that stretches has a break in it.
I'd also say you need to break out a soldering iron and do a better job patching up some of those butt splices I can see. Try a decent solder joint and some dual wall heatshrink to seal the connection. The wires are bare coppen and they will corrode any place that the insulation is broken.
You should be able to figure out what's going on once you get the ALDL cable.
I have seen the EGR valve cause poor off idle operation because it was sticking open.
Edited by 65_Impala on 07-10-12 09:10 PM. Reason for edit: No reason given.
FWIW, my van had the trans out and I found the ground on the back rear of the block was left loose. Cleaned it up and fixed it but I think they didn't do a good job of tying up the back of the motor on the trans swap - the oil pressue sender was replaced, but it reads erratic - pegs the needle frequently - which I found was due to some kind of issue in the plug - if I push the wires in it goes away, if I wiggle them or pull them out, it acts up. Sooner or later I'm replacing the entire plug; I need to change the O2 sensor and I may change out the wire plug on it, too.
And that's not the first truck I've had that's had something out and wasn't put back together quite right, either.
Now you say this is on it's third block, makes me wonder how good of a job they did on the install.
It wouldn't be hard to pull the entire underhood engine harness off a you-pick clunker and replace it and see what that does for you. (I pulled one out of an '89 Suburban with the motor pretty easily).
Those who can, do. Those who can't, criticize it on the internet.
1991 G20 van 5.7L - swap meet spl.
1993 3500 dually 5.7L NV4500 - tow truck
1991 Suburban 5.7
Plus cars for swap and sale
&yes, I once tried a frame swap on a 51 Chevy.
When I pulled the motor out of said Suburban you could find the flat strap pretty easily on the passenger side rear of the engine. Maybe it's missing. Not hard to just run a new wire from say the stud on a manifold bolt to the cowl, though.
Those who can, do. Those who can't, criticize it on the internet.
1991 G20 van 5.7L - swap meet spl.
1993 3500 dually 5.7L NV4500 - tow truck
1991 Suburban 5.7
Plus cars for swap and sale
&yes, I once tried a frame swap on a 51 Chevy.
Well I was super excited to get winadl going, but I can't get anything to track. I did get the new injectors in. They went in easy after all my practice screwing them up last week.
Still pretty drippy, tho, so I guess I'll have a look at the fuel pump next.
If your grounds are poor/missing then your sensor network doesn't have a snowball's chance in Hell of working properly. Excess resistance due to poor connections wreaks havoc on the CTS (coolant temperature sensor) circuit in particular; the higher the resistance reading, the colder the computer thinks the coolant is - which richens up your fuel mixture considerably.
Short version: don't overlook how important good grounds are to how your engine runs.
Got winaldl running. Fantastic program. Cabin temp sensor was up to 250 as I was dragging it around the block in first gear at 3100 rpm, but you can see the CTS never got above 190 no matter what. I did jerk the ground a few times and verified 0 ohms from battery to block. I'll upload the logs if anyone is interested in having a look.
Anyone interested in reading some ADL logs? I found some time to have another whack at this truck, but now I'm thinking it's probably time to cut my losses.
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ThomasG
