'90 F250 351W - Rough Starting after Smog Delete
 

Hi All,

I know this is a subject that's been beat to death, I just feel like I'm missing something on it. I think I've been to the bottom on the interwebs searching but haven't found the detail I'm looking for.

So I have a 1990 F250 351W. In 2020 I had the exhaust redone with a magnaflow catless y pipe to a JBA exhaust system.

Since the smog system was no longer in play, at first I just ran a shorter belt and bypassed the system. No issue.

Last year I started to remove the associated hoses, valves, etc connected to the system. At first, I just took out the can and muffler on the passenger side fender and the few lines that were connected to it. Capped the lines that I didn't remove until I could get to the rest of it. My theory was, if the pump isn't engaged, it shouldn't affect anything.

Now the truck isn't a daily driver and doesn't see a lot of use. When I go in the garage and take the battery tender off, it fires right up. When I go to restart it, is when I have the issue. Doesn't matter if it's restarting 10 seconds after I first start it or 2 hours within 1st start. Engine warm or cold doesn't make a difference. The engine coughs and sputters, the voltage gauge swings like crazy, and does this weird low lopey idle (occasionally stalling) for about 8-10 seconds. Then it straightens itself right out and it runs no problem. The truck sits overnight, I start it the next day, first start is no problem again.

I'm fairly confident I've removed all the right lines, the back of the heads are plugged, I removed the air lines from the OEM exhaust manifolds and plugged the holes. I tend to believe this has to do with the vacuum lines that remain. I ran new lines based off info I'd seen in related threads. The set up in my truck regarding the vacuum canister seems to be different from a lot of the "coffee cans" in the forums I look at. Not sure if that's a factor.

I'm out of ideas on how to fix this so thought I'd list it here. I believe it's related to the smog and not another issue since it began as soon as I removed some lines.

Some pics below:

https://cimg8.ibsrv.net/gimg/www.for...f6a4c6294e.jpg
All lines removed

https://cimg3.ibsrv.net/gimg/www.for...ef2a11aee1.jpg
Belore I had the air lines off the exhaust manifolds removed, but top ports of the tab/tad solenoids are capped. I ran a hose from the top port of the EVR and tied it into the bottom ports of both tab/tad. The bottom EVR port has a line that runs to the EGR.

https://cimg6.ibsrv.net/gimg/www.for...2b56becb8f.jpg
I ran a line from the intake tree over to the plastic reservoir cannister. Split it into 2 ports on the cannister based on something I had seen. Not sure if that's right or not.


I'm kind of at a loss now where to go with this. Any help or ideas would be appreciated.

Thanks

Not sure why you have the TAB and TAB solenoids connected to the EVR... I suggest you remove that. Instead connect the EVR bottom port to the output of the vacuum canister and top port to the EGR valve. Don't connect any vacuum lines to the TAB & TAD solenouds but leave them electrically connected.

That vacuum canister has 2 chambers, if you're not using both you don't need to attach vacuum to both.

https://cimg8.ibsrv.net/gimg/www.for...0f13665eab.gif

Will definitely do that. Thanks for the input!

Made the changes today and I thought it worked on the 2nd start after the initial startup, but it kept doing the same thing. I got a video of it and the voltage gauge going nuts, but it's too big too upload.

https://cimg1.ibsrv.net/gimg/www.for...5e7c46374f.jpg
https://cimg6.ibsrv.net/gimg/www.for...1304dac57e.jpg

Did you note that your EGR solenoid is mounted upside down?

I did, which to my knowledge has been like that a while. Can't say I've studied its orientation before this process. Could've been put that way when the motor was pulled several years ago.

I'll take another look and double check those lines, but so far, same result.

I took another look at the lines and they are in the correct spots. The only thing the change seems to have done is make the 2nd startup slightly smoother, but everything else after that is still the same.

Could be another issue for all I know, but this appeared right after removing the smog system.

Is there any vacuum on the line at the EGR valve at idle? There should not be but if there is that will allow some exhaust gas into the motor which would definitely result in a rough idle. You should flip the EGR solenoid around the other way, I'm not sure it will make any difference but you may have to change it anyway if you do find there is vacuum on the EGR valve constantly.

So to continue this saga, I bought a vacuum gauge to check the EGR valve. I put it on the end of the vac line with it connected to the EVR, no movement at idle and no movement while under throttle.

I did pull the EVR and flip it right-side up.

I reversed the gauge and left the line on the EGR and put the gauge on the other end, same result. No movement at idle and no movement under throttle.

From what I've read, no vac reading under throttle means the EVR is bad. But with my system modified now, I wasn't 100% sure so I didn't get a new one yet.

I tested the electrical connector on top of the EGR and that seemed to read okay.

I keep feeling like this is something vacuum related. I've moved the lines around a bit playing with different variations of what comes off the vac tree to the cannister. But all it does is choke the truck more when starting. With the way I have it now, it starts fine when I first do it after the truck has been sitting. Anything after that other than sitting overnight causes it to choke for a few seconds. Right now I have one line running from the EVR to the EGR and another line running from the EVR to vac reserve cannister. That's it. The port on the vac tree from the oem line set up is capped.

If I start the truck with my foot barely on the throttle, it seems to start normal. But when I take my foot off within the first 8 seconds, it stalls. I have to start it, let it do it's lopey idle for 8 seconds and let it smooth out naturally. If that makes sense at all. Tough to explain it without a video.

https://cimg5.ibsrv.net/gimg/www.for...be2cf25fb4.jpg

You need a line from the engine vacuum tree to the vac resovoir too otherwise the EGR has no vacuum to work with.

That's what I thought as well. Whenever I've done that, the truck still chokes. Unless I'm putting it to the wrong spot on the cannister. I'm using the top chamber. Bottom chamber ports are capped. But there's not too many places the line can go.

I appreciate your feedback on this.

Here's a short video clip as well

Edit: the vac can should be able to be unhooked completely. Vac line from manifold to EVR than to egr.

No. The HVAC system has it's own vacuum reservoir. Yes there is a check valve inline.

yea, I had a brain fart. Had to walk out and look under the hood of mine.