My EGR Thread

[2mbb]

So I'm having this problem where my 1985 FJ60 (CA smog legal) has a hesitation or miss as I'm driving from about 2000 to 3000 rpm. It is apparent if I am driving at a constant RPM or if I am slowly accelerating. It's not as apparent (or non existent if I am quick accelerating). I can make it stop hesitating if I disconnect the vacuum line to the EGR and plug it.

I recently purchase and installed a new OEM EGR modulator (thanks CDan!), but I still have the problem. I spliced a vacuum gauge into the vacuum line between the modulator and the EGR valve. At non-idle RPM I see vacuum that increases with RPM, and at constant RPM the vacuum needle is steady, even when I'm experiencing the hesitation. This leads me to believe that the EGR valve is getting a steady signal from the modulator.

So what's the next step? should I replace the EGR valve, look at a carb rebuild, or try something else?

Other things I should confess:

I do have an exhaust leak when the engine is cold. However, I don't think it is an intake leak, at least I haven't detected one using carb cleaner.

The engine seems to run fine at constant speed on the freeway. This problem is really only apparent when I'm driving around town on surface streets.

Thanks in advance for the help.

 

[Butt Ugly Chuck]

Tuning in for the solution.
Good luck!
Butt

 

[Joe_E]

So I'm having this problem where my 1985 FJ60 (CA smog legal) has a hesitation or miss as I'm driving from about 2000 to 3000 rpm. It is apparent if I am driving at a constant RPM or if I am slowly accelerating. It's not as apparent (or non existent if I am quick accelerating). I can make it stop hesitating if I disconnect the vacuum line to the EGR and plug it.

I recently purchase and installed a new OEM EGR modulator (thanks CDan!), but I still have the problem. I spliced a vacuum gauge into the vacuum line between the modulator and the EGR valve. At non-idle RPM I see vacuum that increases with RPM, and at constant RPM the vacuum needle is steady, even when I'm experiencing the hesitation. This leads me to believe that the EGR valve is getting a steady signal from the modulator.

So what's the next step? should I replace the EGR valve, look at a carb rebuild, or try something else?

Other things I should confess:

I do have an exhaust leak when the engine is cold. However, I don't think it is an intake leak, at least I haven't detected one using carb cleaner.

The engine seems to run fine at constant speed on the freeway. This problem is really only apparent when I'm driving around town on surface streets.

Thanks in advance for the help.

Pre MUD, and internet for that matter, I had a hesitation that bothered the hell out of me. I put a half ass auto parts store rebuild kit into the carb and that still didn't work. I wound up going Weber which took away the hesitation but led me down a road of chasing an inspection sticker. I wish i would of went with a pro aisin rebuild like Jim or Mark but I didn't really know of them back then.
Don't think it would hurt to start there if you've never had one, it'll NEVER be a regret.

 

[sk8salomon]

I had something similar where i heard a slight whistling sound between 2500~2800 right before a shift point. It wouldn't do it at idle by reving up, only when driving so it was difficult to detect. I finally had to pay an engine shop $65 to put it on a dyno so I could drive it while somebody stuck their head under the hood. The guy found my EGR was not working or leaking so I temporarily plugged it until I finally replaced it with a used part. No more whistling but I still have an uneven acceleration. I suspect an intake leak or near the carb. I'm going to use your carb cleaner trick to see if it truely is a leak. Otherwise, I think I will adjust the carb screw by lean drop method.

 

[hank14]

I had luck cleaning out my EGR valve with a thorough spray down (inside and out) with Seafoam spray. It seemed to be the only thing that solved my surging and bucking issue. It would be worth a try before springing for a new EGR valve.

BTW- with a cold engine exhaust leak, do you get any afterfire out the exhaust?

 

[2mbb]

BTW- with a cold engine exhaust leak, do you get any afterfire out the exhaust?

No afterfire, just a psst, psst, psst sound.

 

[LAMBCRUSHER]

I'm guessing weakened egr diaphram, causing it to open prematurely.

 

[chitown40]

I can make it stop hesitating if I disconnect the vacuum line to the EGR and plug it.

That statement above is the key. The EGR valve is leaking. If it were me and I had to keep all of my smog equipment on the engine, I would remove the EGR valve and weld the pipe shut. then re-install it. It would retain your stock look for visual inspection and it would stop the EGR valve from leaking/opening.

 

[LAMBCRUSHER]

Only prob w/ the above trick in cali- and maybe other places-, is if the tech applies vacuum w/ his hand held pump to the valve at idle to see if the engine stalls out as it would w/ a functional egr system, it would not stall out due to the lack of non combustible gasses being able to get to the cylinders

 

[Pin_Head]

It sounds like a lean misfire because closing the EGR makes it go away. Either you are getting too much EGR opening (unlikely) or it is the combination of a leaking intake manifold (associated with the exhaust leak) plus the EGR makes it too lean (more likely).

 

[2mbb]

I can make it stop hesitating if I disconnect the vacuum line to the EGR and plug it.

That statement above is the key. The EGR valve is leaking.

I don't quite understand what makes you think the EGR valve is leaking. When I disconnect the vacuum line to the EGR valve the hesitation problem goes away, indicating that the EGR valve is properly closing when there is no vacuum applied. Can you provide some more details? Thanks.

 

[2mbb]

It sounds like a lean misfire because closing the EGR makes it go away. Either you are getting too much EGR opening (unlikely) or it is the combination of a leaking intake manifold (associated with the exhaust leak) plus the EGR makes it too lean (more likely).

Thanks. I'm not looking forward to replacing the intake manifold gasket again, but...I guess maybe I'm looking at that and pulling the EGR and making sure it's working smoothly.

Any other ideas?

 

[chitown40]

I don't quite understand what makes you think the EGR valve is leaking. When I disconnect the vacuum line to the EGR valve the hesitation problem goes away, indicating that the EGR valve is properly closing when there is no vacuum applied. Can you provide some more details? Thanks.

I apologize 2mbb.. I misread exactly what you were saying. After re-reading it, it makes sense that the valve itself is not leaking per se, but rather another vacuum source is causing the EGR to open at the problem rpm range. My solution was desmogging to eliminate the hesitation, but that's not an option for you. I'm going to dig around for my emissions manual and see if I can give you some more insight. Don't hold your breath though... I usually look to you for insight.

 

[2mbb]

I apologize 2mbb.. I misread exactly what you were saying. After re-reading it, it makes sense that the valve itself is not leaking per se, but rather another vacuum source is causing the EGR to open at the problem rpm range. My solution was desmogging to eliminate the hesitation, but that's not an option for you. I'm going to dig around for my emissions manual and see if I can give you some more insight. Don't hold your breath though... I usually look to you for insight.

Thanks for your help.

 

[chitown40]

2mbb,

I've been going through the emissions manual in my few spare minutes and, without a 2F in the driveway, tried to make the most sense of it that I can. I'm assuming that you havent made much more progress to date, so here are a few things I would check.

First off, there is a huge thread on the 2000-3000rpm hesitation/stumbling/stalling issue that plagues many 60 series -- don't know if you thumbed through it or not -- lots of fluff, but some good info in there.

Second, I would look at the VSV and do the tests outlined in the Emissions manual. I'm going solely off my interpretation of the manual, but it looks like your problem might be in the diagram with the ** on page 3-14. That seems like the conditions you are describing. I'd try the VSV test first.

I'm deducing that the exhaust pressure is high when you are on the freeway and therefore it doesn't meet the condition of the VSV opening the EGR when the pressure is low which might cause the rich condition and the stumble. Does that make any sense?

I'm making this assumption based on the remarks section below the diagram.

If it helps in your diagnosis, great. If not, I'll keep reading though it. Hopefully JimC or Mark can chime in with their thoughts since they know this stuff a little better than I do. Wish I still had my 60 to actually look at and test some ideas I had, and my 62 is desmogged completely already.

 

[NocalFJ60]

My first guess would be the emissions computer sending a signal to the VSV to open the EGR at the wrong time. If it does it consistently when you accelerated the same way, then it could be a electrical failure on the emissions computer in the kick panel. If nothing else, try unplugging the connector at the emissions board and reseating it.

The EGR could be sticking but it would seem like the length of the hesitation would vary if that was the case so I think it is an electrical problem.

I got some spare boards if you want to borrow one to see if the problem goes away.

 

[2mbb]

Thanks for the reply. I'm still collecting parts to replace the manifold gasket. I don't think I'll get to that this weekend, but I will do some more testing with my vacuum gauge and try locate where my exhaust leak is (I don't want to replace the gasket if it is OK).

The emissions manual is a little unclear on this point, but I think the conditions 1 and 2 happen at below 1500 rpm where the emissions computer has the VSV closed. In this condition the exhaust gas pressure will open/close the EGRvalve.

My problem is clearly happening at above 1500 rpm, where the VSV is open and I assume the throttle plate is above the EGR R Port (but I will check this). This will open the EGR valve regardless of the exhaust gas pressure. Because my vacuum gauge shows I have a constant vacuum signal between the modulator and the valve, I assume my VSV is behaving properly, but it's easy to check so I'll do that this weekend too.

2mbb,

I've been going through the emissions manual in my few spare minutes and, without a 2F in the driveway, tried to make the most sense of it that I can. I'm assuming that you havent made much more progress to date, so here are a few things I would check.

First off, there is a huge thread on the 2000-3000rpm hesitation/stumbling/stalling issue that plagues many 60 series -- don't know if you thumbed through it or not -- lots of fluff, but some good info in there.

Second, I would look at the VSV and do the tests outlined in the Emissions manual. I'm going solely off my interpretation of the manual, but it looks like your problem might be in the diagram with the ** on page 3-14. That seems like the conditions you are describing. I'd try the VSV test first.

I'm deducing that the exhaust pressure is high when you are on the freeway and therefore it doesn't meet the condition of the VSV opening the EGR when the pressure is low which might cause the rich condition and the stumble. Does that make any sense?

I'm making this assumption based on the remarks section below the diagram.

If it helps in your diagnosis, great. If not, I'll keep reading though it. Hopefully JimC or Mark can chime in with their thoughts since they know this stuff a little better than I do. Wish I still had my 60 to actually look at and test some ideas I had, and my 62 is desmogged completely already.

 

[Spike Strip]

2mbb - Did ya ever solve this ?

 

[2mbb]

No. So far I have replaced the EGR modulator with new. I removed the EGR cooler and valve and confirmed the valve is not frozen. I replaced the J-pipe with a stainless one from SOR. I tested the operation of the VSV.

I still have an exhaust leak (I think it is at the first tail pipe donut gasket). I'm pretty confident I don't have a vacuum leak at the manifold or carb, at least I've sprayed carb cleaner around and didn't detect anything. Otherwise I've stalled on this because I have some other (non-cruiser) projects I've been working on.

My next steps could be and not necessarily in this order:

1. replace manifold gasket
2. replace EGR valve
3. replace installed carb with a backup carb I have (that was rebuilt a long time ago by Jim C.) and/or send the installed carb out for professional rebuild
4. ??

 

[Spike Strip]

I'm not having this issue, but I've been doing some extensive reading trying to figure out my smog issue, and noticed a similarity with people having mid-range hesitation.

Jim Cs position seems to be it could be an issue with the ICS or emissions computer or even Vacuum switch, as the idle circuit (ICS open) is always adding fuel to the mix, at all throttle positions. If the ICS cuts out during mid-throttle acceleration, you'll get a lean condition.

Try grounding the ICS wire itself temporarily and see if the problem is still there. If you already have that wire grounded then nevermind

Other thing - if you hook up a timing light and check flashes when hesitation occurs, this can rule out the ignition. If flashes cut out when hesitation, then you know problem is spark. If normal, look elsewhere.

btw, did you ever make that SST to check the air pump output ?