I first noticed this on cold start up when the RPMS are high. It would start on really high RPMs, then back off after a minute - and I notice the engine loping. I hit the gas and it went to normal idle and the loping went away. After reading some other posts I thought it might be air in the coolant because I just replaced the radiator. I tried burping it (not sure how good of a job I did), and I was tinkering with it again this morning. When I rev the engine it's fine. At normal idle (700 RPM), it's fine. When I start slowly increasing the RPMs, I'm fine till about 2100, and if I hold it there it fluctuates between 2100 and about 1800. I did this with a tach and light hooked up and it seemed to lope after the timing advanced past the 12 mark. This isn't causing any real problems but I'd like to correct whatever the issue is.

Also, as far as burping the coolant, do you put the cap back on BEFORE you shut down the engine? I didn't and a bunch of coolant spilled out when I shut it down.

 

The timing should be set a 5 degrees before top dead center, and the idle should be set at 750 rpm as per the factory service manual.

Remove and clean the throttle body, and replace the fuel filter if it hasn`t been done in a while.

 

Yea ^ x2 on cleaning throttle body and the coolant passages that run through it. Make sure to get a new gasket for it and clean out all vacuum ports.

 

Does it do it while driving? Possible TPS worn.

 

Sorry if this is a stupid question, but I'm carbureted. I don't have a TPS or throttle body, do I? Also, I just changed the fuel filter.

 

You don`t have a throttle body or TPS on your truck.

Set your timing to factory spec, check for vacuum leaks, and clean the carb. Depending on how many miles are on the carb it might need to be rebuilt.

 

The 22R don't have those things. Only the 22RE.



Is this occuring with the air cleaner and housing all mounted on the carb?

Does it do that while your driving or stoped?

Does it do it when the engine is cold or at operating temperature? You mentioned about it on a cold start, but just need claification.

 

It is occurring with air cleaner in place. I only notice it when stopped - it only happens in that very specific RPM range. I first noticed it on cold start, but was able to duplicate it at operating temperature as well.

I'll do the propane vacuum leak test to see what I find.

 

Ah didn't see carb in the signature... >_<

 

Carbs are normally pretty consitant with fuel deilvery.... possible over the years some trash and or debris developed in the some of the various ports in the carb.... i would try cleaning it or running a good fuel addative for a little while like the "Lucas Fuel addative" or a little bit of sea foam.

Possible drop off in distributor advance.

 

Couldn't find any vacuum leaks, and ran sea foam through the booster vacuum line yesterday. No change. I'm not so OCD that I'm going to rebuild the carb over this, since it's a pretty minor issue...I think.

 

While 300 rpms fluxuation is not a lot, it is not normal.

The only time I'm at 2100 rpms is either on a cold start fast idle or just passing thru it as I'm accelerating. If it occured at crusing speed, then a further diagnostic would be in order.

 

I have exactly the same behavior in my 1988 22RE, so that may rule out the carb. I don't have a tach so I'm not sure what the exact range of RPM fluctuation is, but like you, it doesn't do it at idle or higher RPM. Only if I try to hold it above idle.

It's keeping me from getting an emissions inspection, so it's a serious issue for me. I'm going to try running all new vacuum lines, the existing lines look horrible. Hopefully that's the issue.

 

Could it be the EGR valve? I'm going to check mine today. I just changed my distributor because the vacuum advancer was bad. Apparently the VA has a vacuum line going right into the EGR, so maybe it's related? Read somewhere that EGR kicks in at "cruising" speed, which sounds about right at these RPMs. Anyone offering advice keep in mind that I have a California model (according to the FSM it's a different EGR)

 

I was just reading about the EGR's intended behavior in the FSM, and I think there's a good case for checking it for this issue.

 

Update - good news and bad news:

After troubleshooting the EGR system, I found my BVSV to be defective. Lucky enough to find one off a Camry at the picknpull that fit, and now my EGR system tests out just as the FSM says it should. The bad news is that the idle problem is exactly as it used to be. Totally at a loss at this point.

 

I did learn a lot about my carb and how vacuum lines work - this was my first time ever really messing with this kind of stuff. BTW, I did find that my carb is an Aisin, and I found a metal tag on it with the numbers 35071 on it. Any idea what that might mean? Just curious if that means that the carb was rebuilt already. I know that the idle mixture screw cap has been drilled out already.

 

Close, it's Aisan.

Aisin made your transmission.


My carb tab is similar. It begins with 35xxx. I don't know specifically what it means. Maybe it means the number of the build quantity of the carb?

I do know that my carburetor's electrical plug (choke, outer vent control valve, fuel cut solenoid) is square. Some are round.

With that idle screw drilled out, it is a safe bet that something has been done to it like a rebuild.

 

my 90 22re does something simaler, not long after i got it i noticed a vacum line going to something on top of the motor that was disconected and plugged off with a ball bearing. after i plugged it back in the truck starting revving and falling off abt 300 rpm at warm idle, then i noticed that when its plugged in the thing it goes into makes an odd sound, also my cold aile seems to be extra high at around 2000-2100 rpm. for now i disconected the vacum line and replugged....

 

Can you post some photos of the line and what it's connected to, or should be connected to?