94 pickup, 22RE. Just bought it about a month ago, and everything has been fine with it, until this morning. Started right up just like usual, after running for less than a minute, it started idling significantly higher than it normally does on cold idle (no tach, so don't have numbers), but I would guess around 2k RPM. Then after about a minute or two, it seemed to kick down to about normal idle, then started surging from about normal idle up to 2k. This is constant, up down up down. No lights, engine sounds fine, fluids normal. Ideas? Sure appreciate any help!

 

try cleaning your throttle body with seafoam of another TB cleaner

 

its normal leave it alone the colder it gets the higher the idle will be

 

no thats not normaly, read his entire post.


I would also try cleaning your throttle body and your afm with the proper chemicals..

also try a treatment of seafoam through your pcv or break booster..my idle has never been out of spec but that really smoothed it out.

 

yea sorry i never read the whole thing. the PO probaly set the idle high to get rid of a rough idle or miss. ok then... your idle is set to high or you have bubbles in your cooling system try burping the cooling system

 

I had the same problem with my '94 back in December. I had it at the shop for some other work so I asked them to take a look at the idle problem. Mine was a clogged port in the cold air idle up valve (or whatever it is called).

Does yours surge up and down while you have your foot on the brake? Mine idled high, until I stepped on the brakes. Then it would surge from 1000 to 1500, up an down.
Pressing the brakes drops the idle by cutting the fuel to the injectors (this is normal), but the cold air idle up valve wasn't shutting off like it is suposed to, and it was overriding the brake fuel cut and bumping the idle back up.

Since the port has been cleaned out everything has been running just fine.

 

Start with checking coolant level. Than air filter. Check for vacuum leaks. Could be oxygen sensor, fast idle throttle valve, AIC, etc. Process of elimination.

 

Thanks for the advice. Definitely a few things to look at. Also, I don't know if the brake does anything or not. I haven't driven it since this started. It started doing it while it was warming up yesterday morning, so I just shut it off and let it sit. It seems everything is perfectly normal until it warms up enough to start idling down, then it just starts surging up and down. Maybe a better description is it seems to be going from normal idle to cold idle, and this is fast, about once a second. It never stays at a constant rpm. If I rev it beyond where it's fluctuating, say 2500 rpm, it's smooth as silk. Let off the gas, and back to surging.

 

You might have an airleak somewhere...either in a vacuum hose or the intake tube. I found that my OEM intake tube was cracked near the TB, allowing more air in the system with being metered by the AFM. A little silicon sealant did a quick fix.

 

That's exactly what mine did, except that stepping on the brake (like at a stop sign) exaggerated it and made it even worse.

 

A good and cheap way to check for vacuum leaks is to get a can of starting fluid and spray some wherever you have vacuum. Your lines, intake, intake gasket, throttle body, etc. While doing this, if you have a leak, your RPMs will drop. If you do not have a leak, your surge will continue.

 

Update #1... I haven't actually had the time to work on this, but I decided to drive the truck to see what would happen. Day 1, turns out that after it warmed up just a little bit, everything returned to normal. No surging at all, until it sit all day at work. When I started it up to warm it up for the drive home, back to surging again, once warmed up, it was fine. Day 2, decided to drive it to work again. This time things got more interesting. With the temp guage up almost 1/4, NO heat from the heater. As I'm driving, all of a sudden it starts blowing heat, but not as hot as normal. When I got to work, I went to check the antifreeze and first of all I notice that the radiator cap is completely cold. The coolant was low in the radiator, but had filled up the overflow resevoir almost to the top. (I don't think I lost any coolant, it just pumped it into the resevoir.) When I started it to come home, I left the radiator cap off, and after it started warming up a little, the antifreeze come up (slowly) and started overflowing out of the radiator. I replaced the cap, and drove it home, everything seemed fine. Heater was blowing hot, temp normal, truck run fine. No water in oil, no water from exhaust. My dad swears it's the head gasket. Please advise.

 

I've seen a 22RE headgasket go bad and do exactly the symptoms you described. Good luck.

 

You might want to replace some of the simple/inexpensive parts first. Start with the thermostat and radiator cap since you have irregular heater/heating problems. For all you know, these items are original and should have been replace several times over the years.

I recommend getting the dual thermostat for reasons stated here:

http://www.4crawler.com/4x4/CheapTri...tml#Thermostat

One of the ways the motor adjusts its idle and fuel mixture is by the temperature of the coolant. If there is an issue there, you'll have funky problems.

Also, bad headgaskets almost always cause the motor to overheat, which doesn't seem to be your problem at the moment.

Here is a list of causes for an irregular idle on a 22re:

Low on coolant

TPS out of adjustment. Go here for checking and testing the TPS

http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

Vacuum leak(s)

Idle set above 950 RPM's

Dirty throttle body due to sludge buildup

Sticky dashpot diaphragm

Faulty thermostat/faulty coolant temperature sensor

Bad headgasket

Faulty, misadjusted, air valve/IAC/ A/C idle up valve(s)

 

Also check your timing, mine was off and did the exact same thing, some days would surge really bad, and other day's not so bad. Definitely try the brake test, if it makes a difference if the brake is pressed, than it might not be such a big deal, just something out of adjustment.

 

Most likely dirty throttle body, if you clean and see no improvement try running a diagnostic for defective sensors. Temp sensor, air flow sensor or even tps. Which also leads to possible faulty thermostat or trapped air in coolant. Lastly i would go over vacuum hoses. Good Luck

 

just read your follow up post, since we know it is coolant, now you have to find leak or assume you loosing coolant internally.

 

Well, it looks like the head is coming off. I flushed the coolant this weekend and replaced the thermostat. I also did the Seafoam into the PCV line. And the funny thing is the truck ran fine on Saturday. This morning I took it to work, and when I shut it off, it gurgled really bad for about 10 seconds. On the way home from work, little to no heat from the heater. When I got home from work, I left the truck running, and when I looked under the hood, it is constantly blowing air bubbles into the resevoir. This is really weird, isn't it? At this point, it looks like pulling the head is inevitable.