Dirt Driver

I have a stock 196k '94 pickup with a replacement 22RE longblock I put in last year or about 12k miles ago. Something I started noticing recently is a stumble or miss off-idle before the engine is up to temp. The weird thing is that an identical '94 model my dad used to have(that he bought new) eventually started doing the same thing. It goes away when the temp gage creeps off the "cold" mark.

Anyone with similar experiences, solutions, or ideas? I'm well versed in EFI systems, so don't worry about simplifying anything.

malinjj

My '87 with a rebuilt 22re w/12k on it does the same exact thing. Only when it starts for the first time for the day. After that it's fine. When I first start it if I press on the gas it stalls, does this unless I "feather" the peddle a little. It really sucks trying to pull out of my uphill driveway with a stick. I cherp the tires ever time... LOL...

I did read in another thread to check the "cold start injector timing switch" once I figure out what that is I'll report back.

Dirt Driver

Yeah, mine only does it on a true "cold" start/the first startup of the day. It's worse and lasts longer if the weather is cool. I don't touch the throttle on startup and everything except the cold driving manners seem normal. It seems completely dependent on coolant temp.

thook

The cold start injector timing switch will only affect initial start up when cold. The idling and running is affected by the coolant temp sensor. Check that out. It's right next to the timing switch on the front of the engine.

nineball

bump for answere, mine is doing the same thing

ozziesironmanoffroad

yeah it wouldnt be your cold start injector unless another sensor is messed up. with mine, the wire plug for the cold start injector is messed up and cut off and stuff by previous owner, and was messing up the starting. it would flood the engine. i just disconnected the wires from the sensor, and my truck is running GREAT.

Dirt Driver

I haven't been back to this thread because my truck never threw any codes and otherwise ran alright, so I left it alone. Recently that changed. The economy had started to degrade and a few weeks later it did throw a check engine light. I ran the codes and got a a 21; oxygen sensor deterioration detected. I cleared the code and ordered a new Denso sensor. In the mean time the CEL was out, but it still sucked gas and stumbled. I put the new sensor in as soon as I got it on Friday and WOW! It runs like new! The throttle is crisp at any temp and I suspect the economy will improve quite a bit. Lately I have only been able to get ~27mpg with extremely easy driving. If only I had replaced the sensor back when I was getting 32mpg on the junky one....

I'm actually surprised the original sensor hung in there as long as it did. It already had 200,000mi on it. On top of that, the previous owner the truck blew the head gasket and tried to fix it with a bottle of Blue Devil. The gasket was too far gone and all that quick-fix junk went out the exhaust(along with making a mess of the cooling system and blocking up the heater).