Oh great, Jimmy's acting up again... Please forgive the sorta off-topic post.

My truck is a '91 T-15 Jimmy, 4.3L TBI. It sat outside all day long so it was pretty damned cold when I went to fire it up this evening. It started alright, but just chugged for a few seconds and died. I had to give it a little gas to keep it running (not a big deal, but unusual for Jimmy). I put it in gear (700R4) and chug, stall. Okay... Fire it up again, a little more gas, and I got him moving. Now it's hesitating pretty bad when it's cold (I thought it was going to stall when I went to make a left through a busy intersection), and low on power with a slight hesitation when hot. It seems to idle fine when it's hot though. Any suggestions?

The fuel and air filters, plugs, wires, cap and rotor are all fairly recent and the CES light is not on.

Thanks guys, and again, my apologies for not even mentioning an f-body in this post.

 

This may sound almost stupid- but- I have found on the TBI's that if the PCV valve gets dirty- and then the weather gets cold (i.e. any liquid crap in the PCV solidifies (even oil)- the engine will run screwball. Check it and clean/replace as necessary- this may just be your problem.

 

Thanks for the suggestion, it's worth a look. I'm close to just taking the damned thing to a shop to screw up for me...

Any other ideas guys? C'mon, this thing is almost identical to a TBI 350, just minus two of the middle cylinders...

 

dirty tbi injectors? just throwing out ideas here

 

How much gas is in the tank? Might want to try some gas line anti freeze. Cold weather and a low fuel tank can cause drivability issues

 

Well I ran some injector cleaner through it... No help. I also filled up with Ultra this morning (from roughly a quarter tank of regular), and it's still running like crap. The timing was a little off but tweaking that didn't help one bit. I'm just going to bite the bullet and take it in to get looked at on Friday. The damn thing barely got me through a busy intersection in Burlington today. Screw it, enough's enough.

Thanks for the advise guys. Damn truck...

 

do you use the in tank injector cleaner?...if so try the throttle body spray cleaner as well. also that in tank stuff will take a at least a full tank of driving to work. anyway, maybe drive it a bit more and use the spray cleaner and see what happens...like give it till monday or something.

just wondering why you filled up with premium?

 

Well I filled up with premium because I usually fill up with mid-grade, sometimes regular, depending on my mood. The last time I filled up before this started I filled up with regular. I figured a quarter tank of regular (I always fill up when it hits the quarter level) and three quarters premium should pretty much feed the bloody thing what it's used to. Naturally, that didn't help...

The shop I left it at this morning turned out to be a joke. All he did was move it around back, let it sit there all day without calling me at work (he had the number), and when I went to check up on it at the end of the day he told me it needs a tune-up. Get this, he wanted me to leave it there until next week, when he'd replace just about everything including the parts I replaced last spring (cap/rotor, wires, etc...) and last month (air filter, etc...). He also mentioned that he'd have to buy a timing light first. Yeah alright, I'll see you around. Hell, even I have my own timing light...

So I fought with it all the way to good ol Wilf, a good mechanic who should know what to do but kinda likes to take his time, is out of my way, and is always busy. Hopefully Jimmy will be purring like a rusty ol Chev sometime early next week. At least Wilf should have his own timing light...

 

hmmm.....that one guy sounds a little sketchy to me. good luck with the next guy. by the way....if you dont need high test gas, just buy regular. you will make the most pwoer on the lowest octane without the motor detonating.

 

I've noticed that some cars actually do get better mileage with midgrade rather than regular. I just kind of mix it up now and then between the two just to see if I notice the change. With the Jimmy, not so much, but I definitely notice a difference in the minivan.

Oh yeah, one more comment that mechanic made that I forgot to mention. He said that the valves clacking when cold is caused by pre-ignition and his "couple of hundred" dollar tune up would help. Now correct me if I'm wrong, but doesn't pre-ignition occur when the engine is hot? Y'know, the air/fuel mixture igniting before the plug fires due to hotspots in the combustion chamber? How exactly would that be worse when the engine is cold? lol

Thanks for the advise though. This other guy should be much better, although I'm thinking Tuesday or Wednesday before he even looks at it. Till then, it's either the minivan or I get my brother to come in from Milton and pick me up. (He owes me a few trips anyway... lol)

 

Any more ideas guys? This thing is running so bad that I'm actually taking my father's minivan to work tomorrow.

One mechanic can't figure out what's wrong and claims the computer says it's healthy, another claims that his scanner shows it as running stupidly rich and he thinks the six month old aftermarket cat is probably clogged. This guy also wants me to pay around a grand for an OEM cat and EGR valve, installed... At least the aftermarket cat as a three year warranty so I'll get it checked out.

 

Suggestions,

To elimintate the exhaust being clogged as an issue, remove the egr valve and see if it starts. No valve = another way for the exhaust to get out, but be careful since it could backfire out of there too.

This will require 2 people, crank the engine over and manually open the throttle blades. I had to do it this way to get my car started when the fuel pump busted. Couldn't get it started for the life of me using the gas pedal. Manually open the throttle blades and fires up first attempt...

Check your fuel pressure, ensure its running b/w 9-15 psi, then this will require a mechanic, but check if the GPH rate is enough as well. I've seen cases where the fuel pressure read ok, but the flow rate was barely enough to keep it going. Clogged fuel filter/blocked line/failing fuel pump can cause this

 

Hmm... Removing the EGR valve and letting it run never occured to me. I doubt I'd need an extra set of hands though, sine it does fire up and run as-is. It just runs really bad.

The second mechanic did test the fuel pressure and said it was within spec for a TBI setup, and mentioned that a flow test would be a good idea but I'm not sure if he actually did one or not.

So far the following has been done, in no particular order and probably missing a few:

New cap/rotor
new plugs
timing reset
new fuel filter
new temp sensor (I think he replaced the one for the gauge only though)
new ignition control module (no help, the old one was reinstalled)
injector cleaner
air filter
O2 sensor and aftermarket cat last summer
plug leads last spring (I tried my original coil lead and it didn't help)
fuel pressure test

I'll play with the EGR valve this weekend, when I call the place I got the cat installed. In the meantime, is there anything else I should look out for? Thanks for the suggestions, I'd love to get my truck back. Even dad's minivan died on me this evening...