What a pain in the keister: Here is a test for you!

[mike2004tct]

Originally Posted by rlith

Feel free to ask me about other symptoms, again just wanted to throw this out here for giggles and see what others come up with. Like I said, it's already fixed.

I'm asking.

What are the other symptoms.

Here's my guesses;
Did you drop 3 $20.00 bills in the TB housing?
Did you shread your K&N filter Assembly?
How about the vacumn ball cracked?

(O2 sensor would/should have sent a code, EGR symptoms are similar, but the valve is more $$$$)

[blazes9395]

Originally Posted by rlith

Actually blazee that's come close to happening to me on more than one occasion.... I have come out of someplace and because I tend to walk with my head down, all I see is a teal blazer/jimmy and my brain is on auto pilot... I sit there for a moment going "What the hell, my keyless isn't working) And try to use my key... After about 10 seconds I realize, shit, it's not my truck!!! My truck is over there! And I feel like an idiot and hope to hell that the owner didn't see me trying to get in "their" truck...

Once I had to go pick-up something quickly, as I got back to "a" truck, I got in and not even thinking went to put the key to start it up, the key didn't work, I then looked around inside and realized, IT WASN'T MINE, my truck was in the next row in the parking lot. The truck was identical. So carefully, yet quickly, got out, took my package, got in my truck and drove away.

[mike2004tct]

Originally Posted by blazes9395

Once I had to go pick-up something quickly, as I got back to "a" truck, I got in and not even thinking went to put the key to start it up, the key didn't work, I then looked around inside and realized, IT WASN'T MINE, my truck was in the next row in the parking lot. The truck was identical. So carefully, yet quickly, got out, took my package, got in my truck and drove away.

Similar to, but different than...

My MIL was sitting in our Pontiac TransPort a few years back. Some lady comes up to the back hatch, inserts a key, and twists the lock a few good times and ends up breaking the locking mechanism. She just kept at the darn thing until the mother-in-law got out and asked her "what are you doing?"
"Ooops, I thought this was my Van" , and she proceeded to wander the parking lot looking for her own van.

Didn't find out until a few days later that we couldn't lock the back hatch anymore. It stayed that way for 5+ years (traded the van 2 years ago)

[rlith]

Ok guys... Biv343 was the closest when he mentioned the MAP sensor.

Here's WHY I knew it was the MAP sensor...

If it had been the EGR the truck would have kept idle but would have accelerated though the power band rough until WOT where it would smooth out most likely.

The symptoms indicated the MAP sensor and here's why...(I'm going to cut and paste)

The map sensor is mounted on or connected to the intake manifold to monitor intake vacuum. It changes voltage or frequency as manifold pressure changes. The computer uses this information to measure engine load so ignition timing can be advanced and retarded as needed. It performs essentially the same job as the vacuum advance diaphragm on an old fashioned mechanical distributor.
On engines with a "speed density" type of fuel injection, the MAP sensor also helps the PCM estimate airflow. Problems here may or may not cause an intermittent check engine light (light comes on when accelerating or when the engine is under load if at all), hesitation when accelerating, elevated emissions and poor engine performance, cannot hold idle, and rough starting. The engine will run with a bad MAP sensor, but it will run poorly. Some PCMs can substitute "estimated data" for a missing or out of range MAP signal, but engine performance will be drastically reduced.



My words suck, so this was easier. So at 1st eliminating the egr in my head, I knew it had to be the MAP sensor because at regular running speed everything was alright, Just would stay on at idle. So 60 bux later I swapped out the MAP at a local autoparts store to where I was (they were kind enough to let me borrow a couple of torx drivers) and I was on my merry way...

[biv343]

Sounded almost like what my 85 S-10 did after I rebuilt the engine this winter, except my problem was "installation malfunction". When I first started the truck after putting it all back together, the engine wouldn't idle at all. Found out after a bit of head scratching and Haynes manual reading that I had connected the vacuum line to the wrong vacuum port on the TBI, so the sensor was reading manifold vacuum instead of ported vacuum (or vice versa). Moved the line, and it's been fine since. Mine threw a couple codes though.

[blazee]

MAP sensor? Well of course that's the obvious answer, I would have said that, but I was expecting something unusual.

[rlith]

Originally Posted by blazee

MAP sensor? Well of course that's the obvious answer, I would have said that, but I was expecting something unusual.

Sometimes the most complicated problem has the simplest answer..

[blazin97]

Mine is doing the same thing except it doesnt stall.
Here is a link to mine.

[rlith]

Originally Posted by blazin97

Mine is doing the same thing except it doesnt stall.
Here is a link to mine.

Blazer LT already gave you the solution

[blazin97]

Originally Posted by rlith

Blazer LT already gave you the solution

thats not what it is. MAF sensor is good, I bought a new one and it still is doing the same thing.

[OffRoadSonoma]

Originally Posted by rlith

My truck is giving me probs starting. I finally manage to get it started. But at low RPM it's running rough then stalls. At hwy speeds everything is fine, but at lights
I have to keep the engine revved above 1200 RPM or it just stalls.

Originally Posted by rlith

If it had been the EGR the truck would have kept idle but would have accelerated though the power band rough until WOT where it would smooth out most likely.

I would have guessed for sure it was the EGR. In your first post you said it was hard starting and stalled at low rpm's but ran better at high rpm's. I had the same thing happened to me and hooked my truck up to a scan tool and it said my egr was stuck at open 80% instead of closed to start. I cleaned it and it ran fine. So in your second quote here are you saying this is what would happen if your egr was stuck open or closed? And just for future knowledge do both the tbi and the cpi motors have map sensors? Because I have the tbi and had the motor rebuilt not too long ago but it still kinda hesitates on take off. Just wondering if that could be a cause on the tbi.

[534BC]

Originally Posted by blazee

MAP sensor? Well of course that's the obvious answer, I would have said that, but I was expecting something unusual.

I was going to say that, but wanted to give others a chance.

Anyways it's like saying "my truck won't crank" and give a few symtoms and then try to guess what it is. It could be a number of things. Some very popular, some not so popular.

[blazin911]

bad belt tensioner

intake gasket

[merc81]

OK, I'd like to add to the map sensor story. I just returned from vacation pulling a 4800 pound boat behind my 93 s10 blazer. Its a 4.3 and the boat is as much as it can pull, maybe a bit too much, but it manages.
While backing the rig down the ramp to launch the boat, the car stalled and I had NO brakes! Never stalled before and I almost lost the whole rig in the lake. Anyway, afterwards the engine ran rough, and had trouble starting but ran OK at higer RPMs just as descibed above. I did get a code on the PCM however and it was for the MAP sensor. By the way, there are no power brakes at all when the engine won't idle; there just isn't enough vacuum to run them.

Anyway, I spent my $60 bucks at a nearby Advance Auto store and installed the map sensor in their lot. That fixed my problem at once and I drove away a happy camper--for about 6 blocks and the new map sensor went bad. I returned to Advance and they had to order a 2nd one and I installed it later, this time when the engine was cold.

The new map sensor seems to work, its been a week now, but the car doesn't run as well as it used to. I get an occasional miss at idle and it seems to hesitate at low speeds. I'm wondering if I have a junky sensor from Advance auto and maybe I should try to get another one from Napa--like Advance is going to give me a refund
or if there is something else to check.
I've pulled out and checked/cleaned the IAC and EGR valves and the plugs/cap/wires are 6 months old. I replaced the fuel filter yesterday but it didn't help; it just seems like the map sensor isn't working as good as the old one did.

[rlith]

I'd pull the upper plenum and check for washing...Check plug condition as well., The map sensor could be reading incorrectly due to too much gas in the intake. If that's clean, pull the ECM battery fuse for 10 minutes to reset the computer and let it relearn.