95 Tahoe 5.7 TTBI no start, rough idle, and stuttering

[sull1102]

Bought this truck a little over a week ago, everything was great until a couple days ago it became a struggle to start. Its been cold and snowy up here in Boston for a few days now so that doesn't help. Yesterday wouldn't start at all so I replaced the plug wires cause I knew they were crap. Noticed the belt was real loose, was planning to replace it this week anyways just needed another couple days. It started no problem with the new wires. But ran like crap and I can hear a little pop type noise in the cabin now from the motor. Parked it after running for a couple minutes and then it wouldn't turn over the rest of the night. I noticed on the wires had a black shorter boot and a brown long boot. I put the black ends on the distributor. I am also getting code 15 for coolant temp sensor, the temp guage barely moves in the car but the heat does eventually warm up. This morning it started but I had to hold the gas down to turn over.

The biggest symptom I have nailed down now is that it will start stone cold and run like crap hesitating. Won't turn over when warm.

 

[Dowsewashere]

Timing sounds like its off if its backfiring or popping. You sure 100% your plugs wires are correct too. Or your fuel pump is dying/ fuel filters garbage

 

[retorq]

The temp sensor that reports to the Ecm and the one reporting to the gauges are two different sensors, if the one reporting to the Ecm is bad it will report it's super cold or super hot depending on how it failed, that will effect the starting characteristics of the engine. Fix that and I bet it clears up atleast some of it.

 

[sull1102]

Replaced the temp gauge on top with two wires cpnnecting, not the sensor between plugs 1&3. Didn't do much of anything other than make the stumble a little worse. The idle stays right under 1,000 at idle but doesn't feel as smooth as it did a week ago. Starts with the pedal floored usually, but sometimes even that doesn't do it. Threw a new belt on last night for the hell of it. Bought the new fuel filter, but you can smell gas big time when it doesn't turn over.

---------- Post added at 12:43 PM ---------- Previous post was at 12:42 PM ----------

Also got the popping to stop by using two old plug wires that fit the distributor much better.

 

[95escahoe]

How's the TBI unit look?

Sent from my HTC One X using Tapatalk

 

[sull1102]

The injectors are spraying perfect. Drove it this morning, but when I tried to start it an hour later it won't turn over at all. It cranks and cranks and if I'm holding the peddle down it'll eventually stumble to about 700rpms and die within a second.

 

[retorq]

Are you 100% sure you are getting spark when it won't start?? Perhaps have your ignition module tested ...

 

[Chevrolado]

The new coolant temp sensor you put in up on the manifold.. Was it cheapo or legit AC DELCO?
I had the exact issues in my 95 TBI Tahoe and I replaced with a cheapo and it died on me. Then I replaced the pigtail connector to the sensor and threw in a real AC DELCO sensor and bingo.. Was good.

 

[sull1102]

I did in fact buy a cheapy Duralast from Autozone. Was all set to call it quits and bring it to a shop, but guess I'll try hunting down a ACDelco sensor sith pigtail first. How far back did you go with the pigtail to the old wires, seems like the current pigtail is in okay shape, but I'm not cutting any corners this time.

Is Delphi as good as ACDelco, was a Ford guy before this so I'm use to Motorcraft haha.

 

[Chevrolado]

My pigtail connector looked pretty bad, so that's why I definitely did it. I just went back about 6-8 inches maybe. Not too far back. The new pigtails you buy don't really come with THAT much wire on them so you don't have to go too far back.

I think Delphi is fairly good for some items. But after my debacle with a non ACDELCO.. I'm basically in the mindset moving forward that if I'm hunting for any parts and I see ACDELCO makes it, I'm buying that instead. Just easier to do so and be able to have some confidence in my parts.



Just to add some info since it helped me determine it all.. The coolant temp sensor in this truck basically is like the choke these days. It tells the computer, "we have hot coolant, so run the motor as you are running full operating temperature." or vice versa.. "its cold coolant, run the motor as cold until I tell you further."
Mine was not functioning properly and basically telling my computer, "give it gas! give it MORE GAS!" when in fact, it didnt need that. So it kept flooding my motor (thus, it wouldn't start unless I had full throttle applied). When you apply full throttle when turning it over, it cuts off the fuel delivery, thus its no longer flooding it and it actually will start.

I discovered this when I took off my intake and let someone else turn it over.. I watched the injectors spraying fuel (a lot of fuel), but no start. Then as soon as they threw in full throttle and turned it over, no gas spray and voila! Started up. Ran like crap.. but it started when there was NO fuel spraying.