Another Tahoe Wont Start Thread

[Chevrolado]

So I've been reading through all of these non-starting/won't run/etc threads and I still haven't found much to fit whats going down with mine right now. So I'm just going to bite the bullet and post it up.

History:
Brand new 350 5.7L motor with Edelbrock Performer Heads, Performer TBI Manifold, Performer-Plus Cam, Flowtech shorty headers, and an Edelbrock piggyback ECM chip installed in my 1995 Tahoe 4X4. New MSD Cap, rotor and coil with 8.5MM super conductor wires running to Autolite spark plugs.

Upon initial run, had three issues.
#1; it had coolant leak at the water pump heater hose connection.
#2; On cold start up, the idle would bounce around 500-700 and it would bog down and hesitate every time I pressed the gas pedal. Once it got to operating temperature.. thing ran like a champ! No issue.
#3; thermostat wouldn't open until temp gauge got to ~260 degrees. Then it would open and temp would drop and hold steady at 210. Still too hot in my opinion. It should be lower than that, right?

Attempting to fix it:
I replaced the fitting in the water pump for the heater hose and it has appeared to have fixed the leak in problem #1.

I then replaced the Coolant Temperature Sensor in the manifold thinking it was causing the hesitating issue during cold run to try and fix problem #2. The following day, the SES light came on and the code was for "Coolant Temp - High". Makes sense because of problem #3 I am thinking.

Problem #2 still remained after the new CTS. So I kept running it (driving it to and from work) and I've put about 430 miles on the new motor.

New MAJOR issue:
Then on Friday - full operating temperature - running totally normal - I was at a red light in normal 700rpm idle, light turned green so I press the gas and the thing bogged out and died. Couldn't get it started again.

Now the ONLY way I can get it running again is wide open throttle while cranking it. Then it will idle at 1000RPM. As soon as I give it throttle.. bogs out and dies again.




Things I've tried:
Took out the Edelbrock piggy back chip back to stock ECM - Still the same.
Checked spark at coil - coil produces what looks to be good spark.
Checked spark at end of a wire - spark was seen.
Swapped whole ECM from a 93 Chevy truck (just to see) - couldn't get it started at all (even with WOT).
Checked underside of cap/rotor to see if any visible issues present - all brand new, looks great.
Cleaned out coolant temp sensor plug (electrical side had some gunk/glue looking stuff in the prongs) - seems good, but I still might get a new CTS pigtail installed just to be sure.
Changed injectors/pressure regulator in TBI - still appears to be dumping plenty of gas through it.

 

[97Tahoe2d4x]

Have you checked throttle position sensor? My buddy had a '95 that seem to eat TPS every so often and had similar bogging prob when stepping on go pedal.

Just a thought....

Nice looking 'Hoe BTW.

 

[SunlitComet]

verify proper operation of the tps sensor as well and if you replace any sensor use only a delphi or delco part. Also do some engine vacuum tests while this is going on to see the idle vacuum as well as under load and the during the failures you are having.

---------- Post added at 09:32 PM ---------- Previous post was at 09:30 PM ----------

Have you checked throttle position sensor? My buddy had a '95 that seem to eat TPS every so often and had similar bogging prob when stepping on go pedal.

Just a thought....

Nice looking 'Hoe BTW.

Damn it took me at least 40 minutes from the time I loaded this thread till I got to it after the others to reply.

 

[Chevrolado]

Have you checked throttle position sensor? My buddy had a '95 that seem to eat TPS every so often and had similar bogging prob when stepping on go pedal.

Just a thought....

Nice looking 'Hoe BTW.

Hm. Alright, thanks for the tip!
Oh and thanks for the Kudos. I enjoy it.. when it's running. hah.

verify proper operation of the tps sensor as well and if you replace any sensor use only a delphi or delco part. Also do some engine vacuum tests while this is going on to see the idle vacuum as well as under load and the during the failures you are having.

---------- Post added at 09:32 PM ---------- Previous post was at 09:30 PM ----------




Damn it took me at least 40 minutes from the time I loaded this thread till I got to it after the others to reply.

hah Sunlit, thanks for taking the time to read it all. Sorry for the long winded post.. I just wanted to make sure all my cards were out on the table to get the most accurate response cause I REALLY need to figure out whats going on here.

I'll pull the TPS off my other TB and swap it over. See if that makes any difference.

Thanks y'all.

 

[SunlitComet]

It was not you. I just load all newly updated threads all at once in browser tabs, and pick them off one by one. But I am dozing off at the computer tonight.

 

[Chevrolado]

So I swapped out the TPS for another one and it still had its issue.

So then, as me and my mechanic discussed all of the things that have changed as of the recent that could POSSIBLY send this thing over the edge.. He said, okay, so maybe we should change out your brand new Coolant Temp Sensor for one we know works.
"What brand is yours?" My mechanic says to me, "Mine is AC Delco."
So I say, "This new one I put is NOT AC Delco. Its a sub-standard one that I probably shouldn't have put in it."
"Hmm.. " he says, "Let's try mine in it."

Annnnnd it fires right up and runs like a champ so far.

We have a lower than expected idle to work through, but when it's doing anything OTHER than idling.. its running like a champ.

I will keep this thread updated as I work out the kinks and make sure this is actually the true fix, but as it stands right NOW.. it was my faulty sub-standard brand of Coolant Temp Sensor that everyone told me to put an AC Delco in but I had already ordered the cheap-o.
I immediately regret that and will take all future steps to reconcile this mistake by purchasing the GOOD parts from here on out.

Thanks for the helpful tips everyone. I'll let ya know if this is the true fix.

 

[SunlitComet]

Hmm. If only somebody would have mentioned that in a previous post.

 

[Chevrolado]

Hmm. If only somebody would have mentioned that in a previous post.

Right?!

hah but seriously.. I had already ordered the crappy one before I asked on the forums when you replied with that. Unfortunately, about 3 others also told me "Get a new CTS" "Already ordered one.." "Make sure its AC Delco" "Oh... Hm."

 

[SunlitComet]

 

[Chevrolado]

And you know what they say about knowing...

 

[97Tahoe2d4x]

Glad you got it all sorted out, would've never guessed CTS especially after it was running well for a while.

It's funny how our trucks are particular about electonic sensors.
This reminds me of sticker they used to put on side of air cleaner

 

[Chevrolado]

Glad you got it all sorted out, would've never guessed CTS especially after it was running well for a while.

It's funny how our trucks are particular about electonic sensors.
This reminds me of sticker they used to put on side of air cleaner

Yep.. I believe it. Makes sense.