hesitation/bucking in my 99 Tahoe

[rockenthebowtie]

Now you bought the vehicle with that problem chances are someone replaced the fuel injectors and didn't install them right

 

[Stripermike]

That's just dandy. From what I can see about the process of getting at the injectors it's not something I'd have a very easy time doing myself. I sure hate to pay someone to go on a "hunting" mission only to find that like all of the other roads I've gone down it's the wrong one....

 

[lesterl]

Injectors are easier than LIM gaskets....... You dont even need to pull the distributor for this one..... Gotta move some harness and stuff out of the way, disconnect a few things, pull a series of UIM bolts and voila! you got it apart, back together is another story and make shure you get a UIM gasket set.....

I have heard of this before, glad you found that tidbit Rocken.....

 

[lesterl]

I bet if you unplugged the injector harness there would be no bucking/ lunging at all!!!!

AFAIK the CTS does make the PCM make different decesions.... Also keep in mind that the PCM also controls the transmission as well......

How about hitting up radio shack for a resistor to replace the CTS with? Try in the range of 3000 ohms that will be around 70*, higher would be lower temps....

 

[lesterl]

As far as disabling the EGR, some of the guys on the S10 forum were fond of cutting out a 1 hole gasket for the EGR out of the side of an aluminum pop can........

 

[Stripermike]

Lester - very funny about the injector harness! I'm confused about the resistor thing - do you think if I replace the sensor with the right resistor I can get the truck to run with the right air/fuel mixture, have TCC lockup, etc. but still fool the PCM?

 

[rockenthebowtie]

Was reading some more of your complaints striper and the symptom of clunk bang noise in drive line is also a symptom mentioned I really believe that this is going to be it by chance did the person you bought it from mention anything about any previous engine repairs and or from what you can see has been done look at the upper plenum hold done bolts do they look like they may have freash socket removal markings on them ? For everthing you've gone through its worth taking a looksy.. like lester the master tech there says it's not that hard to do...To me Lester sounds like he knows what he's talking about I've seen and read alot of his postings and let me tell you he is one of the best guys here to get advice from..

 

[lesterl]

Just put a new set of plug wires on my 98 and my bucking when low rpm lugging is gone.... ($33 Bosch at Autozone)......

As far as the resistor you are fooling the PCM into thinking the coolant is around room temperature (with it unplugged it will think that the temperature is -40 and will run pig rich).... Sometimes they wont start/ run with this condition and just flood out, the resistor will at least give the PCM some condition that wont change....

 

[Stripermike]

I get it. I think I'm going to start with a new set of plugs and wires tomorrow and see if it changes things, barring any change I'll likely be diving into pulling the upper plenum and taking a look at things. If I can't figure this out I'll definitely try the resistor - just seems better to fix a problem if I can actually do that before taking the route of just making it go away.

 

[Tex99Tahoe]

:smiley-face-popcorn

The 'popcorn' symbol means I'm watching this show.
You guyz have gone way past my experience...

 

[Stripermike]

Tex - the crescendo will be after I get this thing back together and roll it down the road. I'm in the upper plenum now and guess what - multiple injector sets are REVERSED! Thank you rocken!

 

[rockenthebowtie]

De nada..

 

[lesterl]

Ha! go figure..... Wonder who did that one? When I got mine I took the intake duct off and cracked the throttle, inspected stuff with a small mirror, other than a bunch of black crud and the original poppets at 288k, I am going good......

 

[Stripermike]

Listen - I really don't even consider myself a "backyard mechanic". I mean, I do my own basic maintenance stuff, and out of necessity I have occasionally taken on projects that would probably be best left to someone who fixes cars for a living - I fix houses...

In the end there were 6 of 8 fuel injectors in the wrong cylinder spots. #'s 5&7 were the only ones that were correct, all 3 of the other pairs were reversed. The inside of the plenum was a mess, and I ultimately ended up pulling all of the injectors (had to pull 6 of 8 anyways) and removed the spider so I could clean everything up.

I already knew the guy who sold me the truck wasn't totally up-front about what was done and how/by who, but I was blown away when I pulled that plenum and found what I found.

This is a problem that I would NEVER have found - since the end of May this truck has been in and out of one or another repair shop, the journey is documented in these posts to some extent. Thanks to all of you who gave input and support, and thanks especially to rockenthebowtie - dude you found some info that led me to a HUGE problem and I only hope that someday, somehow I am able to pay that forward.

 

[Slammed]

You already have your detail in this thread will help many new and old users trust me

 

[rockenthebowtie]

Slammed couldn't of said it better myself.. @stripermike it was a journey alright.. your very welcome glad I can help out

 

[Tex99Tahoe]

Just to recap:

I have a 99 Tahoe ... issue with intermittent bucking ... I've had several mechanics look at the vehicle,.. had the transmission completely rebuilt.... but nothing shows on the computer.
The engine was replaced before I bought the truck, and it runs perfectly with the exception of the bucking issue...

Quite an adventure! Previous owner shenadigans do leave a mark...

 

[Stripermike]

Tex - just to sort of close out this thread......

An adventure indeed, and as you can well imagine, a lasting distaste for the previous owner and all of his "misinformation".

I have to say though, today I drove the truck around with NO annoying buck or hesitation, and NO driveline clunk - and a serious permagrin on my face!