HELP! Really odd problems...

[TighTheChevyGuy]

I recently bought a 93 Tahoe w the 5.7L 350 L05. Its the last T.B.I. I do believe. I have put a new alternator, fuel pump, fuel pump relay, ecm, plugs, IAC motor, and i have done a lot of wrenching and cleaning on it, trying to restore it to its chevy pride.

I am having some really odd problems that i cannot seem to fix. I have a normal idle and rpms when my Hoe feels like it, then out of nowhere (in park, drive, neutral, driving down the road, whenever...) it will start to miss out. If i go to half throttle it seems to run quite a bit better until i have to let off the throttle. WOT sucks really bad and it seems to hate it so i stray away from that quite a bit. I thought it was caused by a shorted coil wire (the one straight to the bottom of the distributor) and upon replacing that wire it ran great for about 3 days. Then it randomly started acting up again. The IAC seems to have helped a slight bit. I have cleaned the terminals in the dist. cap and made sure all my connections are good as well. I'm thinking it may be that my TPS is wrong, or that it may be my coil itself (though this is uncommon), or maybe its my fuel pressure regulator.. im not sure. i have a ridiculous exhaust leak on the drivers side (common) from my manifold to the y-pipe which i intend to fix soon. im not sure if that could hurt a whole lot of stuff but my drivers side plugs have been burning extra hot (the ceramic is browning already after two weeks)...

i know this is a lot of info but i just figured it may help someone diagnose without a lot of questions and whatnot. please let me know if you think you are master mechanic enough to solve this humdinger. thanks yall. oh and it sat all winter without a hood hahah but thats not my fault, it was the guy i bought it from. gotta love an idiot.

 

[gpracer1]

How does it run in the first minute or two when cold?
You must fix the exhaust leak as your O2 sensor may see all that extra air. On top of that you may need a new O2 sensor also.

 

[TORONTO 95 GT]

I had the same issue with my 95 many years ago but it did throw a CEL when it was happening. Quick scan showed a TPS. Threw in a TPS and all was good.

 

[chevyboy831]

tps may b the issue, the exhaust issue is definately adding to your problem. fix the exhaust leak and recheck your live data if u can. allow the fuel trims to adjust and c what it does. how are the electrodes on the plugs?

 

[TighTheChevyGuy]

hey GP i am fixing the exhaust leak tonight hopefully. got new flange hardware n whatnot, just hoping nothing is broken off. kinda figured it might be an o2 but it jsut didnt seem to fit symptoms.

and to toronto and chevy, i read something about testing the resistance in my tps and adjusting it that way once upon a time, could i try that? and i dont have any codes, nor can i test it at work and w expired plates on it, i dont wanna risk runnin it to the shop since its obd 1.

 

[fire730]

It could be the O2 or the exhaust leak. Earlier systems relied heavily on the information received by the O2 sensors.

 

[TighTheChevyGuy]

alright i just got done w the coil and plug wires which were much needed regardless lol. also, i installed a dorman exhaust flange kit w the studs and springs which fixed the exhaust leak w a lil elbow grease added in hahah. however, my problems are not fixed. so how exactly do i spot a bad O2?? I have ran the heavy chevy on a modis scanner before and the O2 sends signals but could it be possible that its bad anyways? it runs really rich as i forgot to mention, not sure if the O2 says so or not, but when its idling i can smell the fuel.

chevyboy831, the electrodes look fine even though the ceramic was turning brown so damn fast.

 

[xanatost]

A bad O2 will make your truck run rich. It will run like crap too. Mine went out 2 weeks ago and I watched my gas gage drop. Fix it ASAP or run the risk of burning up your cats.

 

[SunlitComet]

I don't suppose you have the graph results of all four sensors do you?

 

[TighTheChevyGuy]

its a 93. only has one sensor on it from factory. also it has some ***** exhaust job done on it w.o cats. just has what seems to be a glass pack and it turns down just before the rear tires. and no, like i said i have expired plates on it so i keep driving to a minimum. and my mechanics shop is about ten mins away in a small town filled w dick cops. im not sure how to get any kinda reading offa it other than the modis scanner that they use up there. it just gives a live reading i do believe.

 

[chevyboy831]

hmm... electrodes look good.... a lazy o2 sensor definately sounds like its part of your problems. adjusting the tps might help. have you done any timing adjustments? ermember you have to disconnect the brown wire at the firewall to do so or else your timing is goint to b way off. if its running rich the voltage on the o2 will read low. youwont get a code for the tps on this obd1 unfortunately. when they go, they go and its hard to do a simple resistance test on em. you need to run a graph with a scan tool to look for imperfections in the sweep to see if you have a dead spot.

---------- Post added at 11:34 AM ---------- Previous post was at 11:29 AM ----------

WAIT WAIT WAIT!!!!! You fixed the exhaust leak, did u reset the computer? touch the battery cables together for 10 seconds to reset the learning curve then drive.

 

[TighTheChevyGuy]

okay so i threw an O2 in it and now its way worse hah. put a bosch O2 in it. its now dying whenver it pleases. also, apparently i set the IAC wrong. so tomorrow i do believe im gonna test the TPS and then try this wire trick. just disconnect them from the battery and then hold the cables together??? never heard of doin that lol. ive made a lot of changes in two weeks (most mentioned in original post) so it could need some resetting lol. the ECM is only about a month old though. and i havent looked into any timing stuff yet. could it bounce in and out of timing? because sometimes it runs absolutely fine

---------- Post added at 12:17 AM ---------- Previous post was at 12:16 AM ----------

also, when i do the resistance test, which wire is what? its the 3 lead connector.

 

[fire730]

Did the o2 come with a factory plug or was it just wire leads that you had to connect to the OEM plug?

 

[TighTheChevyGuy]

just the wires. plug looked okay though. should i return it and pay the extra ten bucks for NTK instead of bosch? the NTK comes w a new plug and seems to be built a bit better

 

[fire730]

Return it. Bosch makes some good things but O2s and spark plugs are questionable.

The reason why I asked is because I had a customers car that had O2s replaced with ones without plugs. After running for about 5 minutes it would run like crap and basically drop half of the cylinders. I unplugged both upstream O2s and the car ran great. I replaced both O2s with pre wired ones and it's been driving great. I never did go through the hassle of figuring out if it was crappy universal O2s or if they were wired wrong. This was an 02 Mitsubishi Eclipse V6.

 

[geo3xk]

Have you checked the egr?

 

[TighTheChevyGuy]

it sat at a shop for about a month since im short on tools and whatnot so my buddy mike let me use his shop to work on it and we just plugged the vacuum hose that goes to the egr.

and thanks fire, ill return the bosch and spring for the ntk and see it that helps any. gotta go to work tho ill let ya know when im off. also supposed to test the TPS today, hopefully.

also noticed something in another forum about the injectors dumping fuel.. i looked into it.. mine are dumping fuel like crazy. maybe a fuel pressure regulator rebuild?

 

[SunlitComet]

Do not use anything other then Delphi or acdelco Oxy sensors on a one gm vehicle.

 

[farwek]

I had this problem on my 99 Yukon and it kept giving codes for the o2 sensors. I figured it out yesterday the battery cable on the positive side was not getting a good connection so all I had to do was take off the rubber sleeve and it fixed my problem of the last two years... and no more ses codes. Also I always had enough power to start and run but it was causing just a small enough problem.

Sent from my SGH-T959V using Tapatalk 2

 

[TighTheChevyGuy]

took the bosch O2 out and it was scorched all around the base. after driving maybe a half hour total with it. and i prefer acdelco parts but we didnt have one in stock. although my battery cable is definitely corroded where they spliced it to put a system in it...

i also noticed that it doesnt get up to temp... it stays right at about a quarter of the way up (between 100 and 210) but i just put a temp sensor in it about three weeks ago... maybe the pigtail is bad? because i know that has a lot to do with fuel delivery...

also the plugs on the drivers side are getting worse. 1 is not bad, 3 is a lil darker than a cream color, 5 is brown, and 7 is almost black on the porcelain.

i just bought a TB rebuild kit, but it didnt come w a new FPR... and i hooked my egr back up but that hasnt helped any, and also unhooked the battery to try n reset the computer.

someone asked how it runs cold... it throws a lot of smoke right on start up, like the TB is flooding or its putting itself into clear flood mode to start...