help with chevy truck
 

I have a very nice 1995 tahoe and I started having problems upon acceleration. I changed plugs, wires, rotor and cap also fuel filter, no help. the local garage said o2 sensor, no helpI changed fuel pump, fuel reg in TB and TPS sensor, still no help, egr valve and spark controller in distributor. no help, today i changed timing gears and chain, started up but when I went to unplug wire to set timing the engine stops . I 'm lost can anyone help?

Re: help with chevy truck
 

Jim, check the shaft in the distributor for weak magnets. To do that just hook up your timing light, unplug that tan wire, and fire it up. Someone may have to sit inside and keep it runing for you. At idle the timing should be at Zero (TDC), rev it up to 2500 RPM. By 2500 the timing should jump up ten degrees. Won't be gradual, it will jump. If it does not advance, or even retards slightly, you need a new shaft in the dist. Don't go to Autozone,O'Reiley's, etc, for a reman distributor. Go to the GM dealer to buy a shaft, and pray it is still available. I used to keep three or four of those things on the shelf. Also causes stalling at idle when shifted into Drive, or Reverse. Most did it worse going into Reverse, but don't ask me why. Watch the dimple in the gear, it is supposed to align with the rotor blade. Knock the pin out, pull the gear, turn the distributor upside down and spray Berryman's Chemtool B12 down inside the housing, around the shaft. Let it sit a while and the shaft should slide out. Going to make a mess, so don't do it anyplace clean. Knock the shaft out and you will usually break the distributor housing.
Good luck, Ed

Re: help with chevy truck
 

Jim-One thing ya might see with the magnets on the dist. shaft if ya look close ya could see cracks-they can disrupt the signal trying to be generated and can cause a couple different things to happen.While you're there maybe change the pickup coil.Lotsa reman motor guys won't warrantee their stuff if ya don't change that dist. shaft 'cause it can make for real weird timing fluctuations and raising hell in the cylinder.

Re: help with chevy truck
 

Ed , when I unplug the tan wire , the engine stops.

Re: help with chevy truck
 

Doug , I will check for cracks

Re: help with chevy truck
 

Check the timing with it hooked up. Should be some where around 14 to 20 depending on calibration. If not unplug knock sensor. I've chased my tail so much because of a bad knock sensor shorted out. Does it have a lot of miles?

Re: help with chevy truck
 

Jamie, yes very high miles, whatever it is keeps getting worse, it started perfect after timing chain installed, ran about 15 sec and wont start . then it was starting but when I went to set timing it quits when tan wire is unplugged. is knock sensor tied into this system? Almost ready to put HEI and intake with a holley.( not sure if that will affect anything else

Re: help with chevy truck
 

They usually stop when the tan wire is unplugged because the timing is too slow. A second person working the throttle can usually keep it running in that case.
Hope by Holley you don't mean you put a Holley throttle body on it. :-(

Re: help with chevy truck
 

try unpluging your mass air flow sensor

Re: help with chevy truck
 

They don't have one.

Re: help with chevy truck
 

When I worked in parts at Huber Chevrolet, we used to sell a lot of distributor shafts for those and the gasket under the throttle body. Not very many injectors.
Fuel pumps are extremely common, too. Sorry if I missed anything.


Clark

Re: help with chevy truck
 

Can you feel any air coming out the tail pipe when it's running?

Re: help with chevy truck
 

did not try checking for air at tailpipe. Ed I was thinking of changing it to carb and hei, Dont know if thats a possibility or not.

Re: help with chevy truck
 

Jim ,I got a spare 283 you can put in it......

Re: help with chevy truck
 

Jim: If all else fails with the distributor, MSD offers a replacement unit for '87-95 Chevy trucks, pt. no. 8366. Hope to see you soon, Jim

Re: help with chevy truck
 

don't forget to get a new pickup coil when you pick up your distributor shaft. they tend to be brittle and coroded also. replace these 2 parts and you will be good to go.

Re: help with chevy truck
 

I too hyave a 95 Chevy truck with about 200,000 miles on it. Would this dist shaft problem cause low HP/Sluggish performance and lowered fuel mileage?

No missfire I can hear, you do have to pump it a couple times to start it.

Recent plugs wires and cap, maybe 15,000 miles

The truck burns no oil, compression is good in all eight Cyls. It almost feels like the Cat Con is plugged.

Re: help with chevy truck
 

Tod-Have you checked the timing per the advice on this thread? Be certain that you're getting your full ignition advance-we all know how doggy that can feel-if you have never replaced the shaft in the dist. I would just in the interest of good maintenance.The timing tag under the hood will give advice on checking timing also so you should have lotsa help there-good luck. Doug Schriener

Re: help with chevy truck
 

Sound like Tod Lane hit it, I'd look at The Catalytic convertor. Still sounds as if you have a base timing issue after that is resolved if it still has no power remove the frt, o2 sensor and adapt a pressur gage to the hole start engine should not see more than 1-3 psi at 1500 RPM

Re: help with chevy truck
 

The engine still should run with the brown wire disconnected. The initial timing should be enough to at least let the motor idle. Whatever the label says to set the timing, say 4-degrees before TDC, with the brown wire disconnected, should set the MIL light and a code in the ECM, so you'll have to clear both after you're done with the timing.

Did you have any codes stored in the ECM after the motor started to exhibit the stumble? OBD ll vehicles are usually (but not always) easier to diagnose because of the codes they throw. It might pay to have someone hook a scanner to it, if you haven't done so already. I had a neighbor who's Firebird had a terrible stumble off idle, hooked the scanner up and found the ignition system wasn't advancing the timing at all! No hair pulling necessary! :o

Just a few ideas...............

Lew

Re: help with chevy truck
 

If somebody previously set the timing without unplugging the tan/black wire it will be too retarded when it is unplugged. Most of those should show 12 to 16 deg BTDC with the wire plugged in. Might check it that way. If it's on zero, give the dist a twist so it will stay running when unplugged.

Re: help with chevy truck
 

Thank you so much to everyone that responded to help me out. I finally went to the junkyard and bought a distributor out of a running truck, put it in and BINGO the truck fired and runs like new . So now I will fix it properly. Since I changed everything else while chasing the problem it should run well for a long time, Again , thank you very much. It was driving me crazy LOL