Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

Axle ratio by RPO codes.
http://67-72chevytrucks.com/vboard/s...ight=RPO+codes

http://67-72chevytrucks.com/vboard/s...67&postcount=3

Monitoring open or closed loop status on OBD1 vehicles:
http://67-72chevytrucks.com/vboard/s...4&postcount=13

Heated O2 senor upgrade & heated air intake.
http://67-72chevytrucks.com/vboard/s...3&postcount=12

http://67-72chevytrucks.com/vboard/s...=heated+sensor

Mismatched injector on 1987 4.3L light duty truck engines.
http://67-72chevytrucks.com/vboard/s...87&postcount=4

These two long threads cover most problems that can happen with the TBI fuel system trucks.
4 page thread on TBI diagnosis.
http://67-72chevytrucks.com/vboard/s...d.php?t=348308

3 Page thread that EGR fixed.
http://67-72chevytrucks.com/vboard/s...d.php?t=347247

Stalling - Code 54 – Thread covers Fuel relay & oil switch for fuel pump.
http://67-72chevytrucks.com/vboard/s...d.php?t=495054

No fuel – burnt fusible link – code 54
http://67-72chevytrucks.com/vboard/s...d.php?t=460116

Checking OBD1 computer codes without a scan tool.
http://67-72chevytrucks.com/vboard/s...5&postcount=11

V8 Vortec distributor installation & code 1345
Thanks to bwood
http://67-72chevytrucks.com/vboard/s...ighlight=P1345

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

Wow, good ones there, thanks chevytech ;)

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

Thank you Scott!
Here’s another one:
V8 Vortec distributor installation & code 1345
Thanks to bwood
http://67-72chevytrucks.com/vboard/s...ighlight=P1345

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

Excellent thread; subscribing -

K

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

How to set the timng on 1988-1993 C/K trucks:
http://67-72chevytrucks.com/vboard/s...85&postcount=4

In 1994 the connector was moved inside the cab next to the computer.

On the square body TBI trucks the connector is by the brake booster.

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

Great info chevytech. I have a question for you, I have a 98 W/5.7, 4WD, 1/2 ton. The problem is it stumbles at higher speeds when climbing an incline. Example-Driving on the highway at 70 and start to go up a hill it wants to stumble/shake as its trying to downshift. This happens whether I'm pulling or not. Your help is appreciated.

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

1998 k3500 7.4
wiring diagrams
http://67-72chevytrucks.com/vboard/s...d.php?t=577359

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

Testing of the 88-95 EGR system:
http://67-72chevytrucks.com/vboard/s...d.php?t=583327

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

I didn't see this any where. So a a few years ago I replaced the 350 in my 95 K2500 PU with a 350 from a 88 K1500 Suburban after I got it all together and drove it the Trans didn't shift right and before the swap I had no problems with the trans so I started swapping all the electronics and sensors from the 95 350 and still no good. I only had one more thing that I could change and that was the Knock Sensor which I didn't think could have anything to do with the trans. After changing it the trans shifted fine turned out the part number of the sensors were one number different. Hope this helps somebody doing the same swap.

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

I have a 95 c 1500, 350 5.7 TBI I am having problems with the truck starting sometimes.Engine wants to turn over,but doesn't until I pump the gas pedal a few times then the engine starts and runs.Fuel or electric issue? Or both?

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

Identifying Drop Spindles & How to cut Coil Springs.
http://67-72chevytrucks.com/vboard/s...21#post6466621

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

Just got my 1988 Chevy Silverado 350 auto tranny 196000 miles. Seems to run good but in drive with brake on, oil pressure drops to almost 0. I am the 4th owner, 2 older men and an older woman.

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

I have found 2 websites that could be helpful at times and kind of gives a break down on a lot of different components.

www.aa1car.com

www.2carpros.com

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

Stumble only at idle yet normal power everywhere else? Black smoke from the exhaust when you stab the throttle after idling for a few seconds? Do the paper on the exhaust pipe trick, if it gets sucked in, most likely an exhaust valve not sealing, could be a burnt valve, stuck open from carbon, or in my case, a bad mechanic lashed the exhaust valve too tight. The low rpm does not allow the cylinder to build enough pressure to ignite the fuel, at higher rpm the increased piston speed moving the air faster builds enough pressure before it can leak out the exhaust valve to ignite the fuel, hence only the stumble at idle.

http://67-72chevytrucks.com/vboard/s...d.php?t=635082

Re: If you remove the distributor from a First Gen. Vortec engine
 

A crank position relearn should have taken care of that. But I find they run best with -4 degrees

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

For you TBI guys, I found a great website that shows you how to test sensors and breaks down what things to check for certain symptons your vehicle is having.

http://www.tbiparts.com/techinfo.html

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

I am having a few things going on with my 96 Sierra SLE 5.7L 1500 ECSB. First, my gas mileage has dropped off considerably in this past year. I was getting 15 around town, 19 on highway now it is 12.5 city, 17 highway. I have a slight stumble at idle when the engine is 'hot' (more on that later) but no engine codes are thrown for O2 sensors. My scan tool picks up nothing.

The 2nd thing weird is that the temp gauge reads at 120*. I have switched both temp sensors, but nothing is making a difference. Is there any way to test the actual temp of my truck if the gauge is off?

Any help will be most welcome.
Posted via Mobile Device

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

TBI (Throttle Body Injection) powered trucks, common problems.
In one spot, as short as I could make this post.

It is common for the gasket under the TBI unit to leak vacuum causing idle issues.
The throttle shaft can wear the housing creating a vacuum leak on the driver’s side of the TBI unit.

Testing the fuel pressure is a good idea if the idle is erratic or poor. I wish they would have put fuel pressure test ports on these trucks. The fuel filter, fuel pump, fuel pressure regulator (broken spring) and the rubber that connects the fuel pump to the sending unit are all possible causes of low fuel pressure. Low fuel pressure on these TBI trucks shows up as a poor erratic idle, and slow – hard starting, and just because it runs ok on the the freeway under heavy throttle you should not think it has good fuel pressure.

On these distributors the housing/upper bushing area gets so worn out that the shaft will move sideways so far that the points on the pickup coil pole piece get hit by the reluctor points on the shaft. When this happens the ECM receives compromised signal for RPM and timing issues. These distributors can also have problems because of loss of magnetism needed for the pickup coil to work, which cause more problems at low RPMs. If the magnetic material is cracked in pieces you should replace the shaft or the entire distributor.

Distributor modules are a common failure part. They can fail as they heat up. They can fail causing a no start, because of no spark. They can cause the injectors to not get triggered by the ECM even if there is spark. Or they can fail causing all kinds of poor running conditions. Many parts stores can test them. Make SURE you use heat sink compound under the module when you install it, or heat made in the module can't get dissipated and will destroy the module. Many replacement modules fail VERY quickly.

A bad TPS can make it so that the ECM does not know the correct throttle position and the ECM will not move the IAC. A TPS that shows wide open throttle can cause a lack of fuel for starting the engine because the system goes into the clear flood mode and cuts the fuel injected.

Coolant sensor failure on the sensor the the computer uses to set the mixture can cause the mixture the engine gets to be wrong. The most common problem it causes is a mixture that is too rich.

EGR valves can get carbon chunks holding them open. They can also drag on one side of the plunger and catch, sticking open at times. The EGR solenoids can also leak vacuum to the EGR valve at idle. If there is ever vacuum getting to the EGR at idle, unplug the electrical connecter to rule out an electrical problem, and if there is still vacuum getting to the EGR valve at idle replace the EGR solenoid. The solenoids can suck dirt in and stick.

The most common EGR system on the light duty TBI trucks is a “Negative Back-pressure” EGR system in which the EGR valve itself modulates the EGR opening. This system is very picky about the EGR valve operation and low quality replacement EGR valves can cause drive-ability problems that people are unable to find the cause of.

A common condition caused bad a bad EGR valve is a hesitation, or flat spot, at light throttle acceleration.

The TBI trucks from 1987 to 1995 are the OBD1 system and the computer trouble codes can be read without a scan tool. All you need is a paper clip.

You must unplug the set timing connector (wire) to set the ignition timing on these trucks, and if you don't the timing will be wrong. This will set a trouble code.

As these trucks age head gaskets leaking between the cylinders is a problem. As the head gasket fails, often the first symptom is pinging, and sometimes it causes a trouble code caused by high knock counts.

The none-roller lifters used in these engine along with the changes in motor oil removing ZDDP has shown up in the number of flat cam lobes on high miles engines.

Trying a different brand of gas is another thing you can try. It has been my experience that the TBI trucks do not idle as well on ethanol fuel and as they raised the ethanol content this was noticed by many people.

With a search you should be able to find discussion on all these topics in old threads.

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

Hey guys, I have a 97 Sierra 4.3L V6. It idles just fine and under acceleration runs just fine but, at a steady pace, no matter the speed, it kicks/bucks/jerks and has actually backfired once. Always has since the day I bought it. I did notice when I was doing a tune up recently, there is a small chip in the base of the platic distributor where the cap seals to it....could this be my problem? I bought a distributor from a local junk yard but haven't put it on yet.

Any suggestions?

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

Ive found out more great information on this thread dam. Very good job. Thanks very much. Brand new to this forum.

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

My friend has a 94 5.7 and at around 1500 rpm or so and deceleration it hesitates/bogs and has a code 43. We had recently changed the motor out because it was knocking and it ran great until about a week after and started having these issues. From what I read on the egr failure it seems more like that. He still has his old egr valve and will be throwing it on since there were no codes when that engine was in. But I was just wanting an input to see if that may be the issue.

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

Thats great information. Good work.

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

this was one of the known issues on the trucks newer boards are built better replacements today, i fixed mine.

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

whats the part number for the sensor sends a signal to temp gauge in dash

i think mine is reading wrong temp

i know theres 2 temp sensors in the engine block right v6 vortec 1994,
i have 2 new radiator hoses to replace and thermostat , also want to replace this sensor.

thx in advance.

Re: 88-98 FAQ's "Is your truck running weird? Check here it could help"
 

Yea..... this post is a tad old from me... I replaced my wiper motor with the later design. It swapped easily. Same bolts, attachments, etc. Works perfect.

Even the harness plugged into the newer motor.