Surging and bucking when warmed up

[short1500]

Depends on what's wrong.

If the solenoid is stuck open, so that the EGR gets vacuum when it shouldn't, you'd replace the solenoid.

If the EGR valve is stuck open, you'd replace the EGR valve. Some folks have mentioned that the EGR valve vacuum nipple needs to be restricted on some applications, but the replacement valve has a fully-open nipple.

If the vacuum hose is connected to the wrong port on the throttle body, you'd re-route the hose.

And in any event, you ought to look at the intake manifold passages to make sure they're not partially-plugged with carbon. This will require a new EGR valve gasket, and removal of the EGR valve itself.

But all of that assumes that the EGR system is the problem, and you have not confirmed that yet.

Ok so I tried a couple of different ways of unplugging the EGR. I pulled the line from the solenoid to EGR and tried it. No change. The I plugged the line off and no change. The unplugged the solenoid and no change. I just did the paper clip code reading and it popped up code 43. From my search I came up with a ESC module or knock sensor. I also forgot to mention this truck sat for 5+ years before I bought it and put in a new fuel pump and filter and flushed the tank out.

 

[Schurkey]

"Paper clip code reading" is not quite useless. Codes can be helpful, but the real diagnostic power is in the data stream and bi-directional control, which requires a REAL scan tool.

But, since you have a Code 43, download the service manual from the links on this web site, and follow the Genuine GM diagnostic procedure for that code.

 

[short1500]

Can't seem to find the service manual on the site. I went ahead and replaced the knock sensor and plug. Also replaced the O2 sensor just in case. No change. I sprayed some brake parts cleaner around TBI and got a slight change in idle so I pulled the TBI and I'm going to replace the base gasket and do rebuild on it. Pulled it apart and found crude throughout so soaking and going to get a kit. Hopefully this fixes my issue.

 

[Spareparts]

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

 

[short1500]

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Think I might have found my problem. Well at least a problem. Do you all think this is what's causing my issues? After overhaul of TBI and base gasket replacement truck would not start unless pedal was held. After getting it to stay running I took it for a drive and still did the same thing. Bucking and surging.

 

[Schurkey]

Start there, see what happens.

I still think you need to connect a REAL scan tool, verify all the sensors and computer outputs. Look at fuel trim numbers when it's bucking and surging, and perform a fuel pressure test.

How old are the usual "tune-up" items--cap, rotor, plug wires, spark plugs, fuel filter, air filter, etc? When was the base ignition timing checked?

 

[short1500]

Start there, see what happens.

I still think you need to connect a REAL scan tool, verify all the sensors and computer outputs. Look at fuel trim numbers when it's bucking and surging, and perform a fuel pressure test.

How old are the usual "tune-up" items--cap, rotor, plug wires, spark plugs, fuel filter, air filter, etc? When was the base ignition timing checked?

cap, rotor, plug wires, spark plugs, fuel filter, air filter, fuel pump, O2 sensor, knock sensor & plug, temp sensor are all new. Where do I get a real scan tool for the OBD1? How expensive are these?

 

[95 Tahoe]

It's hard to find one that works with the OBD1. You can go to EBay and get the red devil cable. WinADL will probably work on yours. I had to use RTTuner on my 95.

GM OBD1 Scanner Cable & Software - USB to 12 pin ALDL direct. - GM OBDI!! | eBay

USB to ALDL CABLE. Plug your laptop into the ALDL port of your 82 to 95 GM car or truck and see what is happening under the hood. Use as a scan tool. ALDL Vehicles Covered. This cable now works with ANDROID!

www.ebay.com

 

[Schurkey]

cap, rotor, plug wires, spark plugs, fuel filter, air filter, fuel pump, O2 sensor, knock sensor & plug, temp sensor are all new.

When did you check the base ignition timing?

Where do I get a real scan tool for the OBD1? How expensive are these?

When it was me, I bought a used Snap-On Solus Pro from a seller on eBay.

At that time, $350 shipped to my door with a heap of accessories, a rechargeable battery that worked, the instructional DVDs, and a big plastic suitcase to carry it around in. Good from 1980 1/2 to 2007.

As said...there are other solutions.

 

[PlayingWithTBI]

You can go to EBay and get the red devil cable. WinADL will probably work on yours. I had to use RTTuner on my 95.

WinALDL is pretty much obsolete anymore, TunerPro RT is good for pretty much all Chevy OBDI systems and some others. You need to get the corresponding .adx file for your Service Number ECM (I'm guessing it's 1227747) to data log and monitor. Here's a cable that works great, and the link to TunerPro. Make sure you download the RT version, the regular one won't data log or monitor.

OBD Diagnostics

aldlcable.com

TunerPro and TunerPro RT - Professional Automobile Tuning Software

You can get the .adx there or, on GearHead-EFI

GM ECM - Bins - TunerPro Definition Files - Wiring Diagrams - Tuner Info!

Each thread is by ECM number with Bins, definition files, wiring diagrams history and tuner information!

gearhead-efi.com

As @Schurkey said, used scanners are another way to go, some prefer one or both systems...