350 Engine Dies After Warming Up

[oldretiredafguy]

Engine dies sometimes when driving or sitting.

History-Original engine (153,000) removed with trans as a unit. 700R4 rebuilt by master transmission shop in Gainesville TX. Engine broken down and inspected. Bottom end looked perfect-result of religious 3000 mile oil changes. Heads sent to machine shop and completely reworked: new valves, guides and seals. New distributor, sensors, switches installed-all Delco or Standard (Borg Warner) parts. New O2 sensors (Delco or Bosch, can't remember). TBI rebuilt with STD complete overhaul kit. Fuel tank removed, cleaned. New Delco fuel pump installed. Fuel lines cleaned. New unleaded, ethanol free premium gas, with Sea Foam (16oz x2) to remove any moisture

Engine starts on the first key turn. After warming up, idle (600-700 to my deaf ears) and in park-engine sounds like it is having small backfires and smells rich. When driving, seems fine. Slowing down to make a 90 corner, engine died several times at each corner.

Of course, the mechanic who did all the work over a year period sold his shop, and moved to Florida 5 days after I got the truck back.

 

[Snoots]

You didn't mention a new fuel filter but you covered all the other bases so . . . I am not that familiar with TBI so I'll leave that to more knowledgeable folks.
If it were a carb I'd say a low fuel bowl float level and leaky throttle body bushings.

Have you checked the IAC?

 

[oldretiredafguy]

You didn't mention a new fuel filter but you covered all the other bases so . . . I am not that familiar with TBI so I'll leave that to more knowledgeable folks.
If it were a carb I'd say a low fuel bowl float level and leaky throttle body bushings.

Have you checked the IAC?

Thanks for the reply.

Yep. new Delco fuel filter as well as new Delco (Standard) injectors. I tried to replace everything that might move, rotate, swell, or get hot.

What is an "IAC"

 

[SirRobyn0]

Well I was going to say idle circuit problem in carburetor but then you mentioned TBI. I assume it idles ok when cold and runs down the road ok? Does the truck have a check engine light? If so is the light on? Has the ignition timing been set with a light? Otherwise #1 thing I'd be looking for is a vacuum leak, could also be a problem with the idle air control valve, or excessive deposits built up in the throttle body. Could also be a stuck open EGR valve. That's what I can think of right now, I might have more for you if your able to answer some of the questions.

 

[oldretiredafguy]

Well I was going to say idle circuit problem in carburetor but then you mentioned TBI. I assume it idles ok when cold and runs down the road ok? Does the truck have a check engine light? If so is the light on? Has the ignition timing been set with a light? Otherwise #1 thing I'd be looking for is a vacuum leak, could also be a problem with the idle air control valve, or excessive deposits built up in the throttle body. Could also be a stuck open EGR valve. That's what I can think of right now, I might have more for you if your able to answer some of the questions.

Thanks for the help.

Truck is a '88 GMC 350 TBI. Truck does have a Check Engine Light, but is only OBD I (Counting flashes with a paper clip). New distributor (could not find a new Delco or Delphi anywhere). When engine was reassembled, it was correctly timed with a light. New Cloyes Timing set installed during the assembly process. New vacuum tubing installed, new Idle Air Control Valve. Throttle Body completely torn down, cleaned and rebuilt with Standard (Borg Warner) kit. Only thing I couldn't find in my receipts (I keep EVERYTHING!) was a new EGR valve or solenoid notation. Hopefully, the mechanic replaced them, and never gave me the receipt for the parts. Will go check at the parts store this afternoon to see if they have a record under the shop account.

 

[Bextreme04]

Start simple... what is making the computer not happy? What code is it throwing?

 

[SirRobyn0]

Thanks for the help.

Truck is a '88 GMC 350 TBI. Truck does have a Check Engine Light, but is only OBD I (Counting flashes with a paper clip). New distributor (could not find a new Delco or Delphi anywhere). When engine was reassembled, it was correctly timed with a light. New Cloyes Timing set installed during the assembly process. New vacuum tubing installed, new Idle Air Control Valve. Throttle Body completely torn down, cleaned and rebuilt with Standard (Borg Warner) kit. Only thing I couldn't find in my receipts (I keep EVERYTHING!) was a new EGR valve or solenoid notation. Hopefully, the mechanic replaced them, and never gave me the receipt for the parts. Will go check at the parts store this afternoon to see if they have a record under the shop account.

I would do a leak check on the EGR valve, if it passes I would double check routing on vacuum line. I recently had a square body I was working on that was presenting with a massive vacuum leak, turned out there was a huge hole in charcoal canister, so don't forget to rule out the vacuum accessories like that, the brake booster, and other things run off of vacuum.

Is the check engine light on when your running the engine?

Also MAP sensor could have an issue, but in theory at least it should set a code for that, if you happen to have a spare MAP you might swap it on just to check.

 

[broketiredugly]

very first thing, every time, every vehicle with efi is to replace the cts. that is the coolant tempperature sensor. not to be confused with the engine temperature sensor. the ecm only focuses and responds to the cts before responding to the closed loop signals from other sensors like map/tps/o2 etc:.

 

[oldretiredafguy]

Start simple... what is making the computer not happy? What code is it throwing?

Sorry, duplicate answer.

 

[oldretiredafguy]

Start simple... what is making the computer not happy? What code is it throwing?

Thanks for the help.

No Check Engine Light when running, so no code.

 

[Snoots]

What is an "IAC"

As @SirRobyn0 said, Idle Air Control = IAC.

 

[oldretiredafguy]

I would do a leak check on the EGR valve, if it passes I would double check routing on vacuum line. I recently had a square body I was working on that was presenting with a massive vacuum leak, turned out there was a huge hole in charcoal canister, so don't forget to rule out the vacuum accessories like that, the brake booster, and other things run off of vacuum.

Is the check engine light on when your running the engine?

Also MAP sensor could have an issue, but in theory at least it should set a code for that, if you happen to have a spare MAP you might swap it on just to check.

No Check Engine Light with the engine running

Checked with the parts house, and couldn't find a record of the mechanic buying an EGR valve, so ordered a new EGR valve along with the solenoid. Will replace all components, including the vacuum tubes & lines.

Didn't even realize that this old of a vehicle even had a MAP sensor. Will get one on order. Like so many parts, OEM is best if available. Any brands known to be sub-standard or just pure junk?

He was supposed to change everything on the top of the engine. Finding out that's not true. Will order a new charcoal canister, and replace all the vacuum hose. With all new brake components installed, the brake pedal is softer (mushier) than I like, so your thoughts about vacuum leaks is probably correct. Thanks!

 

[oldretiredafguy]

As @SirRobyn0 said, Idle Air Control = IAC.

Thanks. The receipts I have for the new parts purchased and installed call one part "Air Control Valve". I'll assume that is the same thing as an IAC.

Thanks again for your help!

 

[SirRobyn0]

No Check Engine Light with the engine running

Checked with the parts house, and couldn't find a record of the mechanic buying an EGR valve, so ordered a new EGR valve along with the solenoid. Will replace all components, including the vacuum tubes & lines.

Didn't even realize that this old of a vehicle even had a MAP sensor. Will get one on order. Like so many parts, OEM is best if available. Any brands known to be sub-standard or just pure junk?

He was supposed to change everything on the top of the engine. Finding out that's not true. Will order a new charcoal canister, and replace all the vacuum hose. With all new brake components installed, the brake pedal is softer (mushier) than I like, so your thoughts about vacuum leaks is probably correct. Thanks!

You may get a lot of opinions on what are good parts and what aren't. My opinion, ac delco if available is my number 1, standard, Borg Warner are my number 2 everything else is settling for less.i use to have good luck with echlin and bleden but they have gone to crap in the last 10 years or at least that's been my experience lately.