1988 350 tbi sputters while accelerating

[anson1342]

I recently bought a 1988 gmc with the 350 tbi and 700r4 in it. It was my dads truck before, and he never had any issues with the engine much. He did have transmission problems, and I recently finished swapping the tranny and I noticed a very serious sputtering issue on acceleration. It starts alright although you have to crank it for 2 or 3 seconds when cold. Idles great, if maybe a little fast. It depends on the speed you are going when you try to accelerate, but above about 50 percent pedal the engine will sort of cut out for a couple seconds, then just sort of sit there and sputter, going something like a bu-bum very slowly, around 1 every one or two seconds, going steadily though. Then if you keep going wide open it will just sound like a really loud fan and the engine will load up, but not sound like normal at high rpms.
Am very confused on what this would be, and none of the suggestions I've found so far have worked.
Could something in the tranny swap have caused this?
So far I have tried:
Egr delete
Map sensor and tps sensor
Unplugging o2 sensor
Fuel pressure regulator, and am getting a nice cone of fuel while idling at least
In the process of a fuel filter and pump, although the tank looks great and there is a newer assembly in
Have also tried the paperclip method on my check engine light, but it doesn't show a code.
Have also noticed my gauges are not working the best.
Will try to include a video once the truck is back together, but any suggestions off what I've said would be appreciated.

 

[docstoy]

I would suggest looking at grounds , making sure they are clean and tight , also download service manual for your year truck , look at symptoms page in driveability section , the manuals will also give locations of grounds . It was not unusual for first years of tbi for it to have 2 to 3 second crank. You need access to scan tool to look at your sensor data as this will be beneficial as you learn about your truck. There is a sticky for service manuals start there first .

 

[anson1342]

Thanks for the help. I'll look into that

 

[anson1342]

Do you have any suggestions for a site I could look at?

 

[Drunkcanuk]

Do you have any suggestions for a site I could look at?

Your on the site you should be looking at!!! LOL
In the engine and performance section, there are stickys.....the 7th one down is the factory service manuals available to download.
They are a bit tricky to get downloaded, but this idiot was able to do it! Lol

I had almost the same symptoms on my 91. Was the little section of hose that connects the fuel pump to the assembly. Was full of holes from the ethanol in the new fuels.
Would idle fine, spray looked good at the injectors, but would fall flat on its face when under load.

 

[Schurkey]

1988 gmc with the 350 tbi and 700r4

I noticed a very serious sputtering issue on acceleration. It starts alright although you have to crank it for 2 or 3 seconds when cold... ...above about 50 percent pedal the engine will sort of cut out for a couple seconds, then just sort of sit there and sputter,

The Usual Three:

1. Verify fuel pressure at prime, at idle, and under load. How old is the fuel filter?

2. How old are the usual "tune-up" parts and services? Distributor cap, rotor, plug wires, spark plugs? Initial timing checked, along with the electronic spark advance? Verify PROPER EGR operation, PCV operation, EVAP operation. Check the heated-air intake on the air cleaner snorkel.

Have you verified cranking compression pressures for all eight cylinders?

Will the ignition coil reliably fire a spark tester calibrated for HEI? Ideally, with the coil hot from use, and misted with water from a squirt-bottle.

3. Connect a scan tool, find out what the computer wants you to know. Check for "codes", but more importantly, look at the data stream.

Egr delete

Mistake. Return it to PROPER functionality.

Map sensor and tps sensor

Diagnose before replacing parts.

Unplugging o2 sensor

Mistake. Put a new O2 sensor in, and make sure the computer is getting O2 sensor signal.

Fuel pressure regulator...
...In the process of a fuel filter and pump, although the tank looks great and there is a newer assembly in

What is the fuel pressure at prime, at idle, and under load?

Have also tried the paperclip method on my check engine light, but it doesn't show a code.

Faulty computer? Faulty wiring? Burnt-out bulb for the MIL?

Have also noticed my gauges are not working the best.

Could be power, more likely ground. Kinda depends on which gauges are "not working the best".

When my speedo and odometer went intermittent, it was a faulty "chip" in the instrument cluster. I replaced the cluster.

 

[anson1342]

Yeah turned out to have a cheap delphi pump in it. Replaced that and it was fixed immediately. Don't cheap out on parts.

 

[Schurkey]

Delphi is "supposed" to be a "good" brand.

But with everything coming from China, it's hard to know.

 

[anson1342]

Yeah I agree, the whole delphi assembly is about half the price of most though. Happy to have it fixed anyway.