trouble shoot this one.
 

i know this is a boat site, but this suburban is killing me. here's the deal. starts ok, revs ok in park, put it in drive and it falls on it's face coughs and sputters, if you barely give it gas it still misses but not as bad as when you nail it. here's what i've done so far. new plug wires, plugs, dist. cap ,rotor, fuel filter. any help out there?

it's a 88 suburban 454 tbi.
this problem just started and only is getting worse.
thanks
sly

I had a 93' that had a similer problem. I did all the same things you have done, and a little more. I finaly took it to the chevy dealer here in town and had them do a check on the systems. They replaced the injecters and most of the problem went away.

Cramer

Check fuel pressure, and clean injectors.

i thought of the injectors, but wouldn't it stumble in park too if i reved it up.
thanks
sly

This may sound crazy but when was the last time you put injector cleaner in it? Try double ar triple doseing it. It sounds to me like you have very dirty injectors. Pull the air cleaner off it and start it up then while you watch the stream of fuel coming off the bottom of the injector play with the throttle. Is the stream a fine spray or is it a lot of droplets? If it is droplets then do the heavy dose of injector cleaner...

tinkerboater
it's not fun to work on it when you get no where with it. besides i just want to get it running right so i can sell it. i just bought a new dodge RAM RIGHT
see ya
sly

It will only take 10 minutes to just go out and look at the spray pattern coming off the injectors. I'm preatty sure it is just dirty injectors. A friends truck of the same year had the same symptoms and the cleaner fixed it ( like new he said )

engine problems
 

I'm betting either clogged or worn out fuel pump in the tank or clogged fuel filter in the frame rail.

RPM a clogged fuel filter or bad fuel pump wont cause sputtering it will cause loss of top end power and the loss will slowly work its way down the rpm as the problem gets worse. With real dirty injectors the engine will idle fine in neutral and not in gear because in gear it is under a higher load and fuel atomization is more critical.

ok where do i spray the cleaner, it's tbi so the injectors spray down int the carb. both sides spray evenly and there is no loss of fuel supply when you gas it.
and yes i did replace the rail mounted fuel filter
tanks
sly

What about the Cat. converter? My truck had similar symptoms and the cat was blocked up. Changed it and ran like new. Just a suggestion Max.

I think if you check the fuel pressure you will find that the in tank pump has gone away.

It won't hurt to clean the injectors, and you should. But, your symptoms are classic fuel pump.

SLYDOG -- Was it a fine spray or droplets??? If it wasn't a fine spray like paint out of a paint can then they need to be cleaned. You need the stuff that goes in the tank and use 2 to 3 times the recomended amount.

waterfoul,
on my 3/4ton it has 2 converters, the rear one went out over the summer, when that happened it just had no power, right now i have power whenever it doesn't choke out.
thanks and it's good to see you have a computer at home now
seee ya
sly

my first thought is the catilatic convertor as well. I have had a couple go bad over the years and they have the same symtoms as what you are experiencing. Other than if you really punch it or rev it up you (or I) would see quite a bit of black crap from the exhaust.

Hey Sly, if you can wait till Mem. Day, we'll all be there to help you fix it!!!!!!!!!

Yup, puter at home now. Don't have one at work anymore, and I HAVE to have my OSO!!!!!

sputtering
 

Sorry, but had the same problem in a 94 suburban for the exact reason you say, not enough fuel to sustain the load. It was a clogged fuel filter in the frame.

Rpm My work truck has the pluged fuel filter problem on a 6 month basis and it never sputters it just looses power. The sputtering is usually caused by improper air / fuel mix. The TBI injection is highly efected by dirty injectors. The TBI acts just like a carb. only with better fuel control. Did your 94 have TBI or was it port injected?

troubles
 

It was a TBI. Doesn't take much fuel to rev without load. Not saying that its not an injector, just that most people don't even realize there is a filter in the frame or in close proximity to the tank. It looks as though he changed the filter in question so I'd do a fuel pressure check next.

Sometimes when a torque converter is going it will cause the engine to labor and try and engage at idle. Not what you wanted to hear but if you drop the pan and find metal you may be due for one.

I've got an '88 as well but with the 350 TBI- I had similar problems on a trip to Canada- we tried a different ignition module (always carry a spare) but that didn't fix it. Payed good money for an in-tank fuel pump as well- no luck there. The fuel pump is a possibility in your situation.
Mine turned out to be the ignition coil. Ran fine no-load, couldn't get out of its own way under load. BTW, the coil checked OK doing the winding check per the MM.

Is the "check engine light" coming on? If so check & see what code. I would try map sensor. Had 87 ford & had same problem. Turned out to be map sensor.

I was thinking fuel delivery problem.

Jon

Even with a good description in your post, it's really hard for even the best technician to lay his hands on the computer monitor and suddenly have the "fix" come to him as opposed to actually being there and seeing/hearing the signs & symptoms. I must agree with a few that have already mentioned it, Check Fuel Pressure! My first guess would be a fuel pump in the tank going south.

Check gasket between throttle body and intake manifold, common problem.

the four things that come to mind are plug wires, retarded timing, bent or broken push rod, or a flat cam. I have been the victim of all the above and for the valve train stuff pull the valve covers and watch for a short stroking valve while cranking.

ok, i gave up yesterday, truck is in the shop today, i'll pay the $79 to find out what's wrong with it. i did do a sensor check with a code key, it flashed 44, which signals lean exhaust, 02 sensor (2 months old)and map sensor. waterfoul i'm starting to wonder if you are right about the cat. converter, i am starting to get an exhaust leak from the manifold, last time i had one the rear converter was clogged and blew out both exhaust manifold gaskets.
thanks
sly

Ike mentioned somtething that I was thinking as well - a vacuum leak maybe the throttle body gasket, maybe something else.

Whatever you find be sure to let us know!

code 44 and stumble under load,
 

my money is on the fuel pump.you are describing a classic lean missfire condition.

ok, i talked to the mechanic today,he knows what it's doing he just doesn't know why. he said it's running lean at idle,no vaccum leaks found, he doesn't know how to check fuel pressure from the in tank fuel pump, they're rigging somethng up to test it.
at least i'm not theonly one guessing at this one. he also ruled out the fuel injectors.
seee ya
sly

Slydog when you get it running I might be interested in buying it.....Where are you located?

someoneakes an adaptor to check the fuel presure on those models. i believe you unscrewed the fuel line from the TBI and this adaptor screwed in line. i am almost sure it was made by Blue Point but i cant be sure. i had a problem that was similiar and sucked an intake gasket between the intake manifold and head.

ok, the place that checked my fuel pump said the pressure was good but the volume was low. they only want $350 to fix it, that comes with the jar of vaseline, and the guy can't say for sure it will fix it, he said he's 90% sure it's my fuel pump. my buddy is going to do it friday for 150. so i guess i'll wait and see if that's the problem.

dyno, i live in st. louis, mo, by the time i sell it it will have all new parts. it's in good shape though, let me know if your interested.
thanks
sly

Slydog tell me a little about it.....3/4 ton 454 right ? 2wheel or 4wheel drive? how many miles ? what color? you know the basics...I need a new pull truck-bus with the new kid and all. The tahoe just aint big enough....Pictures would be great...
Don

fuel pump
 

Check fuel pressure should be 12 to 15 psi fuel pumps are common, also check for vacume leak at throttle body base gasket GM tech:D :D :D