Suburban: Out of ideas


Heavy Metal

Recommended Posts

Well, I'm throwing myself at the mercy of anybody who may be able to help.

We had to park our '89 Suburban a year ago because it started dying on the road. Acts like it's running out of gas (or spark). Thing has and still does run killer. Lots of power, runs smooth...it just acts like it's running out of gas after a few minutes. Then you can start it right back up....it will idle for a minute or two then cut out, try to save itself then die. Same thing on the highway.

In the past year this is what I've replaced myself:

1. fuel filter

2. relay switch

3. coil

4. Ignition module

5. O2 sensor

6. brand new fuel pump/sending unit ($200!!!!)

And nothing has changed. I've talked to a dealership service manager and he was lost too. He said everything would point to the fuel pump if none of the other things fixed it. Only other thing he recommended was replacing the Idle/throttle control sensor, which just came in at NAPA today and I will do tomorrow. But....I'm fairly certain that aint it. Could it be something as stupid at spark plugs and wires or a coil wire? I don't know. I just don't get it. We desperately need that thing back. We have a big family and for a year now we have to caravan in two small cars to church, soccer, basketball anything we want to go to together. And now...all the seatbelts are broke in my wifes little beater GEO. They're $70 a piece and cannot be fixed.

Anybody got any ideas on the 'burb? It's the 5.7L throttle body injection, 3/4 ton, no cam or crank sensors.

Thanks,

Troy

Link to comment
Share on other sites

First thought as I was reading was fuel pump, but you changed it. Could still be a bad pump maybe? Have heard of pumps being bad new from the factory and not supplying enough pressure. Might have someone check the pressure with a gauge.

We were having issues with our yukon, the filter was plugging up, I think there was trash in the tank. It would run great and then just die, all I could ever figure was that trash would plug up where the pump pickup was in the tank. After it settled back out or down it would crank and run fine again. On a full tank we never had any issues, problems were always when the tank got down between half and quarter full.

Link to comment
Share on other sites

Hey, Troy, you get CEL lights with that? I guess that has OBDI on it. A code scanner will save you a LOT of cash if your registering a light when it starts doing that. Sounds like you've already tried a lot. Backpressure test on the cats? When's the last time you had plugs and wires?

About a year ago my wife's ranger barely made it to work. I had been fighting codes, misfires and everything for a month. Fed up, i told her to take it to ford dealer. After 4 hours they told me i needed a new engine, had no compression on 3 & 4. I took it home, checked comp myself (they put it on a machine and had never even pulled plugs) and all was ok. New plugs and wires put on it and ran like a champ. Only reason i didnt suspect plugs and wires was because they were only about 3 months old, but hey, sometimes the new stuff is crap too! Good luck!

Link to comment
Share on other sites

Hey, Troy, you get CEL lights with that? I guess that has OBDI on it. A code scanner will save you a LOT of cash if your registering a light when it starts doing that. Sounds like you've already tried a lot. Backpressure test on the cats? When's the last time you had plugs and wires?

About a year ago my wife's ranger barely made it to work. I had been fighting codes, misfires and everything for a month. Fed up, i told her to take it to ford dealer. After 4 hours they told me i needed a new engine, had no compression on 3 & 4. I took it home, checked comp myself (they put it on a machine and had never even pulled plugs) and all was ok. New plugs and wires put on it and ran like a champ. Only reason i didnt suspect plugs and wires was because they were only about 3 months old, but hey, sometimes the new stuff is crap too! Good luck!

hmmm....you're the second person this week to mention that. No I have not touched the plugs or wires. I did bring a new box of wires home last night. I also put in a new Throttle position sensor...didn't fix it of course. The new wires were only $20 and plugs are only $2 a piece. I'll go get some today as I am also going to get a can of carb cleaner as my father in law really feals that maybe the two throttle body injectors are plugged and he said they can be cleaned first instead of replaced. THERE $70 EACH! Thanks bro, I'll let you know.

I did have it hooked up on a computer last spring and nothing showed up...but if after this weekend nothing has worked, I think I'm going to take it up the Chevy Dealership in town and have them take a look. I'm out of ideas.:(

Link to comment
Share on other sites

Don't buy a Cat. Converter....just loosen the exhaust at the header pipe so you have a large exhaust leak then try running the engine to see if that's the problem. You can also connect a vacuum guage to a manifold port and see if the guage slowly loses manifold vac as the engine dies....this is also an indicater that the exhaust is plugged. This condition won't show up on a diagnostic check but sure sounds like a real possibility since it happens once the engine is warmed up.

Link to comment
Share on other sites

Is the check engine light on? If so what code does it have in it. How many miles are on you truck? I have seen bad coils. But understand there is a process to narrow down your problem. I have also seen coolant temp sensors go bad where it will read on a scan tool -30 degrees when the sensor goes bad. Are you losing fuel pressure when this happens? Do you have a fuel pressure gauge hooked up when this happens?. I have also seen code 41 set when there is a bad coil pickup in the distributer. That pick up fires the injectors and the coil. Have you checked the rotor and cap? Have you hooked up a vacume gauge I need some info to help you

Link to comment
Share on other sites

I just replaced the throttle position sensor, spark plugs and I took out the injectors and cleaned them with carb/throttle body cleaner. Nothing has worked. It's strange because when it's cold like this morning when I first went out to start it up and work on it, it runs perfect in the cold idle, then as soon as it warms up and drops down to a normal idle, both injectors at the same time start to sputter and intermitently stop spraying....then spray, stopm, then kick itself up into high idle again for a sec then drop down and do it all over again..or die.

The engine light is not on, it has been hooked up to a reader and nothing showed. When the injectors stutter the engine light does flicker a little but never stays on. I was playing with the temp sensor on the intake; when it's warm and I unplug the clip it idles up, when I reconnect it, it goes down. When it's warm, it will die/injectors stutter regardless of the idle (high or low).

Link to comment
Share on other sites

Well one mistake your making is posting mechanic stuff in RT forums :p

Have you joined a chevy/suburban forum? Usually i can find some super great help when i get a vehicle prob in the forums.

If your absolutely sure it's the TBI's screwing up, then i would think it's under the control of the PCM, and could be a host of issues. Good luck.

Link to comment
Share on other sites

Gotta agree here. Might be a bad pump from the factory. Also, may have been a bad fuel filter. You also may have gotten a bad batch of gas and run it through that new filter and pump and clogged it again. It doesn't take much to plug them durn things, even new

First thought as I was reading was fuel pump, but you changed it. Could still be a bad pump maybe? Have heard of pumps being bad new from the factory and not supplying enough pressure. Might have someone check the pressure with a gauge.

We were having issues with our yukon, the filter was plugging up, I think there was trash in the tank. It would run great and then just die, all I could ever figure was that trash would plug up where the pump pickup was in the tank. After it settled back out or down it would crank and run fine again. On a full tank we never had any issues, problems were always when the tank got down between half and quarter full.

Link to comment
Share on other sites

I had something similar on a '88 Blazer. The problem was the baffle in the fuel tank. It kept coming loose and knocking out the fuel pump. They replaced the keeper's for the baffle along with the busted fuel pump and I never had the problem again.

Link to comment
Share on other sites

I've been thinking about this one, I'm pretty stumped myself. Everything I think of you've already replaced. :D Do you know what it's losing? Fuel or spark? Next time it does it pull a spark plug wire off and see if it sparks when someone turns it over. Or pull the breather off and see if the injectors are spraying into the TBI.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.