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Air system

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dave7700

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Does anyone know if the 89 blazer with the 5.7 tbi comes factory with the a.i.r. system? I just purchased a completely unmolested (I think) and it appears to have never been off road as there is no scratches on the frame 1989 Jimmy full size. It runs like a champ but I am getting smell of gas in exhaust and when I took it for smog it was high in hydrocarbons only. I am not too worried I have a buddy owns a smog shop however I don't want to be wasting gas cuz it smells like unburned gas in the exhaust. also it runs like **** when in gear just above idle. after approx 2000 rpms it runs pro. already replaced egr and checked for vacuum leaks.
 
There is nothing on the sticker about it there is however the bracket for the smog pump without the smog pump yet no inlets in the manifolds. I'm more concerned about the fact its running very rich and hesitates just above idle. Thanks for the reply.
 
AIR shouldn't be causing the problems you mention.

Have you done the basics? Checked and/or replaced plugs with the correct Delco's, checked/replaced plug wires with ones appropriate, checked cap/rotor for wear/damage, inspected all vacuum lines for cracks/replaced, and looked for loose or damaged wiring or connectors underhood? Does your check engine light work properly? Is the catalytic converter in place?

Smelling (which is not a good indicator, but an "unusual"/abnormal smell does indicate something) rich could be a variety of things, on a new to you vehicle, best to start with the basics that need done anyway, and move on to more complex stuff from there.
 
Yes to all of the basics. would a bad or sensor maybe cause it? That's the only thing I didn't do. I don't know how to properly check it.
 
a bad O2 will/can keep you in open loop and run rich... no smog pump will not cause those issues...
 
O2 CAN make it run rich, but so can a variety of other things as well...MAP sensor, CTS, exhaust leak forward of the sensor, leaking injector, and so on.

Many people replace the O2 as preventive maintenance, fairly difficult to test them unfortunately. Delco is preferred, but I'm hearing that the Bosch sensors are ok too now...they used to be junk apparently.

If the problem occurs warm or cold, you can essentially rule out the O2 sensor as the primary cause. O2 is not in use when the engine is cold (open loop). Can't remember what temp the O2 goes live (closed loop) in the TBI's, but probably around 160-170*...plenty of time from startup on a cool motor to notice a difference how it runs between open and closed loop if there is a problem. With everything working properly, that transition is seamless. When things aren't working right, either open or closed loop will often have issue(s), that go away or appear depending on what the problem is. Might run good cold but not hot for instance.
 
If its raw fuel you smell,like spilled gas,it could be the charcoal canister is loaded with gas,a defective purge valve on it will let it get saturated with gas,and it'll get sucked into the intake and burned,which will make it run rich and stink out of the exhaust too..and could make it idle poorly and run lousy at lower rpms..
 
Thanks for your help so far. I'm learning a lot however haven't figured it out. It isnt a raw gas smell. Its unburned gas at the exhaust not the engine compartment at all. It does shift hard from first to second when cold and it does run alot better once it is warmed up however it still hesitates above idle and the smell is reduced however still present. I have a set of Doug thorley tri y headers (they do have the bung for O2 in one) I'm wanting to put on along with high flow cat and flow master 40 series. I'm afraid of creating more problems if I don't solve this one first. Am I just being over cautious or could it possibly help?
Yes it is TBI.
 
Headers influence fueling requirements, so you are right in being cautious...fix known problems first, then move on to making your own problems later. :)

Agree with checking codes, even if the CEL isn't on, there might be something stored that is a clue.

Problem getting better when hot tends to indicate either there is too much fueling going on (O2 doing it's job, trying to pull fuel) or something is working better when it heats up.

Another basic I ignored is EGR...EGR on these things tends to plug up with carbon, cleaning the valve (and testing it for operation as best you can) and the passages under it would be something I'd consider preventive at this age, if it's not yet been done, regardless if it's a likely problem here or not.
 
Yes I am running O2 sensor in stock manifolds. No pending codes. Egr has been removed and cleaned as well as tested with vacuum pump. This one is definitely got me scratching my head. I don't want to just start throwing parts at it but I may have to. Just start with egr and move on down the line. Either that or swallow my pride and take it in to someone with the tools and time to go through it thoroughly. Id rather not spend the money but I guess I'm gonna have to before I loose my patience and completely rip it apart. Lol.
 
Thank you all for your replies. I got some good information on things I previously didn't fully understand.
 
Got a laptop? ALDL cable is handy to have, if you plan on monkeying with the motor later (headers, etc) retuning it is going to require this anyway. At the very least, will let you look at things like CTS values, TPS, etc.

What does the injector spray pattern look like, and do they drip after shutdown?

Sounds like you've covered EGR about as good as you can. Exhaust manifold on the O2 side isn't cracked or leaking?
 
dave7700 said:
Yes I am running O2 sensor in stock manifolds. No pending codes. Egr has been removed and cleaned as well as tested with vacuum pump. This one is definitely got me scratching my head. I don't want to just start throwing parts at it but I may have to. Just start with egr and move on down the line. Either that or swallow my pride and take it in to someone with the tools and time to go through it thoroughly. Id rather not spend the money but I guess I'm gonna have to before I loose my patience and completely rip it apart. Lol.
Click to expand...


my bad, misread that post and thought you already had the headers in... :doah:

have you pulled and done a plug reading? not "are they new", but pulled to see how rich it's running? plug reading is an invaluable tool... put a new set in, run it a day, and pull em and see how it's burning....

also, check your injector pattern to make sure they're spraying ok... a timing light flashing on them in the dark helps you see the pattern too...
 
does the truck still have a catalytic converter, I know when I removed mine for a temporary exhaust setup, it smelled really rich of exhaust afterwards.
 
I would start with changing the CTS (Coolant Temp Sensor), then next the O2 sensor.
 
Well after much thought and a lot of testing things I decided what the hell. I installed the Tri y headers, magnaflow cat and flowmaster 40 series. Problems solved. I discovered it was the original exhaust system cat and all. Problem solved and the truck runs and sounds awesome. I ran the headers which are 1 5/8" primary into 2 1/2" collector into the y then 3" after the cat to single 40 series flow master. Couldn't be more satisfied with the outcome. Paid $20 for the headers at the junkyard had em sand blasted and ceramic coated at my buddys shop for $100 and well. $600 headers for $120.
 
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