[Krochus]

Mabye I expect too much hence me asking this question but at best I can only average 16.5 in mixed driving. Sometimes much worse as low as 14 :?: I expect more because my 94 full sized extended cab Chevy witha 350 got better than that.

the specs on my van are
1992 TBI 171K
3.42 axle 215 tires
stripped ex entry level conversion interior
accurate and verified digital instrumentation

here's what I've done so far

I've scanned the system,
replaced the O2,
ditched the cat
all plugs & wires OK,
checked the TPS output
fixed all vacuume leaks
bumped the timing up 2 degrees

but it still drinks gasoline, The scanner showed a max engine temp of only 181 degrees whilst a bit low I doubt this would cause the poor economy I'm seeing. The van runs great and has plenty of power.

 

[Gary]

You didn't say if this is a AWD.

 

[astro355]

Hello,
a couple of question for you.

How do you know the plugs and wires are 'ok'?
When was the last time it had a tune-up (cap and rotor, plugs, wires, oil changed, air filter, fuel filter, etc)?

And with the van running that cold, it will use more gas. ECM logic will try to warm your engine up by dumping more fuel down it.

And like Gary asked, is it AWD? AWD will use more gas also.

 

[Krochus]

I've had the van less than a year. Short wheelbase 2wd since purchasing Everything has been taken to a full tune up. All filters, PCV, ign timing EVERYTHING

The plugs were pulled and checked and appeared to be very recently changed by the previous owner in fact the previous owner appeared to have been very meticulous about matenince. I pulled resistance on the clean looking aftermarket wires and did find one bad that in replacing fixed a cold hesitation the van had..The engine is still strong with very little blow by and uses no oil.

This was a month ago now and I'm averaging no increase in economy. Had I known MPG would have been this bad I would have went ahead and opted for an AWD van. I'm not too worried that my $900 van isn't a fuel sipper but it still bugs me that I know it should do better

 

[astro355]

Well, with an AWD van the gas mileage would be worse. But seeing has how you bought a used van, you should assume that it needs a tune-up. Replace the cap and rotor, plugs, wires, all filters, all fluid, etc. Especially seeing that you have already found one bad wire, you should replace them all. And especially since you have had the van for nearly a year with no maintenance. Spend the money on the tune-up and save the money in petro.

 

[Gary]

I've had the van less than a year. Short wheelbase 2wd

The plugs were pulled and checked and appeared to be very recently changed by the previous owner. I pulled resistance on the clean looking aftermarket wires and did find one bad that in replacing fixed a cold hesitation the van had..The engine is still strong with very little blow by and uses no oil.

This was a month ago now and I'm averaging no increase in economy. Had I known MPG would have been this bad I would have went ahead and opted for an AWD van.

Nope-the AWD versions get worst gas mileage.These vans engines respond better and last longer with Delco cap,rotor,wires,and plugs.I agree that a 195 degree temp and thermostat would help you save on gas.I also agree that a replaced air filter will help as well.To answer your question-high teens city,some get low twenties highway.

 

[Krochus]

I've had the van less than a year. Short wheelbase 2wd

The plugs were pulled and checked and appeared to be very recently changed by the previous owner. I pulled resistance on the clean looking aftermarket wires and did find one bad that in replacing fixed a cold hesitation the van had..The engine is still strong with very little blow by and uses no oil.

This was a month ago now and I'm averaging no increase in economy. Had I known MPG would have been this bad I would have went ahead and opted for an AWD van.

Nope-the AWD versions get worst gas mileage.These vans engines respond better and last longer with Delco cap,rotor,wires,and plugs.I agree that a 195 degree temp and thermostat would help you save on gas.I also agree that a replaced air filter will help as well.

Yeah I realize that, but if I'm only going to get 15mpg I should at least have the benifet of AWD :banghead:

And especially since you have had the van for nearly a year with no maintenance. Spend the money on the tune-up and save the money in petro.

You misunderstand me, since buying the van 10 months ago I've completely gone through everything.

 

[astro355]

And I can understand that, but what I am saying is that you can get better than 15 if you do the tune-up. And what is everything that you have changed?

 

[Krochus]

And I can understand that, but what I am saying is that you can get better than 15 if you do the tune-up. And what is everything that you have changed?

I'm not going to tune the damn thing up again in less than a month

EVERYTHING that's generally considered a tune up part and some that aren't other than the fresh plugs and wires the previous owner had recently changed & those were pulled and verified. I've got no codes,no apparent reason why I would only get 14 to 16mpg

I'm a pretty good mechanic and understand the TBI system well enough to have retrofitted a couple carberated cars. On the scanner the computer is enriching the mixture slightly showing around 136 on the BLM but in my opinion not enough to cause 14mpg

BUT I would like to know what owners with vans similar to mine get. If everyone else gets 17 or 18 I'm simply not gonna worry bout it.

 

[astro355]

With an OBD I setup, you are not going to get any codes that suggest bad fuel mileage. Hey, we are only trying to help you here, there is no reason to get defensive. You are saying that you are getting 15 mpg and I'm telling you that something is wrong.

I don't know why you would not change the plugs and wires. They have almost a year on them since you have had them and they were used when you got the van. Really, who knows how long they have been on your van before you got it. The fact that the ecm is showing a 136 on the block learn suggests that its not burning all of the fuel.

So when was this changed:

air filter?
oil filter?
fuel filter?
cap and rotor?
plugs and wires? don't know

We can help you better if we know this information.

 

[Krochus]

So when was this changed:

air filter? last two months
oil filter? last week
fuel filter? last two months
cap and rotor? last two months
plugs and wires? very recently I can recognize that they were very new when I bought the van 8 months ago they were all pulled and checked and required no attention other than one plug wire. But given the total crapshoot that is replacement wires that doesn't surprise me

I don't know why you would not change the plugs and wires. They have almost a year on them

plugs and wires shouldn't need replacing for the better part of a decade on a EFI vehicle, again they were recently replaced when I bought the van. I had bought a set of replacment plugs but after removing the ones that were in the motor I simply reinstalled them and returned the new ones, they were that nice. In fact after working on the thing I get the impression the previous owner was trying to accomplish what we're discussing in this thread.

 

[astro355]

Umm, no. Spark plugs in your year van should be changed every 30,000 miles or 24 months, not a decade. And the fact that you already found one defective spark plug wire would suggest that they would need to be changed.

What kind of plugs and wires are they?

 

[Matrixx]

Hi Krochus
14-15mpg overall is terrible mileage for something as stripped down as a cargo. When I buy used vehicles from other owners, I personally do a tune-up whether it needs or not. The reason being from my past experiences is that most previous owners didn't put the correct parts in that's required to get the dependability out of them and just got what was cheapest to use.

Anyone can do tune-ups, it's using the correct parts for a particular application that's important here. As astro355 and Gary have already stated, AC Delco is whats needed for these 4.3s to be dependable. This isn't a turkey shoot observation, this is from first hand, tow bill observations from me and other astro/safari vans I have worked on in the shop. You didn't mention the name brand you put in.

Can you at least check the part number on the plugs you have in it now and make sure they are the correct plugs for your year of vehicle? If the plugs are to cold, it won't burn the fuel properly. Also check the tire pressure and make sure they are at least 28psi rear and 30psi front (or what the sticker recommends on the door frame)

Also, when was the last time an alignment was done or checked on your van? This can throw your gas mileage right out the window if it's out. Just a couple more areas for you to check that would cause poor gas mileage as well. Hope this helps Krochus.

 

[Krochus]

Umm, no. Spark plugs in your year van should be changed every 30,000 miles or 24 months,

I disagree as do all my mechanic aquantices. Till you get significant electrode wear 80K + the only thing replacing plugs do is pad your parts stores profit margin.

Either way not my preferd brand but IIRC the plugs were champion gold again very fresh with a perfect gap measurment for the application. IIRC they were something like 2 steps colder than the equivalent AC R45TS

The wires are the "ultra silicone" that oriellies sells

. Besides with a BLM of 136 it shouldn't the ECU be pulling fuel enrichment back towards lean if there was a lot of unburnt exhaust as in the case of a miss.

Also, when was the last time an alignment was done or checked on your van? This can throw your gas mileage right out the window if it out of alignment. Just a couple more areas for you to check that would cause poor gas mileage as well. Hope this helps Krochus.

I haven't had an alignment done and that mey be the next option, but in the past 10K I've put on it since buying the thing and installing new tires front wear is all but nonexistent. I try to run 34 in all the tires and usually stay on top pf pressure changes due to air temp

 

[astro355]

But unburnt fuel ruins oxygen sensors. So who's to say what is really going on if you think that fuel is running past the O2 sensor.

That 30,000 miles is straight from GM's routine maintenance guide. Newer vehicles with OBD II setups will get more mileage out of their plugs but not OBD I setups. And Champion is not the best plug you could use. And two steps colder is killing your mileage.

Let's just look at the obvious. Replace the plugs.

 

[Krochus]

OK I'll change plugs to R45TS this weekend and if there's a change in MPG I'll come on here and admit I'm wrong. But I really don't expect any change with replacing the plugs

And Champion is not the best plug you could use.

we agree on that.

But again I would still like more replies as to what kind of real world MPG do others with TBI vans get?

 

[Matrixx]

Hmm, looks like we all came in the door at the same time,hehe.

Hi Krochus
2-steps colder?

Were here to help Krochus, not hinder or head bunt, but were at a stand still with the plug issue. It's your decision on what you do. Food for thought.

Regardless......Welcome to the board Krochus.

 

[Matrixx]

?????
Hmm ok If you can get the Delco plugs for your year and gapped accordingly that would be great. Most Auto Parts stores carry the AC Delcos now. Please keep us updated Krochus, Thanks.

I see I'm running a bit behind everyone else with their responses here. I guess I better pick it up a bit,hehe.

 

[astro355]

Yes, running the correct plugs will help double-fold. First, they will burn right which in turn will raise your temperature, seeing how it runs really cold. Second, with the engine getting hotter, the ecm will trim back the fuel. Really, your mpg will get a lot better.

 

[Matrixx]

Hi Krochus
Another area to check as well would be the coil itself if you haven't already done it. What I have found with my van and other astro/safari's I have worked on, is the coils usually don't just die out. They (what I call it) is die a slow death (for a lack of better words) and get weak over a period of time. It's the enclosed compartment with all that heat around it that's really hard on them. A strong spark is important as well. Hope this helps. Please keep us updated Krochus, Thanks.