red87

I have a 87 4x4 pickup with a 22R and a 5 speed. On a recent road trip from socal to norcal (550 miles) I had to floor it to go 65 mph on the last part of the trip. Earlier that same trip I could do 70ish on flat ground without flooring it. I used to get around 17-18 mpg but now I'm down to 15-16mpg. Gears are 4.10 and tires are 31s. Truck has 170k and I replaced the fuel filter, air filter, all fluids, spark plugs, plug wires, cap and rotor within the last 2k miles. I checked the cat and it seems fine. Anyone have some ideas for me?

Matt16

Brakes dragging? Extra weight? Winter gas? Headwind? (yes, it can make a big difference).

Just Learning

maybe recheck the cat, kinda sounds like its getting plugged up some

red87

When I looked through the cat, I saw daylight through it. Is there a different way I should check it?

NicCantDecide

^^I just took out my cat and checked mine today... I pointed it at the sun and saw absolutely...NOTHING! I had dropped from 17-18mpg down to 13mpg at the last fillup over the last 2 months.

My loss of power started when I was getting a bunch of rattling from the cat, thought it was just a heatshield...then it went away a couple weeks ago and my truck was getting horrible mileage. I guess the catalyst broke loose and ended up packing up towards the back of the cat or something.

I tried running the truck without the cat and all the power was back and it wasn't stumbling over itself. It sounded like 3 harleys driving down the street, but I'll be getting that fixed soon

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That's just my little story though. If you've changed just about everything like you said, the last thing I'd check is your timing. It could be really retarded, but I dunno how that could happen so quickly. An exhaust leak before the O2 sensor will produce the same results, do you hear any loud ticking? Sounds similar to valve clatter.

Also, check the O2 sensor. Swap it out with one from a different vehicle if you have one since they're $130 a pop. Don't want to replace it unless you really have to.

red87

I didn't think of the O2 sensor, good call. I'll check that out

xxJDxx

what are out options for replacing the cat??

I imagine the stealerships price would be outrageous...

nv4runner

Recently I replaced my O2 Sensor wire cause it was shorted to ground...was getting around 13 MPG. No loss of power though, but wouldn't pass smog either cause of the super rich fuel mixture. Now I'm sitting around 16 MPG.

On a trip to Montana and back I got anywhere from 8 to 23 MPG with the bad O2 sensor wire. The 8 was when I hit I-80 in Winnemucca and was going right into a pretty good storm. Headwind all the way back to Reno. Worst mileage I've ever had...even worse than when I crawl around hills and mountains!

Elevation could make it a difference, and if its more mountainous where you were going in Norcal that could also be the difference.

dunnarunner

Gotta love computer controlled engines. put a new sensor in and dump the cat, would be my option, but you guys have a whole new set of rules to live by. but they are both a potential problem for what you are decribing in my books.

olharleyman

I just replaced mine with a MAGNA FLOW Hi Flow $61 bucks to the door guess he uped the price a little but still pretty reasonable

http://cgi.ebay.com/ebaymotors/Magna...item3ca0175d7a

flyingbrass

I'd start by testing compression.

You said 22R, which means carbureted (22RE is fuel injected). Only the California emission equipped 22R's in 86, and I presume also in 87, have oxygen sensors. My federal 86 doesn't have one. Carbed models in those years have simple computers, but they do very little compared to the EFI systems.

Check your compression. If it's good, then you can move on to troubleshooting other things.

flyingbrass

I just realized this thread is almost a year old.

It's extremely annoying when people don't post solutions or outcomes to the questions they've posed. It's selfish. You aren't giving anything back to the next guy who comes along searching about similar symptoms. And those following along to learn don't learn anything.

rangerruck

inflate tires to at least 35 lbs, and add 3 cans of seafoam to tank. Since you are not fuel injected, you can't do the Seafoam cleaner trick... but you can add right to your tank, and several cans at that. It will deff help.
But like above dude said, this is an old thread, the truck may be dead by
now, so i hope i have helped someone else...

red87

The answer was O2 sensor.

xxJDxx

Did you get a check engine light with the bad O2 sensor??

I have bad MPG and exhaust smells really strongly....